4.0:“: Elma-Hui. ‘ ‘ . -4xfixwwhfiifl‘3fi fwefiwwmwfi wfi v... I . w“. .14 . .... V :1. ‘ 3 ”when. , t2. 1 :. 5.2;»; . -’ 3H,! . U? .lts "r...“flmwm n. he. a . , 2 Ln“ I Cu‘lnzfilitxfio . .1 \b . , 2 i: ‘ ‘ ,nfix , 3.: A I): . 2 ml .r .L a. . Av .331?! ii ‘ ‘ ‘ .. 54%! 13% «fl. :1 t : ‘ :1 ”Writ. WT» 3% l . :31: .5v .9. I}: . . U . 3 ‘ Emabimv I .er :22... "351... it: ‘ : é... _ . . ., L“... .. my . 2 ,3? v9.35 . . in. 5M} .u»... , N. :1. » Q03 «ta .. 55.1%.» a. 3: Ru 2. g . cm dm$mfi£ .nmymb? an. . % A“A¢ Lv his. . igt... unnumuymmhfi .. :3“. 3313...: L .ak.‘ V 11.....‘i92h. .Enwfir , , .7. . 3.. vs... a. . ‘ 3:1; 1 x... a... i .5 ; 2. g 353%»? (ill: .3: a {f ~t’. 9%.: Yb . ').(')lo.: :5 3‘)? .Li .3 11:: 3:5; I .I$.,U.ya I . Aryan}. . ‘ ,1: 4 ct. , . 1... . a 3:... . .. t .1. . . A .13.... M823. " lllTllllll\\\l\\\\\\\\\\ T \\\\\\\\\\\\ Th This is to certify that the thesis entitled Causes of Soft Fruit in Sour Cherry (Prunus cerasus L.) presented by Mario Handuj ano has been accepted towards fulfillment of the requirements for H. S . Hort 1cu1ture degree in Major professor 4 Date Rove-her 15, 1995 0-7639 MS U is an Affirmative Action/Equal Opportunity Institution LIBRARY Michigan State Unlverslty PLACE ll RETURN BOX to remove thle checked from your record. TO AVOID FINES Mun on or More due due. DATE DUE DATE DUE DATE DUE MSU Ie An Affirmetlve Adlai/Bond Opportunlty Imam W ma CAUSE CAUSES OF SOFT FRUIT IN SOUR CHERRY (Prunus W.) By Mario Mandujano A THESIS Submitted to MICHIGAN STATE UNIVERSITY in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Horticulture 1995 ABSTRACT CAUSES OF SOFT FRUIT IN SOUR CHERRY (Prunus gerasus 1..) By Mario Mandujano Michigan cherry growers often have severe problems with soft 'Montmorency' sour cherries. Causal factors may include weather conditions, orchard practices, harvesting methods, and conditions during holding of fruits prior to processing. In this study efforts were concentrated on determining the effects of orchard practices, including shading to reduce solar radiation, irrigation, nutrient level, and application of growth regulators, especially ethephon and gibberellin. Fruit firmness was evaluated with a computer driven measuring device that compresses individual fruits until a preset force is attained. Firmness decreased as maturity approached, then stabilized in both 1993 and 1994. Significant fruit softening occurred only during mechanical harvesting. No treatments consistently increased firmness, but maturity was hastened and firmness reduced by spraying with ethephon. Sprays of calcium and potassium did not affect firmness, and gibberellin increased fruit size slightly without affecting maturity. Some cherry orchards bore softer cherries than others. "Soft" fruit, as defined by industry standards, were observed only rarely in harvested fruit. Soft cherries appeared to be caused by excessive bruising, and were always found in conjunction with mechanical damage. Advanced maturity and heavy cropping appeared to predispose the cherries to greater softening during harvest. Dr scientifit forall hr ————‘__-_—__-— and esp; Tc their sul h member T'fi much of 311d he( Win it his flier. “i H0rticu'. grOWers “11111611, Baage a. 51mg _\ file Dep, The wayr ACKNOWLEDGMENTS Dr. Frank Dennis, Jr. provided me with the opportunity to grow scientifically in an exciting and challenging environment. I thank him for all he has taught me, his guidance and support, encouragement, and especially his friendship and his contagious enthusiasm. To Dr. Daniel Guyer and to Dr. James Flore I am grateful for their support, friendship, suggestions, criticisms, and also for being members of my guidance committee. Although Dr. Galen Brown was not a member of my committee, much of the work described was carried out in conjunction with him, and he contributed greatly to the study. A very, very special thanks must go to Edward Timm, with whom it has been an honor and a pleasure to work. I am grateful for his friendship, support and camaraderie. I thank the Michigan Cherry Committee and the Michigan State Horticultural Society for financial support, and all of the cherry growers who cooperated with me in my research. I also extend my sincerest thanks to Mabel Grannis and Carl Thunell, tutors and friends, and to James Nugent, Bill Klein and Jackie Baase at the Northwest Michigan Horticultural Research Station. To Marcos Morales, John Everard, John Neilsen, Jun Ban and everyone in the Department of Horticulture and elsewhere who assiSted me along the way. and enc and en Fix has help Adrian 1 My sincere gratitude to my parents who always believed in me and encouraged me to work hard and aim high. My father's advice and example have been both inspirational and invaluable. Finally, the unceasing support and love from my wife Lourdes has helped make the impossible possible, and my sons Bernardo and Adrian make my life worth living. IEIOF' USIOFl LISTOF. 5:: ES III 51. LIST OF TABLE- LIST OF FIGURES TABLE OF CONTENTS LIST OF APPENDIX FIGURES AND TABLES - - _ ......... I. II. III INTRODUCTION - ..... REVIEW OF LITERATURE A. Sour cherry farmer's almanac .................................................... B. General aspects of fruit quality .................................................. C. Pectic substances D. Polygalacturonase 13. Conditions and treatments that may affect firmness 1. Shading - - - 2. Leafzfruit ratio _- _ 3. Mineral nutrition ................................................................... 4. Ethephon ............... 5. Gibberellic acid ...... P. Instruments for measuring firmness ............................... MATERIALS AND METHODS - -- - ..... . -- Shading _ - - ........ - Leafzfruit ratio ........................................................... Irrigation rimmewzvr iii Nitrogen application ....................................................... . Foliar applications of calcium and potassium ..... . Gibberellin (GA3) treatment ............................... .Ethephon treatment ....................................................... B. Experiments conducted in 1994 ........................................ 1. Irrigation and nitrogen ............................................ 4 S 8 9 10 12 13 14 16 17 21 21 21 23 24 24 25 25 26 27 27 IV. RE 2. Ethephon treatment 27 3. Foliar application of calcium .......................................... 29 4. Time of harvest over a 24-hour period, soaking, and holding temperature ................................................. 30 C. Methods of sampling and fruit measurements ................... 3 1 D. Statistical analysis 34 RESULTS A. Results, 1993 - - - ....... . - 3S 1. Shading - - - - -- 35 2. Leafzfruit ratio - -- -- -- - 39 3. Irrigation _ - _ - - ......... -- - - - 39 4. Nitrogen application - ......... - ..... 52 5. Foliar applications of potassium and calcium ......... 52 6. Gibberellin (GA3) treatment a. Experiment 1. Belding .............................................. 63 b. Experiment 2. Northport ....................................... 74 7. Ethephon treatment a. Experiment 1. Belding ............................................ 74 b. Experiment 2. East Lansing .................................. 85 B. Results, 1994 _ - - . - ......... ........ 91 1. Irrigation and nitrogen .................................................... 9 1 2. Ethephon treatment .......................................................... 91 a. Plamondon Orchard ................................................ 91 b. Bardenhagen Orchard - -_ - _ - - 102 c. Shimeck Orchard -- 102, d. HTRC, East Iansing . ........ - 102 3. Foliar application of calcium .. ........................................ 102 4. Time of harvest over a 24-hour period, soaking, and holding temperature ................................................. 1 14 V. DISCUSSION A. General - 126 1. Shading ..... __ -- 132 2. Leaf: fruit ratio 133 iv 3. Nitrogen and potassium .................................................... 136 4. Calcium - - ............ 137 5. Ethephon ..... - ....... _ -- 138 6. Giberellic Acid (GA3) .......................................................... 140 7. Irrigation ...... - _ - ................ 140 8. Temperature __ _______ - - - - 141 9. Bruising ...... - ..... ..... 142 LITERATURE CITED ............. 154 Table su ch Ti Table 1. 2. 3. LIST OF TABLES Treatments applied in 1993 ............................................................. Treatments applied in 1994 ............................................................. Main effects of shading limbs with shade cloth (10% full sun) applied 4 and 2 1 June and time of sampling on fruit characteristics of 'Montmorency' sour cherry. Horticulture Teaching and Research Center, East Iansing, MI, 1993 ......... Effects of leaf. fruit ratio and time of sampling on fruit characteristics of 'Montmorency' sour cherry. Heffron Orchard,Belding, MI, 1993 Effect of irrigation applied beginning 28 May and time of sampling on fruit characteristics of 'Montmorency' sour cherry. NWM Horticultural Research Station, Traverse City, MI, 1993 .......................... Effects of nitrogen fertilizer and time of sampling on fruit characteristics of 'Montmorency' sour cherry. NWM Horticultural Research Station, Traverse City, MI, 1993 ..... Effects of potassium and time of sampling on fruit characteristics of 'Montmorency' sour cherry. Gregory Orchard, Traverse City, MI, 1993 ................................................... Effects of calcium and time of sampling on fruit characteristics of 'Montmorency' sour cherry. Gregory Orchard. Suttons Bay, MI, 1993 ..................................................... Effect of gibberellin spray applied 3 July and time of sampling on fruit characteristics of 'Montmorency' sour cherry. Heffron Orchard, Belding MI, 1993 ................................ vi Page 22 28 36 42 53 58 64 69 16. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. Effects of gibberellin spray applied 1 3 July and time of sampling on fruit characteristics of 'Montmorency' sour cherry. Mitchell Orchard, Northport, MI, 1993 ......................... 75 Effects of ethephon spray applied 9 July and time of sampling on fruit characteristics of 'Montmorency' sour cherry. Heffron Orchard, Belding, MI, 1993 ............................ 80 Effects of ethephon spray applied 19 July and time of sampling on fruit characteristics of 'Montmorency' sour cherry. NWM Horticultural Research Station, Traverse City, MI, 1993 86 Effects of irrigation and time of harvest on fruit firmness (MCS) of 'Montmorency' cherry. NWM Horticultural Research Station, Traverse City, MI, 1994 .................................................... 92 Effects of nitrogen application on fruit characteristics of 'Montmorency' sour cherry. NWM Horticultural Research Station, Traverse City, MI. Harvested 27 July 1994 ............... 96 Effects of timing of ethephon application (300 ppm), on fruit characteristics of 'Montmorency' cherry. Plamondon Orchard, Leelanau, MI. Harvested 26 July 1994 ...................... 99 Effects of timing of ethephon application (300 ppm) on fruit characteristics of 'Montmorency' cherry. Bardenhagen Orchard, Leelanau, MI. Harvested 30 July 1994 -_ _ - _ - - 103 Effects of timing of ethephon application (300 ppm) on fruit characteristics of 'Montmorency' cherry. Shimeck Orchard, Maple City, MI. Harvested 2 August 1994 ............. 106 Effects of calcium (CaClz) application and time of harvest on fruit characteristics of 'Montmorency' sour cherry. Gregory Orchard, Suttons Bay, b/fl. Harvested 29 July 1994 .............. 1 14 Effects of time of harvest and method of holding fruits on fruit firmness of 'Montmorency' sour cherry. Horticulture Teaching and Research Center, East Iansing, MI. July 14—15, 1994 _ -- vii C( .C( 11 20. 21. Correlation between firmness and other fruit characteristics in hand-harvested 'Montmorency' sour cherry. 1993 ........ 12 1 Correlation between firmness of 'Montmorency' cherry fruits and other fruit characteristics in orchards used in 1994 -- - - 125 viii LIST OF FIGURES Figure Page 1. The effects of shading (10% full sun) and time of harvest on fruit characteristics of 'Montmorency' sour cherry. Horticulture Teaching and Research Center, East Lansing, MI. 1993 - - _--- -_ - 38 Correlations between firmness and several other fruit characteristics. Shading (10% full sun) experiment. Horticulture Teaching and Research Center, East Lansing MI, 1993 .... _- _- - - - -_ _-- 41 The effects of leafzfruit ratio and time of harvest on fruit characteristics of 'Montmorency' sour cherry. Heffron Correlations between fruit firmness and several other fruit characteristics. Leafzfruit ratio experiment. Heffron Orchard, Belding MI, 1993 - _ - ....... 46 The effects of irrigation treatment and time of harvest on fruit characteristics of 'Montmorency' sour cherry. NWM Horticultural Research Station, Traverse City, MI, 1993 ..... 49 Correlations between firmness and several other fruit characteristics. Irrigation experiment. NWM Horticultural Research Station, Traverse City, MI, 1993 ................................. 5 1 The effects of nitrogen treatment and time of harvest on fruit characteristics of 'Montmorency' sour cherry. NWM Horticultural Research Station, Traverse City, MI, 1993 ..... 55 Correlations between fruit firmness and several other fruit characteristics. Nitrogen experiment. NWM Horticultural Research Station, Traverse City, MI, 1993 ..... 57 10. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. The effect of potassium treatment and time of harvest on fruit characteristics of 'Montmorency' sour cherry. Gregory Orchard, Traverse City, MI, 1993 ................................. Correlations between firmness and several other fruit characteristics. Potassium experiment. Gregory Orchard. Traverse City, MI, 1993 ..................................................................... The effects of calcium treatment and time of harvest on fruit characteristics of 'Montmorency' sour cherry. Gregory Orchard, Suttons Bay, MI, 1993 .................................... Correlations between firmness and several other fruit characteristics. Calcium experiment. Gregory Orchard. Suttons Bay, MI, 1993 ......................................................................... The effect of gibberellin treatment and time of harvest on fruit characteristics of 'Montmorency' sour cherry. Heffron Orchard, Belding, MI, 1993 .............................................. Correlations between fruit firmness and several other fruit characteristics. Gibberellin treatment. Heffron Orchard, Belding, MI, 1993 - _- _ The effects of gibberellin treatment and time of harvest on fruit characteristics of 'Montmorency' sour cherry. Mitchell Orchard, Northport, MI, 1993 ........................................ Correlations between fruit firmness and several other fruit characteristics. Gibberellin experiment. Mitchell Orchard, Northport, MI, 1993 .......................................................... The effects of ethephon treatment and time of harvest on fruit characteristics of 'Montmorency' sour cherry. Heffron Orchard, Belding, MI, 1993 .............................................. Correlations between fruit firmness and several other fruit characteristics. Ethephon experiment. Heffron Orchard, Belding, MI, 1993 - - ....... - . ....... The effect of ethephon treatment and time of harvest on fruit characteristics of 'Montmorency' sour cherry. NWM Horticultural Research Station, Traverse City, MI, 1993 ..... 62 66 68 71 77 79 82 88 20. 21. 22. 23. 24. 23. 26. 20. 21. 22. 23. 24. 25. 26. 27. Correlations between fruit firmness and several other fruit characteristics. Ethephon experiment. NWM Horticultural Research Station, Traverse City, MI, 1993 ..... 90 Effects of irrigation, time of harvest, and soaking in water on firmness of 'Montmorency' sour cherry fruits. NWM Horticultural Research Station, Traverse City, MI Harvested 3 and 9 August,1994 ..................................................... 95 Effects of nitrogen application, harvesting and soaking on firmness of 'Montmorency‘ sour cherry fruits. NWM Horticultural Research Station, Traverse City, MI, Harvested 27 July 1994 ..................................................................... 98 Effects of early (14 days) and late (10 days) application of ethephon (300 ppm), harvesting and soaking in water on firmness of 'Montmorency' sour cherry fruits. Plamondon Orchard, Ieelanau, MI, Harvested 26 July 1994.. -. -- - - - .......... 101 Effects of early (15 days) and late (9 days) application of ethephon (300 ppm), harvesting and soaking in water on firmness of 'Montmorency' sour cherry fruits. Bardenhagen Orchard, Leelanau, MI, Harvested 30 J uly 1994 - __ _ - ...... 105 Effects of early (11 days) and late (6 days) application of ethephon (300 ppm), harvesting and soaking in water on firmness of 'Montmorency' sour cherry fruits. Shimeck Orchard, Maple City, MI, Harvested 2 August 1994 .............. 108 Effects of early application of ethephon (300 ppm) on firmness of 'Montmorency' sour cherry fruits. Horticulture Teaching and Research Center, East Lansing, MI, 1994 - _ - - 1 10 Effects of calcium (CaClz) application, harvesting and soaking in water on firmness of 'Montmorency' sour cherry fruits. Gregory Orchard, Suttons Bay, MI. Harvested 29 July 1994 ..................................................................... 1 12 28. 29. 30. ' 31. 33. 28. 29. 30. 31. 32. 33. Air and fruit temperature changes during 24 hours in 'Montmorency' sour cherry tree. Horticulture Teaching and Research Center, East Lansing, MI, 14-15 July, 1994 .. 118 The effects of time of harvest and methods of holding fruits on fruit firmness of 'Montmorency' sour cherry. Horticulture Teaching and Research Center, East Iansing, MI, 1415 July, 1994 ........................................................................... 120 Correlation between firmness and several other fruit characteristics. Ethephon, nitrogen, irrigation and calcium treatments. Traverse City, MI, 1994 ............................................ 124 Firmness of control fruits in 1993 vs. 1994 .............................. 128 Firmness of 'Montmorency' sour cherry vs. 'Ulster' sweet cherry in 1993. Preset force in grams was 300 for 'Ulster', 150 for 'Montmorency' - - _ -_ __ ....... 130 Effects of shading on the relationship between firmness and fruit color. Horticulture Teaching and Research Center, East Lansing, MI, 1993 ....................................................................... 135 29 3Q 32 33 Cher ISO: Efléc and: East] 28. 29. 30. 31. 32. 33. Air and fruit temperature changes during 24 hours in 'Montmorency' sour cherry tree. Horticulture Teaching and Research Center, East Lansing, MI, 14-15 July, 1994 .. 118 The effects of time of harvest and methods of holding fruits on fruit firmness of 'Montmorency' sour cherry. Horticulture Teaching and Research Center, East Lansing, MI, 1415 July, 1994 ........................................................................... 120 Correlation between firmness and several other fruit characteristics. Ethephon, nitrogen, irrigation and calcium treatments. Traverse City, MI, 1994 ............................................ 124 Firmness of control fruits in 1993 vs. 1994 .............................. 128 Firmness of 'Montmorency' sour cherry vs. 'Ulster' sweet cherry m 1993. Preset force in grams was 300 for 'Ulster', 150 for 'Montmorency' - - 130 Effects of shading on the relationship between firmness and fruit color. Horticulture Teaching and Research Center, East Iansing, MI, 1993 ....................................................................... 135 Figure AI. Sche Table A1. Effec units for S enclt 'Mon onto bruis 1964 A4. 121nm fruits Pit 2C. 193 1 A6. E390 for 6 ' . Comp units 2 A8, King} LIST OF APPENDIX FIGURES AND TABLES Figure Page A1. Schematic drawing of firmness measuring device ................. 148 Table Page A1. Effects of bruising on recovery of firmness (durometer A2. A3. A4. A5. A6. A7. A8. units) of 'Montmorency' sour cherries on soaking in water for 5 hr at 12 °C (Burton, 1979) ..................................................... 149 The effects of raising fruit temperature on the tree by enclosing limbs in plastic bags on firmness of 'Montmorency' cherry fruits before and after drOpping onto a hard surface -_ 150 Comparison of effects of hand vs. machine harvest on bruising (96) of 'Montmorency' sour cherry (Whittenberger, 1964) - _ _ _ -- - 15 1 Firmness of control, hand harvested 'Montmorency' cherry fruits (see Figs. 17,1,5) at three different locations (1993) . 15 1 Effects of soaking treatments on percentage of cull fruit, pit loss and juice loss in 'Montmorency' cherries (Marshall, 1951) 152 Effects of mechanical harvesting and soaking in cold water for 6 hours on firmness (durometer units) of 'Montmorency' cherry fruit (Kenworthy, 1973) ..................................................... 153 Comparison of sour cherry fruit firmness (durometer units) at 3 dates over 4 years (Kenworthy, 1974) ................. 153 Range in firmness as affected by method of harvest and soaking in water for 4 hours (1994) ............................................ 154 A9. Eff fin A9. Effects of dropping hand-harvested sour cherry fruits on firmness (MCS units). Traverse City, 1994 ................................ 154 xiv I. INTRODUCTION The four Great Lakes states (Michigan, New York, Wisconsin and Pennsylvania) together produce 90-95 96 of the US. sour cherry (311mm L.) crop. Michigan is by far the largest producer, with about 75% of the total US. crop (Ricks, et al., 1982). In 1993 Michigan produced 270 million pounds of the approximately 320 million pound U.S. crop (Michigan Agricultural Statistics, 1993). Mechanical harvesting of sour cherries began over 30 years ago. Increased mechanized harvesting has been accompanied by increasing numbers of questions regarding the effects of mechanization on fruit quality. Early research was directed at increasing pitted yield by reducing excessive fruit bruising. Bruising causes a breakdown of the tissues of the fruit and, if severe, can result in "soft" fruit (see below). Improved harvesting, handling, holding and processing methods reduced bruising, but a wide gap remained between ideal and actual pitted yields (LaBelle, et al., 1964; Whittenberger, et al., 1965, 1969; Diener, et al., 1968; Gaston, et al., 1968; Bolen, et al., 1970; Tennes, et al., 1970). Mechanical harvesting of cherries results in additional bruising in comparison with careful hand harvest. Cherries are initially bruised during mechanical harvesting when the falling fruit impacts on hard surfaces and on other fallen fruit, or when they are squeezed or scraped during conveying. Also, additional bruising occurs during between 1993). Th. erraticall} problem ~ 2 processing when fruit is dumped into tanks, conveyed, sorted and dropped onto hard surfaces several times en route toward the pitter. The amount of bruising received during harvesting and handling operations is inversely related to the initial firmness of the fruit (Parker, et al., 1966; Tennes, et al.,1966). In recent years the sour cherry industry in Michigan has been plagued with fruits that lack firmness and do not firm up during soaking. Such fruits are described as follows: the flesh of a soft cherry will collapse and the pit can be felt when the fruit is rolled between the thumb and forefinger with slight pressure (USDA, 1993). The problem of soft 'Montmorency' sour cherries has occurred erratically in the Michigan industry for decades. Soft cherries were a problem even when all tart cherries for processing were hand picked and delivered to the canneries dry in wooden lugs. The adoption of mechanical harvesting did not create this problem, but its use can make it worse (Whittenberger et al., 1965,1968). Soft cherries are not confined to any one area or orchard, since in any given orchard cherries may be firm one year and soft the next. Apparently, fruit firmness is influenced by environmental conditions and cultural treatments; the principal factors implicated have been poor distribution of rainfall, excessive cloudy weather combined with low seasonal temperatures, high temperature during harvest, low calcium, high nitrogen, and heavy cropping (Bedford, et al., 1955). Excessive water or nitrogen may result in the production of soft cherries, particularly during the 3 or 4 week period immediately prior to harvest (Bedford, et al., 1955). Studies with many fruits, including cherries, showed that softer fruit were associated with hem” 3F Beaumon In I cherries stretchec (lthittenl severely I surface. I; weight w removal . han'ested the additi Skin of bn Soft line. A sol 1033 Of int Operation 1992 Mid Cherries C Catching f resulting. The hOmCUItu: be Soft, an defined a‘ gTOinh Yer 3 heavy application of both nitrogen and potassium (Curwen, 1966; Beaumont, 1933). In the 19505 researchers demonstrated that 'Montmorency' cherries dropped 10 ft (3 m) once, or 3 ft (0.91 m) three times, to stretched minnow netting would remain essentially unbruised (Whittenberger and Hills, 1960). However, the same fruit would be severely bruised and softened after 3 drops of 3 ft each to a flat hard surface. Hand-picked cherries normally lose 12 to 14% of their total weight when pitted; about half of this loss is attributed to pit removal (Whittenberger, et al., 1964). However, mechanically harvested cherries lose from 14 to 24% of their total weight; much of the additional weight loss is due to juice lost through the ruptured skin of bruised cherries before pitting (Bolen, et al., 1970). Soft cherries are difficult to handle and pit on the processing line. A soft score of 5% of fruit can lead to rejection and resultant loss of income for the grower, and/ or problems in proper pitter operation and loss in pitter yield for the processor. In 1986 and 1992 Michigan sour cherry growers had severe problems with soft cherries during mechanical harvesting; fruit split on hitting the catching frame or were flaccid on arrival at the processing plants, resulting in a high percentage of cull fruit (Dennis, et al., 1994). The primary objectives of this research were to identify the horticultural factors involved in preconditioning the cherry fruits to be soft, and also to identify on the tree potentially soft fruit as defined above. The principal factors studied were the effects of growth regulators, light intensity, crop load, nutrition and irrigation. II. REVIEW OF LITERATURE A. SOUR CHERRY FARMER'S ALMANAC Following is a sampler of what cherry farmers believe about firmness of sour cherries. This clearly is not scientific evidence, but may provide clues as to the cause(s) of soft cherries. When there is a heavy crop, fruit color tends to be poor. Also, too many cherries are shaken down at one time and bruise each other. Several short bursts with the shaker are thought to be superior to longer ones. When trees are over-fertilized, fruits are larger and the farmer must take special care in handling them. Late harvested fruit contain more sugar, so a longer chilling period is required to firm them. Cherry growers believe that fruit should not be harvested when the temperature is too high, and should not be allowed to build up on the catching frame and conveyer. Farm wisdom also says that the percentage of soft fruit increases in proportion to the number of times the fruit is handled. The problems of cooling the harvested fruit also sit heavily on the minds of cherry farmers. They recommend about 40 to 45 tanks on a semi truck, using a six inch discharge flume into the plant. Water should be added to the bulk tanks on the semi truck in the orchard before the fruit is transferred from the smaller tanks used, in order to cushion the transfer. Water temperature is also important, and if too many tanks are taken to the orchard, water becomes warm before the cherries are harvested. Cherry fa 30 °C, ha under sul such day guides cu problems solutions WIIIOtsy ts There is I certainly B. GEVEI Brox combinau' detenmm' quality (it IEIated to and infect In It themes (hiring So Change in I 110er an any we“ I 3qu Strength . comm-On 5 Cherry farmers also recommend that when temperature rises above 30 °C, harvesting should be suspended. Cherries will not re-firm under such conditions, and should not be harvested after noon on such days. While the wisdom reported above is not scientific, it guides cultural practices. Such practices often provide solutions to problems, or can be used in guiding experimental approaches to solutions. Cherry farmers know that proper pruning eliminates willowy wood, reduces tree height and facilitates mechanical harvest. There is no evidence that such practices result in firmer fruit, but certainly fruit quality will be better. B. GENERAL ASPECTS OF FRUIT QUALITY Brown and Bourne (1988) established that fruit firmness is a combination of skin and flesh strength, and is an important factor in determining sour or sweet cherry quality and in maintenance of this quality during harvest, handling and shipping. Firmness may also be related to the susceptibility of cherry fruits to mechanical damage and infection by rot organisms (Ogawa, et al.,1972). In recent years the cherry industry has been plagued with sour cherries that lack firmness at harvest time, and do not firm up during soaking; these result in a mutilated product in the can. This change in firmness, according to Bedford and Robertson (1955 ) , could not be attributed to any one geographical area or orchard, since in any given orchard, cherries could be firm one year and soft the next. Bedford and Robertson (1955) concluded that the firmness or strength of the cherry structure was influenced directly by growing conditions; the principal factors involved seemed to be water, tempera water 01 particulc‘ to hars'e \t’l sour the with pec gave a 1: soft and nitrogen moisturi apparen' temperat Res the mom IhEII firm The addj fir Illness resulting 1967). 3; Dosthan. Improvec and proe MMmgf hour bell fl‘uit fir tachum (, 6 temperature, humidity and nitrogen fertilizer. Usually, too much water or nitrogen resulted in the production of soft cherries, particularly during the three or four week period immediately prior to harvest (Bedford and Robertson, 1955). Whittenberger (1952) reported that the edible tissues of the sour cherry are composed of thin-walled cells cemented together with pectic substances. If both were strong, the cherry was firm and gave a high drained weight; if one or both were weak, tissues were soft and drained weight was low (Whittenberger, et al., 1952). Excess nitrogen fertilizer also tended to produce soft cherries if sufficient moisture was available for rapid absorption; however, this apparently did not occur at below-normal rainfall or above normal temperature conditions (Bedford and Robertson, 195 7). Research by Bedford and Robertson (1957) also indicated that the addition of calcium to the cherries before processing increased their firmness, and the effect increased with calcium concentration. The addition of calcium to the cherry soak water may increase firmness and eliminate, at least partially, the loss of firmness resulting from tearing or crushing during pitting (Tennes, et al., 1967). Studies in British Columbia and Washington showed that postharvest dips or preharvest sprays of calcium chloride (CaClz) improved fruit firmness of fresh and canned sweet cherries (Drake and Proebsting, 1985). In 1988 Utah cherry growers observed that holding freshly harvested sour cherries in CaClz solutions for a half hour before beginning continuous circulation of cold water improved fruit firmness (Anderson, 1992). Postharvest fruits soaked in 3% calcium chloride for extended time periods always were firmer than ones soai observeC sour the deuce fc WI often can bloyer ( I but not product extent c processir soaked ii cherries time, am (1967) It influence cberries. mOSI rap Unbruise Cberries. Fru Cilnnot b Identifie ' tempera bunting 7 ones soaked in tap water. Moreover, Henderson and Campbell (199 1) observed that a preharvest foliar spray of calcium chloride increased sour cherry protein content and quality rating (no measurement device for firmness was reported). Whittenberger (1953, 1964) found that recurrent bruising often caused serious losses in quality and product yield. IaBelle and Moyer (1960) showed that bruising and elapsed time after harvest, but not soaking in cold water, were important factors affecting product firmness and drained weight. Moreover, the amount or extent of bruising received during harvesting, handling and processing determined whether cherries gained or lost weight when soaked in water. LaBelle (1964), and Parker (1966) reported that cherries largely recovered from a single bruise if given sufficient time, and regained much of their original firmness. Tennes, et al. (1967) reported that bruise level, soak time and temperature all influenced quality, product yield and pitter efficiency of sour cherries. Decrease in soluble solids during the soaking period was most rapid with fruit that was most severely bruised. In general unbruised cherry tissues lost much less soluble solids than bruised cherries. Fruit firmness is an important factor in fruit quality, and cannot be attributed to any one factor. Several factors have been identified as affecting fruit firmness, including water supply, temperature, humidity, nitrogen fertilizer, calcium concentration and bruising due to harvesting, handling and processing. C PECTI Pec linked x and aral the mic lamellac that che have be products File content showed a constant tbereafte C. PECTIC SUBSTANCES. Pectic substances are polyuronides composed mainly of 1,4- linked w-D—galacturonic acid with neutral sugars, typically galactose and arabinose, as side chains (Pilnik and Voragen, 1970) . They are the major components of the primary cell walls and of the middle lamella of plant tissues (Northcote, 1963). Doesburg (1965) showed that cherry fruit are particularly rich in pectic substances, which have been associated with the texture of fresh and processed products. Fils-Lycaon and Buret (1990) reported that the total pectic content of cherry fruit increased during ripening. Their studies showed an increase in total pectin content 6 weeks after anthesis, a constant level from 8.5 to 11 weeks after anthesis, and a decrease thereafter. According to Northcote (1963) degradation occurs just after the ripe stage. However, pectins drastically decreased from 90% for green fruit to 45% for overripe fruit. Fruit firmness declined very quickly until 7.5 weeks after anthesis, then remained constant (Fils-Lycaon, and Buret, 1990). Al-Delaimy, et a1. (1966) reported that the total pectin content of sour cherries picked two weeks prior to commercial harvest was considerably higher than that of fruit from two later harvests. Softening of fruit during maturation is related to changes in the fruit pectic composition. This relationship involves a conversion of water insoluble pectic substances to water soluble forms (Stier et al., 1956, Postlmayr et al., 1956, Gee and McCready, 1957, Hulme, 1958, and LaBelle and Moyer, 1960). Both nitrogen and potassium supply influence the water insoluble pectic content (Curwen, et al., 1966). Increasing resulted i reduction Iormatior fruit Soft changes '1 a convert forms. D. POIl't Dur structure, and a 105 Gross, 19' role in cel The Studied e 3CIII'II)’ if Indy of e 33319, er I Process ( That chat ”Deming I The Undergo SOIIIIIIIIZ; 9 Increasing potassium to a high level in the absence of nitrogen resulted in fruit with a reduced water insoluble pectic content. A reduction of calcium was also noted, which may have resulted in the formation of less water insoluble pectic substances, producing softer fruit. Softening of cherry fruits during maturation is related to changes in the fruit pectic composition, and the relationship involves a conversion of water insoluble pectic substances to water soluble forms. D. POLYGALACTURONASE (PG) During ripening there are significant changes in the cell wall structure, consisting primarily of an increase in soluble polyuronide and a loss of galactose and arabinose (Wallner and Bloom, 1977; Gross, 1979). PG activity increases during ripening and has a major role in cell wall degradation and fruit softening (Sheehy, et al., 1988). The softening of sour cherry fruit during ripening has not been studied extensively. Al-Delaimy, et a1. (1966) could not detect PG activity in either fresh or frozen sour cherry fruits. However, a large body of evidence from other crops (tomato, kiwifruit, orange, banana, apple, etc.) suggests that PG plays a major role in the softening process (DellaPenna, et al., 1987). Seymour, et a1. (1987) reported that changes in the levels of polyuronide solubilization during ripening are not closely related to the levels of PG. The mechanism related to fruit softening is not fully understood. However, PG activity is involved in polyuronide solubilization and softening of tomato fruits (Wallner and Bloom, Prui productic: 10 1977). Changes in firmness occurring during ripening in fruit tissues have been largely attributed to enzymatic dissociation of the cell walls between adjacent cells, and polygalacturonase correlates well with the softening of these tissues (Hall, 1987). E. CONDITIONS AND TREATMENTS THAT MAY AFFECT FIRMNESS 1. Mg. Fruit trees require light for photosynthesis and carbohydrate production, which are necessary for nutritional maintenance of the trees and for new growth. Flore and Layne (1990) showed that good light distribution within the tree canopy was necessary to assure maturity and flower bud formation for the following year. They concluded that shading could have a profound effect on the yield and growth of cherry trees. Flore and Layne (1985) reported that ripening was delayed on closely spaced, short trees and noted that a leaf-to-fruit ratio of less than 2.0 usually resulted in a limited carbohydrate supply, and could delay ripening by several days. Additional research by Flore and Layne (1990) showed that shading had a profound effect on fruit maturation, as indicated by color and fruit retention force. Fruits in the interior of the tree were often greener and harder to remove than those on the exterior of the tree where exposure to sunlight was better. Shading equal to 36 and 21 percent full sun, applied on June 24 ( the beginning of Phase III) delayed attainment of the optimum fruit retention force needed for machine harvest by 6 and 15 days, respectively. Flore and Layne (1990) concluded that light was a major factor associated with unifornti‘ ripening of fruit 0 relations soluble s borticult 1983). So and matt light leve reduced I caused e 1986). V frHits frOi reach a d from pit i Shaded fr regenerat mm Sofie Shaded fr shaded f1 DGIAI fall Clea profoqul Shaded fr Those nor 11 uniformity of ripening and could affect harvest time , especially if ripening of the fruit in the interior of the tree lagged far behind that of fruit on the exterior. In larger fruits, like apples, the most positive relationship between light and fruit quality is usually related to soluble solids, followed by fruit size. Low light reduces size, delays horticultural maturity, and increases firmness (Robinson, et al., 1983). Sweet and sour cherries, by comparison, have a short growth and maturation period, and fruit color will develop at relatively low light levels. In sweet cherries reduction of light to 36 percent full sun reduced flower bud formation, while reduction to below 10 percent caused embryo abortion and fruit drop (Patten and Proebsting, 1986). When Patten and Proebsting (1986) shaded sweet cherry fruits from petal fall to harvest, the cherries took 12 days longer to reach a dark red color. Soluble solids were higher for fruit shaded from pit hardening to harvest than for those not shaded, or for those shaded from petal fall to harvest; this difference was probably due to regeneration of the phloem in the early treated limbs. The degree of fruit softening upon maturity was less for unshaded fruits than for shaded fruits. Unshaded fruits were the firmest, followed by fruits shaded from pit hardening to harvest, with the fruit shaded from petal fall to harvest being the softest. Clearly the literature indicates that shading can have a profound effect on growth, maturation and yield of sour cherries. Shaded fruit generally contain less soluble solids and are softer than those not shaded. 2. _I_§ Of a ratio had (1983) sa natural lo agiven C1 solids, ant Spa; cherry or were low: were less et a1. (19: such as: c 0"a13’dia DTOduce 12 2. mm Of all the tree fruit quality parameters examined, leaf : fruit ratio had the largest variability (Teryl, et al., 1987). Facteau, et a1. (1983) sampled limbs with different leaf : fruit ratios and found the natural log of leaf : fruit ratio to be linearly related to fruit weight at a given color. Fruit firmness was positively correlated with soluble solids, and with the natural log of the leaf : fruit ratio. Spayd, et al. (1986) examined the effect of crop load on sweet cherry quality and found that cherries from heavily cropped trees were lower in color, softer, had lower sugar and acid levels, and were less mature than cherries from lightly cropped trees. Patten, et al. (1986) reported that fruit quality was affected by tree factors such as: date of anthesis, location of fruit within the canopy, and ovary diameter at initial set. Flowers that opened early in the season produced better fruit at harvest than those that opened late, and fruits on young wood were larger and had higher soluble solids at harvest than fruits on old wood. Fruits on shaded limbs were slower to mature, softer at maturity and lower in color and soluble solids than fruits on unshaded limbs (Patten and Proebsting 1986). Teryl and Loescher (1987) also reported a positive correlation between fruit firmness and soluble solids, and between firmness and 1eaf:fruit ratio. Additional research done by Patten, et al. (1986) showed that fruit weight and soluble solids were greater for early-bloom fruit than for late-bloom fruit, but firmness was not affected. Fruit firmness is clearly affected by leaf : fruit ratio. Low leaf : fruit ratios can affect fruit maturity and fruits on shaded limbs are slower to mature, softer at maturity and lower in color and soluble solids. Le variabilitj potassiui cherry 21 B3129111111 moderat m’th fin: fruit If; Characu measura contn'bt “Ere 31)} With 1'6 13 solids. Leaf-fruit ratio is among the most important sources of variability in fruit quality. 3 . Minera nutrition In 1950 Stanberry and Clore investigated the effect of nitrogen and phosphorus fertilizers on 'Bing' sweet cherries. They found that nitrogen application to unproductive cherry trees generally increased the yield and size of the fruit, but that heavy applications resulted in soft fruit . They also reported a common belief among growers that potassium applied in combination with nitrogen produced a firmer cherry and hastened maturity, but indicated that they knew of no experimental data to support the claim. Their research showed that moderate application of nitrogen (2 lb N/ tree) was usually associated with firmer cherries, while potassium application resulted in softer fruit (firmness was graded on the basis of surface pitting characterized by sub-epidermal breakdown, but no actual measurements of fruit firmness were performed). N and NP contributed to the better holding condition of the fruit. When both were applied in medium amounts, an interesting interaction occurred which resulted in firmer fruit. Increasing the calcium content of cherry fruits by spraying several times with calcium chloride during fruit development, or by post-harvest dipping in CaClz solutions, led to an increase in the firmness of the fruit (Cooper and Bangerth, 1976). Sixty percent (Anderson, 1992) of total calcium in plants is associated with the cell wall. Calcium acts as a chelating agent in cross-linking phospholipids and other proteins in the cell membranes. Such stabilization helps mmnmn the cell v tissue se nuiaces cddmn' mmmun ripening Tht mesubs durSm of calciur let'el of ti 14 maintain membrane integrity and the pectin-protein complexes of the cell wall middle lamella. Membrane leakage increases during tissue senescence. Calcium causes a condensation of membrane surfaces and decreases water permeability (Anderson, 1992). The calcium content of tomato cell walls increases to the fully grown immature stage, then drops to a level found just before the onset of ripening and softening of the tissue (Rigney and Wills, 1981). The fundamental role of calcium during fruit maturation and the subsequent redistribution during ripening process is not yet clear. Some research indicates that an increase in the concentration of calcium in the external solution leads to an increase in the calcium level of the leaves and then the fruit. 4. Ethephon Ethephon is a fruit-ripening agent commonly used to promote cherry fruit abscission for improved mechanical harvest and to minimize damage to fruit and tree (Bukovac, et al., 1969; Looney, et al., 1970). No data are known as to its effects on firmness, but one would predict that treatment would result in a softer fruit. Ethephon is a water soluble plant growth regulator that is degraded within plant cells resulting in the liberation of ethylene. The ethylene release within the plant is responsible for biological activity, such as abscission, coloration, maturation and increase in soluble solids (Amchem, 1967; Cooke and Randall, 1968). Wittenbach and Bukovac (1973) reported that the fruit abscission response to ethephon was very temperature-dependent. The optimum range was 16 to 29 °C, with poor performance resulting from ethephon app” (1972 15 application below 16 °C (Bukovac, et al., 1969). Olien and Bukovac (1978) found that with high temperature, particularly for prolonged periods, the ethylene dose could exceed that considered optimal for fruit loosening, thereby inducing leaf abscission and gummosis. They reported that ethephon was the major source of ethylene when applied to sour cherry trees, and showed that the major effect of temperature is on the rate of ethylene generation from ethephon (Olien and Bukovac, 1982b). After application, the ethephon concentration decreased progressively over time, until at some point the concentration was so low that even a large increase in temperature would not release sufficient ethylene to produce a physiological response (Olien and Bukovac, 1 978) . Ethephon is also applied to 'Montmorency' sour cherry trees to speed maturity and thereby permit early harvest. The optimum level is 300 to 500 ppm (Anderson, 1969). Fruits from treated trees were more mature in appearance and were a darker red than those from untreated trees. They were also slightly lower in soluble solids when treated with ethephon plus urea than with ethephon alone (Anderson, 1969). Ethephon apparently increased the ripening rate of all fruit on the treated trees, but such fruit were no more uniform in maturity than were control fruits. The literature relating the effects of ethephon on fruit firmness of sour cherries is scant, but research on sweet cherries indicates that ethephon significantly increased the amount of fruit removed during the first 3-sec shake during harvest, both bruising and the total percent of fruit with persisting stems were consistently reduced following ethephon application (Bukovac, et al., 1979). Subsequent shakes of bruised f: treated tr The as appliec Ithile m; critical or S. Q Gib III of frui (Proebstii firmness i 16 shakes of ethephon-treated trees produced a higher grade and less bruised fruit than was usually obtained from a second shake of non- treated trees. The effects of ethephon are determined by many factors, such as applied dose, absorption, time of application, pH and temperature. While many factors are involved, temperature seems to be the critical one. 5. Gibmeflig Acid (GA3) Gibberellic acid, when applied at 10 to 30 ppm early in stage HI of fruit growth, increased size and firmness in sweet cherry fruit (Proebsting, et al., 1973). Proebsting, el al. (1973) noted that color, firmness and size were more affected by sprays applied in early June (during early stage HI of fruit growth) than either two weeks earlier or later. Other studies indicated that the differences appeared to be due more to a change in fruit characteristics than to a simple delay in maturity (Dostal and Leopold; 1967, Russo et al., 1968; Dilley, et al., 1969). Treatment with GA tends to delay fruit ripening; it delays softening more than it delays coloring or soluble solids development, thus permitting the harvesting of firmer fruit. Multiple applications of GA to sweet cherries by Facteau, et al. (1982, 1985) increased fruit firmness, weight, and soluble solids, and delayed harvest. Firmness was positively related to number of applications (10 - 50 ppm per application) of GA3 , and also to soluble solids and 1eaf:fruit ratio. The higher the soluble solids levels, the greater was the differential in firmness between GA3-treated and control fruit (Proebsting, et al., 1973; Facteau, et al. 1985). GA3 is currentl.V harvesting rate of ap light gre firmness F. INST 17 currently used extensively by Washington growers to delay harvesting of 'Bing' cherries for fresh marketing. The recommended rate of application of GA3 to sweet cherries is 10 ppm when fruit is light green to straw-colored as a method of increasing size and firrrmess and to delay harvest. F. INST RUIVIENTS FOR MEASURING FIRMNESS For many years attempts have been made to measure cherry firmness directly or to discover a parameter whose value is closely related to firmness, but firmness is not easily assessed. Firmness is a textural attribute and an important factor in determining the overall quality of the fruit. In order to measure firmness in a manner approaching that of the human " thumb test", measurement of the deflection of a cherry subjected to a constant force over a fixed area should suffice. In 1925 Magness and Taylor developed a hand-held fruit pressure tester, which is still widely used for measuring firmness in many larger fruits. Whittenberger and Marshall (1950) measured firmness with a spring-loaded compression device. Cherry firmness was also measured by Bedford, et al. (1962) with a tenderometer (developed by Armour Co. Illinois), consisting of a probe assembly and a read-out box. The probe assembly contains ten penetration needles mounted on a manifold, which is in turn attached to an electronic strain gauge. The probe assembly also contains a handle for holding it, and an inverted U shaped member to serve as a penetration stop indicator . In 1964 LaBelle, et al. reported that the resistance of the cherry tissue to the shearing-crushing action of than 0the 58V were low the time plane; d: distance subjecting Cherries compress cherries apparent Various 5 blthout s bmises (ft 18 action of pitting was a more satisfactory guide to cherry firmness than other methods of measuring firmness. Several techniques for measuring firmness of tart cherries were investigated by Parker, et al. (1966). These included: measuring the time required for a cherry to roll a given distance on a sloped plane; dropping cherries on a sloped plane and measuring the distance of bounce; and stacking ten cherries in a vertical tube, subjecting them to a load, and measuring the amount of compression. Cherries stacked vertically and subjected to a specific force should compress a distance inversely related to their firmness. When cherries were drOpped onto an inclined surface, there was no apparent relationship between length of bounce and firmness. Also, various slopes, surface conditions and drop heights were tried without success. This instrument was successful in detecting small bruises (for example, a three foot drop vs. unbruised cherries) but it failed to detect the effects of larger bruises (Parker, et al.,1966). The puncture-load (PL) meter, initially developed to measured diameter, consisted of a rigidly mounted micrometer dial with its rod vertical. It was able to detect differences in cherry firmness following slight bruising (Diener, et al., 1969). Mature cherries have a much higher percentage of soluble solids than immature cherries; thus, this instrument seemed well-suited to measuring both soluble solids and cherry firmness. The disadvantage of this method was its low capacity; only 24 cherries could be measured per hour (Parker, et al., 1966). Parker, et al, (1966) measured the relationship between soluble solids and cherry firmness, but found no apparent relationship when soluble solids were greater than 14 percent. Cheniesc deflecuon Sou duromete the same In 1974 mechanic researchi upon me tooling p geograph firming d and Silsbj Bro pressure Success. I to measu and ourl Berrtsteir (1982), In the "thu during C The)" The M0 Dara here Get. 19 Cherries containing less than 14 percent soluble solids had the lowest deflection. Sour cherry firmness has also been measured using a durometer. Using this method, a pair of measurements are made on the same fruit, one with the skin intact, one with the skin removed. In 1974 research using the durometer showed the effects of mechanical harvesting, cooling and pitting on fruit firmness. The research indicated an initial firmness of 52 units, a loss of 11.5 units upon mechanical harvesting, and 7.7 units of re-firming on the cooling pad. Mechanical harvesting reduced firmness more in one geographical location than in another, and the percentage of re- firming decreased as the harvesting season progressed (Kenworthy and Silsby, 1974). Brown and Bourne (1988) have measured firmness with pressure testers, force gauges and a shear press, but with limited success. Many other methods and instruments have been developed to measure firmness in small fruits: Bouyoucus and Marshall (1950), and Ourecky and Bourne (1968) with strawberries, Lustig and Bernstein (1987) with cherries, and Rohrbach (1981), Wolfe, et al. (1982), and Slaughter and Rohrbach (1985) with blueberries. In 1993 Tirnm, et al. developed a method that approximated the " thumb test" mentioned earlier, involving deflection of a cherry during compression at a constant rate of increase (App. Fig. A1). They measured firmness by slightly compressing the fruit between two parallel surfaces and recording force versus deformation. They also found that many of the instruments used to detect firmness were designed for larger fruits, such as apples, peaches and pears, and wet suhas T1 and acc compre. deflectic suflnea bythe produce mms(e. dope of simplifi distingu fruit ma' 20 and were not sensitive enough to measure firmness in small fruits such as cherries, blueberries and strawberries. This computer-driven device seems to be the most practical and accurate of all the firmness measurement methods. Each fruit is compressed until a preset force (e.g., 150 g) is reached. Force versus deflection is plotted and used to calculate a value (MCS = mean chord stiffness) roughly equivalent to the preset maximum force divided by the distance moved by the compression plate. Firmer fruits produce larger values (e.g., 150 g/me = 75 units) than do softer ones ( e.g., 150 g/3mm = 50 units) Actual values are based upon the slope of the tangent to the force/deflection curve, rather than the simplified examples given above. This system is capable of distinguishing between bruise treatments, harvest treatments and fruit maturity levels. Fruit firmness has been a difficult characteristic to assess in the sour cherry. It has been measured with pressure testers, force gauges and the shear press for many years with limited success. Although the durometer has sometimes proven useful, its use is not recommended due to variability in the readings obtained. The computer-driven testing machine mentioned above has been used effectively to measure components of firmness in sour cherries and other fruit crops. My objective in the research to be described was to determine what factors might be responsible for the soft fruit problem in Michigan sour cherry orchards. Ir cultura Cherry selected age ran were lo< I'nit'ersi 1 mpg Th 1.: 21 III. MATERIALS AND METHODS In 1993, a study was initiated to compare the effects of several cultural and environmental factors on firmness of fruit of sour cherry (m germ cv. Montrnorency). Seven orchard sites were selected in three areas: Traverse City, Belding and East Lansing. Tree age ranged from four to fifteen years. Two of the seven orchards were located on experimental stations operated by Michigan State University. A. EXPERIMENTS CONDUCTED IN 1993 The experiments are outlined in Table 1. 1. Mg, Horticultural Teaching and Research Center (HTRC), East Lansing, MI. Five trees planted in 1982 were selected for vigor and good cropping. Four limbs approximately 4-5 cm in diameter at the base were chosen on each tree. Shade cloth was used to cover two limbs on each of five trees, and the following treatments applied: a) no treatment, b) girdled 1 cm. ring of bark removed at the base; c) girdled and shaded (10 percent full sun) at the beginning of growth stage 11 (June 6), (1) same as (c), but applied at the beginning of stage 111 (June 21). The girdles, which were covered with grafting compound, prevented movement of photosynthates from other parts of the tree during the period of shading. 22 doumuofi 8 930.88.» wfibg Jamaican? a B 92 2 as... v 3.3. bi - 8:63 >3 89:5 tomato a 2 9E 3 1; mm 3.2.. 33 - 83330; .93 335m bowouo w a $2 2 E - m-m 5&2 Ba 5:636 tomatoz :23“: A 2 wee 2 3 mm 3-3 33 mom sonata no 03389 82 o 2 use. 3 3 mm 3-3 3% mom 5852 .36 863.2... 82 m 4 $2 2 E a 8-3%: mom 5:636 520m 8.5% 4 4 $2 2 E a 8-2%: mom 8:85 36.8 noses: m m 92 2 E m 8-3%: mom 2%.. :Efifl 32mm 85...: N E was. a E N 2-2 bi mom wsnanm wanes sum 82 a 95mg 09 88a E232 22me B5 £5. 02575 gommzzoo. éeznmzamfi gage 29.503 E305 gomo Mae 5 8:de 35828:. .H £an Fru beginniIIE over a pe T 2. I Twe- leaf: frui June 1-2. Quarters. clusters t 10 trees . One grOL 58(0le g 23 Fruit samples were harvested at intervals of 5 to 7 days, beginning 2 weeks before commercial harvest (July 1) and extending over a period of 5 weeks (August 3). 2. Leafimimtiq, Heffron Orchard, Belding, MI Twenty-five heavily cropping trees were selected. The effect of leaf: fruit ratio was assessed by partial hand removal of fruits on June 1-2, removing: a) none (control) b) half, c) two-thirds, (1) three— quarters, or e) four-fifths of the fruit clusters. The remaining fruit clusters were distributed evenly throughout the trees. An additional 10 trees that differed in cropload were selected in the same orchard. One group of five trees had good foliage but a light crop and the second group had good foliage and a heavy, crop. Unfortunately, a fungal infection caused abscission of many leaves in this orchard. On July 3, the trees were reclassified into three groups, according to their leaf: fruit ratio at harvest time, as follows: (a) few leaves, many fruits. 1/ F (b) moderate leaf and fruit number. 1/ f (c) many leaves, few fruits. L/ f The numbers of leaves per fruit were estimated to be approximately 0.25, 0.5 and 3.0, respectively, based upon photographs taken just prior to harvest. A total of five trees were selected per treatment, and were blocked by location in the orchard. Sampling began on July 10, and ended on August 13. Three trees were sampled per treatment on each date. into ranc' tree, toral tree time endt tota‘ May (I) h 24 3. Irrigation, NWM Experimental Station, Traverse City, MI. Two rows of 24 trees each were selected and each was divided into six plots of four trees each. Trickle irrigation was assigned at random to one plot in each adjacent pair of plots, the remainder serving as controls (RCB design). Irrigation began on May 28, 1993. An emitter was placed 1.22 m from the trunk on each side of each tree, and each emitter delivered 3.78 liter of water per hour for a total of 12 hours per day (91 liters of water per tree per day). One tree per treatment in each of 3 blocks was sampled at each sampling time. Sampling began two weeks before commercial harvest and ended August 18. None of the trees was treated with ethephon. The total monthly natural precipitation for non-irrigated trees during May, June, July and August 1993 was 69, 163, 94 and 123 millimeter, respectively. 4. Nitrogen application, NWM Experimental Station, Traverse City, MI. 'Montmorency' on Mahaleb rootstock sour cherry trees were planted in 1978. Nitrogen fertilizer was applied, beginning at the sixth leaf, as follows: a) no nitrogen b) low nitrogen (0.23 kg N/ tree per year), c) medium nitrogen (0.45 kg N/ tree per year), and (1) high nitrogen (0.91 kg N/ tree per year), all applied on the surface close to the trunk of the tree. The medium rate is that normally used by Michigan sour cherry growers. Trees that had received a) no nitrogen, c) medium nitrogen and d) high nitrogen in three of the blocks were used for evaluation of firmness. Each plot consisted of 3 trees, and the center tree in each plot I (two [10 BI had Cher of p. ever agab Shite Spra dm 2.1 ahp] 25 plot was sampled. Sampling began on July 21 and ended August 18 (two weeks before commercial harvest to three weeks after harvest); no ethephon was applied. 5. F ' 1i ' f i d 'um, Gregory's Orchards, Sutton's Bay, MI. Fruit samples were collected from two orchards where growers had applied potassium in non-replicated trials. " Nutra-K " [(Custom Chemicides. P.O. Box 11216, Fresno, CA 93772) 27% K20; actual form of potassium is potassium carbonate] (2.1 L/ha) was sprayed on every other drive row on July 7. On July 12, Nutra-K (2.1 L/ha) was again applied in the treated area to drive rows not sprayed on July 7, making a total of 4.2 L/ha. "Trans-Cal" [(Trans National Agronomy, 470 Market St. SW, Suite 101, Grand Rapids, MI 49503) 8% Ca (calcium nitrate)] was sprayed weekly for six weeks beginning June 7, treating alternate drive rows in alternate weeks. During each of the first three weeks 2.1 L/ha was applied; during the last three weeks 3.2 L/ha was applied each week. Ethephon (1.1 L/ ha) was applied in both K and Ca blocks on July 27. Fruits from two trees treated with calcium or potassium were compared with fruits from two non-treated trees close by. Sampling began on July 29 (potassium) or August 3 (calcium) and continued until August 10 or 18, respectively. 6. Gibberellin (GA3) geatment. Exp. 1. Heffron Orchard, Belding MI. Out of approximately 400 wet aPP unt con Tru at 1 C011 sele 13, bar: IOC Nor sele On I Tim Ihrt I233 26 6- year-old trees, fifteen were selected for moderate cropload. These were divided into three blocks with five trees in each block. GA3 was applied at 10 and 20 ppm, using a hand gun; control trees were left untreated. The gibberellin was applied on July 3, three weeks before commercial harvest, during early phase III of fruit development. Fruit color had started to change from green-yellow to yellow-pink at this time (Facteau, 1982). Sampling started on July 14, and continued through August 13. Exp. 2. Mitchell Orchard, Northport, MI. Twelve trees were selected, blocked for uniformity, and divided into four groups of three trees each (RCB). GA3 at 0, 20, and 40 ppm was applied on July 13, approximately three weeks before commercial harvest, with a hand operated high pressure sprayer, each treatment being applied to one tree in each of the 4 blocks. Samples were taken from July 22 to August 18 (Note that fruit maturation is delayed one week in Northport relative to Traverse City). 1W Exp. 1. NWM Experiment Station, Traverse City MI. Non- irrigated trees in the block used for the irrigation experiment were selected for treatment with ethephon. Three branches were selected on each of four trees and the following treatments were assigned at random, using trees as blocks: 0, 150, and 300 ppm applied with a hand-held pistol grip sprayer. The control was sprayed with water. Three trees were sampled at each sampling time. The first sample was taken on July 29 and the last on August 9. with 1 PM too V each used above 13. 3.13 Becau Ehect after Show ItIth I Imam and A 27 Exp. 2. Heffron Orchard, Belding MI. Ten 6-year-old trees were selected and divided into two blocks with five trees in each block. Ethephon was applied at 150 and 300 ppm, using a hand gun; control trees were left untreated. On July 9, two weeks before commercial harvest, 5 trees were sprayed with each concentration of ethephon. The same five control trees were used for both this trial and the gibberellin experiment (see exp. 6 above). Sampling began on July 14, and continued through August 13. B. EXPERIMENTS CONDUCTED IN 1994. All fruits sampled in 1993 were hand picked from the trees. Because no truly soft fruits were found, emphasis in 1994 was on the effect of treatments, ethephon in particular, on firmness before and after mechanical harvest. Orchards used and treatments applied are shown in Table 2. 1. Irrigation and nitrogen. For the nitrogen and irrigation treatments, trees were identical with those used in 1993 (NWM Experimental Station), and the same treatments were applied. Natural precipitation for May, June, July and August 1994 was 34, 48, 121, and 64 millimeters, respectively. 2. Ethephon garment, Experiments were performed in three commercial orchards near Traverse City to evaluate the effects of ethephon treatment. 28 8mm ._ 02> N: and com E ”613885 8:935... m5 5 r. 835x063. .. 2 - mom BEBE mamas gem ._ 82 .c. NH 3a mm - no .condofim bum muoznm 3.83.5 o 2 3.33 a .N - connofim be 2%: #8825 m NH :4 CM - nonaofim hum 383m nowmnconbmm v 3 :4 cm - condofim chum wcotnm concoEmE m 2 3a mm mum cowobwz 55 8329:. 3m: N Nfi Sauna. QM mum gamut: .05 882mb. 3m: H $5. $3 29am H55... m0 m2? inmEEmmxm ghfimh 205504 ”@595 gummy 32 E 633% ”Havana: .N 2.5 29 Ethephon was applied by the growers using airblast equipment. Growers selected the dates based upon their harvesting schedules; in several orchards early vs. late applications were made to permit evaluation of time of treatment; ethephon (300 ppm) [1 pint Ethrel (21.7% AI)/ 100 gallons/A= 125 ml/ 100 L/Ha]. The orchards chosen all had a history of soft cherries, and most had heavy crops. Three groups of 3 trees each were selected in each orchard to receive the ethephon treatments. Adjacent untreated trees were used for comparison, when available. An additional experiment was conducted at the Horticulture Teaching and Research Center, East Lansing. Fruits from the orchard in East Lansing were not mechanically harvested. Twelve trees were selected for each treatment (RCB) as follows: ethephon (300 ppm) applied a) 14 days (July 1), b) 10 days (July 5), or c) 7 days (July 8) before commercial harvest. Three additional trees were left as untreated controls. Samples were hand harvested beginning just before the first ethephon application on July 1, and ending on August 3. 3. What. The calcitun experiment was performed at Gregory's orchard near Traverse City. A calcium foliar application [Trans-cal (8% Ca)] was applied by the grower using airblast equipment. A series of Sprays in outside alternate rows was applied at the end of fruit set (June 7) and at fruit development (July 5). 3O 4. Time 9f har_vest ever a 24—hgur period, soaking, Ed holding temxgagge, HTRC, East Lansing. Three 'Montmorency' sour cherry trees with similar crop load were chosen, and all were sprayed with ethephon (300 ppm) with a hand gun on July 1, twelve days prior to harvest. On July 12, one day before the experiment began, 24 pails of water (9.5 L/pail) were left at room temperature (23.3 ° C), 24 pails in a cold room (2.8 °C), and 24 paper plates were placed in both locations. Four different treatments were applied: warm wet (fruits in pails of water at 22 ° C), warm dry (fruit in plates at 23.3 ° C), cold wet (fruits in pails of water at 1.1 ° C) and cold dry (plates with fruits in the cold room at 2.8 ° C). Temperatures are those measured; water temperature may have been lower than air temperature in the cold room because of evaporative cooling and/ or contact with the cold floor. On July 13 at 0700 hr one thermometer was placed in each of the three trees and the air temperature was recorded every hour. The fruit temperature in each tree was also measured every hour, using a thermocouple thermometer. For each harvest on July 13-14, five samples of 30 fruits without stems were randomly selected from each tree at 0800, 1100, 1400, 1700, 2000, 2300, 0200 and 0500 hrs. One of the five samples was used to measure diameter, color and firmness. The additional four samples were used for the 4 different treatments described above. At the end of the four hour holding period, firrrmess and fruit weight were measured. 31 C. METHODS OF SAMPLING AND FRUIT MEASUREMENTS. 1993. Thirty fruits with stems attached were harvested from each limb (limb treatments) or tree (whole tree treatments). Larger samples were taken for comparison, but 30 fruits was found to be sufficient to give minimal coefficients of variation. Random samples were taken from the limb, or from around the circumference of the tree within 2 meters of the ground, placed in zip-lock plastic bags, and transported on ice from the orchard to the evaluation area in an adjacent building. Fruit measurements: W (:0.1 mm) was measured with an electronic caliper. mm was measured on one (cheek) side of each fruit using a tristimulus color analyzer (Chroma Meter, Model CR 200, Minolta, Ramsey, NJ). This instrument records in L*a*b* color space coordinates. The L* scale represents a light-dark axis and ranges from zero (black, no reflection) to 100 (white, perfect diffuse reflection). The a*-scale value represents a red/ green axis, with positive value indicating a red hue and negative values a green hue. The b*-scale represents a yellow/blue axis with a positive values indicating a yellow hue and a negative value a blue hue. When representing color measuring, the L* axis is positioned in the center of, and perpendicular to, the a* and b* plane (Tim and Guyer, 1995). Only values for L* are reported. In this thesis the term "color" 32 will be used to indicate the value of L*, high values indicating greener, less mature fruit, low values deeper red, more mature fruit. Fmit firmness was evaluated using the computer-driven measuring device (Timm, et al., 1993) described previously (see p. 20). Firmness was measured across the cheek diameter, using fruits with attached stems, unless otherwise noted. In 1993 a preset force of 150 g was set for sour cherry fruit. This was established based upon tests of several preset forces from 150 to 350 g. It was observed that forces greater than 150 g did not give symmetrical displacement curves. Firmness values increased with increasing force, but the structure and elastic properties of the fruit were destroyed and the fruit was damaged. In contrast, a preset force of 300 g is optimum for sweet cherry fruits. Fg_1it removal force (FRF), or the force in grams required to remove the fruit from its stem, was determined by using a Hunter push-pull mechanical force gauge, model LKG-l, fitted with a curved stainless steel claw (1.27 cm wide, 0.076 cm thick, 7.62 cm long). A slot (0.46 cm wide ) extended from the open end of the claw around the curve to hold the fruit during separation. The fruit stem was inserted in the slot, and the pull force exerted in the center of the claw. Fruit weight was recorded after removal of the stems (30 fruits/ sample). The fruits were then held at -20 °C until soluble solids were evaluated. 33 Selu ble solids, The 30 fruits in a zip-lock bag were allowed to thaw at 20 °C, then crushed with the fingers. A sample of the expressed juice was placed on the prism of a refractometer ( Mark II refractometer, Reichert Scientific Instrument). The readings give percentage values (brix) of the soluble constituents, primarily sugars. 1994. In blocks harvested mechanically, the first sample was hand harvested. Thirty fruits with stems attached were harvested from each tree and the following data were recorded as described above for 1993: fruit removal force, diameter, color, firmness, weight, and soluble solids. The second sample was taken just after the fruits were mechanically harvested; fruits were collected as they dropped into the tanks of water on the harvester and were placed in a plastic container. A sample of approximately 8 kg of fruit was divided into three equal parts and each sub-sample placed in a 20 L pail of cold water taken from the cooling tanks. The first subsample was used to measure firmness immediately after harvest, while the remaining two were put into mesh bags, each containing about 1.5 kg of fruit. The two bags were placed in tanks on a cooling pad and well water was circulated through the tanks for four hours (the approximate time they are held in the cooling tanks prior to processing). Water temperatures ranged from 50° to 56° F (10° to 13° C) in the orchard, and 40° to 48° F (4° to 8° C) on the cooling pads. The two bags of cherries were then combined and divided into three portions (two portions of about 1.0 kg each and the third of 300 g), each being placed in a pail through which cold water was circulated. The first portion was weighed, pitted with a hand-operated pitter, and then reweighed to evaluate percent loss in pitting, the second 34 was used to measure firmness, and the third sample was graded subjectively for firmness and postharvest mechanical injuries. D. STATISTICAL ANALYSIS A randomized complete block design was used for the studies, using trees as blocks, and Tukey’s test was used to determine differences between treatment means. 35 IV. RESULTS A. RESULTS, 1993 1. Mg Shading, combined with girdling, delayed fruit ripening three weeks, based upon fruit removal force, although the firmness of mature fruits was not affected (Table 3 ). Fruit growth, coloration and accumulation of soluble solids were similarly delayed. The effects of later shading (June 2 1) were similar but much less pronounced. Dates of maturity, based upon fruit removal force, were July 7 for the unshaded controls, and July 26 for limbs shaded either June 4 or June 21 (Fig. 1). Girdling alone had no significant effect except for a small increase in soluble solids. Shaded fruits were consistently lighter in color than controls, but still reached maturity; both shading treatments reduced fruit weight. Early shading in particular resulted in smaller, less mature fruits (Fig. 1). Fruit removal force started decreasing very rapidly just before harvest time (July 14) and was higher in shaded fruit on all sampling dates. Fruits on shaded limbs had markedly lower soluble solids in early samples, but the content increased with time. Soluble solids in fruit on late shaded limbs remained low even on the last sampling date; values ranged from just over 5 to slightly below 10 brix. This difference in response between shading treatments was probably due to regeneration of the phloem following early shading/girdling 36 .806 mm a 38$qu a... a .6852 Roads 86 mm .8 Amuofiofi :35 mod on E 38$qu 8830me .68 93x5“. .3 88mm GEE GEE; doumuwmow 882 N is. .2... .3... tr. .3... at. A zofiuémHzH < m NmA U U AoN < a N.mA m< nu CAN Q U m.Nm m D Afio macro < 9m 02 U U me m< nu TNA m< as AAN Q U m.mm m n N.w© wa<-N < m mmA U U mAm m n oAA < a VAN DU U m.¢m m a 060 AaroN < n OVA m u 3v 0 u VOA m< 0.x EON U u wdm m n wéo ASTON m u oNA m n owv GU Uo ad m n mdN m 0. NAV m< Dd fivw 37.: U U VOA < d wwm Q U Ad 0 u h.wA < w m.wv < m NUOA 37.x. mHAM02mm Emu— m 7/8 7/18 7/217/27 8/5 8/12 HARVEST TIME 45 Figure 4. Correlations between fruit firmness and several other fruit characteristics. Leafzfruit ratio experiment. Heffron Orchard, Belding MI, 1993. MCS (g/mm) MCS (g/mm) MCS (g/mm) 46 y = ~6.121x + 194.959 E] r = 0.574 *** El E] [3 El l I l 30 40 50 6O 7O 15 20 25 30 FRUIT COLOR (*L) FRUIT DIAMETER (mm) 175 y = -6. 766x + 149.081 = 0 095x + M_35 078 150-50 ‘= 0 709“ yr=o.7 7***9s D 125- D 100- q: n D 75- & ”m a d [It] 50 D l I I F l l I 6 8 10 12 14 16200 400 600 800 1000 FRUIT SOLUBLE SOLIDS (96) FRUIT REMOVAL FORCE (g) 175 y = -O.658x+ 149.796 5’ = '6595263X + 101 226 ._ *‘k‘k = 150‘ CID r— 0.729 g 1' D D 125— D 100— El '3 :1 E! I: 75- El El E] n B 50 50 I I r 100 125 150 175 FRUIT WEIGHT (g) 75 I l I I I r 7/8 7/16 7/21 7/27 8/5 8/12 TIMEOF HARVEST 47 nggwa you a .9852 Bag 8.0 mm 5 98:2 :25 mod mm “a 38%me 839$me .38 raga. an 38% ES: 36? nouwbwmmm 882 N an n: mu m: 8 3 > 205055sz < m v3 Q U o: < a WNH < a CAN 0 u Vdm m< 5 9mm an??? m< aw. H3 0 0 0mm < m WNH < an VON u u mdm m u m.~m w:<-oH m< na 34 m n wmm < m QNH < aw. WON um on mam < 9w 93 wall» m n mNH m n nmm < a Q: < n 0.8 m n QNM < a“ me 373 o u NoH < a Hmv m a mg: m u Q3 < a w.wm < a me ETNN m2? m 02 m: mam an Q: m v.o~ an fimm 9 flow + n mNH m: 03 a: E: 9 WE m: o.mm N a 0.5m - 2034525 EB: 2553 A3 EOE?» Amy ”Em Gav mm Mmgm on: MBOU mmmzzmfi Hommmm 222 82 .3 56 8325 dousm 538mm gauuhom 232 .355 .38 .zquuogcoz. mo mubmtuuugmnu 55 no wfiflfimm mo can 95“.. .32 mm mfiqfimwn gamma nonmwg ho Spam .m 223. 48 Figure 5. The effects of irrigation treatment and time of harvest on fruit characteristics of 'Montmorency' sour cherry. NWM Horticultural Research Station, Traverse City, MI. 1993. 49 I I I 7/22 7/29 8/4 8/10 8/18 I _ Ifi _ 4 fl — — _ — — 5 m 5 0 5 4 3 2 1 0 9 5 0 5 0 S 4 3 3 2 1 1 1 1 1 7 5 2 0 7 a: «38 55% 33 8:8 Emaom :BE 1 1 1 1 m m m R l l A m m T M O N I l — — — u < — q — _ — — m e m g m n u m w m .7. m m m m m m €8wa mo: :95 EEZSQ EB: 3 80% .25sz 95% 7/22 7/29 8/4 8/10 8/18 HARVEST TIME 50 Figure 6. Correlations between firmness and several other fruit characteristics. Irrigation experiment. NWM Horticultural Research Station, Traverse City, MI, 1993. 51 70 y=0.15 9x+39.811 y=-1488x+8679fi = 0 497 r = 0. 405* 65- I: I I: A on DD u: g 60' E ‘ DE g D D § [I] v a: d: E] 8 55 7 U ' D :1 EDI-£1933 I: 501 1 45 I I I T I I I 25 3O 35 40 45 17 18 19 20 21 22 7O FRUIT COLOR (*L) FRUIT DIAMETER (mm) = -2. y = 0.018x + 51.047 )I"-060%5x+ 81229 r=0.543*** 65‘ ‘ El CI 260- - a D I: 3» ‘1: "3 In 55- 7 EP 9 39% 501 7 45 I I I I I ' r ' ' 8 9 10 11 12 13 14100 200 300 400 500 600 70 FRUIT SOLUBLE SOLIDS (%) FRUIT REMOVAL FORCE (g) y = -0.071x + 66.294 y = -1. 124x + 60.220 =0.419** r= 0.**461 A65“ El - El 5 EU I: m n D 360' D E: D I: ' B U B ;; 'EI D Q] :1 u D on D 2 55" D " U D U 1%? '3 E 50- a I: - :I 45 I I I I I I I I 75 100 125 150 175 7/22 7/29 8/4 8/10 8/18 FRUIT WEIGHT (g) TIME OF HARVEST 52 (Table 5). Correlations between firmness and each parameter were also highly significant at Ps 0.01 or Pg 0.001 (Fig. 6). 4. Nitrogen application Fruits on trees receiving the highest rate of nitrogen were consistently firmer overall than those from trees receiving none (Table 6, Fig. 7), but the effect of the lower rate was not significant. Trees receiving the least nitrogen (0 kg N/ tree) bore somewhat larger fruits (possibly because of reduced cropload), with higher soluble solids but reduced color (Table 6, Fig. 7). Color and fruit removal force were not affected by nitrogen. For most characteristics, only the 22 July sample differed from later samples. However, fruit removal force decreased and weight increased consistently during the Mpling period. There was no interaction between harvest time and nitrogen level (Table 6). The correlations between fruit firmness and the other parameters measured were all significant (Fig. 8). Firmness decreased as fruit color (*L values) and fruit removal force decreased, and as fruit diameter, soluble solids, and fruit weight increased. Therefore fruit firmness was affected gradually as maturity advanced and the fruit became softer. S. Fohar‘ applicag’on of mtassium and calcium Potassium, Potassium sprays had no consistent effect on firmness (Table 7, Fig. 9), and correlations of firmness with other parameters were non-significant, except for fruit removal force and time of harvest (Fig. 10). Potassium treatment appeared to accelerate 53 28533». nos % .9532 8:988 5.0 mm .8 3.832 #883 mod mm 8 280$qu 828.8th .38 950:5. NE mnooto G88 55? 839898 882 N on m: m: on on on ElouémHzH < 3.2 n 38 m< 3.: < 3.8 m ooom m< «now 83.2 < n8 u: 8 BEN < 3.2 < n8 ooN m no.8 m no.8 onion < nmE on onomm m< at: < no hoN m ononm m< «mom 9&4 m :2 m< n8 E. < «w: < nNoN m n48 m< «oom 373 o 3: < «.34 m noon m 8.2 < «mow < :8 BEN E5 o noon 258 no.3 m nmoN < 3.8 < 3.8 8n\z§8.o m nod mnonm n8 d: m no.o~ < «4.4m m< na ”.3 852mm moo < «own :58 3.: < «8.3 < no.8 am ntmm mob\Zmnoo.o 250 :55 3:53 an :8nt no E so mm Ego rd 888 mmmzzma 593m 222 mama AZ 55 8.88;. .qouonm 5.8me”“ 8§3oEom 232 .385 .38 .baonogqoz. no 8958985 39¢ no 95988 no «EU 98 bum—ha couch? no 38% .o 032. 54 Figure 7. The effects of nitrogen treatment and time of harvest on fruit characteristics of 'Montmorency' sour cherry. NWM Horticultural Research Station, Traverse City, MI. 1993. 55 I 0.0 kg N/tree 0.45 kg N/tree 0.91 kg N/tree r 7/22 7/29 8/4 8/10 8/18 o I T _| - f — A _ — - _ u 4 q _ q — 0 5 m 5 0 5 4 3 2 1 0 9 oo 5 0 5 m 5 2L xenon 95% 3.: 8:8 58:8 FEE 48 Eva; EDE 8 .IO.|.=.O I. .. ./.. x... 8 . O TILE. I. u a sun .... 8 . . 4 I / 8 9 l 2 / . 7 X. 2 ..lO‘iv ._ I a 7 _ . _ - - _ _ n m .50 m o w w m m 5 1 A883 82 Ana: EEZSQ FEE HARVEST TIME 56 Figure 8. Correlations between fruit firmness and several other fruit characteristics. Nitrogen experiment. NWM Horticultural Research Station, Traverse City, MI. 1993. 57 80 y = 0.569x + 38.916 y = - .106x + 101.066 r=0.4 4** r=0.386** 70~ U _ I: E E! E 60- U) U 2 50- D I: 40 1 ' ‘ ' I I I I 25 30 35 40 45 50 17 18 19 20 21 22 FRUIT COLOR (*L) FRUIT DIAMETER (mm) 80 y = -2.637x + 87.858 y = 0.018x + 51-711 r= 0.558“ r= 0.429“r A 70- — U a n E El Hymn El 33 60- 15’ - q: V) g 3%. E] El 0 50_ ca .3 o o 40 I l l l l l l I I 7 91011121314100200300400500600700 SOLUBLE souos (96) FRUIT REMOVAL FORCE (g) 80 y = -0.104x + 72.368 y = -0.143x + 63.145 r = 0.399 ** r = 0.272 * 70- U - '3 A o S ” Ch I“ 9 an E a B 3 60- n " D Q 8 on” D a E o I: Z 50- - n I: 40 I l l l I fl 1 I 75 100 125 150 175 7/22 7/29 8/4 8/10 8/18 FRUIT WEIGHT (g) TIMEOF HARVEST 58 .86 mm an 58%me 0.83 82898:: gaugfimfiomv 39.8% on N 02 m3 6.: SN m.~m Om $2-3 v5 8m 6.: v.- mm m.~m $2-2 on: Sm n: 9: «.mm 3m weave mead SH 3N 9: 3m mam NNm + vi 2% n: N.- m.mm Ndmm - 25992 3:5 32.53 3 E053 E "E 3e mm $.52an rd «88 mmmzzma swam zHSz .mmmH dz 55 wfiw>§b 635.5 303.5 cabana .89. .3douocbqoz. mo 8.5380585 35 co ”259:3 Mo cat 98 83888 no 8qu K 2an 59 Figure 9. The effect of potassium treatment and time of harvest on fruit characteristics of 'Montmorency' sour cherry. Gregory Orchard, Traverse City, MI. 1993. 6O 3L mgou ESE 8/10 8/4 d 4 w fi 0 45‘ 38$ 82 9 2 / 7 0 III.- In. no 4 .o/o K + 9 III. In 7 q A . . q a n n m m m m :95 EEESQ :35 02mm ESE HARVEST TIME 61 Figure 10. Correlations between firmness and several other fruit characteristics. Potassium experiment. Gregory Orchard. Traverse City, MI. 1993. 62 65 y = 2.090): - 16.369 y = 1.739x + 14.258 r - 0.546 ns r = 0.299 ns 60 - _ [II D 5 55 -1 [g Eu 5? D 51 22) 50-1 El 45 - 0 ~ 0 40 I I T If I T I 31 32 33 34 35 36 20 21 22 23 24 65 FRUIT COLOR (*L) FRUIT DIAMETER (m) y = -1.375x + 68.601 y = 0.066x + 33.308 r = 0.240 ns J r . 0.697 * 60% [1 Cl g 55 " D an: 3 Nah m d g 50 D 45 4 U 40 I I I fi 10 ll 12 13 200 250 300 350 65 FRUIT SOLUBLE SOLIDS (96) FRUIT REMOVAL FORCE (g) y = 0.085x + 38.195 y = -2.853x + 58.374 r = 0.279 ns r = 0.664 * 60- .. D D 5 55 “ D on D '4 u I: B D a 5? .J D B D 45 4 1:1 - n 4() T I I I T I I I 140 150 160 170 180 190 200 7/29 8/4 8/10 FRUIT WEIGHT (g) TIME OF HARVEST 63 maturation of the fruit, reducing fruit removal force and increasing soluble solids on the first sampling date (July 29); however, this effect was not evident in later samples (Fig. 9). Calcium. The calcium spray did not increase firmness, but both soluble solids and fruit removal force were higher in treated fruits (Table 8). Firmness decreased between 29 July and 4 August, but values for 10 August were similar to those for 29 July. Interaction between calcium and time of harvest was not significant, nor were correlations between firmness and fruit color, diameter, soluble solids, fruit removal force or fruit weight (Fig. 11, 12). 6. Gibberellin (GAS) treatment a. Exp. 1. Belding. Gibberellin increased fruit weight and delayed maturity, slowed color development (higher *L values), and increased fruit removal force, but did not affect fruit firmness, fruit diameter or fruit soluble solids (Table 9). Although both color and weight continued to change with time, firmness, diameter, fruit removal force and soluble solids changed little after 2 1 July (Table 9, Fig. 13). Interactions between gibberellin and time of harvest were significant for firmness, color, and soluble solids, but these interactions did not reflect consistent patterns over time (Fig. 13). Correlations between fruit firmness and fruit color, diameter, soluble solids, fruit removal force and fruit weight were highly significant when all sampling times were included (Fig 14). However, none of these relationship was significant when data for the first sampling were excluded (data not shown). On this date fruit removal force was 64 .36 mm 3 EmuflEmu Ho: .3 A .8632 :33an 8.0 mm .8 8.832 $.83 mod mm 3 “885:2.“ mmucouota .38 38x3. .3 88% :88 ESE cougmmwm :82 N mg mg wG mG mg m: ZOHHUémHZH mahoa m n ©MH m: m.MH ma méN ma mdm w N.mm maxi: me m< n mON m4: MAN mdm n m.Nm w=<-v an < m vnN Ema mAN Hm m fimm BTaN mg; as moH w MMN w WMH we QAN m: Ndm we 046m + omH n o: a QNH HAN mdm ofim - 220.35 BE: 2558 A3 EOE; $3 ”an 33 mm ”EEO rd M800 mmmZZME Hummmm 222 .mma dz Sam 383m 6.8:qu .0835 5.55 98 .xuqmuogcoz. mo muumtwuofigu 55 co 3:983. no man was 830:8 mo 88am .w 2an 65 Figure 1 1. The effects of calcium treatment and time of harvest on fruit characteristics of 'Montmorency' sour cherry. Gregory Orchard, Suttons Bay, MI, 1993. 66 3 3 . . _ J _ - q _ q a q a M a w B n u m. w m m m w m m 3 3 2 2 1 l 2553 mUZ 255 $.52an :33 5 UmOm 4<>02mm .EDME 8/4 8/10 8/18 7/29 HARVEST TIME 8/10 8/18 8/ 4 7/29 67 Figure 12. Correlations between firmness and several other fruit characteristics. Calcium experiment. Gregory Orchard. Suttons Bay, MI. 1993. 68 60 y = 0.901x + 26.745 y = -1.804x + 92.806 58- r = 0.335 ns _ r = 0.405 ns ”'5 56 - E 3 54 - V) g 52 - 50 - a 48 l l I I l 29 30 31 32 33 20 21 22 23 60 FRUIT COLOR (*L) FRUIT DIAMETER (m) y = -0.718x + 63.663 y = -0.005x + 55354 58- r = 0230 HS - r = 0.210 us A _. m u — D D D a 56 D D E! E54- D -I\$\B_\ :7, a u n E g 52 - u - a El E1 501 - 48 I j l l I I I 11 12 13 14 50 100 150 200 250 300 350 FRUIT SOLUBLE SOLIDS (96) FRUIT REMOVAL FORCE (g) y = -0.028x + 58.838 y = 0.039x + 54.202 58- r=0.139 ns .. r=0.019 ns A u 15D - El '3 356 D U D a EL 3054-\11\D _ a - 8 D D E] D 2 52 - u — a El E1 50 - - 48 I I I I l I 140 150 160 170 180 8/4 8/10 8/18 FRUIT WEIGHT (g) TIME OF HARVEST 69 533898 20.0 mm 8 m0.0 mm 3.. 8838me 8 880303 8: .3. ... .8 a .3832 3880 20.0 mm 8 3832 05:3 m0.0 um um 3505:me 888205 .32 9.823. .3 88% ES: 3333 noumbwmom =82 N .33 .md I .md .3. * a zofiuémg < .3de o 3.2m < 8. m2 < 3.: o 2.8 m 2 Now m=<-~H < 3.42 o 8.322 e... m2 < «SN 8 8 0.: on n mam ”firm < «.32 o 2.8m < no.2 < 2.3 no 8 3m o 5% BEN m... a 32 o 3.6% 9. on 3.2 < 3.3 o 3.3 o 5% BEN m 23:3 m 293...? on o2 m... a. m.o~ m atom on 2.3.3 33.2 o 8.0: < «3.3 m u w: m “3.2 < 3.9. < «6.90 33 3,5 m 302 < a 33. 8 4.2 8 EN < a 9mm 8 33 can 8 n 3.3 m Q So. 3 0.2 8 SN < a 5% 8 4.3 8% 2 e. 33 m a 03m 8 mfi 8 NAN m a 5m N 8 gm 88 o 23.3838 955 €an 30 3833 E "E 00 mm 85238 rd 88o mmmzzmm 833 222 .mmfl .22 “3:23 6.83qu carom $328 .88 105.833qu. 00 83288988 35.3 no 052938 8 23.3 98 33. m 028% .88» 356.8003» 8 82% .0 2an 70 Figure 13. The effect of gibberellin treatment and time of harvest on fruit characteristics of 'Montmorency' sour cherry. Heffron Orchard. Belding, MI. 1993. hi(’ '1“ ( g/rn ) [1&1 ll'l' l’lAhll:‘l‘lz’l¢ (nun! p—. :15 (g) 1"{1 II’I' It! 1'RI( )VAI. l"( )l{( Ix I 71 MCS (g/mm) FRUIT DIAMETER (mm) FRUIT COLOR (*L) 3 I W 0) 0 U1 1 l N Ul h—I (II p—I A l FRUIT SOLUBLE SOLIDS (96) 160- ) 8 1:ng quHT ( 8 3 I l 7):; 7/I167/'21 7/I27 8;5 8/l12 HARVEST TIME 100 I I I I T 7/8 7/167/217/27 8/5 8/12 72 Figure14. Correlations between fruit firmness and several other fruit characteristics. Gibberellin treatment. Heffron Orchard. Belding, MI. 1993. MCS (g/mm) 73 y = 0.796x + 30.557 1' = 0.660 *** y = -5.145x + 167.624 r = 0.587 *** I I l I I 25 30 35 40 45 50 5 FRUIT COLOR (*L) 19 20 21 22 23 FRUIT DIAMETER (mm) y = -3.443x + 100.512 y = 0.032x + 45.133 1' = 0.37%“ r = 0.765 *** n n a EU a D n ‘21” u D D 40 I I I I I l I 10 11 12 13 14 15 200 400 600 800 1000 SOLUBLE SOLIDS (96) FRUIT REMOVAL FORCE (g) y = —0.217x + 90.343 y = -1-240x + 62-761 D r=0.539*** El r= .02* D a E B E D u D E g 40 I I I I I I l I l 100 120 140 160 180 7/8 7/16 7/217/27 8/5 8/12 FRUIT WEIGHT (g) TIME OF HARVEST 74 very high (755 8), indicating that the fruit was immature. b. M Gibberellin increased fruit size and soluble solids and delayed red coloration, but did not influence fruit firmness or fruit removal force (Table 10). During the four week sampling period, the most significant changes in fruit characteristics occurred between 22 and 29 July (normal harvest), as the fruit matured (Fig. 15). However, fruit color, fruit removal force, and fruit size continued to change with time. Fruit firmness was highly correlated with all other parameters, indicating a strong association with changes in fruit maturity (Fig. 16). Again, however, none of these correlations was significant when the data for the earliest harvest (July 22) were excluded, as these fruits were immature. 7. Ethephon treatment a. Exp, 1, Belding, Ethephon markedly reduced fruit firmness, fruit removal force, and fruit size (Table 11, Fig. 17). Treated fruits were consistently softer than controls within one week of treatment (13 July), but differences were non-significant thereafter; no further softening was observed in either treatment (Fig. 17). Both concentrations reduced fruit removal force, as well as fruit size. Interactions between ethephon and time of application were significant for firmness, fruit removal force and fruit weight. Fruit weight continued to increase with time in control fruits, but ethephon-treated fruits stOpped growing within 10-14 days of treatment (Table 1 1). Fruit firmness was significantly correlated with 75 38$:me Hon an x .3632 28:33 5.0 mm do aan 82:3 mod mm om 38%me 828.8wa .58 mania. .3 38% 3%: GE“? nowabmmom 882 N m: m: an m: w: m: azopoémz < a E o um: < e... 1: < «mew o omdN m n wmm w=<-3 < a v3 8 oh: < 3.2 $5“ 0.8 o 3.3 m numm $2-2 m< a a3 om 9 m3 < n NS. 93“ WON o 5.8 m a 3m “:23. m n 92 m 33. < e... 3H m a SN m no.8 m a new 373 o 52 < «03 m 5.: 0 33 < «o? < «9% 372 E5 < 9: 8 am < E2 < 98 < 3% 8 qmm can ow m N2 8 mm m mi. m 0.2 m Em N 8 gm 8% o zddmfimma 355 rd €83 a: $053 a: b: 33 mm MmEzSQ 550 mmmzzma Home—m 222 .82 .3 $095.82 .9280 H6532 Stone .38 .zoqouogdoz. mo muumtouowgu “Sb no 3:958 yo man 98 33. MH commas >39. Enouonfiw mo 88am .3 2an 76 Figure 15. The effects of gibberellin treatment and time of harvest on fruit characteristics of 'Montmorency' sour cherry. Mitchell Orchard, Northport, MI. 1993. 77 T 1 7/22 7/29 8/4 8/10 8/18 I I _ _ — u — u d u u d — a. m s m u .1. n. u u m m m m m m m 33 8:8 Badom :23 E E053 ESE TJIT I. - r — d — - $553 82 :55 MmmeSD .EDyE V65! 100 7/22 7/29 8/4 8/10 8/18 HARVEST TIME 78 Figure 16. Correlations between fruit firmnessand several other fruit. characteristics. Gibberellin experiment. Mitchell Orchard, Northport, MI. 1993. MCS (g/mm) MCS (g/mm) MCS (g/mm) 79 75 y= =.0 779x + 30. 480 y = -3.203x + 120.788 r= 0870 r=0.723** 70- El — D 65 _ (Du _ n: 5': an 60 - .. U 55 - ‘ Epfl D U E] [D D 50 I I I I I I I I 25 30 35 40 45 50 17 18 19 20 21 22 23 FRUIT COLOR (*L) FRUIT DIAMETER (mm) 75 y= 4489x+ 113 99C y= 0.0.26x+48967 70 _ D r = 0. 709“ r = 0.87 3H D U E1 65 - U U D 60 _ U U 55 dfi [1 EU 50 I I I I I I I I I 10 11 12 13 14 15 100 200 300 400 500 600 700 SOLUBLE SOLIDS (96) FRUIT REMOVAL FORCE (g) 75 y: -O._158x+78 608 = -1. 960x+62. 256 r = 0. 750** r = 0.600“ 70 -I - L'] 65 _ Du: _ B on B 60- .. U 55 - a [F U - E E U D 50 1 1 ID f I f I I I 75 100 125 150 175 200 7/22 7/29 8/4 8/10 8/18 TIME OF HARVEST FRUIT WEIGHT (g) 80 53.8on8 .306 mm 8 8.0 mm .36 mm as 3.85qu Ho 888%me “oz we... ...... ... an a .8838 3.8358 Hod mm .8 9.8882 33 mod mm 8 8858me 888.8me .88 9.98:5. 3 88mm 88: GEES douaumaom 882 N .3. «. .wd .wAH .wd «LI. % ZOHFUémHFZH < «N: m 389.. 93.8 88.8 m 3.8 M28 93 w=<-m < 83 m .38 < «8.2 80.8 m 8.8 m 8.8 3.8 < a H: m 38 m 28.8 8 0.8 m 8.8 m< stem 378 m .32 < «08 m 22.8 23.8 < 8.8 < «QR 3-2 8.8 m n 88 o U Q: 8 0.8 < .38 8 0.8 m 8.8 can o8 o 52 m .38 8 8H m 9 m8 8 8m m 3.8 68 ofl < «a: < a 8m 8 8.8 < a n8 8 0:8 3. no.3 8&0 20885 ASE 2:53 a: Eggs 3 "E 33 mm 88239 EV ~88 mmmzzmm 88mm 222 .33 42 3.63m 685.5 newton .883 .88 $888882. Mo 8.538885 35 no 85958 no 8:.5 U8 3% m U838 >89. nonaofim mo 88% .3 888. 81 Figure 17. The effects of ethephon treatment, and time of harvest on fruit characteristics of 'Montmorency' sour cherry. Heffron Orchard. Belding, MI. 1993. 82 5 uo/o 7 F2 / 7 1 12 / 7 6 ll / 7 _ _ — _ — — — _ C m m H m m C wwwmuwmumnnumnmmmmuu 3: 5,50 ESE A5 858 Baden ESE a: .5295 FEE m m s m w WI... , i101 T 1. Timfiiuo/o D. O m .. ~ ... w. 5 .. ~ N" 1 3 . ~u .. . 7 . . TI. 0.. 1 TI. 0.. ..m u " —.— + 0 ‘ .. _ u .. . u _ . .. 1 _ . . . T T +25. 1 _. ¢ .0.. LN. . \ ... 7 a. \ . \ .. . x . 6 T OI. . T .. TO+O.. -n 7 q _ u u — _ % u fi m g m n u m m m m m m m m S 3 2 1 2:83 82 3:5 EEESQ :BE 9 women .2525 95% HARVEST TIME 83 Figure 18. Correlations between fruit firmness and several other fruit characteristics. Ethephon experiment. Heffron Orchard, Belding, MI. 1993. 84 70 y = 0.379x + 43.586 y = 0.016x + 55.619 r = 0.19Sns r = 0.002 us A 65 - u - E D D D 0 DD ['1 I3 El El Fe 60 ‘ u ‘ u ‘9,“ Q1 . n c: n , u 55- D .. 2 fig ID a n 1 a mi :13:in a IE! 50- n U 4 n D 45 l r I 1 I 30 32 34 36 38 19 20 21 22 FRUIT COLOR (*L) FRUIT DIAMETER (mm) 70 y - -1.086x + 69.492 y - 0.018x + 51,314 6 r=0.212 ns r= 0.422“ 5 "‘ D “ D A n D U u n n E II] E] El 60‘ .. \ D D 29 u m 55- u d D g 0 .9 0°an 9°33 50- U u + Ch 45 I I I I I I I 10 ll 12 13 14 15100 200 300 400 500 70 SOLUBLE SOLIDS (96) FRUIT REMOVAL FORCE (g) y = -0.050x + 62.927 y -- 0.432x + 54.446 r=0.133 ns r=0.133 ns 65 "‘ .4 D A D D B D S . ED El 0 604 .I 3 D a u H V D m 55 -W ...—E/BT LE): on Ch D030 :1 B B 50- Du .. El E1 45 T I I r I I l I 120 130 140 150 160 170 7/16 7/21 7/27 8/5 FRUIT WEIGHT (g) TIME OF HARVEST 85 fruit removal force, but not with other parameters (Fig. 18). The apparent increase in firmness between July 16 and August 5 in fruits treated with 300 ppm may be an artifact, as few fruits remained for sampling at the last two dates b. Exp, 22 NWM Horticultural Research Station. Ethephon treatment again had a marked effect in reducing firmness. The main effect of 300 ppm, but not 150 ppm, was significant at ps 0.01 (Table 12). Fruits treated with 300 ppm were consistently softer than controls within 5 to 7 days after treatment (Fig. 19); differences on 10 August were not significant, as control fruits had softened by this time. Both concentrations significantly reduced fruit removal force regardless of sampling time, but did not affect soluble solids content consistently. Time vs. ethephon interaction for data on diameter, fruit removal force, and weight reflected different effects depending upon time of sampling. Differences in fruit removal force were quantitative only; treated fruits were always easier to remove than controls (Fig. 19). However, diameter and weight differences changed over time, with treated fruits being larger than non-treated ones in the first harvest, but not thereafter. Sampling error may have been involved here. Although treated fruit were larger on 29 July, thereafter their growth essentially stopped, whereas control fruits continued to enlarge. Several correlations between firmness and other parameters were significant, including fruit color, soluble solids, fruit removal force, and time of harvest (Fig. 20). These correlations generally 86 53809on .806 mm 98 .36 mm “a 38$qu .8 38%me uoz was. ...... a: k A9832 338V 8.0 mm .8 3.852 5.83 mod mm 3 :58qu moucmuwgm .58 9.303% .3 38% GEE ESE noumumaom 382 N is. .32.. m: .1 w: m: A zopusmm—HZH 8 e: m u a: < 3.2 8 VS m 9 NR m a 5m ”3-2 8 02 < a 0.3 m n w: 8 3m m a QR < a $3 wait 8 N3 < a 9A m n n: ...: Em < a m.mm < a 3m 37% m2; < a 02 m 0 MS a t: « 3N ...: 3m m 2 NR 8% 0% < « omfi m a N3 a Q: a now 8 3m m< a #3 6% 02 m n H2 < a 2m nu Q: a mi 8 3m N < a 0.3 8% 0 20¢ ASE ESE av Eggs E "E 3e mm mmgo SV «88 mmmzzmz SEE 222 mama dz .35 8.828% doufim 5588M REEqum 232 .355 .38 ..Onouocbnoz. mo muumtwuufimnu HE no mgnfiwm we 25. can 3,3. 3 BEEN >89» aoanofio Ho 88% .NH 2an 87 Figure 19. The effect of ethephon treatment and time of harvest on fruit characteristics of 'Montmorency' sour cherry. NWM Horticultural Research Station, Traverse City, MI, 1993. 88 65 35 34 — 60‘ «333 E E 5 8 y, 55 a O 32 — a E . z 5 31 -‘ 50 - BE 30 — 45 r r . 29 22 14 A 39‘ E V 13 - V) E 21 - g o (I) 5 12 - S a d E_ 20 51 5 W 11 - °‘ E u" E 19 I [ l 10 450 150 59400- T 0 ppm 8 350- .L 140 ' == 9 ”‘ 300- .L E > T 0130 - o 250— E E _'_ 150 ppm 200‘ "Mm-~- " 5120- E 0..-. ~g.....--_.--.__.,9 E 1 0 ppm 55150“ J- 300 pIIII'I! """""" 100 I I r 110 I f I 7/29 8/4 8/10 7/29 8/4 8/10 HARVEST TIME 89 Figure 20. Correlations between fruit firmness and several other fruit characteristics. Ethephon experiment. NWM Horticultural Research Station, Traverse City, MI, 1993. 90 MCS (g/mm) 45 FRUIT COLOR (*L) y=0.991x+23.418 y= -O.292x+ 61.172 r=0.350* r=0.042 ns . 1: El _ D U D an D U D D CID --— nl‘l E] " LuljJu'h u n 1:] _1:1 1:1 1:1 :1 E1]: [13:1 [1 I If I l l l l I T j 29 30 31 32 33 34 35 36 19 19.5 20 205 21 21.5 FRUIT DIAMETER (mm) MCS (g/mm) y = -1.851x + 77.090 1' = 0.458 ** y = 0.029x + 49.076 r = 0.631 *** 45 1 | I l l T 10 11 12 13 14 100 200 300 400 500 SOLUBLE SOLIDS (9s) FRUIT REMOVAL FORCE (g) 70 y = -0.066x + 64.208 y = -2.510x + 62.813 6 r= 0.156 ns r=0.560** ... 5 ' 1:1 1:1 2 ° .. g 60 - El CF] U -1 D \ :9 1:1 19 U :1 1:1 1: U) U - U .. 2 55 W E u m a“ mu :1 50 a 113 - 1:1 1:1 45 I I l l f l l l 110 120 130 140 150 160 7/29 8/4 8/10 FRUIT WEIGHT (g) TIME OF HARVEST 91 reflected changes in maturity, with fruit firmness declining as fruit matured. B. RESULTS, 1994 1. t'n'no; a i 02‘ NWMH -' alReS‘. _Sn'n. Irrigation had no consistent effect on firmness or other fruit characteristics, but fruits harvested 9 August were consistently softer than those harvested 3 August (Table 13, Fig. 21). Irrigation vs. harvest time interaction reflected only quantitative differences in response. The loss on firmness during harvest was similar for both treatments (Ps 0.01), and soaking did not increase firmness significantly. Nitrogen. Trees fertilized with 0.45 kg N/ tree produced firmer fruits than did trees receiving no nitrogen (Fig. 22). Mechanical harvest reduced firmness for both treatments; fruits regained 50 to 60% of the loss after soaking in cold water for 4 hours. Nitrogen had no significant effects on other parameters measured, although fruit removal force appeared to be reduced (Table 14) . 2 . Ethephon figment. a. Plamondon Orchard. Main effect means (Table 15) indicated that early ethephon treatment reduced firmness significantly, but the effect of the later treatment was non-significant. Fruit firmness was reduced by mechanical harvest; 30 to 60% of the loss was regained upon soaking (Fig. 23). Ethephon-treated fruits, however, recovered less (53-55%) than did non-treated fruits (81%). Early 92 Ans Hod mm .38 modwm 65.6me% 85 m: ”3.8 95x3. an v.38 USN ”:8566 ES? nouménom 882 N m on. m mi. < d8 2%: 8 0.? a? now how 829%: we. 34 4.? 4.8 854026202 m N? 3... Em mom m=<-o < 0.3 New nmv #8 ws<-m zm“; douSm 536mg REEoEom 232 .535 ..Gcmuognoz. mo 60?: 86g 65 so H83“: mo man can newswth mo 38E .2 2an 93 .36 mm on 55mg .8 gumbo Shannan 02 N ...: mm 8 4.2 ...: EN 8 4.: 8 3m 8 gm 8.295: 4w mfl Nmm m2 NAN Sm 8653: .82 so Emma so 838 2.3 BEE @538 3 E 3 Emma mmgo 3L mgoor zofim3 5 Bumwtmm dz .35 omb>fie douflm 5.83mi figaouuom 232 ..Cuono 38 .xofixogaoz. mo 8558836 Era no coumoaaaw ammonia no 385 .3 29.8. 99 .81: Hod um .33 mod mm A3895? 85 3 EB many—3. an 8:38 55? 598.838 882 a 8 E a 8.: 8 Ma a m3 a am < a 0.8 57.: mm a mfi 2% n E a mg m 0 SN 573 mm . a oi NNN « m: 8 EN .2 a 3m mzoz 3 E53 33 85m 55 BEE @838 § E 3 E985 figs 3.; 580 BE 85558.85 55 .850 .m mod mm 8 3555?. Hannah 98 85 5953 “Snowman“ .85 86 .8 33 mod mm 8 35mm :88 98:8 98 .33 mod mm mo flawgmmb =8 macaw scumbag 832 N m 3%, 0 38 < mi. 52 m< a 3... an N? 8 3m 8 N5. .573 m a 8.08 3 3v 8 3m 8 W? .572 < 8 0.9. a Ev up N? 8 Nov mzoz 23.2 888 8%: 86.20 53 NmmmSEE .< .82 .8: cm @838: dz .882qu 6.85.5 Gouaofima .55 $389852. mo 85558.85 HE so . 3:5 83 coumunaam 955:5 «0 mg no 85km . m H 228,—. 100 Figure 23. Effects of early (14 days) and late (10 days) application of ethephon (300 ppm), harvesting and soaking in water on firmness of 'Montmorency' sour cherry fruits. Plamondon Orchard, Leelanau, MI, Harvested 26 July 1994. *Tukey's mean comparison significant to Ps 0.01 101 *A IIIIII'IIIIII'IIIIIIIIIIIIIIIIIII’IIIIII’II I 10 IV‘IITIII’" VrII/IIIIIIIII c—t *IIIIIIIIIIII \\\\\\\\\\\\ IIIIIIIIIIIII \\\\\\\\\\\\\W\\\\ l;44;41:1411 I I I I I I I I I I I I I 'MIIIIIIII‘Ij'IIII'I‘I'II' 0.0.0.... ......IIIO.:.I 10 --‘AAA {IIIIIIIIA \\\\\\\\\ VUIIIIIIIIJ xxgxxgx l I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I. I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I. I I I I I I I I I I I I I I I I I I I. I. I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I... V 0.0 \ . IIIIIIIIIIIIIIIIIII \\\\\\\\\\\\\\\\\\\\\\ IIIIIIIIIIIIIIIII I \\\\\\ II I \\\\\\\\\\\\\\\\\\ I \\\\ I \\ \ I I I \ \\ N\\\\\\\\\\\\\\\\\ I IIIIIIIIIIIIIIIIII I\\ IIIIIIIIIIIIIIIIII I II I \ \ \\\\\\\\\\\\\\\\\\\\\\\\ IIIIIIIIIIIIIIIIIIII \\\\\\\\\\‘lu\\\\\\\Hu\\\\\\ 1111111111 1 A A ‘fik‘I \ 55 I l '9 8 (mm/8) sow 35 - 30 SOAKED HARVESTED INITIAL 102 ethephon hastened fruit coloration, reduced fruit size and increased soluble solids, whereas the late treatment only reduced fruit size. Fruit removal force and pitted weight were not significantly affected by ethephon. b. Bardenhagen Orchard. Time of ethephon treatment did not affect firmness or any other fruit characteristic (Table 16). Mechanical harvest reduced firmness in both treatments, and soaking increased it (Fig. 24) c. Shimggk Orchard. Timing of ethephon treatment did not affect fruit firmness, although fruit removal force was lower with early treatment (Table 17). Firmness was reduced by harvesting (10 and 11 units), but soaking did not increase firmness significantly (Fig. 25). d. urn-1 1-- -.Te hin . 0 RS"; hC--ntr - thin :3 MI Early ethephon treatment reduced fruit firmness significantly within one week (Fig. 26). The effects of later treatments were non- significant (data not shown). 1W Calcium sprays did not affect firmness or any other fruit parameters including fruit color, diameter soluble solids, fruit removal force and pitting weight (Fig. 27). Fruit firmness was reduced by mechanical harvest (18 to 20 units). The fruit recovered 6.2 (-Ca), and 4.6 (+Ca) units on soaking. Firmness was similar for the 103 mod mm a mafia no ammo 389:? 02 N we 3 8 Q: 8 ”S 8 EL 8 SN N 8 3m 3% 3 mm n: 9: m2 SN 0.2 .3: 2 so E05? 3 8:8 3:5 BEE BESS A3 E E E053 mmgo at ”~88 meg woumCouowon HE .850 .m m0.0 Mm um ugugflwmw HOG GOUUNHQHE uggdwb X mama ~A .83 8.0 mm .33 mod mm .3889qu ~05 ma 3on mania. .3 958 odd 8838 Ears nonmanom 882 N m3 Em mu 3% N SW 3v 2%,: z 8 No... cam mi N? .3: a 3m 3m 5mm a? bi a 2&2 @28 Egg H5. 20 mead mmogm .< 32 be, Om woumogm dz 53563 65580 nowgouam .gno .xonouognoz. mo moumtouofimnu 35 no ESQ 008 consonaaa nonaofim mo wanna go muootm .3 2pm... 104 Figure 24. Effects of early (15 days) and late (9 days) application of ethephon (300 ppm), harvesting and soaking in water on firmness of 'Montmorency' sour cherry fruits. Bardenhagen Orchard, Leelanau, MI, Harvested 30 July 1994. *, ** Tukey's mean comparison significant at Pg 0.05(a) and P5 0.01(A) 105 QmMm5 HN NHDH ma :0..- + ow (mm/3) sow 106 .36 mm as u§o§aw8 you avoid: mo oEu mo ...oohm N 8 3w 8 N: 8 mvN 8 ...: 8 SN N 8 3m BEN mm n: m2 3; SN m.~m 37% 3 Emma 3 838 E5: BEA BEES as ”an 3 E985 $52an at mSoo mead moumtflogu 35 860 .m .36 mm as 38%? no: nouumbafi h .83 56 mm .33 mod mm .3885:me ~05 an 38 mania. .3 v.30.” can 8838 35? nouwgaom 982 N m 90¢ m Tam N< m.w¢ Zm00008 .0000 00 .00 00.0 00 .000 v.0 0000 00 00080000000 00 00080-000000 82 ...... .t ... .00 000 000.0 000 000.0- .... 00+.0- .... 000.0- .1. 000.0- 0.0000003 .. 000.0 000 000.0- tr. 0000.0 .3 -0.0 .... 000.0 5000 000 000.0- 000 00~.0- .1 03.0- .... 000.0- .... 000.0- 00 000 00~.0 0: 00+.0- .... 0000.0- .... 000.0- .2. 30.0- mmHBzSQ 000 0000.0 000 0 00.0 ...... 3+0 ...... 000.0 .... 000.0 00000 2200.00.00 20000-20 20055000000 0.5000030 000090000 .3. 000.0- .3. 000.0- I... 00 0.0- 000 000.0 000 000.0- 0.0000003 .... 0.0-v.0 ...... 00.0.0 I... 000.0 .... 000.0- 000 ~0~.0 0000-0 .... 000.0- .3. 000.0- .I 00.0.0- ...0 0000.0- 00 +5.0- 00 .... 000.0- .... 000.0- ...... +500- 0: N0000- 0: 000.0- $000239 I +000 .3. 00.0 is. 000.0 .. 000.0 000 000.0- 0900 75000.32 0: 2000000000000 :08 2000000000000 00 2000000000000 0008200000005 0000 00.0.8000 .88 0008-8080002. 0800200008000 000 00000080000000 0000.00 .8005 0080 000008.00 000030000 0000000000000 .0N 000.00.0- 122 data for hand-harvested fruits were combined for 1994, and firmness plotted against other parameters (Fig. 30), r values (Table 21) were significant for color (-O.358*), soluble solids (+0.574***) and fruit removal force (+O.SOO**). Firmness was also correlated with the firmness of mechanically harvested fruit both before and after soaking. 123 Figure 30. Correlation between initial firmness and several other fruit characteristics. Ethephon, nitrogen, irrigation and calcium treatments. Traverse City, MI. 1994. 124 80 y = -0.994x + 84.983 75 - r = 0.358 * 70 - D g 65- D 3 60- m , U S - 2 5 50 1 4S 1 40 . 25 30 35 40 45 FRUIT COLOR (*L) 80 y = 3.859x + 6.345 75 7 r = 0.574 m 70 - D a 65 - 39 60- 8 55- 2 50 . 45 - 40 j I I I 10 11 12 13 14 FRUIT SOLUBLE souos (brix) 80 y = 0.039x + 47.531 75 . r = 0.093 ns 70 '1 D g 65 - D 1:: 3- 60‘ '3 12° 1:] "’ 55- U ‘2’ 3 D U u 50- 19 D t? It] El 45 - 40 I I I 120 140 160 180 FRUIT WEIGHT (g) y = -0.070x + 55.150 r= 0.008 ns C] E [3 DD Dunno” 1210' D D Doc] [3 DUDE! D a” D BED CD CD I I I I I I 20 20.5 21 21.5 22 22.5 23 23.5 FRUIT DIAMETER (mm) y = 0.065x + 39.728 r = 0.500 ** 15 100 I I I I 150 200 250 300 350 FRUIT REMOVAL FORCE (g) I r = 0.283 ns y =-86.124x + 126.608 El 200 0.75 I I I 0.8 0.85 0.9 0.95 PIT WEIGHT (96) 125 53.0808 400.0 0 8 8.0 mm .000 M0 06 00 0580200 8 038.5000 “oz ...... .... .. .8 0d 050- 3 H000- 0: H000 0a 00N.0 * $00.0 .. :10- .35. N000 05?. 00 0NN.0- 0G 00H.0- ... 000.0 3. 000.0 ... #000 mu 000.0- .3; 000.0 DE 0G 00N.0- 0: 000.0 ...... 000.0 .I V000 0G 000.0 3. 000.0- - 0.04:2 HIGH-H; 0.2033 E 000300 ”EEO 088 00902000 mmmzzma amp-HE MEMO-00 HAD-:7: +03 5 08: 00030.8 5 80020000005 .HN 030.0 03.0 .850 080 008.0 0.085 108008282. 00 08950 Gauges 300008.80 126 V. DISCUSSION A. Mil Although considerable research has been devoted to solving the soft cherry problem, its physiological basis remains obscure, and methods of control are limited, at best. In this thesis, a range of treatments were applied and the effects of a number of factors that might be associated with the production of soft cherries were evaluated. In 1993 only the firmness of carefully hand-harvested fruit was measured. Firmness at maturity ranged from 67 to 48 MCS, depending on orchard and treatment, thus none of the fruits could be considered soft by industry standards. Values for 1994 were generally lower than those for 1993, with a range of 47 to 61 units (Fig. 31). Firmness of sweet vs. sour cherries in 1993 are compared in Fig. 32. The former were much firmer, as would be expected. After the data had been analyzed, additional information was obtained from a receiving station at Shelby, MI, where soft cherries had been a problem that year. Hopefully the percentage of soft fruit could be correlated with some factor(s) related to site, soil, or harvesting method. Inspection slips were available for 88 loads of cherries harvested between 18 and 31 July. The percentage of soft cherries was low (0-2%) for all samples and no trends were evident that could be related to time of harvest or other known variables. 127 Figure 31. Firmness of control fruits in 1993 vs. 1994. 128 0.030720 v0. 000022090 00. 0827500 0? -00 ..00 00 (tum/3) sow 129 Figure 32. Firmness of 'Montmorency' sour cherry vs. 'Ulster' sweet cherry in 1993. Preset force in grams was 300 for 'Ulster', 150 for 'Montmorency'. MCS (g/ mm) 130 ZOO SWEET CHERRY 180‘ 160- 140- 120q 65 I I I I I I I 551 SO I I I I I I I 7/9 7/17 7/22 7/29 8/4 8/10 8/18 HARVEST DATE 129 Figure 32. Firmness of 'Montmorency' sour cherry vs. 'Ulster' sweet cherry in 1993. Preset force in grams was 300 for 'Ulster', 150 for 'Montmorency'. MCS ( g/ mm) 130 200 SVflflflNCHERRY 180* 1601 140- 1201 65 I I I I I I I 60- 55* SO 7}9 7/I17 7/'22 7/'29 8}4 8/'10 8/'18 HARVEST DATE 131 The only fact that stood out was that the number of fruits with attached stems was high early in the season-mot surprising, given that many fruits were still immature at this time. The lack of soft cherries in the record apparently indicated that such fruits were diverted to juice and never inspected. Most of the orchards sampled in 1994 were chosen because they had a history of producing soft fruit, yet in none was this a problem that year. Although this was beneficial for growers, it was frustrating for those of us who were attempting to solve the riddle. Firmness was evaluated both in hand harvested and machine harvested samples, the latter both before and after soaking for 4 hours in cold water--a standard industry practice. Soft cherries were found only rarely, even in machine harvested fruit. In some orchards considerable fruit flesh was evident in the soak tanks-— an indication that a significant proportion of the fruits had been crushed during harvesting. Even in these orchards, however, the number of soft fruit was insignificant. In additional experiments (Brown, et al., unpublished data) fruits were dropped from various heights to a hard surface to simulate mechanical harvest, and the firmness measured before and after dropping. Several cushioning materials were also evaluated. Some data on firmness before and after treatment are given in Table A1. These data indicate that: a) damage increased with height of fall and with number of drops; b) fruits of the Ufehertoi Furtos cultivar are much more resistant to injury than are 'Montmorency' fruits; and c) injury can be reduced by using padding materials. Cultivar replacement is a long-term solution to the problem, but growers 132 should evaluate the padding materials on shaker arms, etc., as well as the materials used for catching frames, in order to limit bruising. B. Pagers evglggted in 1993-94 a. Envirenmentgl effeets; Light intensity (shading); 1eaf:fruit ratio (although leaf-fruit ratio is not a true environmental variable, it determines the amount of photosynthate per fruit, and therefore is included with environmental effects); water supply during the critical stage of fruit development; temperature. b. Culturfl pragtices; Mineral nutrition (N, K, Ca); growth regulators, including ethephon and gibberellin (GA3). The information obtained is discussed below. 1. Shading. Shading can have a profound effect on the yield and growth of cherry trees (Flore and Lane, 1990) and on fruit maturation, as ' indicated by color and fruit retention force (Flore, et al., 1990). Flore, et al. (1990) also determined that light is a major factor associated with uniformity of ripening, and fruit quality, soluble solids and fruit size in particular. Patten and Proebsting (1986) had previously established that shading cherry trees delayed fruit maturation and red color development; shaded fruits were softer (durometer test) at maturity and lower in soluble solids than unshaded fruits. In my work with 'Montmorency' sour cherry at East Lansing in 1993 shading delayed fruit ripening by three weeks when treatment was 133 applied early in the season, but firmness of mature fruit was not affected significantly. Shading at this time reduced fruit growth, coloration and soluble solids content. Iater shading produced similar, but less pronounced results. Shading appears to have maximum effect in term of delaying fruit development and fruit ripening when applied at the beginning of pit hardening. However, my firmness data differ from these obtained by Patten and Proebsting (1986) with sweet cherries. They reported that shading increased firmness at every sampling date, early shading being more effective than late shading. This effect on firmness can be at least partially explained by the immaturity of shaded fruits. Patten and Proebsting (1986) compared firmness at the same fruit color. To determine if firmness paralleled color change in shaded vs. non-shaded samples, my 1993 data for fruits with similar color ratings were plotted (Fig. 33). Shaded fruits were consistently firmer than the controls at the same stage of coloration. Thus, my firmness data parallel those of Patten and Proebsting when corrected for fruit color. The fruits were not mechanically harvested in 1993 nor were fruits dropped to a hard surface as was done in 1994; had this been done, different results might have been obtained. Shading clearly delays maturation, but its effects on firmness after mechanical harvest remains to be determined. am The most obvious conclusion gleaned from previous research regarding 1eaf:fruit ratio in tree fruits is that quality parameters are 134 Figure 33. Effects of shading on the relationship between firmness and fruit color. Horticultural Teaching and Research Center, East Iansing, MI, 1993. 135 rd moqoo 95mm 5.8 n c «:28 + 528 n s _ _ h _ — _ _ OI Q In D-U I l ..... ........ O ---E---.O-O.- -----O. :1--- . Q nnnnnnnn O .000 O 0 .................................. I we ...... cod 0 C C C . too O PTO n h Noo.Nm + mebé u m @225 ©2325 85 . I ma: ~26 u u Omoom + #880 n a 8:50 33% beam 0 U225 6950 I r ONH IESS (mm/3) sow 136 affected (Teryl, et al., 1987; Facteau, et al., 1983). Spayd, et al. (1986) showed that trees with heavy crops produced cherries that were softer, greener and lower in sugar than those from trees with light crops. Teryl and Loescher (1987) also reported positive correlations between 1eaf:fruit ratio and both fruit firmness and soluble solids. Flore (1985) reported that leaf to fruit ratios less than 2.0 resulted in a limited carbohydrate supply and delayed ripening of sour cherry for several days. Unfortunately many of the trees that I used in 1993 were partially defoliated by a fungal infection. I did not record the final 1eaf:fruit ratio, but low ratios were associated with delayed fruit ripening, and reduced fruit size, soluble solids and fruit color. Heavy cropping of sweet cherries results in soft fruit and low soluble solids (see above). My data with sour cherries confirms the effect on soluble solids but not on firmness. 3. W In 1950 Stanberry and Clore determined that soil application of nitrogen to unproductive 'Bing' cherry trees greatly increased yield and fruit size. Nitrogen alone usually increased firmness, whereas potassium alone reduced it (firmness was measured by surface pitting). Combinations of nitrogen and potassium in medium amounts improved firmness, but heavy applications resulted in soft fruit. At Traverse City, Michigan, in 1993-1994, the higher rates of nitrogen application increased firmness of 'Montmorency' sour cherries. The trees given no nitrogen produced somewhat larger fruits with higher soluble solids. Trees with medium and high nitrogen yielded between 60 and 75 kg/ tree vs. 30 to 40 kg/ tree for trees receiving no 137 nitrogen. Thus fruit size and soluble solids content were inversely related to both yield and firmness. The relationship between nutrition and firmness was therefore confounded by differences in cropload. Nitrogen application could have increased cropload, which in turn delayed maturation, leading to firmer fruit. However, the fruits on high nitrogen trees remained firmer well after the time of optimum harvest (Fig. 7). In 1994, mechanical harvest reduced firmness of fruit from both nitrogen treatments and no differences were apparent in recovery on soaking in cold water for 4 hours. Although nitrogen delayed fruit maturation it did not affect the other parameters measured, with one exception; fruit removal force was reduced. Research in 1993 showed no consistent effects on firmness when potassium sprays were applied, although potassium appeared to accelerate maturation of the fruit, reduce fruit removal force and increase soluble solids. However, the treatments were not replicated, thus conclusions must remain tentative. 4. Calcium. In 1976 C00per and Bangerth determined that calcium application increased apple firmness by stabilizing cell membranes and helping to maintain the internal integrity of the fruit. Anderson (1992) concluded that the role of calcium in cherry firmness was not certain, but that it clearly caused condensation of water on membrane surfaces and decreased permeability of the fruit to water. In my experiment, foliar applications of calcium in 1993 and 1994 did not affect fruit firmness. However, both soluble solids and fruit 138 removal force were increased. There was no interaction between calcium treatment and time of harvest, nor were correlations significant between fruit firmness and fruit color, diameter, soluble solids, pull force, or fruit weight. In 1994 calcium treatments had no effect on firmness during mechanical harvest or gain in firmness on soaking in cold water for 4 hr. Bedford and Robertson (195 7) observed that adding calcium during soaking increased sour cherry firmness (tenderometer) in comparison with those soaked in cold water. Anderson (1992) reported that soaking sour cherries for extended time periods in calcium solutions reduced the percentage of split fruit. In 1993 I soaked cherries in solutions of CaClz for 30 minutes before transfer to running water. Fruit firmness was not affected when measured after 4 hours of soaking (data not reported). Although soaking in water increased firmness, CaClz had no effect. Calcium is very important in fruit growth and development. It is involved directly in the cell wall and the middle lamella in which it binds to pectin groups (polygalacturonic acids). The degradation of pectates is mediated by polygalacturonase, which is drastically inhibited by high Ca2+ concentrations. Cassells and Barlass (1976) reported that a large proportion of the pectic material exists as calcium pectate, making the tissue highly resistant to degradation by polygalacturonase. As shown by Rigney and Wills (1981) in experiments with tomato pericarp tissue during fruit development, the calcium content of the cell walls increases to the fully grown immature stage, then drops just before the onset of ripening and 139 tissue softening. In future research the role of Ca2+ and pectins in cherry fruit softening may be a profitable area of study. 5. 221312110; The biological activity of ethylene in growth and development, e.g., fruit abscission, coloration, and maturation, is well established. Ethephon, an ethylene-releasing chemical, _ is used to promote cherry abscission and to minimize damage from harvesting procedures. Both Anderson (1969) and Olien and Bukovac (1978) reported that exceeding optimum ethephon dosage led to excessive leaf abscission and gummosis. The optimum level of 300-500 ppm was established by Anderson (1969) who noted that treated fruit was darker red in color, and more mature in appearance. Also, a critical factor in ethephon application is temperature. Olien and Bukovac (1983b) recognized that the major effect of temperature is to increase or decrease the rate of ethylene generation from ethephon. As yet, no one has reported a direct relationship between ethephon treatment and fruit firmness. In 1993 I found that the firmness of treated cherries was significantly reduced 5 to 7 days after ethephon application (300 ppm and 150 ppm). In 1994, the orchards (Plamondon and HRC, East Lansing) in which untreated controls were available showed similar results (see Fig. 23 and 26), but time of ethephon application did not affect firmness significantly. Although ethephon reduces firmness by hastening maturation, these softer fruit are more easily removed during mechanical harvest, and therefore exhibit less bruising (Bukovac, et al. 1979). 140 6. W31. Limited studies involving gibberellic acid in the 1960s suggested that it tended to delay fruit ripening, allowing harvesting of firmer fruit (Dostal and Leopold, 1967; Russo, et al., 1968; Dilley, 1969). Additional work in the 1970s and 1980s demonstrated that an application of 10 to 30 ppm at stage III of fruit growth would increase size and firmness of sweet cherries. Both Proebsting, et al. (1973) and Facteau, et al. (1985a) found that the difference in firmness was due to the presence of more soluble solids in the treated fruits. Facteau, et al. (1985b) also discovered that multiple applications of gibberellic acid not only increased fruit firmness and weight, but also delayed harvest time. GA3 is used extensively in Washington State on 'Bing' cherries destined for fresh market. In 1993 GA3 was applied to 'Montmorency' sour cherries at Belding, Michigan, at 10 and 20 ppm, resulting in increased fruit weight, delayed maturity, slower color development and increased fruit removal force. However, firmness, fruit diameter and soluble solids were not affected. In a second experiment at Northport, Michigan, GA3 at 20 and 40 ppm increased fruit size and soluble solids, and delayed color development, but again did not affect fruit firmness. At present GA3 can not be recommended for improving fruit quality in sour cherries , although it is used to reduce flower bud initiation (Hull, et al., 1959; Stang and Weidman, 1986; Bukovac, et al., 1987). 7. mama. Poor distribution of rainfall has been suggested as an 141 environmental factor that may favor soft sour cherries (Bedford, et al., 1955). Too much or too little water, particularly during the 3 week period of fruit development immediately prior to harvest, may result in soft cherries. The effect of irrigation was studied in 1993 and 1994 at the NWM Experimental Station, Traverse City. Cherries from the irrigated trees were softer and larger than those from non- irrigated trees, but fruit color, soluble solids and fruit removal force were not affected. In 1994, irrigation. had no effect on fruit characteristics at the normal time of harvest, but, when harvest was delayed about one week, fruits from irrigated trees were again softer. In both years, rainfall was not limiting; irrigation may have more pronounced effects in dry years. 8. Temperature. Mechanical harvesting of sour cherries by shaking results in additional bruising. Cherry farmers always are concerned about fruit temperature both during harvest and in the cooling tanks. lowering water temperature from 24 to 13 °C increased the product yield of the fruit, but temperatures lower than 13 °C did not further increase yield (Tennes, et al., 1967). Also, Tennes, et al. (1967) reported that soluble solids and fruit firmness reached maximum values at midnight, with minimum values at noon. The effects on firmness of air and fruit temperatures at harvest and after harvest were measured over a 24-hr period in 1994. Initial firmness was lowest at 17:00 and highest at 20:00 pm. (difference not significant with three replicates). Soaking had no consistent effect upon firmness of harvested fruit, but fruits held at 3.3 °C were significantly firmer 142 than those held at 23 °C. The lack of effect of soaking may indicate that non-bruised, hand-harvested fruits will not respond, whereas bruised fruits will. Burton (1979) observed that soaking affected firmness of sour cherries only after several drops to a hard surface (Table A1). Although not a part of this thesis, two experiments were performed at Traverse City in 1994 to test the effects of fruit temperature on resistance to bruising. limbs were enclosed in plastic bags for 4-5 hr to raise fruit temperature on a sunny day. Subsequently the fruits were dropped from several heights. The trials were performed in the NWM Experimental Station (no ethephon used) and Gregory's Cherri-ke Orchard (with ethephon) at Traverse City in 1994. The firmness of fruits enclosed in bags was lower than that of controls before bruising, but higher after bruising, resulting in a noticeable reduction in total loss of firmness in bruising (Table A2). These data, though limited, did not support the view that high temperatures increase the problem of soft fruit. In the same orchard, adjacent trees were harvested at 9:00 am. (20 °C) or at 3:00 p.m. (26 °C), but firmness was not affected by time of harvest. The data for bagged fruit support the observations of Crisosto, et al. (1994) who reported that sweet cherries that were cold at the time of impact were more susceptible to bruising and pitting than were warm cherries; thus internal and external bruising damage decreased as temperature increased. 9. gn’sing. Whittenberger, et al. (1964) observed that in some years 143 cherries were better able to withstand rough treatment during harvesting and handling operations than in other years (Table A3). Bedford and Robertson (1962) evaluated cherries from the same orchard and trees for three consecutive years. Using identical handling methods they observed that in 2 of the 3 years the fruits were firm and bruise-resistant, but in the other year (1961) the cherries were relatively soft. My studies indicated that some orchards have softer cherries than others (Table A4). But, soft cherries, as defined by the USDA, were rarely observed even after mechanical harvesting. Soft cherries appear to be caused by excessive bruising; they were always found in association with split fruits. No cultural practice was identified that would prevent the occurrence of soft cherries, but immaturity or over maturity, heavy crops, mineral nutrition, excessive rainfall, etc., seem to pre-dispose the cherries to greater bruise damage (Brown, et al., 1994). Correlations between the firmness of hand harvested fruits in 1993 and other fruit characteristics, summarized in Table 20, indicated a preponderance of negative correlations with color and fruit removal force. Thus firmness was high when fruit were small and low in soluble solids (immature), and low when values for color and fruit removal force were low (mature). As noted before, such correlations were usually not significant when early samples were omitted. In 1994, when only mature fruits were sampled, firmness was best correlated (Table 2 1) with color (negative) and with soluble solids and fruit removal force (both positive). Except for soluble solids, therefore, the relationships were similar in both years. Marshall, et 144 al. (1951) reported that following hand harvest immature fruits exhibited higher losses in cull fruit, pit loss and juice loss (33.8%) than mature fruits (20.4%) when not soaked; during 6 hours of soaking in water immature fruits lost 46.7% of juice vs. 26.4% for mature fruits (Table A5). Soft cherries were a problem even when all sour cherries for processing were hand picked; the adoption of mechanical harvesting did not create this problem, but it can make it worse (Whittenberger, et al., 1965). Cherries are initially bruised during mechanical harvesting, and additional bruising occurs during handling and processing (Tables A6, A7, A8). Fruits withstand one serious bruise, but two serious bruises spaced a few hours apart resulted in a rapid deterioration of cherry quality (Whittenberger, et al., 1964). Kenworthy and Silsby (1974) reported that firmness prior toharvest varied between seasons and that as the harvest season progressed fruit firmness decreased (Tables A3 & A7). Bruising and the loss of fruit firmness are problems that growers face every year. Since mechanical harvesters were introduced different ways of evaluating the effects of bruising and the loss of firmness have been used. Dropping is a common practice to compare and measure the deterioration (firmness-bruise) of the fruit. Hand-harvested fruits were dropped onto different surfaces from several heights to simulate mechanical harvest. Whittenberger, et al. (1965) and Burton, et al. (1979) reported that the number of drops was directly related to bruising and loss of firmness (Table A1). Also Brown, et al. (1994) found that a single dr0p from 3 ft onto a hard surface softened the fruit and dropping three times caused 145 splitting. A drop from 12 ft onto a hard surface caused splitting, whereas the use of different fabrics used for harvester catching frames reduced or prevented injury (Appendix A9). Accumulated data on bruising indicate the importance of controlling bruising during all harvesting and handling operations to maintain maximum quality and pitted yield of cherries. In 1994 studies, fruit firmness was evaluated on the tree just before mechanical harvesting, after mechanical harvesting and four hours after soaking. Soft cherries could not be identified on the tree, and initial firmness was reduced by harvesting and handling operations. Cherry farmers are probably tired of hearing the same recommendations with regard to the soft cherry problem. Nevertheless, experience has shown repeatedly that mechanical harvesters, when operated by competent personnel and under proper conditions, can harvest cherries with a minimum of bruising. Most of the initial injury occurs in harvesting; this can vary from 8 to 32 percent (Whittenberger, et al., 1964). Brown, et al. (1994) indicated some of the problems in mechanical harvesting, and suggested that growers, harvester dealers, and harvester manufacturers have some management decisions to make in relation to the soft fruit problem. Harvesting, handling and holding conditions which are acceptable one year may not be acceptable in another year. Developing and adopting new methods that will reduce both harvest and post-harvest bruising will be very beneficial for the cherry industry. 146 APPENDICES 147 Figure A1. Schematic drawing of firmness measuring device 148 I 100.0 llllll ‘J Spring Steel Stepping Motor W 0'09I <—Alumlnum Body \——— RS-232 Port: 149 Table A1 . Effects of bruising on recovery of firmness (durometer units) of 'Montmorency' sour cherries on soaking in water for 5 hr at 12 °C (Burton, 1979). I No. of drops 2 I SOAKING I Before After 0 43.6 42.4 1 38.3 39.7 2 34.9 33.9 3 26.7 29.5 Z Dropped 3 ft to hard surface 150 SN 3m 7% m.m~ S 2% Na. 2. + 24820 Q2 $3. 3% E 3 :4 New mdm - @232 < Baden RES 6; nonamfim EH: 8:: mmmzzmz mmaémmzme “5.65 .oomtsm 6.8: a 8:0 nuance has one 383 83 E5 10562882. Mo «.8qu do muss obmfiq E 8.8: 332qu .3 web 65 do 833388 “E ”5&3 do 88% one .~< 2an 151 Table A3 . Comparison of effects of hand vs. machine harvest on bruising (96) of 'Montmorency' sour cherry (Whittenberger, et al. 1964). I I BRUISING (96) I Year Hand Machine 1962 4.8 8.3 1963 4.4 6.7 1964 17.0 19.4 Mean 8.7 1 1.5 Table A4. Firmness of hand harvested 'Montmorency' cherry fruits (MCS Units). Control fruits only (see Figs. 17,1,5) at three different locations (1993). BEIDING NWMES (Ethephon) (Irrigation) 1 2 62.8 53.7 59.7 3 54.3 58.1 59.8 4 54.3 55.5’ 53.4 5 55.7 62.3 57.3 152 de mN ad Nd Nov 0.2 m.NH WM: o 33 ms ha 3 m WON Qm 5m wé w.mm mg: ad HS 0 $$ 33v AXV 6e 39 A5 6e $$ £59638 82 Bo... 3.2 8:: 32 DE SE 2.5 $2 :88. 82 83a 82 DE 55 :50 ,EDME BEE/dz FEMS mmaéza Egg .fimoH .3935 8.5.65 .bauogdoz. 5 $2 8:: USN 9.2 to Spa :8 «0 $8583 no anogmob manque» wo fiumtm .m< 2an 153 Table A6. Effects of mechanical harvesting and soaking in cold water for 6 hours on firmness (durometer units) of 'Montmorency' cherry fruit (Kenworthy, 1974). Week On Tree Mech Harv Soaked Orchard 1 1 S 1.4 43.2 53.9 2 45.0 37.0 47.4 Orchard 2 1 50.4 37.6 47.2 2 52.9 39.5 44.6 MEAN 49.9 39.3 48.3 Table A7. Comparison of sour cherry fruit firmness (durometer units) at 3 dates over 4 years (Kenworthy, 1974). [ J J TIME OF HARVEST (week) I YEAR 1 2 3 MEAN 1966 49.9 48.7 47.1 43,6 b 2 1967 53.7 48.2 47.7 49.9 ab 1968 52.2 50.9 46.9 50.0 ab 1969 54.4 52.1 51.4 52.6 a MEAN 52.6 A 50.0 AB 48.3 B 2 Mean separation (Tukey's test) following reanalysis of published data, using years and times of harvest as main effects. 154 Table A8. Range in firmness as affected by method of harvest and soaking in water for 4 hour (1994). Mechanical harvest Before soaking After soaking gmm‘ I MCS (g/mm) I and harvest 45-65 33-45 37-52 Table A9. Effects of dropping hand-harvested sour cherry fruits on firmness (MCS units). Traverse City, 1994. I I Cultivar I Treatment Montmorency Ujfehertoi furtos 'tial SS 78 IAfter dropping 3ft to hard surface 35-40 - Same, then soaked 4 hr 40-50 - 3 ft, 3 times Split - 12 ft to hard surface Split 42 12 ft to MW foam 2 54 ' 12 ft to "No Bruze" Y 45 '- Z Merryweather. 1-inch charcoal polyester foam, 2-pound density with a black skin. Y 1/2-inch "Softer No Bruze". LITERATURE CITED 155 LITERATURE CITED Abeles, F. B. 1973. Ethylene in Plant Biology. Academic Press, New York, N. Y. Al-Delaimy, K. L., G. Borgstrom, and C. L. Bedford. 1966. Pectic substances and pectic enzymes of fresh and processed Montmorency cherries. Michigan Agr. Expt. Sta. Quarterly Bulletin 49: 164-171, Nov. 1966. Anderson, J. L. 1969. The effect of ethrel on the ripening of 'Montmorency' sour cherries. HortScience 4: 92-93. Anderson, J. L., E. J. Seeley and R. L. Olsen. 1989. Effect of calcium chloride on 'Montmorency' sour cherry quality. HortScience 24: 10 (abstract). Anderson, J. L. and W. F. Campbell. 1991. Calcium chloridenwhat can it do for the cherry growers7. Proc. Utah State Hort. Assoc. 19-22. Anderson, J. L. and W. F. Campbell. 1992. Effective methods to mantain cherry firmness. Annu. Rpt. Michigan State Hort. Soc. 122:79-82. Anonymous, 1967. Ethrel technical services data sheet. Is-37. Amchem Products, Inc., Ambler, PA. Anonymous, 1995. Michigan agricultural statistics 1994. Michigan Department of Agriculture, East Lansing, MI. 96 pp. Banks, B. A. 1971. A comparison of methods for measuring tenderness of raw and cooked meat samples. MS. Thesis, Michigan State University. Barbier, M. and J .F. Thibault. 1982. Pectic substances of cherry fruits. Phytochemistry 21: 111-115. 156 Bedford, C. L. 1962. The quality of hand picked and mechanically harvested processed red cherries. Annu. Rept. Michigan State Hort. Soc. 92: 94-96. Bedford, C. L., and W. F. Robertson. 1955. Effects of various factors on the drained weight of canned red cherries. Food Tech. 9: 321-323. Bedford, C. L. and W. F. Robertson. 1957. Effect of handling and processing methods on the firmness and quality of canned and frozen red cherries. Michigan Agr. Expt. Sta. Quart. Bul. 40:5 1-58 Bolen, J. S., B. F. Cargill, and J. H. Levin. 1970. Mechanized harvest systems for red tart cherries. Michigan Coop. Ext. Bul. 660. Bourne, M. C. 1967. Squeeze it gently. New York (Geneva) Agr. Exp. Sta. Farm Res. 32(4): 8-9. Bourne, M.C. 1982. Effect of temperature on firmness of raw fruits and vegetables. J. Food Sci. 47: 440-447. Bourne, M.C. 1982. Food Texture and Viscosity: Concept and Measurement. Academic Press, New York, NY. Bouyoucos, G. J. and R. E. Marshall. 1950. A pressure tester for small fruits and fruit and vegetable tissue. Michigan Agr. Exp. Station Bull. 1168: 211-213. Brown, G. K., F. G. Dennis Jr., D. Guyer, E. J. Tirnm and M. Mandujano. 1995. Soft tart cherries--physical or physiological? Annu. Rept. Michigan State Hort. Soc. 127: 222-228. Brown, K. S. 1988. Assessment of fruit firmness in selected sour cherry genotypes. HortScience 23: 882-884. Brown, K. S., and C. M. Bourne. 1988. Assessment of components of fruit firmness in selected sweet cherry genotypes. HortScience 23: 902-904. Bukovac, M. J. 1979. Machine-harvest of sweet sweet cherries: Effect of ethephon on fruit removal and quality of the processed fruit. J. Amer. Soc. Hort. Sci. 104: 289-294. 157 Bukovac, M. J., J. Hull, Jr., C. D. Kesner and R. P. Larsen. 1987. Prevention of flowering and promotion of spur formation with gibberellin increases cropping efficiency in 'Montmorency' sour cherry. Annu. Rept. Michigan State Hort. Soc. 116: 122-13 1. Bukovac, M. J., F. Zucconi, R. P. Iarsen, and C. D. Kesner. 1969. Chemical promotion of fruit abscission in cherries and plums with special reference to 2-chloroethylphosphonic acid. J. Amer. Soc. Hort. Sci. 94: 226-230. Burg, S. P., and K. V. Thimann. 1959. The physiology of ethylene formation in apples. Proc. Nat. Acad. Sci. (U. S.) 45: 335-344. Cassells, A. L., and M. Barlass. 1976. Environmentally induced changes in the cell wall of tomato leaves in relation to cell and protoplast released. Physiol. Plant. 37: 239-246. Cooke, A. R., and D. I. Randall. 1968. Z-Haloethanephosphonic acids as ethylene releasing agents for the induction of flowering in pineapples. Nature 218: 974-975. Cooper, T., and F. Bangerth. 1976. The effect of Ca2+ and Mg2+ treatment on the physiology, chemical composition and bitter pit development of 'Cox's Orange' apples. Sci. Hortic. (Amsterdam) 5: 49- 57. Crisosto, C. H., H. Andris, K. R. Day and D. Garner. 1994. Cold 'Brooks' cherries suffer more pitting and bruising. Cal. Agr. 48: 18-19. Curwen, D., F. J. McCardle, and C. M. Ritter. 1966. Fruit firmness and pectic composition of Montmorency cherries as influenced by differential nitrogen, phosphorus, and potassium applications. Proc. Amer. Soc. Hort. Sci. 89: 72-79. DellaPenna, D., D. S. Kates, and A. B. Bennett. 1987. Polygalacturonase gene expression in Rutgers, rin, nor, and Nr tomato fruits. Plant Physiol. 85: 502-507. Dennis, P. G., Jr., M. Mandujano, D. Guyer, E. J. Tirnm and J. Nugent. 1994. Soft cherries-causes and solutions. Proc. Michigan State Hort. Soc. 123:177-181. 158 Diener, R. G., J. H. Levin, and R. J. Wolthuis. 1969. An instrument for automatically measuring the firmness of red tart cherries. Food Technology 23: 125-131 Dilley,’D. R. 1969. Hormonal control of fruit ripening. HortScience 4:111—114. Doesburg, J. J. 1965. In pectic substances in fresh and preserved fruit and vegetables. I.B.V.T., Communication No. 25 Wageningen, Netherlands. Dostal, C., and A. C. Leopold. 1967. Gibberellin delays ripening of tomatoes. Science 158: 1579-1580. Drake, S. R. and E. L. Proebsting, Jr. 1985. Effects of calcium, daminozide and fruit maturity on canned 'Bing' sweet cherry quality. J. Am. Soc. Hort. Sci. 110: 162-165. Edgerton, L. J. 1968. New compound aids regulation of fruit abscission. New York's Food and life Sciences 1(1): 19-20. Facteau, T. J. 1982. Levels of pectic substances and calcium in gibberellic acid-treated sweet cherry fruit. J. Amer. Soc. Hort. Sci. 107:148-151. Facteau, T. J., N. E. Chesnut, and K. E. Rowe. 1983. Relationship between fruit weight, firmness, and leaf/ fruit ratio in Lambert and Bing sweet cherries. Can. J. Plant Sci. 63: 763-765. Facteau, T. J ., K. E. Rowe, and N. E. Chesnut. 1985a. Response patterns of gibberellic acid-treated sweet cherry fruit at different soluble solids levels and leaf/fruit ratios. Scientia Hort. 27:257-262. Facteau, T. J., K. E. Rowe, and N.E. Chestnut. 1985b. Firmness of sweet cherry fruit following multiple applications of gibberellic acid. J. Amer. Soc. Hort. Sci. 110: 775-777. Fils-Lycaon, B., and M. Buret. 1990. Loss of firmness and changes in pectic fractions during ripening and overripening of sweet cherry. HortScience 25: 777-778. Flore, J. A. 1985. The effect of carbohydrate supply on sour cherry fruit size and maturity. HortScience 20: 568 (abstract). 159 Flore, J. A. 1992. Influence of light interception on cherry production and orchard design. Annu. Rept. Michigan State Hort. Soc. 111: 161- 169. Flore, J. A., and D. R. Layne. 1990. The influence of tree shape and spacing on light interception and yield in sour cherry. Acta Hort. 285: 91-93. Gee, M. and R. M. McCready. 1957. Texture changes in frozen Montmorency cherries. Food Res. 22:300-302. Gross, K. C., and Wallner, S. J. 1979. Degradation of cell wall polysaccharides during tomato fruit ripening. Physiol. Plantarum 63: 117-120. Hall, C. B. 1987. Firmness of tomato tissues according to cultivar and ripeness. J. Amer. Soc. Hort. Sci. 112: 663-665. Huber, D. J. 1983. The roll of cell wall hydrolases in fruit softening. Hort. Rev. 5: 169-219. Huber, D. J. 1984. Strawberry fruit softening: The potential role of polyuronides and hemicelluloses. J. Food. Sci. 49: 1310-1315. Hull, J., Jr., and L. N. Lewis. 1959. Response of one-year-old cherry and mature bearing cherry, peach and apple trees to gibberellin. Proc. Amer. Hort. Sci. 74: 93-100. Hulme, A. C. 1958. Biochemistry of apple and pear fruits. Adv. Food Res. 8: 337-350. Kenworthy, A. L., and L. Silsby. 1974. Red tart cherry fruit quality: measuring fruit firmness objectively. Michigan State Univ. Agr. Expt. Sta. Res. Rpt. 253. Klee, H. J. 1993. Ripening physiology of fruit from transgenic tomato (Lyeepersigon eseulenturn) plants with reduced ethylene synthesis. Plant Physiol. 102: 911-916. Knee, M. and I. M. Bartley. 1981. Composition and metabolism of cell wall polysaccharides in ripening fruits. pp. 133-148 In: J. Friend and M.J.C. Rhodes (eds.), Recent Advances inthe Biochemistry of Fruit and Vegetables. Academic Press, New York, NY. 160 IaBelle, R. L. and J. C. Moyer. 1960. Factors affecting the drained weight and firmness of red tart cherry. Food Tech. 14: 347-352. LaBelle, R. L., E. E. Woodams, and M. C. Bourne. 1964. Recovery of Montmorency cherries from repeated bruising. Proc. Amer. Soc. Hort. Sci. 84: 103-109 Iidster, P. D., S. W. Porritt, M.A. Tung, and P. W. Voiscy. 1978. A texture measurement technique for sweet cherries. HortScience 13:536-538. Looney, N. E. and AD. McMechan. 1970. The use of 2- chloroethylphosphonic acid to aid mechanical shaking of sour cherries. J. Amer. Soc. Hort. Sci. 95: 452-455. Lustig, I. and Z. Bernstein. 1987. An improved firmness tester for juicy fruit. HortScience 22: 653-655. Magness, J. R. and G. F. Taylor. 1925. An improved type of pressure tester for determination of fruit maturity. USDA Cir. 350: 1-8. Marshall, R. E., W. F. Robertson, C. L. Bedford and W. H. Case. 1951. The effect of the length of soak on the quality of canned and frozen 'Montmorency' cherries. Food Technology 5: 1 16-1 18. Northcote, D. H. 1963. The biology and chemistry of cell walls of higher plants, algae, and fungi. Int. Rev. Cytol. 14: 223-265. Ogawa, J. M., E. Bose, B. T. Manji, and W. R.Schreader. 1972. Bruising of sweet cherries results in internal browning and increases suceptibility to fungi. Phytopathology 62: 579-580. Olien, W. C. and M. J. Bukovac. 1978. The effect of temperature on rate of ethylene evolution from ethephon and from ethephon-treated leaves of sour cherry. J. Amer. Soc. Hort. Sci. 103: 199-202. Olien, W. C. and M. J. Bukovac. 1982a. Ethylene generation, temperature responses, and relative biological activities of several compounds with potential for promoting abscission of sour cherry fruit. J. Amer. Soc. Hort. Sci. 107: 1085-1089. 161 Olien, W. C. and M. J. Bukovac. 1982b. Interaction between temperature and ethylene in sour cherry fruit abscission. HortScience 17: 795-796. Ourecky, D. K. and M. C. Bourne. 1968. Measurement of strawberry texture with an Instron machine. Proc. Amer. Soc. Hort. Sci. 93: 3 17- 325. Parker, R. E., Levin, J. H. and R. T. Whittenberger. 1966. An instrument for measuring firmness of red tart cherries. Michigan State Agr. Expt. Sta. Quart. Bull. 48 :471-482. Patten, K. D., M. E. Patterson, and E. L. Proebsting. 1986. Factors accounting for the within-tree variation of fruit quality in sweet chenies. J. Amer. Soc. Hort. Sci. 111: 356-360. Patten, K. D., and E. L. Proebsting Jr. 1986. Effect of different artificial shading times and natural light intensities on the fruit quality of 'Bing' sweet cherry. J. Amer. Soc. Hort. Sci. 111: 360-363. Pilnik, W. and A. G. J. Voragen. 1970. pp. 53-87 In: A. C. Hulme, ed., The Biochemistry of Fruits and their Products Vol, 1. Academic Press, New York, NY. Postlmayr, J. L., B. S. Luh, and S. J. Leonard. 1956. Characterization of pectin changes in freestone and clingstone peaches during ripening and processing. Food Tech. 10: 618-625. Proebsting, E. L. Jr. 1972. Chemical sprays to extend sweet cherry harvest. Wash. State Univ. Ext. Multilith 3520. Proebsting, E. L. Jr., G. H. Carter, and H. H. Mills. 1973. Quality improvement in canned 'Rainier' cherries with gibberellic acid. J. Amer. Soc. Hort. Sci. 98: 334-336. Proebsting, E. L. Jr., and H. H. Mills. 1981. Effect of seasonal crop load on maturity characteristics of 'Bing' cherry. J. Amer. Soc. Hort. Sci. 106: 144-146. Proebsting, E. L. Jr. and A. S. Murphey. 1987. Variability of fruit quality characteristics within sweet cherry trees in Washington. HortScience 22: 227-230. 162 Ricks, D. J., L. G. Hamm, and W. C. Chase-Iansdale. 1982. The tart cherry subsector of US. agriculture: a review of organization and performance. North Central Regional Reseach Publication 278, 80 pp. Rigney, C. J. and R. B. H. Wills. 1981. Calcium movement, a regulating factor in the initiation of tomato fruit ripening. HortScience 16: 550- 551. Robinson, T. L., E. J. Seeley, and B. H. Barritt. 1983. Effect of light environment and spur age on 'Delicious' apple fruit size and quality. J. Amer. Soc. Hort. Sci. 108: 855-861. Rohrbach, R. P. 1981. Sorting blueberries to improve fresh market shelf life. ASAE Paper No. 81-1551. Amer. Soc. Agr. Eng., St. Joseph, MI. Russo, 1., Jr., H. C. Dostal, and A. C. Leopold. 1968. Chemical regulation of fruit ripening. BioScience 18:109. Seymour, G. B. , S. E. Harding, A. J. Taylor, G. E. Hobson, and G. A. Tucker. 1987. Polyuronide solubilization during ripening of normal and mutant tomato fruit. Phytochemistry 26: 1871-1875. Sheehy, R. E., M. Kramer, and W. R. Hiatt. 1988. Reduction of polygalacturonase activity in tomato fruit by antisense RNA. Proc. Natl. Acad. Sci. USA. Biochemistry 85: 8805-8809. Slaughter, D. C. and R. P. Rohrbach. 1985. Developing a blueberry firmness standard. Transactions of the Amer. Soc. Agr. Eng. 28: 986- 992. Spayd, S. E., E. L. Proebsting Jr., and L. D. Hayrynen. 1986. Influence of crop load and maturity on quality and susceptibility to bruising of 'Bing' sweet cherries. J. Amer. Soc. Hort. Sci. 1 11: 678-682. Stanberry, C. 0., and W. J. Clore. 1950. The effect of nitrogen and phosphorus fertilizers on the composition and keeping qualities of 'Bing' cherries. Proc. Amer. Soc. Hort. Sci. 56: 40-45. Stang, E. J., and R.W. Weidman. 1986. Economic benefit of GA3 application on young tart cherry trees. HortScience 2 1: 78-79. 163 Stier, E. F., C. 0. Ball, and W. A. Macllinn. 1956. Changes in pectic substances of tomatoes during storage. Food Tech. 10: 39-43. Tennes, B. R., R. G. Diener, J. H. Levin and R. T. Whittenberger. 1967. Firmness and pitter loss studies in tart cherries. Amer. Soc. Agr. Eng. paper No. 67-333, St. Joseph, MI. Teryl, R. R. and W. H. Loescher. 1987. Relationships between leaf area per fruit and fruit quality in 'Bing' sweet cherry. HortScience 22: 1273-1276. Tigchelaar, E. C., W. B. McGlasson, and Buescher R. W. 1978. Genetic regulation of tomato fruit ripening. HortScience 13: 508-5 13. Timm, E. J., D. E. Guyer, G. K., Brown, and N. L Schulte. 1995. Michigan sweet cherry color measurement and prototype color chip deve10pment. Amer. Soc. Agr. Eng. paper 11(3): 403-407. Tirmn, E. J., G. K., Brown, P. R. Armstrong and R. M. Beaudry. 1993. A portable instrument for measuring firmness of cherries and berries. ASAE Paper No. 93-6539. St. Joseph, MI. Voragen, A. G. J., J. P. J. Tirnmers, J. P. H. Iinssen, H. A. Schols, and W. Pilnik.1983. Methods of analysis for cell wall polysaccharides of fruit and vegetables. Z. Lebensm. Unters. Forsch. 177:25 1-256. Wallner, S. J., and H. L. Bloom. 1977. Characteristics of tomato cell wall degradation in vitro. Plant. Physiol. 60: 207-2 10. Wittenbach, V. A. and M. J. Bukovac. 1973. Cherry fruit abscission: effects of growth substances, metabolic inhibitors and enviromental factors. J. Amer. Soc. Hort. Sci. 98: 348-351. Whittenberger, R. T. 1952. Factors which affect the drained weight and other characteristics of heat-processed red cherries. Food Res. 17: 299-306. Whittenberger, R. T., H. P. Gaston, and J. H. Levin. 1964. Effect of recurrent bruising on processing of red tart cherries. Michigan Agr. Expt. Stat. Res. Rept. No. 4. 164 Whittenberger, R. T. and C. H. Hills. 1953. Studies on the processing of red tart cherries. Changes in fresh red cherries caused by bruising, cooling and soaking. Food Tech. 7(1): 29-31. Whittenberger, R. T. and R. B. Marshall. 1950. Measuring firmness of red tart cherry. Food Tech. 4: 311-312. Wolfe, R. R., M. L. Abrams, and W. F. Probasco. 1982. Controlling postharvest decay of bluberries using firmness separation and hot water treatments. Transactions of the Amer. Soc. Agr. Eng. 25: 312- 315. HICHIGQN ST t "14114101 31