'-4 .l ‘6‘ ES"; as _ _ .-. - TH 5} ‘ s :«1 Y '3, . ' "" " 'd (e l L“! ti grggty ,1 * This is to certify that the thesis entitled PHYSIOLOGICAL AND QUANTITATIVE DETERMINATION OF DIFFERENTIAL SUGAR ACCUMULATION IN CARROT (DAUCUS CAROTA L.) presented by Gene Edward Lester has been accepted towards fulfillment of the requirements for Ph . D . degree in Horticulture Date November 7, 1980 0-7 639 . ' -. ; m3 '11-. " '~ 25¢ per any per item 1 “fix. j mamas LIBRARY MATERIALS: ,5 1-3;, '5’”, ' Place in book return to remove . r ‘U " . charge from circulation records PHYSIOLOGICAL AND QUANTITATIVE DETERMINATION OF DIFFERENTIAL SUGAR ACCUMULATION IN CARROT (DAUCUS CAROTA L.) BY Gene Edward Lester A DISSERTATION Submitted to Michigan State University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Department of Horticulture 1980 ABSTRACT PHYSIOLOGICAL AND QUANTITATIVE DETERMINATION OF DIFFERENTIAL SUGAR ACCUMULATION IN CARROT (DAUCUS CAROTA L.) BY Gene Edward Lester The concentration of the root sugars fructose, glucose and sucrose of carrot (Daucus carota) from differ- ent cultivars and breeding lines were determined using high pressure liquid chromatography. Over a three year study, three Michigan locations had no significant influ- ence on sugar content, but years did differ. Genetic vari- ation was apparent because cultivars and parental lines were consistently high or low for fructose/glucose with concomitant sucrose levels. There were no cultivars and only one parental line, 9541, that exhibited a significant difference for fructose and glucose content over all three years. However, one parental line 6000, and one hybrid cultivar, 'Spartan Fancy,‘ exhibited a significant differ- ence for high sucrose and high total sugars compared to the other entries over all three years. General combining ability estimates demonstrated that parent 9541 was a strong combiner for high fructose/glucose content and parents 872 and 6000 were good combiners for sucrose from the group of Gene Edward Lester six parental lines. Based on total sugar content, parents 5986, 6000 and 9541 were good combiners in relation to other lines. Cultivars and breeding lines of carrot with estab- lished differences in sugar accumulation capacity were studied by growth analyses to identify associations with high and low sugar content. Carrots were grown on both organic and sandy loam soils. At both locations the sea- sonal pattern for sugar content of high sugar accumulating lines (HSL) and low sugar accumulating lines (LSL) was similar. There was little or no association of growth indi- cators (dry weight accumulation, tap root dry weight and leaf area index) with high or low sugar accumulation. Dif- ferences in sugar yields were associated with mean net assimilation rate (NEE), mean relative growth rate (EGE) and leaf area ratio (LAR) late in the growing season. HSL had increasing EEE, EGE and LAR, whereas LSL had decreasing EEE and LAR and a stabilizing EGE. In general, carrot cultivars and breeding lines producing high free sugar concentrations were distinguished from low sugar accumulating carrots by delayed physiological maturity resulting in prolonged photosynthetic activity late in the growing season. IN MEMORIAL TO GWEN WHOSE LOVE AND ENCOURAGEMENT TRANSCENDS HER DEATH ii ACKNOWLEDGMENTS Appreciation is extended to the author's committee chairman, Dr. J. F. Kelly, who has provided guidance and appraisal in manuscript preparation. Thanks is extended to Dr. L. R. Baker who pro- vided the plant material for this study and who served as major professor prior to his leaving the University. Dr. J. N. Cash is acknowledged for his service on the guidance committee, his many valuable suggestions and for the use of his laboratory space. Dr. G. L. Hosfield is acknowledged for the use of his high performance liquid chromatograph and his service on the guidance committee. 0 Drs. R. Herner and J. Flore are also thanked for their valuable suggestions and for their service on the guidance committee. A special thanks is extended to Robin Bellinder for her reliable and invaluable laboratory assistance. The author also wishes to thank his colleagues in the Departments Of Horticulture and Food Science for their contributions of advice and labor. iii Guidance committee: The journal-article format was adopted for this dissertation in accordance with departmental and university requirements. Sections I and II were prepared and styled for publication in the Journal of the American Society of Horticultural Science. iv TABLE OF CONTENTS LIST OF TABLES . . . . . . LIST OF FIGURES . . . . . COMPARISON OF HPLC DETERMI PARENTAL LINES, HYBRIDS SECTION 1 NED ROOT SUGARS FROM AND COMMERCIAL CULTIVARS OF CARROT (DAUCUS CAROTA L.) FOR QUALITY IMPROVEMENT . . . . . . Abstract . . . . . . . Materials and Method Results and Discussion Summary . . . . . . . Literature Cited . . . Appendix . . . . . . . PHYSIOLOGICAL BASIS FOR DI ACCUMULATION IN CARROT (DAUCUS CAROTA L.) . . .. SECTION 2 FFERENTIAL SUGAR Abstract . . . . . . . Materials and Method Results and Discussion Conclusion . . . . . . Literature Cited . . . Page vi 33 33 36 41 70 71 LIST OF TABLES Table Page SECTION 1 1. Carrot lines and cultivars, utilized to determine endogenous sugars of carrot roots grown in three consecutive years . . . . . . . 6 2. Endogenous sugar content (mg/g root fresh weight) of carrot parental lines grown over three years on three Michigan locations on organic soil . . . . . . . . . . 9 3. Endogenous sugar content (mg/g root fresh weight) of carrot cultivars grown over three years on Michigan locations on organic soil . . . . . . . . . . . . . . . . . 10 4. Estimates of general combining ability effects for hybrid performance of endo- genous sugars by six MSU parental lines grown in 1976, 1977 and 1978 on Michigan organic soil . . . . . . . . . . . . . . . . . 13 A1. Summary of raw data of fructose (mg/g root fresh weight) for growing location, carrot parental line, year and replica- tion . . . . . . . . . . . . . . . . . . . . . 21 A2. Summary of raw data of glucose (mg/g root fresh weight) for growing location, carrot parental line, year and replica- tion . . . . . . . . . . . . . . . . . . . . . 22 A3. Summary of raw data of sucrose (mg/g root fresh weight) for growing location, carrot parental line, year and replica- tion . . . . . . . . . . . . . . . . . . . . . 23 A4. Summary of raw data of total sugar (mg/g fresh weight) for growing location, carrot parental line, year and replica- tion . . . . . . . . . . . . . . . . . . . . . 24 vi Table A5. A6. A7. A8. A9. A10. A11. A12. A13. A14. A15. Page Summary of analysis of variance of fruc- tose raw data for carrots by replications, years, parental lines and growing loca- tions . . . . .'. . . . . . . . . . . . . . . 25 Summary of analysis of variance of glucose raw data for carrots by replications, years, parental lines and growing loca- tions . . . . . . . . . . . . . . . . . . . . 25 Summary of analysis of variance of sucrose raw data for carrots by replications, years, parental lines and growing loca- tions . . . . . . . . . . . . . . . . . . . . 26 Summary of analysis of variance of total sugar raw data for carrots by replications, years, parental lines and growing loca- tions . . . . . . . . . . . . . . . . . . . . 26 Summary of raw data of fructose (mg/g root fresh weight) for growing location, carrot cultivar, year and replication . . . . 27 Summary of raw data of glucose (mg/g root fresh weight) for growing location, carrot cultivar, year and replication . . . . 28 Summary of raw data of sucrose (mg/g root fresh weight) for growing location, carrot cultivar, year and replication . . . . 29 Summary of raw data of total sugar (mg/g root fresh weight) for growing loca- tion, carrot cultivar, year and replication . . . . . . . . . . . . . . . . . 30 Summary of analysis of variance of fruc- tose raw data for carrots by replica- tions, years, cultivars and growing locations . . . . . . . . . . . . . . . . . . 31 Summary of analysis of variance of glucose raw data for carrots by replications, years, cultivars and growing locations . . . . 31 Summary of analysis of variance of sucrose raw data for carrots by replications, years, cultivars and growing locations . . . . 32 vii Table Page A16. Summary of analysis of variance of total sugar raw data for carrots by replica- tions, years, cultivars and growing locations . . .'. . . . . . . . . . . . . . . 32 SECTION 2 1. Total root sugars from foreign and domestic cultivars and MSU breeding lines of carrots grown near Bath, MI., 1978, on organic soil . . . . . . . . . . . . . . . . . 37 2. Fructose concentrations (mg/g fresh weight) of high and low sugar accumulating carrot cultivars and breeding lines on sandy loam soil at East Lansing, MI. and organic soil near Imlay City, MI. during the 1979 growing season . . . . . . . . 42 3. Glucose concentrations (mg/g fresh weight) of high and low sugar accumulating carrot cultivars and breeding lines on sandy loam soil at East Lansing, MI. and organic soil at Imlay City, MI. during the 1979 growing season . . . . . . . . 43 4. Sucrose concentrations (mg/g fresh weight) of high and low sugar accumulating carrot cultivars and breeding lines on sandy loam soil at East Lansing, MI. and organic soil near Imlay City, MI. during the 1979 growing season . . . . . . . . . . . 44 5. Total sugar concentrations (mg/g fresh weight) of high and low sugar accumulating carrot cultivars and breeding lines on sandy loam soil at East Lansing, MI. and organic soil near Imlay City, MI. during the 1979 growing season . . . . . . . . . . . . . . . . 45 6. Dry weight accumulation (9 total dry weight) of high and low sugar accumulating carrot cultivars and breeding lines grown on sandy loam soil at East Lansing, MI. and organic soil near Imlay City, MI. during the 1979 growing season . . . . . . . . . . . . . 51 viii Table 10. 11. Simple and multiple regression statistics between total sugars and growth analysis parameters of high and low sugar accumu- lating carrot cultivars and breeding lines Dry weight of the tap root (9 tap root dry weight) of high and low sugar accumu- lating carrot cultivars and breeding lines grown on sandy loam soil at East Lansing, MI. and organic soil near Imlay City, MI. during the 1979 growing season Root/shoot ratio (9 root dry weight/g shoot dry weight) of low and high sugar accumulating carrot cultivar and breed- ing lines grown on sandy loam soil at East Lansing, MI. and organic soil near Imlay City, MI. during the 1979 growing season Leaf area index (leaf surface cm2/soil surface area cm ) of high and low sugar accumulating carrot cultivars and breeding lines grown on sandy loam soil at East Lansing, MI. and organic soil near Imlay City, MI. during the 1979 growing season . Leaf area ratio (leaf surface cmZ/g total dry weight) of high and low sugar accumulating carrot cultivars and breed- ing lines grown on sandy loam soil at East Lansing, MI. and organic soil near Imlay City, MI. during the 1979 growing season ix Page 52 53 55 56 58 LIST OF FIGURES Figure Page 1. Total endogenous sugars and the increase in total plant dry weight per harvest of high and low sugar accumulating carrot cultivars and breeding lines grown on sandy loam soil at East Lansing, MI. during the 1979 growing season . . . . . . 48 2. Total endogenous sugars and the increase in plant dry weight per harvest time of high and low sugar accumulating carrot cultivars and breeding lines grown on sandy loam soil at Imlay City, MI. during the 1979 growing season . . . . . . . . . . . . . . . . . . . . 50 3. Mean relative growth rate of high and low sugar accumulating carrot cultivars and breeding lines grown on sandy loam soil at East Lansing, MI. during the 1979 growing season . . . . . . 60 4. Mean relative growth rate of high and low sugar accumulating carrot cultivars and breeding lines grown on organic soil near Imlay City, MI. during the 1979 growing season . . . . . . 62 5. Mean net assimilation rate of high and low sugar accumulating carrot cultivars and breeding lines grown on sandy loam soil at East Lansing, MI. during the 1979 growing season . . . . . . 65 6. Mean net assimilation rate of high and low sugar accumulating carrot cultivars and breeding lines grown on organic soil near Imlay City, MI. during the 1979 growing season . . . . . . 67 SECTION I COMPARISON OF HPLC DETERMINED ROOT SUGARS FROM PARENTAL LINES, HYBRIDS AND COMMERCIAL CULTIVARS OF CARROT (DAUCUS CAROTA L.) FOR. QUALITY IMPROVEMENT COMPARISON OF HPLC DETERMINED ROOT SUGARS FROM PARENTAL LINES, HYBRIDS AND COMMERCIAL CULTIVARS OF CARROT (DAUCUS CAROTA L.) FOR QUALITY IMPROVEMENT ABSTRACT The concentration of the root sugars fructose, glucose and sucrose of carrot (Daucus carota) from differ- ent cultivars and breeding lines were determined using high pressure liquid chromatography. Over a three year study, three Michigan locations had no significant influence on sugar content, but years did differ. Genetic variation was apparent because cultivars and parental lines were con- sistently high or low for fructose/glucose with concomitant sucrose levels. There were no cultivars and only one parental line, 9541, that exhibited a significant differ- ence for fructose and glucose content over all three years. However. one parental line, 6000, and one hybrid cultivar, 'Spartan Fancy,‘ exhibited a significant difference for high sucrose and high total sugars compared to the other entries over all three years. General combining ability estimates demonstrated that parent 9541 was a strong com- biner for high fructose/glucose content and parents 872 1 and 6000 were good combiners for sucrose from the group of six parental lines. Based on total sugar content, parents 5986, 6000 and 9541 were good combiners in rela- tion to the other lines. This and other reports suggest that the sugar content of carrot roots may be enhanced through appropriate breeding procedures. Carrots (Daucus carota L.) are an important vege- table crop from the standpoints of crop value, food pro- duction and nutritional contribution to the human need for vitamin A (15). A 100 9 portion of most commercial carrot cultivars supplies 200% of the recommended dietary allow- ance (RDA) of provitamin A (13, 28). Hence, an increase in the utilization of this vegetable in the human diet would be beneficial. One method for achieving increased consump- tion would be to improve carrot flavor. Carrot flavor is characterized by bitter, oily and sweet components in an otherwise relatively bland background (1, 12, 16, 24). Sucrose, the major endogenous sugar, plays an important role in flavor and sweetness. Increased total sugar concentrations in the carrot results in more sweet- ness (6) and total sugars are negatively correlated with harsh flavor (23). The free sugars in carrot are fructose, glucose, sucrose and maltose (l, 16, 17, 18, 20). The standard sweetness rating for sucrose is 100, while fruc- tose, glucose and maltose have relative values of 173, 74, and 33 respectively (9, 11). The sugar content of carrot depends upon the stage of maturity (17, 18, 30), portion of the root (17, 18, 29), cultivar (6, 7, 13, 23, 29) and growing location (14). The ratio of nonreducing to reduc- ing sugars decreases following harvest and subsequently in cold storage, but total sugar concentration remains unchanged (17, 18, 19, 29). If carrots could be selected for increased levels of sucrose and/or fructose sweeter tasting and more palatable carrot cultivars may be devel- oped. Previously reported methods of determining free sugars in carrot did not offer a quantitative, rapid and reproducible assay necessary to screen large numbers of individual roots in breeding and selection programs for high sugar content. Prior to the 19705 standard methods for carbohydrate analysis consisted of various coloration measuring techniques. Others were correlations between soluble solids and total sugars (19, 20, 21), relative specific gravities of individual roots in brine solution (5) and gas-liquid chromatography using volatile trimethyl- silyl sugar derivatives (6). These methods suffered because they were either indirect, nonquantitative or too labor intensive. Recently developed analytical procedures using high pressure liquid chromatography (HPLC) are particularly useful because they permit rapid quantitative measurement of soluble sugars in large numbers of carrot roots. HPLC, although very beneficial, may be too expensive for most breeding programs. The purpose of this study was to utilize the HPLC to quantify fructose, glucose and sucrose in parental lines, hybrids and cultivars for culinary quality, and to determine if differential sugar accumulations are main- tained when carrots are grown on organic soils in three different locations and years. MATERIALS AND METHODS All carrots (Table l) were grown at three locations near Grant, Inlay City and Bath, MI. during 1976-1978 using standard cultural practices for organic soils (3). Carrots were planted in mid-May and harvested in mid-October for all three years. The hybrid cultivars and parental lines were recently described (4). Tops were removed at harvest. Roots were washed, surface-dried and stored at 4 C. Sample preparation was within 48 hr of harvest. Root samples were prepared by slicing cross- sectionally to provide a 4 cm mid-section that was saved for sugar analysis. The 4 cm section was sliced into 2 mm discs; then three 50 9 samples from each carrot line were selected randomly and frozen at -10 C. ‘The samples were 1y0philized in an automatic Virtis unit at a plate tempera- ture of 60 C, a condensor temperature of ~60 C and vacuum of less than 5.0 um. The lyophilized samples were weighed, ground through a no. 40 mesh screen in a Wiley mill, col- lected and capped in glass jars and stored under dry atmosphere at -10 C to prevent the loss of sugars at room temperature (6). Sugars were determined by extracting 1 g of carrot powder with 50 ml of 80% ethanol (stirring 5 min at 98 C) 5 Table 1.--Carrot lines and cultivars, utilized to determine endogenous sugars of carrot roots grown in three consecutive years. Parental Line 'Line No./ No./Cu1tivar Pedigree Source Parent Original Cultivar 872 MSU 872 Long Chantenay 1302 MSU 1302 Danvers 5931 MSU 5931 Long Chantenay 5986 MSU 5986 Waltham HiColor 6000 MSU 6000 Empress 9541 MSU 9541 Danvers Cultivars Company Danvers Open-pollinated Crookham Gold Pak Open-pollinated Crookham Spartan Bonus MSU (872 x 5931) 9541‘ Crookham Spartan Delite MSU (5931 x 6000) 5986 Crookham Spartan Fancy MSU (5931 x 5986) 6000 Crookham Spartan Sweet MSU 5931 x 6000 Crookham filtering (no. 5 Whatman paper) and rewashing the residue with an additive 25 ml hot (98 C) 80% ethanol, followed by filtration. A 2 m1 sample of combined filtrate was purified by passing through a C Sep-Pak filter (Waters 18 Associates) prior to injection into a Waters HPLC equipped with a Waters R-401 differential refractometer. Twenty ul of Sep-Pak filtrate were injected onto a Waters C18 carbohydrate HPLC analysis column with a solvent of 80:20 acetonitrile:water (v/v) at a flow rate of 3.5 ml/min. Solutions containing 1 mg/ml fructose, glucose and sucrose were used as sugar standards to determine peak retention times. An internal standard of 1 mg/ml of xylose was injected with each sample. Peak area was measured by tri- angulation. Estimates of general combining ability were on progeny from a diallel cross involving six parents. Six crosses (no reciprocals) were made to determine parental effects. The diallel was analyzed according to Griffing's (10) model 1 (fixed genetic material), method 4 which restricts inferences to the parental lines used in the experiment. RESULTS AND DISCUSSION Samples extracted from carrot roots cochromatographed with standards fructose, glucose and sucrose (3.0, 3.5 and 5.8 min retention times respectively). The three locations had no significant effects on sugar accumulation. Therefore, locations were combined for within year statistical comparisons of cultivars and parental lines. Significant differences (p = .05) in fruc- tose and glucose concentrations of the parental lines, hybrids and cultivars occurred in different years, both sugars exhibited two- to four-fold higher concentrations in 1977 than in 1976 or 1978 (Tables 2 and 3). The reasons for the large differences among years may be explained by 1977 having averaged 380 more growing degree days (base 40) than 1976 or 1978 (25, 26, 27). This increased number of growing degree days in 1977 would permit photosynthesis and resultant increased free sugar accumulation at harvest. Sucrose content was also generally high in 1977, but the magnitude was less than that for reducing sugars. Total sugar concentrations remained more constant for a given line over all three years than reducing sugar concentrations for both parental lines and cultivars. The more stable content of total sugars over years was expected because 8 Table 2.--Endogenous sugar content (mg/g root fresh weight) of carrot parental lines grown over three years on three Michigan locations on organic soil. iiiznfig} 1976 1977 1978 1976 1977 1978 Fructose Glucose 872 5.2bz 6.6b 8.0a 5.6b 7.3c 8.1a 5931 5.6b 6.2b 3.0C 5.8b 7.0c 3.6c 5986 4.5b 7.5b 5.0b 4.8b 9.7b 5.6b 6000 5.4b 7.1b 3.6b 5.1b 8.0b 3.50 9541 7.4a 14.6a 8.7a 7.8a 14.6a 9.4a mean 5.6 8.4 5.7 5.8 9.3 6.0 Sucrose Total Sugars 872 39.0a 50.6a 53.1b 49.8ab 64.6b 69.3a 5931 36.5a 42.2b 23.7d 47.9abc 55.5c 30.3b 5986 36.1a 51.5a 42.3c 45.4c 68.8a 53.0c 6000 40.4a 54.1a 64.2a 50.8a 69.3a 71.3a 9541 31.6b 38.8b 45.3c 46.8bc 68.0ab 62.4b mean 36.7 47.4 45.7 48.1 65.2 57.2 zMeans separated within columns by Tukey's HSD test, 5% level. 10 Table 3.--Endogenous sugar content (mg/g root fresh weight) of carrot cultivars grown over three years on Michigan locations on organic soil. Cultivar 1976 1977 1978 1976 1977 1978 Fructose Glucose Danvers 6.6az 11.1a 7.8a 6.8a 13.2a 6.6ab Gold Pak 5.6ab 5.9d 5.9b 5.2b 5.6b 5.0c S. Bonus 4.8bc 9.1b 7.4a 5.3b 9.8a 7.4a S. Delite 4.7bc 10.4a 4.8bc 3.8c ll.2a 4.5d S. Fancy 5.1ab 10.2a 4.5c 4.9bc 11.6a 5.9bc S. Sweet 3.4c 7.7c 3.9c 3.9c 6.3b 5.7de mean 5.9 9.1 5.7 5.0 9.6 5.8 Sucrose Total Sugars Danvers 23.4d 47.9b 37.9d 37.0d 72.2b 52.3c Gold Pak 34.5c 48.0b 34.4d 45.4c 59.6c 45.4d S. Bonus 41.6b 53.5ab 55.1bc 51.7b 72.4ab 69.9a S. Delite 41.1b 53.3ab 60.2ab 49.6b 74.9ab 69.5a S. Fancy 48.4a 59.3a 62.7a 58.5a 81.2a 73.1a S. Sweet 44.7ab 53.2ab 53.4c 52.0b 67.3bc 63.0a mean 38.9 52.5 50.6 49.0 71.3 62.2 zMeans separated within columns by Tukey's HSD test, 5% level. 11 changes in fructose and glucose are accompanied by con- comitant changes in sucrose, with resulting total sugar concentrations relatively unchanged (17, l8, 19, 29). The parental lines over all years and pooled loca- tions, demonstrated a greater variation in fructose, glu- cose, sucrose and total sugar content than the cultivars (Table 2 and 3). The high variability among parental lines, compared with variability of cultivars may be due to their unfavorable genotypic-environmental interaction (2) which would reduce the ability of the parental lines to withstand environmental stresses. Dobzhansky (8) related the reduced variability of hybrid genotypic-environmental interaction to the type of breeding system an organism exhibits. Out- breeding organisms, such as carrot, are influenced less physiologically in the heterozygous condition. Thus, hybrid carrots will exhibit greater heterozygosity than their comprising inbred parental lines; The decreased vari- ability in sugar concentrations over years expressed by hybrids versus parental lines is supported by this concept. Parental lines exhibited various degrees of phenotypic stability by maintaining somewhat consistent rankings for sugar concentrations across all three years (Table 2). If one parental line was significantly high in either sucrose or fructose and glucose in one year, it was gene- rally found to be high for the same sugar in other years. However, no parent maintained a year by year significant 12 difference from all other parental lines for both reducing and nonreducing sugars. Parent 9541 was consistently high in fructose and glucose each year while 5931, 5986 and 6000 were consist- ently low and 872 was variable (Table 2). Parent 6000 was consistently high in sucrose each year and 9541 was con- sistently low, while 872, 5931 and 5986 were variable. Parent 6000 was also consistently high for total sugar accumulation, whereas 872 and 9541 were variable for high total sugars. Parental lines 5931 and 5986 demonstrated relatively low total sugar accumulation. Ranking the parents over years for fructose and glucose content showed 9541 to be significantly greater than all the other lines except 872 in 1978. The ranking of the parents for sucrose concentration showed 6000 to be greater than 5931 (except in 1976) and 9541. In 1978, 6000 was significantly more concentrated in sucrose than any other parental line. The ranking for total sugar accumulation demonstrated 6000 to contain the most sugar, although not always significant from other lines, while S931 and 5986 varied across years and 872 and 9541 were intermediate. General combining ability (GCA) in hybrid perform- ance for sugar accumulation by 872, 1302, 5931, 5986, 6000 and 9541 over three years yielded rankings similar to the parental line study (Table 4). Parent 9541 demonstrated high GCA for fructose and glucose while 872 and 5931 were generally low. Parents 6000 and 872 were always high 13 Table 4.--Estimates of general combining ability effects for hybrid performance of endogenous sugars by six MSU parental lines grown in 1976, 1977 and 1978 on Michigan organic soil. Parental Line No. 1976 1977 1978 1976 1977 1978 Fructose Glucose 872 -0.26 -0.41 -0.31 -0.27 -0.26 -0.31 1302 0.02 0.04 0.02 -0.22 -0.21 -0.26 5931 -1.16 -1.86 -1.26 0.01 -2.18 -1.41 5986 0.47 0.74 0.53 0.66 1.12 0.72 6000 -0.11 -0.18 -0.11 -0.04 —0.33 -0.06 9541 1.04 1.67 1.15 1.16 1.87 1.32 Sucrose Total Sugars 872 1.20 1.55 1.42 0.66 -0.73 0.81 1302 -2.70 -3.50 -3.22 -2.94 -2.96 -3.47 5931 0.15 0.20 0.15 -2.67 —3.01 —2.52 5986 0.10 0.12 0.10 1.21 2.77 1.33 6000 1.77 2.30 2.17 1.61 3.49 2.05 9541 -0.50 -0.62 -0.62 1.71 1.39 1.83 14 general combiners for sucrose while 1302 and 9541 were poor. Parental lines 5986, 6000 and 9541 were relatively high general combiners for total sugars while 1302 and 5931 were poor. Cultivar performance for sugar content generally followed a repeatable trend over all three years (Table 3). Significant differences for fructose and glucose accumula- tion were noticed between 'Danvers,‘ (high) and 'Spartan Sweet' (low) for each of the three years. The cultivar with high sucrose and total sugar content was 'Spartan Fancy' which was within the group for high sugar content all three years had high sucrose and total sugar content. An arithmetic ranking of cultivars for total sugar accumulation within each of the three years showed 'Spartan Fancy' to be greater than 'Spartan Delite,‘ 'Spartan Bonus' and 'Spartan Sweet' and always to be significantly greater than the standard open- pollinated cultivars 'Gold Pak‘ and 'Danvers.‘ The high levels of sucrose and total sugar for 'Spartan Fancy' relative to the other hybrids, including 'Spartan Delite' which has the same parental lines but in different order, is probably due to the strong GCA of breading line 6000 for high sucrose and total sugars. Thus the use of 6000 as a pollen parent with strong GCA performance for sucrose and total sugars would predictably produce hybrids of a similar sugar content. Implications on culinary quality. A negative corre- lation exists between reducing sugars and fiber content (7) 15 and between total sugars and harsh flavor (22). Parental lines 9541 and 6000 were significantly high accumulators of and exhibited strong GCA for reducing and total sugars reSpectively, all three years. Thus, parental lines 9541 and 6000 should produce hybrids of a similar sugar content and possibly result in high reducing sugar/low fiber or high total sugars/reduced harsh flavored carrots. It is Empor- tant to emphasize that the stability that was exhibited by 6000 and 9541 for nonreducing and reducing sugars respectively does not imply a general consistency of the phenotype in varying environments. It only implies sta- bility in one aspect of phenotype, specifically sugar. This phenotypic stability may depend on holding some aspect of morphology or physiology in a steady state while others vary. Thus, the breeder should not neglect root color, shape or type. SUMMARY Significant differences did exist among carrot parental lines and cultivars for fructose, glucose and sucrose concentrations. These differences among parental lines and cultivars were exhibited over three consecutive years. Specific parental lines and cultivars exhibited significantly higher concentrations of either reducing or nonreducing sugars than other lines and cultivars in a given year. However, no single parental line or cultivar exhibited a significantly higher concentration for all sugars. Therefore, it appears that selecting for high concentrations of both reducing and nonreducing sugars in a single line is not possible within this genetic material. However, heritability studies for sugar accumulation and subsequent breeding for reducing or nonreducing sugar con- tent should be feasible. The HPLC has proven extremely useful in detecting quantitative differences of fructose, glucose and sucrose in carrot parental lines, hybrids and cultivars. Con- tinued utilization of HPLC should aid breeders in genetic- ally improving carrot sugar content. Such improvements in sugar content should contribute to enhanced carrot flavor l6 17 and culinary quality, all of which will possibly promote increased carrot consumption. LITERATURE CITED 10. LITERATURE CITED Alabran, D. M. and F. Mabrouk. 1973. Carrot flavor. Sugars and free nitrogenous compounds in fresh carrots. J. Agr. Food Chem. 21:205-208. Allard, R. W. and A. D. Bradshaw. 1964. Implication of genotype-environmental interactions in applied plant breeding. Crop Sci. 4:503-508. Anonymous. 1970. Vegetable Production Recommenda- tions. Ontario Ministry of Agric. and Food, Publ. 363. 72 pp. Baker, L. R. 1978. Spartan hybrid carrot series 1968—1976. Mich. State Univ. Agric. Exp. Sta. Res. Rep. 359. 8 pp. Bassett, M. J. 1973. Screening of carrot roots for high soluble solids by specific gravity. HortScience 9:232-233. Bittenbender, S. A. E. 1975. A study of the solids, sugar and sweetness content of selected inbred carrot lines and their hybrids. M.S. Thesis, Michigan State University. Carlton, B. C. and C. E. Peterson. 1963. Breeding carrots for sugar and dry matter content. Proc. Amer. Soc. Hort. Sci. 82:332-340. Dobzhansky, T. and B. Wallace. 1953. The genetics of homeostasis in Dros0phila. Proc. Nat. Acad. Sci. 39:162-171. Green, L. F. 1971. The balance of natural and syn- thetic sweeteners in food. Sweetness and sweeteners. Ed. G. G. Birch, L. FL. Green and B. C. Coulson. Applied Science LTD. London. Griffings, B. 1956. Concept of general and specific combining ability in relation to diallel crossing systems. Aust. J. Biol. Sci. 9:463-493. 18 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 19 Guthrie, H. A. 1971. Introductory nutrition. 2nd ed. C. V. Mosby Co., St. Louis. Heatherbell, D. A.; R. E. Wrolstad; and L. M. Libbey. 1971. Carrot volatiles. I. Characterization and effects of canning and freeze drying. J. Food Sci. 36:219-224. Kraut, C. W. 1974. A study of the nutritional com- position of selected carrot varieties. Ph.D. Disser- tation, Michigan State University. Leveille, G. A.; C. L. Bedford; C. W. Kraut; and Y. C. Lee. 1974. Nutritional composition of carrots, tomatoes and red tart cherries. Fed. Proc. 33:2264- 2266. MacGillivary, J. H.; G. C. Hanna; and P. A. Minges. 1942. Vitamin, protein, calcium, iron and caloric yield of vegetables per acre and per acre man-hour. Proc. Amer. Soc. Hort. Sci. 41:293-297. Otsuka, H. and T. Take. 1969. Sapid components in carrots. J. Food Sci. 34:392-394. Phan, C. T. and H. Hsu. 1973. Physical and chemical changes occurring in the carrot root during growth. Can. J. Plant Sci. 53:629-634. Phan, C. T. and H. Hsu. 1973. Physical and chemical changes occurring in the carrot root during storages. Can. J. Plant Sci. 53:635-641. Platenius, H. 1934. Physiological and chemical changes in carrot during growth and storage. Cornell Ag. Exp. Sta. Memoir 161:1-18. Rygg, G. L. 1945. Sugars in the root of carrot. Plant Physiol. 20:47-50. Scheerens, J. C. and G. L. Hosfield. 1976. The feasibility of improving eating quality of table carrots by selecting for total soluble solids. J. Amer. Soc. Hort. Sci. 101:705-709. Simon, P. W.; C. E. Peterson; and R. C. Linsay. 1980. Genetic and environmental influences on carrot flavor. J. Amer. Soc. Hort. Sci. 105:416-420. 23. 24. 25. 26. 27. 28. 29. 30. 20 Sistrunk, W. A.; G. A. Bradley; and D. Smittle. 1967. Influences of preharvest factors on carbohydrate in carrot. Proc. Amer. Soc. Hort. Sci. 90:239-251. Sondheimer, E. 1957. The isolation and identifica- tion of 3-methyl-6-methoxy-8-hydroxy-3,4-dihydro isocoumarin from carrot. J. Amer. Chem. Soc. 79: 5036-5039. Van Den Brink, C. 1976. Western Michigan Summary: Temperature-growing degree days-precipitation. Dept. Entomology: Mich. State Univ. Van Den Brink, C. 1977. Western Michigan Summary: Temperature-growing degree days-precipitation. Dept. of Entomology. Mich. State Univ. Van Den Brink, C. 1978. Western Michigan Summary: Temperature-growing degree days-precipitation. Dept. of Entomology, Mich. State Univ. Watt, B. K. and A. L. Merrill. 1963. Composition of foods-~raw, processed, prepared. Handbook No. 8, U.S.D.A., Washington, D.C. Werner, H. O. 1940. Dry matter, sugar and carotene content of morphological portions of carrot through the growing and storage season. Proc. Amer. Soc. Hort. Sci. 38:267-272. Yamaguchi, M.; B. Robinson; and J. H. MacGillivary. 1952. Some horticultural aspects of the food value of carrots. Proc. Amer. Soc. Hort. Sci. 60:351-358. APPENDIX APPENDIX Table A1.--Summary of raw data of fructose (mg/g root fresh weight) for growing location, carrot parental line, year and replication. 1976 1977 1978 Location Paiiggal . Rep 1 Rep 2 Rep 1 Rep 2 Rep 1 Rep 2 872 5.5 5.7 - - 7.9 8.5 5931 5.3 5.3 - - 3.4 3 4 Bath 5986 5.4 5.4 - - 5.1 5.3 6000 4.6 5.0 - - 4.0 4.0 9541 7.6 8.0 - - 8 3 8.9 872 5.1 5.1 7.7 7.7 - - 5931 4.4 4.4 6.1 6.5 - - Imlay _ _ City 5986 4.1 4.3 7.9 8.1 6000 6.5 6.5 6.7 6.7 - - 9541 7.1 7.1 12.2 12.4 - - 872 4.7 5.1 5.4 5.8 7.8 8.0 5931 6.7 7.3 6.2 6.2 2.6 2.6 Grant 5986 3.7 4.3 6.9 7.1 4.8 4.8 6000 4.5 5.1 7.5 7.7 3.1 3.3 9541 7.2 7.2 17.2 16.8 8.9 8.9 21 22 Table A2.--Summary of raw data of glucose (mg/g root fresh weight) for growing location, carrot parental line, year and replication. 1976 1977 1978 Location Parigzal Rep 1 Rep 2 Rep 1 Rep 2 Rep 1 Rep 2 872 5.5 5.9 - - 8.6 8.9 5931 5.9 6.3 - - 4.1 4.5 Bath 5986 5.8 5.8 - - 4.8 5.6 6000 3.8 3.2 - - 3.8 4.4 9541 7.2 7.2 - - 8.8 8.6 872 5.8 6.2 7.5 8.2 - - 5931 4.1 4.5 6.7 7.1 - - Imlay - - City 5986 4.4 4.4 8.0 8.0 6000 6.4 6.8 8.4 8.8 - - 9541 7.0 7.4 12.9 13.3 - - 872 4.8 5.2 6.6 6.8 7.4 7.8 5931 7.1 7.1 7.2 7.2 2.7 3.1 Grant 5986 4.1 4.1 9.7 9.9 6.0 6.2 6000 4.8 4.4 7.3 7.5 3.0 3.0 9541 8.9 9.3 16.6 15.6 9.7 9.5 23 Table A3.—-Summary of raw data of sucrose (mg/g root fresh weight) for growing location, carrot parental line, year and replication. 1976 1977 1978 Location Paiigzal Rep 1 Rep 2 Rep 1 Rep 2 Rep 1 Rep 2 872 35.0 37.0 - - 53.1 51.3 5931 38.6 42.6 - - 24.6 26.8 Bath 5986 34.3 34.3 - - 43.3 43.3 6000 37.8 43.0 - - 66.2 60.2 9541 33.0 33.0 - - 47.8 41.2 872 40.4 40.4 51.0 51.0 - - 5931 29.0 33.4 42.9 40.7 - - Imlay _ _ City 5986 35.3 41.9 49.9 49.9 6000 37.6 43.6 49.7 52.7 - - 9541 30.4 30.4 42.7 42.7 - — 872 38.3 42.7 48.1 52.5 54.0 54.2 5931 36.7 38.7 41.6 43.8 20.5 22.9 Grant 5986 34.2 36.4 53.2 53.2 41.2 41.6 6000 40.6 40.6 56.0 58.0 62.0 68.2 9541 29.2 33.6 31.6 38.2 45.0 47.2 24 Table A4.--Summary of raw data of total sugar (mg/g fresh weight) for growing location, carrot parental line, year and replication. ' 1976 1977 1978 Location Paiifizal Rep 1 Rep 2 Rep 1 Rep 2 Rep 1 Rep 2 872 46.0 48.6 - - 67.6 70.7 5931 49.8 54.6 - - 32.4 34.7 Bath 5986 45.5 45.5 - - 53.2 54.2 6000 45.4 51.2 - - 68.0 74.6 9541 47.8 48.2 - - 58.3 67.3 872 51.3 51.7 66.2 67.0 - - 5931 37.5 42.3 53.5 56.8 - - Imlay _ _ City 5986 43.8 50.6 65.8 66.0 6000 50.5 56.9 64.8 68.2 - - 9541 44.5 44.9 67.9 68.4 - - 872 47.8 53.0 60.1 65.1 69.2 70.1 5931 50.5 53.1 55.0 57.2 25.8 28.6 Grant 5986 42.0 44.8 69.8 70.2 52.0 52.6 6000 49.5 50.5 70.8 73.2 68.1 74.5 9541 45.3 50.1 64.4 71.6 63.0 65.8 25 Table A5.--Summary of analysis of variance of fructose raw data for carrots by replications, years, parental lines and growing locations. Source d.f.' M.S. F P Rep. 1 .680 .264 .609 Year 2 52.362 20.339 .001 Parental Line 4 54.767 21.273 .001 Location 2 1.096 .426 .655 Error 60 2.574 Table A6.--Summary of analysis of variance of glucose raw data for carrots by replications, years, parental lines and growing locations. Source d.f. M.S. F P Rep. 1 1.605 .712 .402 Year 2 67.010 29.707 .001 Parental Line 4 54.435 24.132 .001 Location 2 .541 .240 .788 Error 60 2.256 26 Table A7.--Summary of analysis of variance of sucrose raw data for carrots by replications, years, parental lines and growing locations. Source d.f.. M.S. F P Rep. 1 120.127 2.960 .090 Year 2 827.316 20.389 .001 Parental Line 4 617.793 15.225 .001 Location 2 1.603 .040 .961 Error 60 40.577 Table A8.--Summary of analysis of variance of total sugar raw data for carrots by replications, years, parental lines and growing locations. Source d.f. M.S. F P Rep. 1 170.352 3.224 .078 Year 2 1697.417 32.120 .001 Parental Line 4 604.570 11.440 .001 Location 2 8.612 .163 .850 Error 60 52.847 27 Table A9.--Summary of raw data of fructose (mg/g root fresh weight) for growing location, carrot cultivar, year and replication. 1976 1977 1978 Location Cultivar Rep 1 Rep 2 Rep 1 Rep 2 Rep 1 Rep 2 Danvers 5.5 5.7 - - 7.4 7.4 Gold Pak 4.8 4.8 - - 5.0 5.6 S. Bonus 5.5 5.5 - - 7.7 7.7 Bath S. Delite 3.8 4.2 - - 4.7 4.9 S. Fancy 3.9 4.5 - - 3 8 3.8 S. Sweet 4.2 4.2 - - 4 5 3.9 Danvers 6.7 6.3 10.8 11.0 7.2 7 0 Gold Pak 5.7 5.5 5.9 6 3 7.1 7.1 Imlay S. Bonus 4.3 4.1 9.1 9.3 7.4 8 0 CltY s. Delite 6.0 6.0 9.9 9.5 4 4 5.0 S. Fancy 5.6 5.8 10.3 10.3 4 9 4.9 S. Sweet 3.3 3.7 7.8 8.0 3.2 3 0 Danvers 7.7 7.7 11.2 11.4 8.7 8.9 Gold Pak 6.6 6.6 5.7 5.7 5.5 5.1 S. Bonus 4.5 4.7 9.0 9.0 6.7 6.7 Grant S. Delite 4.4 3.8 11.3 10.9 4.8 4.8 S. Fancy 5.3 5.7 9.5 10.1 4.4 5.0 S. Sweet 2.9 2.3 7.8 7.2 4.4 4.2 28 Table A10.--Summary of raw data of glucose (mg/g root fresh weight) for growing location, carrot cultivar, year and replication. 1976 1977 1978 Location Cultivar Rep 1 Rep 2 Rep 1 Rep 2 Rep 1 Rep 2 Danvers 6.2 6.4 — - 5.6 5.6 Gold Pak 4.9 4.9 - - 5.4 5.0 S. Bonus 6.1 6.1 - — 7.8 8.4 Bath S. Delite 4.3 4.1 - - 4.4 3.8 S. Fancy 4.3 4.5 - - 5.2 5.8 S. Sweet 4.2 4.2 - - 5.7 6 1 Danvers 5.8 6.4 11.3 11.3 7.4 8.0 Gold Pak 4.9 5.1 5.9 6.1 5.6 5.8 Imlay S. Bonus 4.3 4.7 8.8 9.0 6.3 6.3 City s. Delite 4.1 4.1 10.1 10.7 4.5 4.5 S. Fancy 5.3 5.3 11.8 12.2 6.4 6 4 S. Sweet 3.6 3.8 6.1 6.3 5.4 5.6 Danvers 7.9 7.9 15.1 15.1 6.2 6 6 Gold Pak 5.4 6.0 5.2 5.4 4.2 4.2 S. Bonus 5.7 5.1 10.5 10.9 7.7 7.9 Grant S. Delite 3.0 3.2 12.0 12.0 4.9 4.9 S. Fancy 5.1 5.1 11.0 11.6 5.8 5.8 S. Sweet 3.4 4.0 6.4 6.6 5.6 6.0 29 Table All.--Summary of raw data of sucrose (mg/g root fresh weight) for growing location, carrot cultivar, year and replication. Location Cultivar 1976 1977 Rep 1 Rep 2 Rep 1 Rep 2 1978 Rep 1 Rep 2 Bath Imlay City Grant Danvers Gold Pak S. S. S. S. Bonus Delite Fancy Sweet Danvers Gold Pak S. S. S. S. Bonus Delite Fancy Sweet Danvers Gold Pak S. S. S. S. Bonus Delite Fancy Sweet 18.0 38.0 38.3 36.8 47.9 43.9 26.6 29.0 41.8 40.4 48.5 39.7 20.5 29.0 38.5 43.1 48.8 46.3 20.0 42.0 43.3 36.8 47.9 45.9 26.6 33.6 41.8 40.4 48.5 41.9 24.9 35.6 44.0 49.1 48.8 50.7 48.3 48.3 49.4 51.2 56.4 51.4 46.6 43.7 57.7 54.5 57.2 52.1 48.3 50.5 49.4 52.2 60.8 51.4 48.6 49.7 57.7 56.7 63.2 57.1 26.0 36.1 53.1 60.6 63.4 46.9 38.0 26.8 55.9 59.7 59.8 56.7 35.8 38.3 50.2 59.3 62.9 47.5 38.0 38.3 57.5 60.6 63.4 52.9 40.0 28.8 57.9 61.9 63.8 62.7 38.8 38.3 56.2 59.3 62.9 53.5 30 Table A12.--Summary of raw data of total sugar (mg/g root fresh weight) for growing location, carrot cultivar, year and replication. 1976 1977 1978 Location Cultivar Rep 1 Rep 2 Rep 1 Rep 2 Rep 1 Rep 2 Danvers 29.7 36.1 - - 49.0 51.0 Gold Pak 47.7 51.7 - - 46.0 49.3 S. Bonus 49.9 54.9 - - 68.6 73.6 Bath S. Delite 44.7 45.3 - - 69.6 69.6 S. Fancy 56.1 56.6 - - 72.4 73.0 S. Sweet 52.8 54.3 - - 56.5 63.5 Danvers 38.7 39.7 70.4 70.6 52.4 55.2 Gold Pak 39.4 44.4 60.1 62.9 39.5 41.7 Imlay S. Bonus 50.2 50.8 67.3 67.7 69.6 72.2 City s. Delite 50.5 50.5 70.8 72.8 68.6 71.4 S. Fancy 59.4 59.6 76.0 83.3 71.1 75.1 S. Sweet 56.6 49.4 65.3 65.7 65.1 71.5 Danvers 36.1 40.5 72.9 75.1 50.7 54.3 Gold Pak 41.0 48.2 54.6 60.8 47.6 48.0 S. Bonus 48.1 54.4 77.7 77.6 64.6 70.8 Grant S. Delite 49.9 56.7 77.4 80.0 69.0 69.0 S. Fancy 59.2 59.6 77.7 84.9 73.1 73.7 S. Sweet 52.0 57.6 65.7 71.5 57.3 63.9 31 Table Al3.--Summary of analysis of variance of fructose raw data for carrots by replications, years, culti- vars and growing locations. Source d.f.' M.S. F P Rep. 1 1.378 1.034 .312 Year 2 104.336 78.280 .001 Cultivar 5 21.183 15.893 .001 Location 2 .957 .718 .491 Error 85 1.333 Table A14.--Summary of analysis of variance of glucose raw data for carrots by replications, years, culti- vars and growing locations. Source d.f. M.S. F P Rep. 1 1.170 .585 .446 Year 2 146.141 73.084 .001 Cultivar 5 24.162 12.083 .001 Location 2 1.666 - .833 .438 Error 85 2.000 32 Table A15.--Summary of analysis of variance of sucrose raw data for carrots by replications, years, culti- vars and growing locations. Source d.f.. M.S. F P Rep. 1 84.402 3.617 .180 Year 2 9079.981 389.109 .001 Cultivar 5 1132.651 48.538 .001 Location 2 11.071 .474 .624 Error 85 23.335 Table A16.--Summary of analysis of variance of total sugar raw data for carrots by replications, years, cultivars and growing locations. Source d.f. M.S. F P Rep. 1 23.250 .945 .339 Year 2 10136.556 412.215 .001 Cultivar 5 999.750 40.656 .001 Location 2 24.206 .984 .378 Error 85 24.590 SECTION 2 PHYSIOLOGICAL BASIS FOR DIFFERENTIAL SUGAR ACCUMULATION IN CARROT (DAUCUS CAROTA L.) PHYSIOLOGICAL BASIS FOR DIFFERENTIAL SUGAR ACCUMULATION IN CARROT (DAUCUS CAROTA L.) ABSTRACT Cultivars and breeding lines of carrot (Daucus carota L.) with established differences in sugar accumu- lation capacity were studied by growth analyses to identify associations with high and low sugar content. Carrots were grown on both organic and sandy loam soils. At both loca- tions the seasonal pattern for sugar content of high sugar accumulating lines (HSL) and low sugar accumulating lines (LSL) was similar. There was little or no association of growth indicators (dry weight accumulation, tap root dry weight and leaf area index) with high or low sugar accumu- lation. Differences in sugar yields were associated with mean net assimilation rate (NEE), mean relative growth rate (EGE) and leaf area ratio (LAR) late in the growing season. HSL had increasing EEE, EGE and LAR, whereas LSL had decreasing NEE and LAR and a stabilizing EGE. In general, carrot cultivars and breeding lines producing high free sugar concentrations were distinguished from low sugar accumulating carrots by delayed physio- logical maturity resulting in prolonged photosynthetic activity late in the growing season. 33 34 The utilization of growth analysis with time has been a valuable aid in identifying the mechanisms contribut- ing to diversity among genetically divergent lines and to exploit further the existing diversity (5). In common bean (Phaseolus vulgaris L.), mean leaf area was defined as an important component influencing economic yield differ- ences among cultivars (16). Comparisons of common bean reduced-leaf mutants with nonmutants for total plant yield could be determined by leaf area index (cm2 leaf surface area/cm2 land area covered) and leaf area duration [(cm2 leaf surface area/cm2 land area covered) (number of days of leaf duration)] (7). Harvest index (seed weight/ total plant dry weight) in common bean (17), and certain cultivars of dwarf wheat (13) have been positively corre- lated with biological yield and has aided in genetic improvement of these crOps. However, inmungbean (Phaseolus aureus Roxb.) growth analysis revealed no direct associa- tions with yield expression, but seemed to be a valuable supplementary criterion for detecting genetic diversity among parental lines in a breeding program (4). In cotton (Gossypium hirsutum L.), measuring for differences in net assimilation rate (increase in plant material per unit of assimilatory material per unit of time) and leaf area index aided in the selection of higher yielding cultivars (8). Improvement in kale (Brassica oleracea var. acephala) yields in existing crOpping systems was brought about 35 mainly by selecting for high leaf area index (18). In sugar beet, cultivars with high root/shoot ratios main- tained higher net assimilation rates during the later stages of plant growth and produced greater sugar yields than cultivars with a low ratio (6). Also in sugarbeet, selecting for large tap root to leaf weight ratio (TLWR) in the seedling stage resulted in increased sugar yields at harvest (14). In carrot, breeding for high total sugar yield has been recommended (2, 3, 11, 12) as a valuable aid in genetically improving the culinary quality of this crOp. The objective of this study is to identify what growth analysis factors may be influencing differential sugar accumulation, so that carrot breeding programs may consider the physiological mechanisms contributing to the diversity in sugar yield. MATERIALS AND METHODS Investigations of 24 carrot cultivars and breeding lines revealed three-fold differences in total water soluble sugars (Table 1). These differences were of a magnitude to call the genetic material used in this study diverse. From these, two high sugar lines (HSL) and two low sugar lines (LSL) were selected for detailed study. The high sugar selections were 'Farba,‘ a cultivar from the Netherlands and MSU-6000, a breeding line from Michigan State University (MSU). The low sugar selections were 'Gosinoostrovakaja 13' (Gosin), a cultivar from the U.S.S.R., and MSU-5986, a breeding line from MSU. All four selections were planted May 16, 1979 in a randomized complete block design utilizing three replica- tions with split plots for ten harvest dates. Plantings were in East Lansing, Michigan on a sandy loam soil and on organic soil near Imlay City, Michigan. Carrot seedlings were thinned to stand 2.5 cm between plants, rows 45 cm apart. Plots were fertilized with a preplant application of 400 kg/ha 19-19-19 (N-PZOS-KZO). The plots on sandy loam were watered by sprinkler irrigation and hand- cultivated as needed and on the muck by using standard cultural practices for organic soil (1). 36 37 Table l.--Tota1 root sugars from foreign and domestic cultivars and MSU breeding lines of carrots grown near Bath, MI., 1978, on organic soil. Total Sugars Name Origin (mg/g fresh weight) Farba Netherland 96.7az MSU-6000 USA 88.9a Flamm Netherland 87.3a 44C Netherland 86.9a Vitaminaya 6 USSR 85.8a Kuronan Brazil 85.1a Kinko Chantenay 6 Japan 84.4a Nacional Brazil 69.2 b King Imperator USA 68.9 b Imperial Long Scarlet Japan 68.9 b Kuroda ESALQ Brazil 67.0 b Shin Kuroda Japan 65.3 bc MSU-9541 USA 64.7 bcd Imperial Long Scarlet Japan 60.7 bcde MSU-1410 USA 60.5 bcde Criolla Argentina 59.2 bcdef MSU-1385 USA 58.8 bcdef Kokubu Japan 57.2 bcdef Birinoekutskaja 415 USSR 55.4 bcdef Waltham HiColor USA 51.2 cdefg MSU-5986 USA 50.1 defg San Nai Japan 49.5 efg Mirzoi Krasanaja USSR 45.2 fg Gosinoostrovakaja 13 USSR 39.8 g zMean separation by Tukey's HSD test, 5% level. 38 Five representative plants from each line were selected at random from each replication at every harvest for growth analysis. Whole plants were sealed in plastic bags and placed on ice in a styrofoam chest for transport to the laboratory for same day analysis. The roots were washed free of soil and the plants were separated into leaf blades, petioles with hypocotyl attached and tap root; and weighed immediately. Fibrous roots were not harvested. Leaf areas were measured, after weighing using a Ll-3100 area meter.1 Leaf blades and petioles with hypocotyl were placed in separate paper bags and dried for five days in a forced draft oven at 80 C for dry weight determinations. Roots were sliced longitudinally then radially in the center, then frozen at -10 C. For sample preparation, all root samples were lyophilized in an automatic Virtis unit at a plate temperature of 60 C, a condensor temperature of -60 C and vacuum of less than 5.0 um. The lyOphilized samples were weighed, ground through a #40 mesh screen in a Wiley mill and collected in capped glass jars. Jars with carrot powder were stored in dry atmospheric conditions at -10 C. Sugars were determined by extracting one 9 carrot powder with 50 m1 of 80% Ethanol (stirring 5 min at 98 C) filtering (#5 Whatman paper) and rewashing the residue with additive 25 m1 hot (98 C) of 80% Ethanol, followed by fil- tration. A 2 ml sample of combined filtrate was purified 1Ll-COR, Inc., Lincoln, NE. 39 by passing through a C18 Sep-Pak filter (Waters Assoc.) prior to injection into a Waters high pressure liquid chromatograph (HPLC) equipped with a Waters R-401 differ- ential refractometer. Twenty ul of Sep-Pak filtrate were injected onto a Waters C18 carbohydrate analysis HPLC column with a solvent of 80:20 acetonitrile:water (v/v) at a flow rate of 3.5 m1/min. Solutions containing one mg/ml fructose, glucose and sucrose were used as standards for peak retention time associations. An internal standard containing one mg/ml xylose was injected with each sample. Peak area was measured by the technique of triangulation. Growth analysis formulae were: 1. Increase in total plant dry weight = (9 total plant dry weight2 - 9 total plant dry weightl/sample time2 - sample timel) (subscript numerals (1 and 2) in growth analysis formulae indicate sampling at a given point in time = 1, followed by a sampling two weeks later =2). 2. root/shoot ratio (R/S) = dry weight root/dry weight shoot, 3. leaf area index (LAl) (cm2 leaf surface/cm2 of land area), 4. leaf area ratio (LAR) = (cm2 leaf surface area/g total plant dry weight), 40 mean relative growth rate (EGE) = (loge total plant dry weight2 - loge total plant dry weightI/sample time2 - sample timel), mean net assimilation rate (EEE) = [(total plant dry weight2 - total plant dry weightl/cm2 leaf sur— face2 - cm2 leaf surfacel) (loge cm2 leaf surface2 - loge cm2 leaf surfacel/sampling time2 - sampling timelll (10). RESULTS AND DISCUSSION Sugars extracted from carrot root cochromatographed with standards (3.0, 3.5 and 5.8 min retention times respectively). The final harvest at the Imlay City location was terminated earlier than at the sandy loam location in East Lansing because of frost damage. The seasonal pattern for sugar content of all cul- tivars and breeding lines was similar for both locations. Fructose and glucose concentrations were relatively high in both HSL and LSL during the early part of the growing season, but there was a general decline in fructose and glucose and a corresponding increase in sucrose as the season progressed. 'Farba' was the only carrot that had a significant difference in fructose and glucose accumulation over the growing season (Tables 2 and 3). There were few significant differences in sucrose and total sugars among the lines early in the growing season (Tables 4 and 5). Later in the season (September 19 at East Lansing and September 26 at Imlay City), the HSL ('Farba' and 6000) accumulated significantly higher concentrations of sucrose and total sugars than LSL ('Gosin' and 5986). 41 42 .853 mm :63 am: mafia—5. an msfipaoo afinufl3 coaumnmmom cmozu I no.~ nm.m na.b am.m amo.m na.m Am.v I I Amway mmmm I pa.m mm.m nm.m Am.> nm.o mm.oH mm.m I I “Away :wmoo I 38>.m na.m no.m hm.m Am.m Av.@ nom.m I I “Ammo ooom I mm.m cm.m mm.oa mm.HH mo.~a cm.mH om.m I I Aqmmv couch 3 em 2 mm 2 a .3 4 cu m 6:3 Honouoo nonaoumom Honaoumom unamsd unamsd “nomad hash hash wash mash \Ho>wuaao uaHo >¢A2H am.H nh.m am.~ mm.w Am.m am.v nmv.m n¢.m am.v om.m AAmAv mmmm na.m Av.m nom.v amH.¢ na.m AH.m amm.m MH.HH mm.m nom.w Aquv cameo mm.m an.m no.m pm.~ pm.m am.¢ 35.0 na.m n¢.v onm.o Aammv ooom ow.m cm.m mm.o no.5 cv.n oa.m mm.~H ow.oH mv.h New.m Aqmmv onuom 5H m ma m «N m mm Ha nu ma mafia monouoo Honouoo Honfioumom Monsoumom umflbfld umsmsd hash hash cash cash \nm>wuaso UZHmZfluaso uounmo unevennesoom Human 30H can amen mo Aunmwo3 amoum m\mfiv m:0fiumuucoocoo omouoanhII.N magma 43 433 am $66... on: 63839 an mcsbaoo cwnuwz c0wumummom smozN I am.~ am.m nom.m one.o acm.m AMH.~H Amm.m I I AAmAV mmmm I noo.v nov.v ona.m na.m nm.m n>.HH na.m I I Aqmqv canoe I nv.v no.m om.h om.v na.m Amm.ma na.o I I Aammv 0000 I mo.m m~.m mH.~H om.md co.¢a oH.mH m~.~a I I “Ammo mnnmm 0H om NH mm ma H ma v om m mafia Honouoo HonEoumom nonsoumom umamsm unamafl umnmsa hash mach cash cash \Hm>wuaso MBHU Mwuaao UZHmzHuaso uouumo UGAUMHSESUUm woman 30H can now: mo Ausmfioz Amman m\mfiv mcowumuucoocoo omoosaoII.m manna .Hoboa am .umou am: m.>ox:a an maesaoo cfinuwz GOAuMHmmom cmozN 44 I no.m~ mm.om pm.ma Am.oa nub.aa om.m I I Aqmqv ommm I nu.h~ Am.mm hm.mm nmo.mm An.va mm.mH n~.m I I AAmAV Genoa I mm.mm w~.mm mv.mm m~.om mb.v~ nmm.ma mv.> I I Agmmv oooo I mm.Vm mm.am Am.v~ Am.hH AH.mH Am.m m~.> I I Aqmmv onumm 0H mm NH mm ma H ma v cm 0 ween Honouoo Honaoumow Honaoumom umnmnm unamsa umsmsd hash hash mash ocsn \Hc>wuaso waHU Mcqu m~.0m na.m~ Am.~m mw.m~ ama.bm m~.m~ am.H~ na.ma mo.o mo.m AAmAV mmmm no.ma n5.m~ am.Hm ma.mm ma.om ma.v~ Am.HN om.va av.m m~.m AAmAv camoo mm.wm mm.mv om.o¢ om.mm Am.mm nom.m~ m~.mm om.ma om.v om.m AAmmV oooo mv.Hv mo.mv mH.¢m om.mm no.mm mm.om mm.ma am.aa nm.m unm.¢ Aqmmv couch 5H m ma m mm m mm Ha hm ma mafia nonouoo Monouoo nonfioumom Hwnaoumom umnma< umaozd mash mafia mash oGSb \Hm>wuaso UZHmz¢A Bmflm .QOmmom mcw3oum mhma oz» useusp .Hz .auwo mmaeH Home Aflom oficmmuo was .Hz .OCAmcmn ummm um Hwom EmoH avcmm so nosed weapooun can mum>wuaso uouumo mcwumasasoom Human 30H can amen mo Aunuwo3 amoum m\mav mcowuouusoosoo omouosmII.v canoe 45 .Ho>oH wm .umou om: m.>oxsa ha mGESHoo :HnuH3 GOHumummom amass I om.om am.¢m mm.hv om.mm n¢.mm hm.Hm am.mH I I AHmHv wmmm I av.mm no.0m no.5m amm.~v nH.om nom.hm mh.mm I I AHmHV cHmoo I mv.mv nom.mm no.~w pH.mm mm.H¢ am.mm now.o~ I I AHmmv ooom I mm.mv mo.mv mH.>v om.mv mh.ov m~.vq mm.wm I I Aqmmv manna 0H om NH mm mH H wH c om m ocHH umnouoo Honsmumom uoflfioumom um505¢ umamad “mound ath hHsn oGSH econ \um>HuHso uBHo MHHZH ah.mm no.wm nH.>m Am.mm noo.mm m~.om am.Hv Am.mm mH.m~ mo.v~ AHmHV mmmm Am.m~ nH.om Am.mv m~.m¢ mv.H¢ mo.om Am.Hv mm.mm om.m~ wh.m~ “Away :Hmoo m~.mv mv.mm mm.~m Ah.vm Am.mm nH.mm n>.Hv n¢.om no.mH ah.mH Aqmmo ooom mm.mm mm.mm m~.m¢ cm.ov mm.Hv M¢.nm mm.mv ah.mm cm.om umm.wm flammv conch 5H m mH m mm m mm HH hm MH ocHH nonouoo nonouoo nonfioumom uoflfioumom unsosm unamsa mHsn thh cash cash \nm>HUHsU wZHmZ¢H amflm .commom mcH3oum mbmH on» mCHunc .Hz .>UHU hMHEH “do: HHOn 0Hcmmuo can .Hz .mchsma ummm um HHom EmoH meson so mocHH msHUooun can mum>HuHso uouumo mcHHMHaevoom Human 30H can an3 mo AuzmHoz ammum m\mEv msowumuusoocoo Human HMHOBII.m oHnt 46 At the end of the growing season, total sugar accu- mulation tended to decrease in all four lines; however, the decrease in total sugars was approximately one month earlier for the LSL than for the HSL (Figures 1 and 2). A change in the increase in total plant dry weight coin- cided with the decrease in total sugars for both HSL and LSL (Figures 1 and 2). The increase in total plant dry weight was more pronounced at the East Lansing location than at Imlay City. Possibly the growing season at Imlay City was insufficient to permit an increase in total plant dry weight and a decline in total sugars for the HSL. Significant differences in dry weight accumulation were not exhibited between HSL and LSL during the growing season (Table 6). Also there were no significant regression coefficients for total plant dry weight regressed with total sugars for either HSL or LSL (Table 7). 'Thus, there was little or no association over the growing season of dry weight accumulation with sugar accumulation. However, during most of the growing season the cultivars were sig- nificantly higher for dry weight accumulation than were the breeding lines. There were no consistent significant differences between HSL and LSL for root dry weight (Table 8), or any significant regression coefficients for root dry weight regressed with total sugars. This indicated that root dry weight had little association with sugar accumulation over 47 Figure 1.--Tota1 endogenous sugars and the increase in total plant dry weight per harvest time of high and low sugar accumulating carrot cultivars and breeding lines grown on sandy loam soil at East Lansing, MI. during the 1979 growing season. 48 mh43... >435 m2:... m2:—. or v ON 0 wh._._o >52. 1|. 3w: comm .. r... 3m... 2600 .8. 3m... coco .1... 3a.... <92... 1‘ o O’Fc u v 1% ('3 In In“; a/am 8186!" "”01 a: O Q on 4—1 51 .Ho>oH am .umou emu m.>oxsa an mcsuHoo anuH3 :oHumummom comic I n~.HH nH.oH Qw.m no.5 nm.v no.~ nm.o I I Aquv mmmm I cm.0m oH.vm mv.mm nom.MH mo.¢H mm.m mH.H I I AHmHV cHmoo I n~.v am.m av.v am.v AN.¢ n5.H n¢.o I I .Hmmv 0000 I mo.Hm mm.mH mv.HN mm.mH Amb.0H nom.m Amm.o I I Aqmmv manna 0H mm NH mm mH H .mH e om o oCHH Honouoo Honewumom Honfioumom umzmam umsmam umsmsm aHSh >Hah mash ouch \Hm>HpH9U MBHU M¢HZH om.MH Am.mH ah.mH £5.5H nN.HH no.0H m.m nmq.m nm.o mH.o .HmHv mmmm om.mm m~.@m mH.mv ow.mm mm.m~ ow.mm mm.mH mH.v mo.H mH.o Amway :Hmoo om.mH Am.~H Am.mH QH.~H am.vH no.0H am.m am.H n¢.o mH.o Aqmmv ooom am.om mm.>~ m~.wm mo.mm mo.hm mm.m~ amm.HH m~.v Ach.o NMH.o AHmm. chasm 5H m mH m mm m mm HH hm MH ocHH nonouoo nonouoo Honsoumom umflfimumom unsws< umsmsfl mHSU mHah cash cash \Hm>HuH:U UZHmZ€H Bmflm .commom mcH3oum mhmH on» mcHHSp .Hz .muHo >MHEH Home HHom oHcmoHo can .Hz .ochsmq ummm um HHom EMOH meson so czonm mocHH msHpooHn can mum>Hano uounmo mcHUMHSEDoom Human 30H can ann no Ausmwo3 who Hmuou my coHHMHassoom uanoz huQII.m oHnme 52 Table 7.--Simple and multiple regression statistics between total sugars and growth analysis parameters of high and low sugar accumulating carrot cultivar and breed lines. . . . . Multiple Cultivar/ Simple RegreSSIOn Coeff1c1ent Regression Breeding Line TPDWyb RDbe R/Sb LAlb LARb 'EEEb ‘EEEb Coeffi§c1ent Farba (HSL) .71 .03 1.36 1.02 1.03* 2.78* -4.02** X X .80** X X .91** X X .69* 6000 (HSL) .91 2.41 .73 .64 -3.40 4.87* -3.03** X X .86** X X .92** X X .69* Gosin (LSL) .57 .80 10.65* .45 -6.27 2.35 -5.16 X X .80* X X .51 X X .24 5986 (LSL) .96 3.20 8.37* 2.13 -5.23 -5.22 -3.64 X X .83* X X . 74* X X .68 Y'rpnw = total plant dry weight xRDW = root dry weight * P < 5% due to chance ** p < 1% due to chance b = standard deviation change in total sugars/standard deviation change in regression variable X = interaction of associated simple regression variable in multiple regression with total sugars 53 .Ho>oH mm .umou 0mm m.>oxsa an mGEBHoo cHnuHs coHumuomom :mozu I Amm.w amm.h an.m amm.m AB.H am.0 QH.0 I I AHmHV 000m I mm.vH mm.mH mH.vH nmv.h we.m m0.m mm.0 I I Aqmqv ch00 I £0.H hm.N am.m Am.~ nu.H am.0 nm0.0 I I AHmmv 0000 I mH.vH m~.HH m¢.MH me.m non.m nm0.H m~.0 I I Aammv manna 0H 0N NH mm mH H 0H V cm 0 och nonouoo Honsoumom Honsoumom umsmsd pm909¢ unsusfl >H=0 >H50 0:50 0:90 \Hm>HuHso maHo mmHzH £0.0H an.~H £0.0H no.0H no.5 Am.m am.m nw.0 mH.0 300.0 “Away 000m mm.mv mm.m~ 80.nm mm.mm mm.0H mm.hH mH.m AMN.H mH.0 cH0.0 “quv ch00 n0.mH nH.m hm.0H nm.m awh.m nah.m om.m m~.~ m.H.0 n00.0 AHmmv 0000 nmm.hm o¢.mH an.~m amo.vH amn.mH Am.n am.m n0.H mH0. mH0.0 Amway couch hH m 0H m «N 0 mm HH hm mH ocHH nonouoo Honouoo Honsoumom Honaoumom umnmsd umsmsm hHsh mHsh mash mash \um>Hquo UZHmZ€H Bmflm .COmmom mcH3oum 050H 0:» mcHuso .Hz .muHU >MHEH “do: HHOm 0Hcmmuo can .Hz .0chcmq ummm um HHom EmoH hogan co :3oum mocHH mchooun can mum>HuHso uouumo mcHHMHsEboom ucmsm 30H can 50H: «0 “usmHos amp uoou no» my uoou mm» on» no uanos auoII.m mHnme 54 the growing season. In general, though, the cultivars exhibited higher root dry weights than did the breeding lines, especially in the second half of the growing season. There were no significant differences between HSL and LSL for root/shoot ratio (R/S) (Table 9). However, regression coefficients between R/S and total sugars were significant (P = .05) for the LSL only. There was a sig- nificant interaction between R/S and NEE (mean net assimila- tion rate) with total sugars for the HSL (P = .01) and 5986 (P = .05) indicating that R/S may be influencing sugar accumulation. The R/S ratio for all four lines was less than 1.0 early in the growing season and greater than 1.0 later on. This indicated that over the growing season carrots partitioned more photosynthate to the roots than to the leaves. The breeding lines generally had a signifi- cantly higher R/S than did the cultivars throughout the growing season. Hence, the breeding lines were partitioning a greater proportion of assimilates to the root than the cultivars. Significant differences were not detected between the HSL and LSL for leaf area index (LAl) (Table 10) and there were no significant regression coefficients for LAl regressed with total sugars. Significant differences for LAl occurred only between the cultivars and the breeding lines after June 27 at the East Lansing location. There were significant differences for LAl between HSL and LSL 55 .Ho>oH am .umou am: m.>oxsa an mGESHoo cHnuH3 COHumummom manoZN I mh.m m0.m n0.H AMH.H mh.0 m>.0 nm~.0 I I Aqmqv 0000 I nom.m Ah.H am.H mN.H m0.0 380.0 nw~.0 I I Amway sHmoo I Am.H oH.m mo.m 30.0 05.0 no.0 nH.0 I I AHmmv 0000 I amm.H n>.H Q>.H noo.H am.0 n¢.0 om.0 I I A400. mnumm 0H 0N NH mm 0H H 0H 9 0m 0 och nonouoo Honaoumom Honsoumom unamsm umnmam um509< hHsn thh 0:90 0:90 \HM>H»H:U uBHU MEHSH no.0 cm.m nom.~ Am.H mh.H cN.H m>.0 m0.0 A~.0 nMH.0 AHmHv 0000 £00 n0.~ nomH m0.m ade e.0.H AH00 Amvd a~.0 A”$0.0 330 :Hmoo mm.m n0.m om.m cv.m nov.H m0.H nom.0 nm.0 m.m.0 om.0 “Hmmv 0000 no.m av.~ Av.H n~.H n0.H nm.0 Av.0 am.0 QH.0 AMH.0 “Ammo onuom 5H m 0H 0 mm 0 mm HH hm MH ocHH nonouoo nonouoo nonsoumom Monsoumom umsmsm unamad >Hsb hHsn ouch 0:90 um>HuHao UZHmz¢A Bm¢m .:Ommom msHson mhmH on» 0CHH50 .Hz .auHo >MHEH new: HHOm OHQMOHO 0cm .Hz .mchccH ummm um HHom EmoH accmm so nacho moCHH uchooun 0cm mum>HuHso uouumo mcHHMHseuoom woman 30H: 0cm 30H 00 Auanoz who poonm m\u£mHo3 who #00» my oHumu uoosm\uoomII.m oHnma 56 .H0>0H 00 .3003 00: 0.00399 03 0:59H00 :H33H3 :OH303000m 0:00:N I 30.H 30.H 30.0 30.0 30.0 30.H 30.0 I I 33030 0000 I 300.0 00.0 00.0 300.0 00.0 00.0 00.H I I 33030 :3000 I 00.0 00.0 00.0 30.H 30.0 30.H 30.0 I I 33000 0000 I 00.0 00.0 00.0 00.0 00.0 00.0 300.0 I I 33000 03300 OH 00 0H 00 0H H ,0H 0 00 0 0:HH 3030300 303603000 303503000 309090 309090 309094 >H90 >H90 0:90 0:90 \30>H3H9U mBHo N¢H=H 30.0 30.H 30.H 300.0 30.0 3H.0 30.0 30.H 300.0 300.0 33030 0000 00.0 00.0 0H.0 300.0 00.0 00.0H 00.0 00.0 00.H 0H.0 33030 :Hmoc 30.H 30.H 30.0 30.0 3H.0 30.0 30.0 30.H 30.0 0H.0 33000 0000 00.0 00.0 00.0 00.0 00.0H 00.HH 00.0 00.0 300.0 N0H.0 305 033.00 0H 0 0H 0 00 0 00 HH 00 0H 0:HH 303O300 3030300 303803000 303303000 309090 309094 0H90 >H90 0:90 0:90 \30>H3H9U UZHWZdH Bmflm .:Om00m 0:H3030 000H 033 0:H390 .HS .0330 >0HEH 300: HHOm 0H:003o 0:0 .Hz .0:Hm:03 300m 30 HHOm E0oH 00:00 :o :3030 m0:HH 0:H00033 0:0 m30>H3H90 3O3300 0:330H9s9000 30090 30H 0:0 30H: 00 A080 0030 0000390 HHom\020 0000390 000H0 x00:H 0030 m00HII.0H 0H30B 57 at the Imlay City location but they were inconsistent over time. The lack of significant differences in LAl with HSL and LSL indicates the HS; may be more efficient in fixing CO2 and/or more efficient in transporting assimilate to the roots than the LSL. Significant differences between HSL and LSL for leaf area ratio (LAR) occurred after October 3 at East Lansing and after September 12 at Imlay City with the HSL having significantly higher LAR than LSL (Table 11). The time in the growing season at which significant differences occurred between HSL and LSL for LAR coincided with the time LSL were decreasing in total sugar accumulation. This indicates that LAR, which is a measure of photosynthetic assimilation might affect the accumulation of sugars at the end of the growing season in HSL and LSL carrots. However, signifi- cants (P = .05) for the regression coefficient for LAR regressed with total sugars occurred for 'Farba' only. The mean relative growth rate (fiEfi) was high for all lines at the beginning of the growing season (Figures 3 and 4). However, the REE decreased steadily throughout the season for the LSL and eventually leveled off late in the growing season, while total sugars continued to decline. The HSL showed the same decline in fiafi until September when the EEE began to increase. This increase in §E§ was associated with an increase in sucrose and total sugars for the HSL, suggesting that RGR is associated with increased 58 .333 mm .303 am: P0933. .3 93.538 5533 :033030000 :00:N I 30.0H 30.03 30.00 300.H0 00.00 30.00 30H.00H I I 33030 0000 I 3H.0H 300.00 30.00 30.00 30.00 30.00 00.H0H I I 33030 :3000 I 00.0H 33.03 300.00 30.00 30.00 300.00 30.00H I I 33000 0000 I 0H.0H 00.00 00.00 00.00 300.00 300.00 00.00H I I 33000 03300 03 00 03 00 0H H .03 0 00 0 0:33 3030300 303803000 303803000 309090 309090 309090 0H90 0390 0:90 0:90 \30>33H90 0BHO 0032H ”30.0 30.0 30.0H 30H.00 300.00 30.00 30.30 30.00 0H.00H 00.003 33030 0000 30.0 30.0 300.0H 30.0H 30.00 30.00 300.00 300.00 300.0HH 300.003 33030 :3000 00.0 300.0H 300.0H 300.0H 30.00 300.00 300.00 300.00 30.00 3H.003 33000 0000 00.0 00.0H 00.H0 00.00 00.00 00.00 00.00 00.00 300.0HH N300.00H 33000 03300 0H 0 0H 0 00 0 00 HH 00 0H 0:33 3030300 3030300 303803000 303803000 309090 309090 0H90 0390 0:90 0:90 \30>33H90 UZHmz0A 9000 .:00000 0:33030 000H 033 0:3390 .Hz ~0330 00HaH 300: H300 0330030 0:0 .Hz .0:30:03 3000 30 H300 800H 00:00 :0 33030 00:3H 0:300033 0:0 030>33H90 303300 0:330H989000 30090 30H 0:0 3033 no 3330303 030 30303 0\080 00030 03303 0030 0003II.HH 03300 59 Figure 3.--Mean relative growth rate of high and low sugar accumulating carrot cultivars and breeding lines grown on sandy loam soil at East Lansing, MI. during the 1979 growing season. Mean relative growth rate mg/mg/2wk 60 — RGR 300- EAST LANSING, MI FARBA(HSL) 60 6000 (HSL) (0 700- ‘ GOSIN (LSL) «.9 5986 (LSL) 0» soo- 500- 400- 300- 200- 100- 00:70, n l"...- C 1 l ""1"""ll I I l l l J JUNE JULY AUG SEPT OCT DATE 13 27 11 25 8 22 5 19 3 17 61 Figure 4.--Mean relative growth rate of high and low sugar accumulating carrot cultivars and breeding lines grown on organic soil near Imlay City, MI. during the 1979 growing season. BOOl 700r 600‘ N 0 b (n O O O O (1) O O O i V ' Mean relative growth rate mg/mg/zwk .5 O O G 62 RGR IMLAY ennui FARBA (HSL) (m) 6000 (HSL) M GOSIN (LSL) (nu) 5986 (LsL) H 1 l l n 1 J 1 JUNE JULY AUGUST SEPT OCT DATE 6 2O 4 18 1 15 29 12 26 1O 63 sugar accumulation late in the growing season. This associ- ation may be partially explained by the fact the ififi, for a given point in time may be calculated from net assimila- tion rate (NAR), where RGR = (NAR)(LAR) (10). Thus, the significant differences in LAR between HSL and LSL late in the growing season and a possibly dramatic association of Fifi with HSL and LSL might be the reason EEE was closely associated with the HSL. Also there was significants (P = .05) for the regression coefficient for §§§ regressed with total sugars for the HSL only. However, the lack of association of §§§ with LSL may be explained by the fact that fiEfi is basically a function of the change in dry weight over time. It is known that the different weight measurements (R/S, dry weight accumulation and tap root dry weight) did not show a significant difference between the HSL and LSL over the growing season. Therefore, the association of §§§ with sugar accumulation may be only superficial. The fiXfi decreased for both HSL and LSL from the beginning of the growing season until September (Figures 5 and 6). In September, the HSL exhibited an increasing fiifi while the LSL continued to show decreasing fiXfi. The fiXfi increase in the HSL was associated with an increase in total sugars and the fiifi decrease in LSL was associated with a decrease in total sugars. However, significants (P = .01) between NAR and total sugar occurred for the HSL only, 64 Figure 5.--Mean net assimilation rate of high and low sugar accumulating carrot cultivars and breeding lines grown on sandy loam soil at East Lansing, MI. during the 1979 growing season. 15 14 13 12 11 .5 0 Mean not assimilation rate mg/cm3’2 WK I U O 65 NAB EAST LANSING, Ml FARBA (HSL) (mi 6000 (HSL) (co) GOSIN (LSL) ("I-i 5986 (LSL) (—I l l’ ,k I l l l j I J 1 JUNE JULY AUG SEPT OCT DATE 13 27 11 25 8 22 5 19 3 17 66 Figure 6.--Mean net assimilation rate of high and low sugar accumulating carrot cultivars and breeding lines grown on organic soil at Imlay City, MI. during the 1979 growing season. 67 _ NAR IMLAY CITY, Ml FARBA (HSL) (m) 6000 (HSL) (no) 13. Gosm (LSL) ("-0 5986 (LSL) i-) I 14 ssimilation rate mg/cmg'z WK Mean net a 0 DATE 6 JUNE 20 1AUGUST I 15 29 I J SEPT 12 26 OCT 10 68 while multiple regression coefficients had fiXfi interacting at a significant level (P = .01) for HSL and (P = .05) LSL with fiafi and total sugars. Loach (9) also found high fiifi to be associated with high sugar yield late in the growing season in sugar beet. Fifi is primarily a function of photosynthesis (9). Therefore, the increasing fiXfi of the HSL indicates that photosynthesis remains active in the plants late in the growing season. In contrast, the decreasing MAE of the LSL was probably related to decreased photosynthesis. This observation of possible variability in photosynthetic activity is supported by the significant differences in LAR between HSL and LSL. The lack of significant differences in LAl indicated that the HSL and the LSL were not dis- tinguished by their ability, or lack of ability, to accu- mulate sugar by producing new photosynthetic material. More likely, differences in sugar accumulation between HSL and LSL occurred because of the ability of HSL to remain photosynthetically active late in the growing season as represented by increasing iii. Subsequently, the photo- synthate produced by HSL was translocated and stored in the roots as soluble carbohydrates. EXP varies with leaf age (15). Thus, fiifi may be affected by differing patterns of leaf production and leaf senescence within the canopies of the four varieties. Rate of leaf production and senescence were not directly 69 measured; thus it cannot be unequivocably determined if fififi in carrots is influenced by leaf age. However, LAl, a measure of photosynthate production area, was measured. Assuming that the change in LAl may be taken as an indica- tion of the number of leaves produced, it can be inferred that late in the growing season carrots have little new leaf production because of the general decline in LAl. Therefore, it is hypothesized that fififi is more dependent upon the photosynthetic activity of mature carrot leaves than on the production of new photosynthetic area. fififi is controlled by two factors: (1) the ratio of immature to mature leaves and (2) the photosynthetic rate of mature leaves. Multiple regression. Multiple regressions were cal- culated for the combinations of fififi, fiafi and R/S. The best multiple regressions used fififi and fiafi although significant regressions were found with fiafi and R/S, but only in the HSL. Thus, the generalization of fififi contribution to high sugar yield in carrot seems clear. _CONCLUSION In general, HSL were distinguished from LSL in their ability to accumulate free sugars by time of physio- logical maturity. Physiological maturity in carrot occurs when total sugars decline late in the growing season and this decline coincides with the largest biweekly increase in total plant dry weight. If carrot genotypes were selected for photosyn- thetic activity late in the growing season based on high fififi, it would be expected that high sugar yield would result and the resultant high sugar content would possibly improve carrot culinary quality. 70 LITERATURE CITED 10. LITERATURE CITED Anonymous. 1970. Vegetable Production Recommenda- tions. Ontario Ministry of Agric. and Food, Publ. 363. 72 pp. Bittenbender, S. A. E. 1975. A study of the solids, sugar and sweetness content of selected inbred carrot lines and their hybrids. M.S. Thesis, Michigan State University. Carlton, B. C. and C. E. Peterson. 1963. Breeding carrots for sugar and dry matter content. Proc. Am. Soc. Hort. Sci. 82:322-340. Chandra, 8.; A. K. Yadav; and P. Sagar. 1977. Growth attributes in mungbean. Indian J. Genetics and Plt. 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