STUDIES ON STARCH GRAIN SIZES AND SPECIFIC GRAVITY IN POTATO VARIETIES By KAILASH Na RAIN SHARMA AN ABSTRACT Submitted to the School of Graduate Studies of Michigan State University of Agriculture and Applied Science in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Department of Farm Crops Year 195& Approved 1 KAILAGH NAHAlN BHAitMA ABGTiiACT In 1955 seventeen varieties of potatoes were grown in four replicated plots at five locations in Michigan, Five tubers of about the same size (U,3, Grade No, 1) were taken from each plot at harvest. These constituted the samples used for the studies on specific gravity, percentage of four sizes of starch grains and chip color rating. By microscopic analyses the starch grains in each tubers were classified as large - above 75 microns, medium - between 75 to 50 microns, small - between 50 to 25 microns, and very small - less than 25 microns. Approximately 1,700 tubers were analyzed in these in­ vestigations. Although there was a considerable variability between the five tubers in each sample, at the five locations, each variety in general: 1. Assumed a characteristic rank - high, medium, or low in specific gravity; 2. Had a specific pattern of starch grain size; 3. Had a characteristic rank in potato chip color. 2 KAiLAbH N a HAIN BH a HMA ABSTRACT bven in varieties, tubers: 1. With high specific gravity tended to make lighter colored chips than tubers low in specific gravity; 2. With a high percentage of starch grains larger than 25 microns, were high in specific gravity and made lighter colored chips* 3* With high percentage of very small starch grains, less than 25 microns, were low in specific gravity and made darker chips. STUDIES ON STARCH GRAIN SIZES AND SPECIFIC GRAVITY IN POTa TO v a r i e t i e s By KAILA3H NARAIN 3HARMA A THESIS Submitted to the School of Graduate Studies of Michigan State University of Agriculture and Applied Science in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Department of Farm Crops Year 1956 Ap p ro v e d ProQuest Number: 10008663 All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is dependent upon the quality of the copy submitted. In the unlikely event that the author did not send a complete manuscript and there are missing pages, these will be noted. Also, if material had to be removed, a note will indicate the deletion. uest ProQuest 10008663 Published by ProQuest LLC (2016). Copyright of the Dissertation is held by the Author. All rights reserved. This work is protected against unauthorized copying under Title 17, United States Code Microform Edition © ProQuest LLC. ProQuest LLC. 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Ml 48106- 1346 ACKiM 0 i/i/LEDGMENTS The author wishes to express his sincere appreciation i to Dr. S. T. Dexter, Professor of Farm Crops and Dr. N. R. Thompson, Assistant Professor of Farm Crops under whose in­ spiration, constant supervision and unfailing interest this investigation was undertaken. Grateful acknowledgments are due to Dr. C. M. Harrison, Professor of Farm Crops for his supervision and generous assistance in the establishment of the techniques employed and to Dr. D. R. Isleib, Assistant Professor in Farm Crops for his suggestions and assistance. The writer is indebted to Professor H. M. Brown, Farm Crops for his willing cooperation and guidance in presenta­ tion of statistical data. Thanks is also extended to the members of the guidance committee, Dr. K. T. Payne, Head, Department of Farm Crops, Dr. R. L. Cook, Head, Department of Soil Science, Dr. W. J. Hooker, Associate Professor of Botany and Plant Pathology for their helpful suggestions. The writer deeply appreciates the financial support of a Graduate Research Assistantship provided by the Agricultural Experiment Station, Michigan State University, which enabled him to undertake this investigation. ii TABLE OF CONTENTS INTRODUCTION ~f- iliiVTiiW OF LITERATURE 3 Varietal Variability Specific Gravity Starch Potato Chips 3 4 6 9 MATERIALS AND MR'iTioDS 11 Varieties and Locations Sampling Specific Gravity Starch Grain Chip Making and Color Rating Computations 11 12 12 13 22 24 RESULTS 25 experimental Specific Gravity Percentage of Sizes of Starch Grains Chip Color Ratings Density of Starch Grain Sizes Relationship of Percentage of Sizes of Starch Grains to Specific Gravity Relationship of Percentage of Sizes of Starch Grains to Chip Color Rating Relationship of Specific Gravity to Chip Rating Variety Partial Correlations 25 27 35 37 46 52 59 64 DISCUSSION 66 SUMmARX AND CONCLUSIONS 76 LITERATURE c i te d 61 APPENDIX 66 iii LIST OF TABLES Table 1. Page Analysis of variance for specific gravity of seventeen potato varieties grown in 1955 in five locations. 26 2. Analysis of variance for percentage of starch grain size group 1 - large - above 75 microns from seventeen potato varieties grown in 1955 in five locations. 28 3. Analysis of variance for percentage of starch grain size group 2 - medium - 75 to 50 microns from seventeen potato varieties grown in 1955 in five locations. 30 4. Analysis of variance for percentage of starch grain size group 3 - small - 50 to 25 microns from seventeen potato varieties grown in 1955 in five locations. 32 5. Analysis of variance for percentage of starch grain size group 4 - very small - less than 25 microns from seventeen potato varieties grown in 1955 in five locations. 34 6. 7. Analysis of variance for chip color rating from seventeen potato varieties grown in 1955 in five locations. 36 Average specific gravity (x), percentages of four starch grain sizes (y), and chip rating (z) of seventeen potato varieties grown in Montcalm County in 1955, together with their coefficients of correlation. 38 S. Average specific gravity (x), percentages of four starch grain sizes (y), and chip rating (z) of seventeen potato varieties grown in Emmet County in 1955, together with their co­ efficients of correlation iv 39 Page Table 9. 10 . 11 12 . . 13. 14. 15. 16 . Average specific gravity (x), percentages of four starch grain sizes (y), and chip rating (z) of seventeen potato varieties grown in Bay County in 1955, together with their coef­ ficients of correlation. 40 Average specific gravity (x), percentages of four starch grain sizes (y), and chip rating (z) of seventeen potato varieties grown in Arenac County in 1955, together with their coefficients of correlation. 41 Average specific gravity (x), percentages of four starch grain sizes (y), and chip rating (z) of seventeen x>otuto varieties grown in Allegan County in 1955, together with their coefficients of correlation. 42 Average specific gravity (x), percentages of four starch grain sizes (y), and chip rating (z) of seventeen potato varieties combined from five locations grown in 1955, together with their coefficients of correlation. 43 Average specific gravity (x), calculated per­ centages of four volumes of starch grains (y) and chip rating (z) of seventeen potato varie­ ties grown in Montcalm County in 1955, to­ gether with their coefficients of correlation. 44 Density of different potato starch grain sizes from variety Cherokee grown at Montcalm County in 1955. 45 Analysis of variance for density of potato starch grain sizes. 45 Coefficients of simple correlation for varie­ ties between specific gravity (x) and percent­ age of starch grains (y), between percentage of starch grains (y) and chip rating (z) and between specific gravity (x) and chip rating (z) by locations and all locations combined. 53 v Table 17. Id, 19. Page Coefficients of simple correlation within varieties between specific gravity (x) and percentage of starch grains (y), between percentage of starch grains (y) and chip rating (z) and between specific gravity (y) and chip rating (z) by locations and all locations combined. 60 Coefficients of partial correlation for varie­ ties between specific gravity (x), percentage of starch grains (y) and chip ratings (z) by locations and all locations combined. 65 Average coefficients of simple and correlations for varieties between gravity (x), percentages of starch and chip ratings (z) regardless of 67 partial specific grains (y), sign. Appendix 1. 2. Weekly precipitation in inches at five counties in Michigan during May to September 1955. d6 Specific gravity, percentages of four starch grains and chip color rating of individual tuber from four potato varieties grown at Montcalm County in 195 5* d7 vi LIST OF FIGUiiFS Figure 1. 2. 3. 4. 5. 6. Page Modified Hanson "diet scale", a spring balance of 500 grams capacity on a raised horizental surface supported on retort stands - showing weight of the tuber in air. 14 Modified Hanson "diet scale" - showing weight of the tuber in water. 15 Projection microscope in vertical position with camera fitted on the top. 16 Potato starch grains. A tuber with an un­ usually high proportion of large starch grains (50$ largo, 25$ medium, 15$ of small, 10$ very small). 15 Potato starch grains. A tuber with an un­ usually high proportion of medium starch grains (15% large, 45% medium, 20% small, 20% very small)• 19 Potato starch grains. A tuber with a high proportion of small starch grains (0% large, 0% medium, 60% small, 40% very small). 20 7. Potato starch grains. A tuber with a high proportion of very small starch grains (0% large, 0% medium, 10% small, 90% very small). <3. 9. 21 Proposed color reference standard for quality control in potato chip manufacturing by F. J. Coughlin. 23 Scatter diagrams of variety means between per­ centage of large starch grains, above 75 mi­ crons size, and specific gravity obtained from potato tubers grown at five counties in Michi­ gan, 1955 crop* 47 vii Page Figure 10. 11. 12. 13. 14* 15. 16. 17. 1$. Scatter diagrams of variety means between percentage of medium starch grains, between 75 to 50 microns size, and specific gravity obtained from potato tubers grown at five counties in Michigan, 1955 crop. 4$ Scatter diagrams of variety means between percentage of small starch grains, between 50 to 25 microns size, and specific gravity obtained from potato tubers grown at five counties in Michigan, 1955 crop. 50 Scatter diagrams of variety means between percentage of very small starch grains, less than 25 microns size, and specific gravity obtained from potato tubers grown at five counties in Michigan, 1955 crop. 51 Scatter diagrams of variety means between percentage of large starch grains and chip color rating obtained fio m potato tubers grown at five counties in Michigan, 1955 crop. 54 Scatter diagrams of variety means between percentage of medium starch grains and chip color rating obtained from potato tubers grown at five counties in Michigan, 1955 crop. 55 Scatter diagrams of variety means between percentage of small starch grains and chip color rating obtained from potato tubers grown at five counties in Michigan, 1955 crop. 57 Scatter diagrams of variety means between percentage of very small grains and chip color rating obtained from potato tubers grown at five counties in Michigan, 1955 crop. 53 Scatter diagrams of variety means between specific gravity and chip color rating ob­ tained from potato tubers grown at five counties in Michigan, 1955 crop. 61 Scatter diagrams of variety means between percentage of volume of starch grains and specific gravity obtained from potato tuber grown at Montcalm County in Michigan, 1955 crop. 62 viii igure 19. Scatter diagrams of variety means between percentage of volume of starch grains and chip color rating obtained from potato tubers grown at Montcalm County in Michigan, 1955 crop* 20. Weekly precipitation during five months in 1955 at five counties in Michigan. INTRODUCTION tr - - - these roots ought to be exempted from all suspicion of lying heavy on the stomach of those who use them for food, since every pound contains 11 1/2 ounces of water, and the 4 1/2 ounces of solid parts remaining, afford scarce a drachm of earth.” A. A. Parmentiar, 17&1* (10) The potato is one of the most important agricultural pro­ ducts in terms of money value. As well as being used in several forms as one of the staple foods for man industry in various ways. ties of the potato. it is utilized in The uses depend on the various quali­ The kinds of dry matter, such as starch, sugars, and proteins and their proportions, are very important and have a considerable effect on the food value and culinary quality. The composition, as well as the amount of dry matter in a tuber, depends upon several factors, such as variety, climate, soil, fertilizer, culture, etc. Quality is defined as a combination of factors which relate to the external and internal characters of the tuber and it is mainly considered in three aspects: (1) market quality, (2) culinary or cooking quality and (3) food quality for nutritive and health values. Color, flavor and texture of cooked potatoes are characters for culinary quality. potatoes is measured by mealiness. The texture of cooked A generally accepted index of mealiness of the cooked potato is specific gravity. The major variable fraction of the total solids of the tuber is 1 2 starch. Specific gravity may be used as a quantitative measure of starch content, and is commonly used to estimate the yield of potato chips. A linear relationship of specific gravity and starch content has been established. Other investigations have shown that the starch is in the form of discrete starch grains, with a considerable range of sizes. However, very little information is available concerning the effect of the various sizes of starch grains on the quality characteristics of the potato tuber. As a consequence, this study was made to explore the effects of varieties and environment on the proportions of the various starch grain sizes found in suspensions made from potato tubers and the relationships of these sizes to specific gravity and chip quality. REVIEW OF LITERATURE Varietal Variability The effects of varieties on measures of culinary quality have been mentioned by many workers• Within a variety, Gilmore (23) reported a variation in table quality within a potato variety. Goldthwaite (23) concluded from the results of analysis of several hundred individual tubers that no two potatoes, whether of the same variety or from the same hill, have exactly the same composition. John­ son and Boyle (2d) found the percentage of dry matter in tubers of the same variety varying from 21.07 to 2?-Id and the per­ centage of starch from 14*63 to 20.76. Vanasse, et al (43) noted that variety and location of production have a statisti­ cally significant effect on the specific gravity - dry matter relationship. Between varieties. V/illaman and West (46) stated that American early varieties had lower contents of dry matter than had later varieties, and a similar tendency was shown by the data of Akeley and Stevenson (1). Burton (9) and Whitehead, et al (47) reached the same conclusion in the case of British varieties. Stevenson and Whiteman (39) showed that inherent differ­ ences among the varieties were apparent and that some varieti­ es tend to maintain better quality than others over a wide range of conditions# tal adaptation. They also indicated differential varie­ They said that if comparisons were to be 3 4 made between two varieties, it must be known that they were grown under very similar conditions. Aleeley and Stevenson (1) also reached the same conclusion. Akeley and Stevenson (2) discovered that the tendency for the tubers of a potato plant to have a high or low content of dry matter was heritable, and that the character for a high content of dry matter was dominant over that for a. low content of dry matter. Stevenson (3$), after examining the varieties Parnasia and Green Mountain, considered starch production to be the ex­ pression of a genetic character in the development of which, environment is as important as the genetic factor. Akeley and Stevenson (1) made studies on starch calculated from spe­ cific gravity, and found inherent differences between seed­ lings in the same progeny as well as between progenies and between varieties. Between locations. Metzer, et al (31) demonstrated statis­ tically significant differences in the composition of potato varieties, and that potatoes from one locality differ in starch and dry matter from those of another locality. Dunn and Nyland (17) stated that the greatest differences in average specific gravity were found between locations. Akeley and Stevenson (1) mentioned that wide differences in the same variety were found when grown in different parts of the country. Specific Gravity The specific gravity of the tuber has been used as a rapid measure of the content of dry matter and of starch. 5 According to Burton (10) Von Scheele et al, gave their results on 560 samples, including a number of varieties and found highly significant correlations and relationships be­ tween - specific gravity and dry matter; specific gravity and contents of dry matter and content of starch. They noticed "no differences in the relationships between specific gravity and the content of starch and of dry matter in tubers from different parts of thecountry or in different years," Fur­ ther rrthe relationships between specific gravity and the con­ tents of dry matter and of starch did not differ significantly in different varieties. The coefficients of the correlations between specific gravity and the dry matter and starch con­ tents did, however, differ.” Clark et al, (11) pointed out differences in specific gravity of tubers of different sizes. Glynne and Jackson (24) and Shutt (35) also found a high correlation between the content of dry matter and that of starch. Dry matter and starch were found to be associated with mealiness of potatoes after cooking. Freeman (20) claimed a significant correlation between the specific gravity of a tuber and the mealiness of its texture when baked, as in­ dicated by his TItoluene index”. Asby (4) and Clark et al. (11) obtained a high correlation between dry matter content and mealiness of the cooked potato and Clark et al (11) suggested that specific gravity was a practical method for making a preliminary selection for mealiness. 6 Starch The starch in the potato is in the fora of discrete starch grains of a considerable range in sizes* Since it is a major proportion of the total solids, it is an important fraction in quality studies. Structure and content, Sjostrom (36) noted that potato starch granules vary greatly. Commercially the starch of the highest average granule size is graded best, if other qualities are equal. The largest granules are usually egg-shaped, although granules of oyster shape are not uncommon. As a rule they show concentric striations, which often give them an ornamental ap­ pearance. Garner (22) showed that one axis of potato starch particles is longer than the other. According to Brautlecht (7) Rathsack found that the starch content of the potato is at a maximum in the third layer or zone from outside, when the potato is divided into seven zones. Total solids and starch are present in smaller quantities in the skin than elsewhere in the potato. Relationship of granule Johnson and Boyle (29) gave the starch grain size of a number of British varieties of potato. Their values for the average size of the largest starch grains in the tuber varied from 116ux 71u (var. Shamrock) to 71u x 51u (var. Royal Kidney); and for the average size of medium starch grains from 71u x 51u (var. Br. Queen) to 39u x 25u (var. Windsor Castle). There was no evidence of starch grain size being a varietal characteristic. 7 Fitch and Barnnet (21) found from a microscopic examina­ tion of different potatoes that the starch granules differ in size with different varieties. They further mentioned that cooking quality differs probably owing to the difference in the size and number of the starch granules. Veselovsky (44) sug­ gested that the qualitative composition of potato starch and the percentage of large and small grains should be considered varietal characteristics. Barham, et al. (5) observed that varietal and environ­ mental factors affect the structure and size of starch granules. The average size of the granules was either small or large, de­ pending upon the variety. He claimed that five hundred granules seemed to be a sufficient number to measure in order to obtain the average size and the size frequency. Meiss, et al. (30) made a comparison of an average cumulative particle size dis­ tribution curve of white potato starch produced in Maine with that produced in Idaho, Minnesota and Oregon and found notice­ able differences. Briant, et al. ($) using a hydrometer method, obtained from their starch sample a cumulative distribution of particle size which followed a sigmoid curve. Relationship of granule. ..siz.e. with. .me.aline.s.s. Veselovsky (44) concluded that the size of starch grains for the most part de­ termines the quality of starch. Large-grain potato starch may be readily converted into a soluble starch while small-grain starch gives a more viscous paste. He further established a direct relation between large size of starch grain and hydrolys­ 5 ing capacity, namely, starch grains longer than 60 microns hydrolyze more rapidly than those smaller than 60 microns* Szego [1+2) and Janieki (26) also stated that the viscosity of a paste is directly related to the average size of the gran­ ules, that is, the smaller granules produce ’£ . more viscous paste• Briant, et al (8) presented evidence that there was no correlation between the mealiness of potatoes and the per­ centage of granules above 30 microns diameter. However, there was a significant negative correlation between the percentage of granules below 20 microns diameter and the mealiness of the cooked potatoes. He concluded that the degree of mealiness of a cooked potato may be associated with some of the physical properties of the starch. Hadley (34) showed a close connection between the gran­ ule size and the gelatinization temperature. The larger granules appear to swell at a lower temperature than the smaller ones and require less heat for the conversion of dex­ trine. Alsberg (3) pointed out that as potato starch grains get bigger, the ratio of volume (or weight) to surface area gets bigger. Therefore, large grains as they take up water, inevitably swell more rapidly than small grains. Sweetrnan (41) reported no important correlation between size of starch and mealiness, r being +0.330 +0.123. Bar- more (6), Sweetman (41) and Mash (33) demonstrated a direct significant correlation between the content of starch and the mealiness of cooked tuber. 9 jtelataonshiP .of granule size with other fact-oxa.. Whitten- berger and Nutting (49) treating Green Mountain seed potatoes with 63 ppm of either indoleacetic acid or indolbutyric acid found almost no effect on the size of the starch granules in the offspring tubers* According to them this is contrary to Zika and Malcher and Zika (52) who reported that treatment of potato seed piece with indoleacetic acid resulted in a con­ siderably larger average size of the potato starch granules, Whittenberger and Nutting (49) were of the opinion that the size of starch granule was related in general to the size and probably to the age of the tuber. The average smallest granules were obtained from the smallest of the youngest tubers. The largest granules were found in the largest tub­ ers of full maturity. Johnson and Boyle (27) mentioned that the starch grain size was smaller in small tubers than in large ones. East (1&) found that the starch grains were smal­ ler in immature than in mature tubers. Vilikovski (45) stated that dry seasons reduced the size of the starch grains and that potash fertilizer increased the size* Potato Chips Several investigators have presented evidence that the color of potato chips depends mostly on varieties, specific gravity and content of reducing sugars. 10 Variety* Wright and Whiteman (50) and Wright, et al. (51) stated that the quality of potato chips depends largely on the variety of potato used. Stuart (40) and Denny and Thorn­ ton (15} reported that the superiority of the Rural group for the production of good color in potato chips was clearly shown, and that these varieties were low in reducing sugars* Specific gravity* Cochram, et al. (12) claimed that the re­ ducing sugar content was found to vary inversely with specific gravity. Wheeler and Salunkhe (46) emphasized that early planting produced high specific gravity tubers and in turn made light colored chips. Wright and Whiteman (50) and Kunkel, et al* (29) found that the color of potato chips from high specific-gravity potatoes was lighter than that of chips made from low specific-gravity group. Mikuljskil (32) de­ monstrated that ripening of potato tuber is characterised by an increase in the content of dry matter and starch and a de­ crease in the ratio of sucrose to reducing sugars. Reducing: sugar content* Denny and Thornton (14) showed a direct correlation between the amount of reducing sugar in the juice of potato tubers and the extent of browning when chips 'were made from them. Dexter and Salunkhe (16) concluded that the amount of reducing sugars seems to be one of the causes for the formation of the dark brown color of potato chips. Smith (37) also pointed out that the content of re­ ducing sugars determines the color of potato chips and hence the quality of chips. MATERIALS AND METHODS Varieties and Locations In 1955, seventeen varieties of potatoes were grown at five locations in Michigan for the present investigations. The varieties grown were: O —1 Waseca 2. Early Gem 11. la 961-1 3* Dazoc 12. Red LaSoda 4• Osage 13. Cherokee 5. Redburt 14. Sheridan 6. Pungo 15. Rushmore 7. MS 1363 16. Sebago 3. la 803-3 17. Merrimack 9. Redkote 1 1. Irish Cobbler • The five locations together with kind of soil and dates of planting and harvesting were as follows: Date of Soil . ._.JP_lantin£ Date of Harvesting County Town Montcalm Edmore Mineral May 7 Oct. 4 Emmet Levering Mineral May 11 Sept. 21 Bay Bay City Mineral May 5 Sept. 16 Arenac AuGres Muck May 20 Sept. 30 Allegan PIainwell Muck May 9 Sept. 29 11 12 The design at each location was a simple randomized plot with four replications. Each plot was a single 20 foot row. The distance between rows was 34 inches and between plants in a row, ten inches. Sixteen feet of row was harvested for yield determinations. Sampling A fifteen pound sample of U. S. Grade No. 1 tubers from each plot at each location was taken at harvesting time. From each sample, five tubers of approximately the same size were taken and were numbered individually by India Ink to keep the identity for the following tests: 1. Specific gravity. 2. Percentage of starch grains of different sizes. 3. Chip color rating. Specific Gravity tX The specific gravity determinations were made on the individual potato tubers. The weights in air and in water were obtained and the data used in the following formula: Specific Gravity = _________ Wei ght in Air________ Weight in Air - Weight in Water These weights were taken on a modified Hanson - "diet scale", a spring balance of 500 gram capacity. The platform of the balance was removed and replaced by an iron rod to the lower end of which a thin wire, 1/32 inch in diameter was attached. The end of the ware was bent in the shape of a hook. Each potato tuber was placed on the hook for weighing. The 13 balance was supported on a raised, horizontal, five-inch-wide, wooden surface supported on three retort stands for f ree move­ ment of the potato tuber. The position for the "weight in air" reading is shown in Figure 1. To take weight in water, a deep pan of water was so placed that the tuber was completely im­ mersed as shown in Figure 2. The scale was read to. the near­ est half gram* Starch Grain Percentage of starch grain. half* Each numbered tuber was cut in One half was used for determining the percentages of starch grains of various sizes; the other half was used for making chips. From the half-tuber used for starch percentages fine scrapings from inner and outer medulla were made* The scrapings were placed on a slide with a drop of distilled water, and stained with potassium iodide-iodine solution. The slide with the stained material was placed on a ver­ tical projection microscope and the image examined on the ground glass back of a camera. (Figure 3). An ocular with an inserted micrometer was used for measuring the sizes of the starch grains. The ocular micrometer was calibrated with the stage micrometer. One division of ocular micrometer was equal to 12.5 microns. A piece of cardboard with an aperture of two inches by two inches was placed on the ground glass camera view finder to standardize the area observed. The starch grains visible in the 2" by 2" opening were classified into the following four groups. 14 Figure 1. Modified Hanson *diet scale1 a spring balance of 500 gram capacity on a raised horizontal surface supported on retort stands - showing weight of the tuber in air. 15 Figure 2. Modified Hanson ’diet scale1 showing weight of the tuber in water. 16 Figure 3. Projection microscope in vertical position with camera fitted on the top* 17 Group 1 - Large - above 75 microns (Fig* 4) Group 2 - Medium - 75 to 50 microns (Fig. 5) Group 3 - Small - 50 to (Fig. 6) Group 4 - Very small - less than 25 microns 25 microns (Fig. 7) In most instances the entire area under observation was not covered by starch grains. As a result, the total area covered by starch grains was estimated at 100 percent and pro­ portion of this total which was occupied by the starch grains of each of the above four groups of sizes was estimated. This estimated proportion of area is here termed "percentage of starch grain"♦ Five readings from different fields per slide were taken and the average of these was used for each tuber. Percentage volume of starch grain. The volume of starch grain was obtained by multiplying the percentage of starch grain of each size group (a) by the mid-point diameter of granule of the same size (b). The percentage of volume for each group was calculated by using a x b • S(a x b) The percentage volume of starch grain was calculated for Montcalm County in order to see wheth­ er the percentage volume has the same relationship with speci­ fic gravity as the percentage fic gravity* of starch grain had with speci­ These calculations were made with the assumption that all particles of starch have a spherical shape* Density of starch grain* Starch was extracted from two sam­ ples of the Cherokee variety from Montcalm County. The starch was separated into three group sizes, large - above 60 microns Figure 4# Potato starch grains (Magnification X 140) A tuber with an unusually high proportion of large starch grains (50$ Large, 25% Medium 15% Small, 10$ Very Small)# 19 Figure 5. Potato starch grains (Magnification X 140) A tuber with an unusually high proportion of medium starch grains (15$ Large, 45$ Medium, 15$ Small, 20$ Very Small)# 20 ure 6. Potato starch grains (Magnification X 140) A tuber with a high proportion of small starch grains (0$ Large, 0$ Medium, 60$ Small, 40$ Very Small)* 21 Figure 7. Potato starch grains (Magnification X 140) A tuber with a high proportion of very small starch grains (0$ Large, 0$ Medium, 10$ Small, 90$ ?ery Small). 22 medium-60 to 30 microns and small-less than 30 microns. These sizes were verified by examining the starch samples under the microscope. The density of these three different starch sizes from each of the two samples was obtained b3^ the picnometer method. Chip Making and Color Rating The half tuber saved for potato chips was sliced, in a rotating chipper, to a uniform thickness of 3/64 inch to 4/64 inch. Beginning with the cutside of the half tuber, the first four or five slices were discarded, the next slice was saved for the chip color test. Thus twenty slices per variety from each location were rated. All twenty slices of a variety were threaded together. For identification, patterns of holes were punched in the slice from the first tuber and the slice from the twentieth tuber. They were washed in running tap water to remove adhering loose starch grains. They were fried in TPrimexT vegetable oil at a temperature of 3$5° F (196°C). Frying was judged completed when bubbling from chips in the oil stopped. Each chip was rated according to "Proposed Color Refer­ ence Standard" of Coughlin (13) (Figure £). 1- white to 10- dark. Ratings are from Chips falling within the 3 to 5 color range were considered desirable, those rated 1 and 2 too light and those rated 6 to 10 too dark. PROPOSED COLOR REFERENCE STANDARD 24 Computations The readings of five tubers per plot were added and these sums used for calculations. lated, Analyses of variance were calcu­ Linear Correlation Coefficients were obtained between Specific gravity (x) and Percentage of starch grain (y), Specific gravity (x) and chip ratings (z), and Percentage of starch grain (y) and chip ratings (z) By means of covariance the coefficients of correlation between varieties and within varieties were calculated for each county. up. Two-way tables of variety x location were set From these there were obtained by covariance the coeffi­ cients of correlation between varieties and within varieties. Scatter diagrams were made to show the relationship. The three partial correlations, (rxy.z, rxz.y and ryz.x) were calculated by the method suggested by Ezekiel (19)• Correlation coefficients for varieties were calculated between percentage of volume of starch grain sizes and speci­ fic gravity and chip rating. The density of starch grain size readings were examined by the analysis of variance. EXPERIMENTAL RESULTS Samples of fifteen pounds of potato tubers were taken at harvest time from each plot of seventeen varieties replicated four times at five locations. From each fifteen-pound sample five tubers of approximately the same size were taken. The data obtained in these studies are given as the averages of specific gravity, t’he percentages of four groups of starch grains and the chip color rating from these five-tuber samples. Specific Gravity The comparative specific gravities of the different pot­ ato varieties are shown in the data from the individual coun­ ties given in Tables VII to XI. Waseca and Redkote had the lowest specific gravity in two trials each while Merrimack had the highest reading in three counties. The statistical significances of differences exhibited at each location are shown in Table I. All the F-values for "Varieties" were highly significant indicating appreciable varietal differences in specific gravity. The differences between varieties were also significant when the specific gravities from all the five counties were combined (Table I). Early Gem, Redkote and Waseca had the lowest specific gravity (1.056) while Merri­ mack had the highest (1.073)• Table XII. Differences between specific gravity of potato tubers in different locations were partly indicated by the county 26 TABLE I ANALYSIS OF VARIANCE FOR SPECIFIC GRAVITY OF SEVENTEEN POTATO VARIETIES GROWN IN IN FIVE LOCATIONS 1 Source . d.f. . _ Montcalm F .. M.S. Rep. 3 262 Var. 16 1114 Error 43 117 Source 9 Emmet . M.S. F 1.6 65 9.6** 754 5 5 .... Bay M.S. F 0.7 39 7.6** 401 .59 ....... 32 Arenac______ Allegan Td.f.______ ■! . M.S. F _ M.S. F _ 3.3* Rep. 3 971 15.1** 210 Var. 16 660 10.3** 7 0 7 Error ... 43 64 1 1 . ** 0 64 All Locations . M.S. .. J£.... Source Loc. 4 9514 Var. 16 2142 Error 64 2 1 6 44.1** 9 . ** 9 _ * Exceeds 5% level of significance ** Exceeds 1% level of significance 0.5 4•9** 27 averages. These ranged from 1.053 for Bay County to 1.071 for Emmet County (Tables VIII to IX). The average for min­ eral soil trials (Montcalm, Emmet and Bay) was no different from that for the two muck soil trials (Arenac and Allegan)* The magnitude of variation in specific gravity that might occur within a variety was indicated by the F-value for "Replication”• (Table I). At two locations, Arenac and Allegan, there were highly significant differences between replications (Tables X to XI). Using five tuber samples of a variety considerable variations in average specific gravity were observed in most of the varieties. Percentage of Sizes of Starch Grains The starch suspensions exhibited starch grains of many sizes. These sizes were classified into four groups - large, medium, small and very smallf The data on percentages of starch grains are given by size group from tubers of individ­ ual county. Tables VII to XII). Group 1 - large, - above 75 microns. Between varieties, the differences in percentage of large starch grains above 75 microns were highly significant in each of five counties or when all were combined (Table II). Early Gem had no large starch grains at any location, while Osage showed the larg­ est average percentage of large starch grains (Table XII). Waseca had no large grains at two locations. the highest percentage at three locations. Osage produced Pungo?3l#5 in Mont­ calm County, produced the highest single percentage of large starch grains in the entire experiment. TABLE XI ANALYSIS OF VARIANCE FOR PERCENTAGE OF STARCH GRAIN SIZE GROUP 1-LARGE-ABOVE 75 NilCRONS FROM SEVENTEEN POTATO VARIETIES GROWN IN 1955 IN FIVE LOCATIONS Source d_.f_.-_ Rep. 3 192 1.0 Var. 16 2071 10.7** Error as Source Montcalm M.S. F Emmet M.S. F 7.0 0.2- 1312 33.$** 73 3U Arenac ._ .. Allegan M.S. F M.S. F Rep. 3 426 Var. 16 1003 Error US 122 Source d.f. 3. 5* 69 8.2** 1163 1*6 "p 23.3=r .5.0..... . All Locations M.S. . . F— Loc • 4 1761 4.1* Var. 16 5269 12.2*; , « Error 64 * ** 43 5. _ Exceeds 5$ level of significance Exceeds V fo 0.6 1461 15.7** 39. 19A ___ d.f. Bay M.S. F level of significance 29 Osage, rungo, Xa £>03-3 > Cherokee, and Rushmore produced a higher percentage of large starch grains than did Early Gem, Dazoc, Redburt, Waseca, Red LaSoda and Sheridan at each location (Tables VII to XII)* Location had a statistically significant effect on the percentage of large starch grains as shown by the F-value for "Locations”. Average percentage of starch grain at Montcalm was highest, 13*5, while Allegan County was lowest, 7.6 (Table XII). In tubers grown in mineral soil the average percentage of large starch grains was higher than in those grown in muck soils. The variation in percentage of large starch grains in the tubers of a given variety was noticeable. The F-value for "Replication" at Arenac County was significant (Table II). Group 2 - medium between-.? 5.jto....5.Q microns^ Varietal dif­ ferences in the percentage of ne diunj sized starch grains were evident from Tables VII to XI for the various counties. The differences between varieties were highly significant at all locations as indicated by the F-values for "varieties" in Table III. Waseca and Early Gem had the lowest percentage of medium starch grains at two counties each while Osage had the highest reading at three counties. When all counties were combined and averaged, Early Gem (6.4) and Osage (27.5) pro­ duced the minimum and maximum percentages of medium starch grains respectively (Table XII). 30 TABLE III ANALYSIS OF VARIANCE FOR PERCENTAGE OF STARCH GRAIN SIZE GROUP 2-MEDIUM-.75 TO 50 MORONS FROM SEVENTEEN POTATO VARIETIES GROWN IN 195$.IN.FIVE LOCATIONS Source d.f. Montcalm ..__.I1._S_.. F Emmet M.S. F Rep. 3 424 5.7** 29 Var. 16 909 12.3** 628 Error Source - _-43 ... 74 Bav M.S. 5 0.5 11.4** 51 d.f.____ _Arer\aq______ Allegan.... ____________________ F___ JLS,.___ F .. 3 514 6.9** Var. 16 1414 19.0** 236 4.3** 3S4 13.4** Error_____ 43______ Z5___________ 6^______ Source d.f. All Locations M.S*____ 1 . Loc. 4 307 0.9 Var. 16 3397 11.9** Error 0.1 1372 26.7** . ...55... Rep. F .....6.4. ..... . 323 * Exceeds 5$ level of significance ** Exceeds 1fo level of significance 31 Osage, Pungo, la 603-3, la 961, Cherokee and Merrimack gave comparatively higher percentages of medium starch grains when compared to Early Gera, Dazoc, Redburt, Waseca, Red LaSoda and Sheridan at four locations excepting Emmet County or when all the five locations were combined (Figure 10)* The variability in county averages of percentage of med­ ium sized starch grains was not great. The average of mineral soils, 16.3, was no different from that of two muck soils, 18*2 (Table XII). The differences in percentages of starch grains of this group within varieties were indicated to some extent by the F-valuos of "Replications" in Table III. At three locations Montcalm, Arenac and Allegan, there were high­ ly significant differences between replications. Group 3 - Small - Between 50 to 25 microns. The differences in percentage of small starch grains among varieties were ap­ parent from the data of individual counties (Tables VII - XI). These differences were highly significant (Table IV)* Waseca produced the smallest percentage of small starch grains in four counties. There was a wide range in percentages from the lowest, Waseca with 10.3$ in Bay County, to the highest, Cherokee with 27*5$ in Emmet County. Within a variety, there was no great fluctuation between percentages at the five locations. The analysis of variance Table IV did not show significance for "Replications" and "Locations"• 32 TABLE IV ANALYSIS OF VARIANCE FOR PERCENTAGE OF STARCH GRAIN SIZE GROUP 3-SMALL-50 TO 25 MICRONS FROM SEVENTEEN POTATO VARIETIES GROWN IN 1955 IN FIVE LOCATIONS Source d.f. Montcalm Rep. 3 50 Var. 16 209 Error 48 . d.f. ... 1.0 ... Bay M.S. F 0.2 5 4.0** F 140 6.7** 21 53 .Arenac F M.S. . Allegan F A Rep. 3 101 2.8 22 1.2 Var. 16 162 4.5** 37 4.8*:Y* Error LB .. „ J 6 Source d.f. _.Ifi.. All Locations. ... M.S. _ F . Lo c. 4 286 1.9 Var. 16 272 1.8* Error 64 151.. * Exceeds ** Exceeds 15 277 .36 CO le-5 Source Emmet F . 5°/o level of significance ifo level of significance 0.4 7.7** 33 Ij£QJA&Jj^_.y.Qry Varietal differ­ ences in the percentage of very small sized starch grains are snown in the data from the individual counties or all combined, Tables VII to XII. Osage tubers had the lowest percentage of very small grains in three counties. The statistical differences between varieties are shown in Table V. The F-values for "Var­ ieties" at all five locations individually or combined were highly significant, indicating large differences between vari­ eties in percentage of very small starch grains. There were wide differences between minimum percentage, Osage, 21.3% at Emmet, and maximum, Waseca, 36.0% at Bay County. Osage, Pungo, la 303-3, la 961-1, Cherokee, Rushmore and Merrimack were low in percentage of very small starch grains as compared to Early Gem, Dazoc, Redburt, Waseca, Red LaSoda and Sheridan which have higher percentages as seen from the combined averages of all locations (Table XII). The differences due to location on the percentage of very small starch grains were not significant. These range from an average of 47.2% for Montcalm County to an average of 33.9% for Allegan County (Table XII). Variation within a variety in the percentage of very small starch grains was evi­ dent between replications as indicated by the F-values for "Replications" (Table V). At two muck soil trials, Arenac and Allegan, there were highly significant differences between replications. 34 TABLE V ANALYSIS OF VARIANCE FOR PERCENTAGE OF STARCH Grain SIZE GROUP 4-VERY SMALLLESS THAN 25 MICRONS FROM SEVENTEEN POTATO VARIETIES GROWN IN 1955 IN FIVE LOCATIONS Source d.f. Montcalm __ M._S_*_ _ F Rep. 3 304 0.6 Var. 16 5672 11.2** Error 4$ Source d.f. ... 5QJL. ..... ___ Arenac M.S. F ._Emmet M.S. F 55 Bav M.S. F 0.3 14 293^ 17.1** 172 Rep. 3 3344 12.2** 90$ 4.3** Var. 16 5926 21.6** 3557 18.$** Error 4$ 274 Source d.f. 7095 32.6** 21$ Allegan___ M.S. F 190 All, L9.catiQ.n3 F M.S.. .. Loc. 4 2316 1.7 Var. 16 19676 14.3** Error 64 137$ ❖ Exceeds 5% level of significance ** Exceeds Vfo level of significance 0.1 35 Chip Color Rating There were marked varietal differences in chip color rat­ ing of tubers as seen from the data of all five counties con­ sidered individually or combined {Tables VII - XII). These differences were highly significant as is evident from F-values for "varieties” (Table VI). Osage produced the lightest color­ ed chips in three counties while Early Gem made the darkest chips in two counties. When comparing the average of all counties Osage was rated 3.7, the best, and Red LaSoda rated 6.3, the poorest, in chip color (Table XII). The effect that location had in influencing chip color rating was indicated by the county averages. for Bay County to 5.4 for Montcalm County. These range 4.7 The differences between locations were highly significant (Table VI) although comparatively small. The average chip color from the two muck soil trials was lighter (4.8) than the three mineral soil trials (5.1). The magnitude of differences of chip color rating between replications was not very great as may be seen from F-values for "Replications”. These differences were not statistically significant (Table VI). The data from Tables VI - XII indicate that in Michigan the varieties could be classified as generally lignt or dark color for chip production as judged by chip color rating of twenty tubers for each variety from five locations. 36 TABLE VI ANALYSIS OF VARIANCE FOR CLIP COLOR RATING FROM SEVENTEEN POTATO VARIETIES GROWN IN 1955 *"1VE LOCATIONS Source d.f. Rep. 3 Var. 16 Error AS Source d.f. Rep. 3 Var. 16 A# __ _J.rrpr_ . Source Montcalm _____M.S_. _.. F 0.7 Emmet F _M.S.. 0.3 0.7 0.3 31.4 12.6** 9.6 4.5** ____ 2.1 2.5 Arenac M.S. F.._ 1.0 17.5 11.9** ... 1.5...... 1.0 0.3 15.1 11.5** _ 1*1_ All JLQcation^.. _ M.S. ....F ___ d.f. Loc. 4 39 7.0** Var. 16 71 12.7** Error 6A . 1.3 0.7 20.1 11.2** 1.-3.. Allesan F M.S., 0.7 Bay M.S. F 5.6,.. * Exceeds 5% level of significance ** Exceeds 1% level of significance 37 Light colored potato cnips were obtained Iron Irish. Gob­ bler, Osage, la 603-3, la 961-1, Cherokee, Eushraore, Sebago and Merrimack while Early Gem, Redburt, M.S. 1363, Redkote, Vaseca, Red LaSoda and Sheridan produced undesirably dark chips (Tables VII - XII). Percentages of Volume of Starch Grain Sizes The data for the four percentages of starch grain sizes for all varieties for the Montcalm County trial were converted into percentages of volume of starch grain sizes, and were given in Table XIII. The means of the four sizes were in the descending order of medium (31*0 ), large (26.3 ) small (22.3) and very small (20.4). Density of Starch Grain Sizes Three different sizes of starch grains separated from two Cherokee potato tubers showed that their density or specific gravity varied according to size (Table XIV). The differences in density due to these sizes were highly significant (Table XV). From Table XIV it is evident that as the size of potato starch grain increased, the density also increased. The aver­ age density of the different starch sizes was in the descend­ ing order of Large - above 60 microns, Medium - 60 to 30 mi­ crons, and Small - less than 30 microns, the densities being 1.579, 1.356 and 1.531, respectively. 38 TABLE VII AVERAGE SPECIFIC GRAVITY (x ), PERCENTAGES OF FOUR STARCH GRAIN SIZES (y) AND CHIP RATINGS (z) OF SEVENTEEN POTATO VARIETIES GROWN IN MONTCALM COUNTY IN 1955, TOGETHER WITH THEIR COEFFICIENTS OF CORRELATION No* Varieties Specific Gravity tyl Percentages of Starch Grain Sizes (v) Chip Large - Medium Small V.Small Rating Above 75 75-50 50-25 Below 25 microns microns microns microns 1 Irish Cobbler 1.062 10.0 26.0 21.£ 34.3 5.0 2 Early Gem 1.056 0.0 11.5 21.3 67.3 6.1 3 Dazoc 1.053 4.8 16.3 25.0 54.0 5.7 4 Osage 1.059 24.£ 25.5 19.£ 27.0 3.2 5 Redburt 1.052 1.0 7.£ 16.£ 74.5 6.8 6 Pungo 1. 06a 31.5 22.3 17.3 29.0 6.0 7 M.S. 1363 1.054 11.0 22.5 20.0 46.5 6.9 £ la £03-3 1.061 24.3 26.0 21.5 25.3 4.0 9 Redkote 1.055 16.£ 19.3 17.5 46.5 5.9 10 Waseca 1.047 0.0 6.3 13.£ £0.0 7.0 li la 961-1 1.061 19.0 25.0 22 .£ 33.3 4.0 12 Red LaSoda 1.059 2.0 20.3 25.£ 52.0 7.3 13 Cherokee 1.070 23.3 24.3 21.5 31.0 3.6 14 Sheridan 1.057 2.0 12.0 19.8 66.3 6.0 15 Rushmore 1.054 21.3 17.£ 17.3 43.8 5.2 16 Sebago 1.059 15.0 14.0 19.3 51.8 4.8 1.0-72. JL5u_l JD-JL 24. £ -3-6.0. U.LL 20. JL A1*jL XL Merrimack . A v e r a g e.,, XL*± +0.623** +0.551* -0,678** -0.702** -0.656** -0.259 +0.732** +0.525* rxy ryz rxz_ * Exceeds 5fo level of significance ** Exceeds 1% level of significance -0.571* 39 TABLE VIII AVERAGE SPECIFIC GRa Vi TY (x ) PERCENTAGES OF FuUii STARCH GRa IN SIZi^S (y) AND CHIP RATINGS (z) OF SEVENTEEN POTATO VAk IET-Lh S GROWN IN EMMET COUNTY IN 1955. TOGETHER WITH THEIR COEFF1CINNT S OF CORRELATION No. Varieties Specific Gravity Tx T Percentages of Starch Grain Sizes (v)______ Chip Large - Medium Small V.Small Rating <7! Above 75 75-50 50-25 Below 25 tz microns microns microns microns 1 Irish Cobbler 1.079 7.3 13.0 25.O 49.3 4.3 2 Early Gem I.O64 0.0 5.5 26.3 67.3 5.6 3 Dazoc 1.071 3.3 14.3 25.5 56.5 4.6 4 Osage 1.076 27.5 23.0 20.3 24.3 4.0 5 Redburt 1.063 0.5 15.3 25.0 53.3 5.3 1.068 14.5 20.3 21.3 44.0 6.0 6 Pungo 7 M.S. 1363 1.070 9.0 13.5 19.3 52.3 5.1 3 la 803-3 1.083 19.5 23.2 20.2 37.5 3.4 9 Redkote 1.067 17.3 23.3 21.3 37.3 5.2 10 Waseca 1.061 0.0 7.0 13.5 74.5 4.7 11 la 961-1 1.069 1.3 13.0 24.0 61.3 4.0 12 Red LaSoda 1.068 4.5 16.0 21.5 53.0 5.7 13 Cherokee 1.074 1.3 13.3 27.5 57.5 4.5 14 Sheridan 1.080 4.3 14.3 22.5 53.0 4.3 15 Rushmore 1.073 13.0 13.0 20.0 44 •0 4.2 16 Sebago 1.066 6.3 16.0 22.0 55.3 4.0 1Z. Mprri ttiaok 1.071 7.5 19.3 21*3 Average xy yz xz * 1.0.71.. ji-YL +0.443 - 0.296 , . 51.0- 4.6 16..3 ..,.22*5-.... -52.2,.- ......... A17 .. . ... ■0.532* +0.505* - 0.030 -0.199 -0.159 + 0.261 -0.5145 Exceeds 5% level of significance 40 TABLE IX AVERAGE SBEGlFIG GRAVITY (x ), PEACESTAGES OF FOUR STARCH GitAIL SIRES (y) AND CHIP RATINGS (z) OF SEVENTEEN POTATO VARIETIES GROWN IN BAY COUNTY IN 1955, TOGETHER WITH THEIR COEFFICIENTS GF CORRELATION No. Varieties Specific Gravity »xT Percentages of Starch Grain..Sizes (v) Chip Large - Medium Small V.Small Rating Above 75 75-50 50-25 Below 25 'zT microns microns microns microns 1 Irish Cobbler 1.061 7.0 17.0 17.a 58.3 4.7 2 Early Gem 1.052 0.0 5.a 14.3 80.0 6.9 3 Dazoc 1.059 1.0 10. a 22. a 65.5 4.7 4 Osage 1.055 24.3 2a.a 22.3 24.8 3.8 5 Redburt 1.057 0.8 16.a 21.a 60.8 6.2 6 Pungo 1.062 19.0 25.3 22.5 33.3 4*4 7 M.S. 1363 1.057 17. a 27.5 24.0 30.8 5.3 a la £03-3 1.061 20.8 24.0 23.a 31.5 4.3 9 Redkote 1.049 7.5 20.0 24.0 48.5 5.3 10 Waseca 1.051 0.3 3.0 10.a 86.0 6.8 11 la 961-1 1.065 12.0 25.5 25.3 37.3 3.7 12 Red LaSoda 1.057 0.0 5.0 21.a 73.3 6.5 13 Cherokee 1.066 21.2 23.3 23.0 32.5 4.5 14 Sheridan 1.059 2.0 17.0 21. a 59.3 5.6 15 Rushmore 1.057 9.5 21.3 21.3 48.0 5.1 16 Sebago 1.053 10.a 26.0 22.5 40.8 5.4 Merrimack 1.060 17.1 25.5 . 22^8 34^.5. 4.4— ... 1.05# Average_ V'-+ -■ rxy ryz rxz 21*1_ 49.6 .. ..5.1 +0.54a* -0.479* +0.435 +0.437 - 0 .7 7 6 * * -0 .7 9 4 ** -0.666* * +0.815* -0.639** 10.1 * Exceeds 5fo level of significance ** Exceeds 1$ level of significance 41 table x AVERAGE SPECIFIC GRAVITY (x ), PERCENTAGES OF FOUR STARCH GRAIN SIZES (y), AND CHIP RATINGS (z) OF SEVENTEEN POTATO VARIETIES GROWN IN aRENaC COUNTY IN 1 9 5 5 , TOGETHER WITH THEIR COEFFICIENTS OF CORRELATION No* Varieties Specific Gravity ,x f Percentages of --- vStarch Grain Si 7fl.q (y) Large — Medium Small Chip V.Small Above 75 75-50 50-25 Below 25 Rating microns microns microns microns Tz 1 1 Irish Cobbler 1.060 6.8 19.3 21.5 52.5 4.1 2 Early Gera 1.051 0.0 3.3 15.3 81.5 5.9 3 Dazoc I.O64 11.d 16.0 19.6 50.5 4.7 4 Osage 1.066 14.5 26.0 23.8 33.8 3.7 5 Redburt 1.054 0.5 4.3 14.0 81.3 5.4 6 Pungo 1.060 19.0 24.5 21.5 35.0 3.9 7 M.S. 1363 1.056 13.3 25.5 21.3 40.0 6.1 8 la 803-3 1.065 19.5 26.5 23.0 29.0 3.9 9 Redkote 1.051 7.5 13.5 20.3 58.8 5.4 10 Waseca 1.059 1.3 13.0 23.0 62.8 4.1 11 la 961-1 1.066 9.0 24.6 22.0 44.3 3.4 12 Red LaSoda 1.052 0.0 4.6 16.3 79.0 6.3 13 Cherokee 1.065 12.3 27.0 23.5 27.3 3.9 14 Sheridan 1.060 0.0 14.6 19.5 65.8 4.9 15 Rushmore 1.061 16.5 24.5 21.5 30.5 3.7 16 Sebago 1.062 16.3 21.5 18.8 43.5 3.9 17 Mprrimack 1.069 11*0. 20^6 .£Q..5_ ..JfeZiiL- &VPiT'flP*0 1.060 rxy ryz rxz 4*5. ...4.6. .. 18.6 ._5J=*iL ,I£Q*.3 9. 5_._ +0.672*: * -0.723** +o. 576* +0.768** -0.5#9* -0.723** -0.716*=if- +0.704^°^ -0.769** * Exceeds 5% level of significance ** Exceeds 1% level of significance 42 TABLE XI AVERAGE SPECIFIC GRAVITY (x ), PERCENTAGES OF FOUR STARCH GRAIN SIZES (y) AND CHIP RATINGS (z ) OF SEVENTEEN POTATO VARIETIES GROAN AT AtLEGAN COUNTY IN 1955, TOGETHER WITH THEIR COEFFICIENTS OF CORRELATION No. Varieties Specific Gravity »xf Percentages of Stzar_o.h .-feaIn JHaejL.Cx)_______ Chip Large - Medium Small V.Small Above 75 75-50 50-25 Below 25 Rating microns microns microns microns T-Z-T 1 Irish Cobbler 1.071 7.$ 22.0 21.3 49.0 4*4 2 Early Gem 1.059 0.0 6.0 23.0 71.0 6.0 3 Dazoc 1.062 1.$ 13.3 17.0 6$.0 5.7 4 Osage 1.070 26.3 24.0 19.3 30.5 3.7 5 Redburt 1.064 0.0 4.5 21.3 74.3 5.7 6 Pungo 1.064 $.0 19.$ 19.$ 52.5 4.9 7 M.S. 1363 1.062 5.3 1$.0 22.0 54.3 6.0 3 la $03-3 1.060 6.0 20.3 21.3 52.0 4.4 9 Redkote 1*05$ 5.0 1B.0 20.0 57.0 4.9 10 Waseca 1.060 1.3 10.0 16.5 72.3 5.$ 11 la 961-1 1.063 6.5 24.8 23.3 45.5 3.9 12 Red LaSoda I.O64 2.3 10 .$ 20.5 66.5 5.9 13 Cherokee 1.071 15.0 25.3 24.0 35.$ 4.6 14 Sheridan 1.063 3.3 17.3 22.3 57.3 5.5 15 Rushmore 1.072 24.0 22.5 1$.5 35.0 3.9 16 Sebago 1.067 9.$ 1$.5 21.0 50.$ 4.0 XL Merrimack,------1«0£L 12LL Averages. +0.55$* Xxy +0.599* 20.$ +0.046 -0.725** -0.323** -0.045 ryz -_Ll$ .21^ XZ*3 L rX2_ * Exceeds 5°Jo level of significance ** Exceeds 1% level of significance 53.^9, L mSL -0.635* +0.$45** -0.626: 43 TABLE XII AVERAGE SPECIFIC GRAVITY (x ), PERCENTAGES OF FOUR STARCH GRAIN SIZES (y) AND CHIP RATINGS (z) OF SEVENTEEN VARIETIES COMBINED FROM FIVE LOCATIONS GROWN IN 1955. TOGETHER WITH THEIR COEFFICIENTS OF CORRELATION Varieties Specific Gravity 'x* 1. Irish Cobbler 1.067 9.4 20.5 21.5 46.6 4*6 2. Early Gem 1.056 0.0 6.4 20.1 73.5 6.1 3. Dazoc 1.063 4.6 14.5 22.0 56.9 5.0 4. Osage 1.066 23.5 27.5 21.1 26.1 3.7 5. Redburt 1.058 0.6 9.6 19.6 69.9 5.9 6. Pungo 1.065 IS.4 22.4 20.5 36.6 5.0 7. M.S. 1363 1.060 11.3 22.4 21.4 44.9 5.9 a. la 303-3 1.066 16.0 24.4 22.1 35.7 4.0 9. Redkote 1.056 10.a 16.9 20.6 49.6 5.3 10. Waseca 1.056 0.6 7.9 16.5 75.1 5.7 11. la 961-1 1.065 9.7 22.6 23.5 44.3 3.6 12. Red LaSoda 1.060 l.a 11.4 21.2 65.6 6.3 13. Cherokee 1.069 14.6 22.7 23.9 36.6 4.2 14. Sheridan 1.064 2.4 15.2 21.2 61.3 5.4 15. Rudamore 1.063 IB.3 20.6 19.7 41.3 4.4 16. Sebago 1.063 11.7 19.2 20.7 46.4 4.4 1.073 11.7 22^ „ 42.9_ 1.063 9.a No. Mprrimack 17.-t■ J cAw-J.* ...— Average --f kY.VA^nVi.. Percentages of . . Starch Grain Sizes fv) Large - Medium Small Chip V.Small 50-25 Above 75 75-50 Below 25 Rating microns microns microns microns 1z1 ..,2,3^2.. ... 4*3. .16.2 _ _JLLLL_..5.Q.& . +0.719** +0.679* * -0.692* rxy +0.566* ryz -0.756** -0.602** -0.502*: +0.799** -0.744*; rxz * ** Exceeds 5$ level of significance Exceeds V fo level of significance 44 TABLE XIII AVERAGE SPECIFIC GRAVITY (x ), CALCULATED PERCENTAGES OF FOUR VOLUMES OF STARCH GRAINS (y) AND CHIP RATING (z) OF SEVENTEEN POTATO VARIETIES GROWN IN MONTCALM COUNTY IN 1955, TOGETHER WITH THEIR COEFFICIENTS OF CORRELATION No, Varieites Specific Gravity fx f Percentages of Starch .drain .Siaaa„■(y.) Large - Medium Small V.Small Chip Above 75 75-50 50-25 Below 25 Rating microns microns microns microns TzT 1 Irish Cobbler 1 . 0 6 2 34 37 19 1 0 5.0 2 Early Gem 1 . 0 5 6 0 30 34 36 6 . 1 3 Dazoc 1 . 0 5 8 1 0 32 33 25 5.7 4 Osage 1.059 4 2 36 15 7 3.2 5 Redburt 1 . 0 5 2 4 2 0 2 8 6 Pungo 1 . 0 6 8 53 27 1 7 M.S. 1363 1.054 25 8 la 803-3 1 9 Redkote 10 Waseca 4 8 6 . 8 2 8 6 . 0 38 2 1 1 6 43 33 17 7 4.0 1.055 34 30 17 19 5.9 1.047 0 19 2 6 55 7.0 37 35 19 9 4.0 5 41 32 31 1 . 0 6 1 6.9 11 la 12 Red LaSoda 1.059 13 Cherokee I 14 Sheridan 1.057 7 29 30 34 6 . 0 15 Rushmore 1.054 43 27 1 6 14 5.2 16 Sebago 1.059 36 25 2 0 19 4.8 XL Merrimack 1.07_9____ 32 35 2 2 1 1 9 6 1 - 1 Average 1 . 0 6 1 . 0 7 0 4 2 1.056---- 2-6*3 31.0 +0.534* y» yz -0.689** -0 .2 6 6 9 8 7.3 3.6 .. . 4.3 _22.3.. .20.4_____ U L — -0.325 -0.663** +0 .564 * +0.681** -0.571* rxz ^ 2 2 Exceeds 5$ level of significance 3! ij{c Exceeds 1$» level of significance TABLE XIV DENSITY OF DIFFERENT POTATO STARCH GRAIN SIZES FROM VARIETY CHEROKEE GROWN AT MONTCALM COUNTY IN 1955 Starch Grain Sizes Sample No. Specific Gravity of tuber 1 2 Average Large Above 60 microns Medium 60 to 30 microns 1.034 1*579 1.553 1.531 1.032 1.579 1.555 1.532 1.033 1.579 1.557 1.531 Small Below 30 microns table x v ANALYSIS OF VARIANCE FOR DENSITY OF POTATO STARCH GRa IN SIZES d.f. Source M.S. Total 5 0.000454 Between Sizes 2 0.001130 Within Sizes 3 0.000003 * Exceeds 1% level of significance tp 1 376** 46 Rela.t-ion.ship of Percentage of Sizes of Starch Grains To Specific Gravity £lTqujp_1_ ■"_..large - above 7S rni The between variety correlation for percentage of large starch grains versus specific gravity was positive at each county, but was statis­ tically significant only at Montcalm, Emmet and Allegan Counties (Table XVI), The variety averages over all loca­ tions (Table XII) when correlated also gave a positive signifi­ cant correlation, r = +0,566, This means that as the per­ centage of large starch grains increased from one variety to another, the specific gravity also increased (Figure 9). The correlation within varieties was highly significant and positive between percentage of large starch grains and specific gravity in all five locations. The highest correla­ tion was +0,949 at Emmet County and the lowest was +0.65$ at Arenac County (Table XVII). When all locations were put together in a two-way table the correlation within varieties was also highly significant and positive, r being + .523. ftrrmp 2 - medium - between 75, to ,5Q_.mi crons.. correlation between percentage The between variety of medium starch grains and specific gravity was positive at all locations and also sta­ tistically significant, excepting Bay County. The variety averages over all locations had a highly significant correla­ tion, r +0.719 (Table XVI). This may be seen in Figure 10. 47 Montcalm Emmet • 1.030 • •• • 1.060 __ •• • •• • •• •• ' 1 • • • » 1.040 Bay Arenac Specific Gravity 1.080 • • 1.060 1# • • •• • •• • • 1 • • » • • • * • * • • 1.040 Allegan All Counties Combined • 1.080 •• • • * %>••• 1.060 f .* 0 10 20 30 0 • • • ■ 10 * 1. 20 * 30 Percentage of Large Starch Grains Figure 9: Scatter diagrams of variety means between percentage of large starch grains, above 75 microns size, and specific gravity obtained from potato tubers grov/n at five counties in Michigan, 1955 crop. 43 Montcalm Emmet • 1.030 • • • • * • 1.060 • • • * • 1.040 Bay Arenac • • 1.060 • • • • • . • • • . •% 2 .. • .* ••% t • a .*• • • 1.040 Allegan All Counties Combined • • • • * • • . • . • • % 1 . 1.060 \ • 1.030 .. •• • * • • • —r — Specific Gravity 1.030 1.040 0 10 20 0 10 20 30 Percentage of Medium Starch Grains Figure 10 Scatter diagrams of variety means between percent,age of medium starch grains, between 75 to 50 microns size, and specific gravity obtained from potato tubers arown at five counties in Michigan, 1955 crop. 49 The correlation within varieties between percentage of medium starch grains and specific gravity was positive and highly significant at all locations, r ranging from +0.546 at Emmet County to +0.622 at Montcalm County (Table XVII). The correlation within varieties from the two-way table of variety x location also showed a highly significant and posi­ tive correlation, r +0.766 (Table XVII). Group 3 - small - between 50 to 25 microns. The between variety correlation for percentage of small starch grains versus specific gravity was positive and statistically signi­ ficant at three counties, Montcalm, Bay and Arenac (Table XVI and Figure 11). At the other two counties, Emmet and Allegan, they were not significantly different from zero. This shows that at three locations specific gravity increased with the percentage of small starch grains. The coefficient was posi­ tive and highly significant, r +0.679, when the variety aver­ ages over all counties were correlated (Table XII). The correlation within varieties was positive at all locations and significant at Bay, Arenac and Allegan Counties. (Table XVII) Group L - very small - less than 25 microns.. The percentage of very small starch grains and specific gravity were negative­ ly correlated between varieties at all the five locations, individually or combined. The coefficients of correlation wore statistically significant (Table XVI). This means that as the percentage of very small starch grains increased the specific gravity decreased (Figure 12). 50 Montcalm Emmet 1.030 1.060 •• •• f 1.040 Bay Arenac Specific Gravity 1.030 •h * •• 1.060 •• J T - 1*040 All Counties Combined Allegan 1.080 ••••• /I** .c 1.060 1.040 15 25 5 15 25 Percentage of Small Starch Grains Figure 11: Scatter diagrams of variety means between per­ centage of small starch grains, between 50 to 25 microns size, and specific gravity obtained from potato tubers grown at five counties in Michigan, 1955 crop. 51 Montcalm 1.030 Emmet 1 • • ' • » - • • 1 . 0 6 0 # • •• • # • • •• * • • • • - 1.04C Bay Allegan • • •• • • • 1.06C — Specific Gravity 1.03C — - •% • • • • ## • • • • ••• • . ft # •• • « • 1.04C All Counties Combined Arenac 1.03C — • • • • • 1.06C -- M- • • • ^9 • •• • • •• • • f • • • # •• • A •• I.OZlC 4 0 55 70 25 40 55 7 0 Percentage of Very Small Starch Grains Figure 12: Scatter diagrams of variety means between percentage of very small starch grains, less than 25 microns size, and specific gravity obtained from potato tubers grown at five counties in Michigan, 1955 crop. 52 The within varieties correlations between percentage of very small starch grains and specific gravity at all counties were negative, strong (all greater than -0.310) and highly significant. The correlation within varieties from the two- way table of variety x location was also highly negatively correlated, r = -0.569 (Table XVII). Relationship of Percentage of Sizes of Starch Grains to Chip Color Rating Group. 1 - large - above 75 microns. The between variety correlations between the percentage of large starch grains and chip rating were negative at all counties, individually and combined and were statistically significant at all but Emmet County (Table XVI and Figure 13). Thus varieties with a large percentage of large starch grains tended to produce light colored chips. When considering the within variety correlation the coefficient was also negative but was signi­ ficant at only three counties, Montcalm, Bay and Allegan. The correlation within varieties from the two-way table of variety x location was significant and negative between the two factors. (Table XVII). Group 2 - medium - between 75 t.O-5-Q. All individual counties, except Emmet, showed negative and highly significant variety correlations between percentage of medium starch grains and chip rating (Table XVI, figure 14)• The coirela­ tions within varieties were negative and significant only at Montcalm and Bay County, r — —0.647 and -0.531* respectively. 53 TABLE XVI COEFFICIENTS OF CORRELATION FOR VARIETIES BETWEEN SPECIFIC GRAVITY (x) AND PERCENTAGE OF STARCH. GRAINS (y) , BETWEEN PERCENTAGE OF STARCH GRAINS (y) AND CHIP RATING (2) AND BETWEEN -SPECIFIC GRAVITY (x) AND CHIP RATING (z) BY LOCATIONS AND ALL LOCATIuNS COMBINED Starch Grain Size r Group 1 - Large xy Above 75 microns yz All 1 Montcalm Emmet Bay Arenac Allegan Locations Table 7 Table 6 Table 9 Table 10 Table 11 Table 12 +0.525* +0.443 -0.702## -0.296 +0.435 +0.576* -0.776**-0.569* +0.556* +0.566* -0.725** -0.756** Group 2-Medium75 to 50 microns xy yz +0 #623** +0.505# -0.437 +0.766** +0.599* +0.719** -0.656## -0.199 -0•794**—0•723** -0.828** -0.802** Group 3- Small 50 to 25 microns xy yz +0.551* -0.259 Group 4-V.Small Below 25 microns xy yz -0.676## -0.532# -0.479* -0.723** -0.635** -0.692** +0.732## +0.261 +0.815**+0.704** +0.845** +0.799** Entire tuber xz -0.571* * ** 1 -0.030 -0.159 +0.546* +0.672** +0.046 -0•666**—0•716** -0.045 +0.679** -0.502* -0.514* -0 .639**-0 •789** -0.626** -0.744** Exceeds 5% level of significance Exceeds 1% level of significance The coefficients were obtained fromthe two-way of variety x location rather thanfrom averages individual location correlations# tables of the 54 7.C • wontcalm Bmmet • • • 5.0 1• • • • • • • • • • • • • • • • • • • • Rating • Bay \ ! * • j Arenac i • ft Color • 5.0 • • • ••• Chip .. » • • • . • • • ••• : _ 1 7.0 • ... Allegan i ;. • > ___ All Counties Comb i n e d • • V \ • • 5.0 ---# ! i ~ • • . • • • • * • • • • • • • 3.0 0 10 20 30 0 10 • 20 30 Percentage of Large Starch Grains Figure 13: Scatter diagrams of variety means between percentage of large starch grains and chip color rating obtained from potato tubers grown at five counties in Michigan, 1955 crop. 55 7. 0 Montcalm! • ! • • • 5.0 Emmet • • • • • A W • ---- • . • • • • • • a •• • • # • • • 3.0 Hay Areriad • • • A • • 5.0 • — • • J.u f 7.0 _Allegan ■ • • * • • • •• • • • o 20 • • • • • • • • • • • • Counties Combined • • • • • • All • • • t j 10 • * • i 5.0 3.0 • •• • • ra Chip Color Rating 7.0 • • • • •• • ••• • •••• 0 10 20 • 30 Percentage of Medium Starch Grains Figure 14: Scatter diagrams of variety means between percentage of medium starch grains and chip color rating obtained from potato tubers grown at five counties in Michigan, 1955 crop. 56 Tli© correlation within varieties from the two—way table of variety x location between percent medium starch size and chip rating was negative and significant (Table XII). 3— -— small - between .50 to. _25 microns. . The between variety correlation for percentage of small starch grains versus chip color was negative and highly significant at Bay and Arenac Counties (Table XVI). The combined averages of all the counties also gave a negative significant correlation coefficient, -0.502 (Table XVI). correlation within varieties. There was no significant (Table XVII) As the percentages of large (above 75 microns), medium (between 75 to 50 microns) and small (between 50 to 25 mi­ crons) , sizes of starch grains increased in the potato tuber, the lighter were the chips as seen from chip color ratings (Figure 13 to 15)* Group L - very small - less. .than. 2 5 microns... The between variety and within variety correlations between percentage of very small starch grains and chip rating showed positive highly significant correlation at all locations except Emmet County, where it was positive but not significant. (Tables XVI - XVII, Figure 16). Those varieties -which had higher sums of percentages of starch grains above 25 microns, naturally had the lower per­ centage of very small starch grains - below 25 microns - 57 7-0 Montcalm Emmet •• • 5.0 •. • • • 3.0 Chip Color Rating 7.0 Bay Arenac 5.0 • • • • •• 3.0 7.0 All Counties Combined Allegan • •• •• • •• •• 5.0 •• • • • 3.0 15 15 25 Percentage of Small Starch Grains Figure 15: Scatter diagrams of variety means between per­ centage of small starch grains and chip color rating obtained fio m potato tubers grown at five counties in Michigan, 1955 crop. 58 . M o n t c a l1m 7 * • _ ! hmmet •• I i • • • • • 5. . • -• • i • * v • • • • Bay Allegan 7. Chip Color Rating • * • 3. 1 • « '• • * • • 5. • • • .. • • • > » 3. 7. • • • •• • • • i • All Coun t i e s C o m b i n e d Arenac • • 5. ■' " • • • • • •• • • • • • • • •• • • • • • • • • • • • • • 3. 25 40 55 70 25 40 55 70 Percentage of Very Small Starch Grains Figure 16: Scatter diagrams of variety means between percentage of very small starch grains and chip color rating obtained from potato tubers grown at five counties in Michigan, 1955 crop* 59 and were lighter in chip color (Table VII to XII). These varieties, which were lower in percentages of the three large sizes of starch grains had higher percentages of very small starch grains and were darker in chip color (Figures 13 to 16). Relationship Of Specific Gravity To Chip Rating The between variety correlations for specific gravity versus chip color rating were negative and statistically significant at each of five counties or when all were com­ bined (Table XVI). From examination of Figure 17 it may be seen that as the specific gravity of a tuber increased, the chips became lighter in color, irrespective of location. The correlations within varieties at all counties were negative and significant. The correlation within varieties from the two-way table of variety x location between specific gravity and chip rating was -0.475 and highly significant (Table XVII). Relationship Of Percentage Of Volume Of Starch Grain Sizes To Specific Gravity And Chip Rating From the variety correlation between volume of different starch grain sizes and specific gravity, it was determined that the percentages of volume of large and medium starch grains have positive and significant correlations (Table XIII). The other two sizes - small and very small - had negative correlations and only that for very small starch grains was 60 TABLE XVII COEFFICIENTS OF .CQBaELATIQM WITHIN VAHIETIES.HETWEEN SPECIFIC GAhVITI .(x) AND PERCENTAGE OF STARCH GraINS (y) bbltf'iiEEH PiiiAOAbTAGE OF STARCH GRalNS (y) AND CHIP RATING (2) AND BETWEEN SPECIFIC GRAVITY (x ) AND CHIP RATING (z) BY LOCATIONS AND nLL LOCATIONS COMBINED Starch Grain Size r Group 1-Large Above 75 microns xy yz +0.683** +0.949***0.754** +0 .658** +0.671** +0.523** -0.563** -0.257 -0.312* -0.174 -0.313* -0.282* Group 2-Medium 75 to 50 microns xy yz +0.822** +0.54&**+0.573** +0 .632** +0.725** +0.766** -0.260* -0.647** -0.258 -0.531** -0.058 -0.079 Group 3-Small 50 to 25 microns xy yz +0.273 -0.213 Group 4-V.Small Below 25 microns xy yz -0 .-810** -0.812**-0.852**-0.878** -0.872** -0.569** +0.911** +0.266 +0.62 3** +0.29 8* +0 .508** +0.391** xz -0.720** -0.332* -0.455**=-0.392** -0.403** -0.475** Entire tuber * ** 1 Montcalm Emmet +0.243 -0.053 Bav Arenac +0.443** +0.302* +0.109 -0.134 Allegan All1 Locations +0.388** +0.233 -0.051 -0.311* Exceeds 5%level of significance Exceeds 1% level of significance The coefficientswere obtained fromthe two-way of variety x location rather thanfrom averages individual location correlations* tables of the 61 Montcalm | i • 5 Emmet ' | •V j >. --- • • • • • • • • •• M ♦ • •• • • Color Rating • Bay •• Arenac • • # • • • • •• _________ • •• ...... # • Chip • • • •• * • • Allegan All Counties Combined • V.• — - V : • « • • : •••• • • *--------- 1 1 i ■■ ,-i«------, ---1 1,040 1.060 l.Q&Q 1.040 . •• • • •• i— " ' -- 1.060 1.03Q Specific Gravity Figure 17: Scatter diagrams of variety means between chip color rating and specific gravity obtained from potato tubers grown at five counties in Michigan, 1955 crop. 62 Group 1 - Large Group 2 - Medium 1,080 | • • I } Specific Gravity 1,060 • • • . •• _________ ••• * • + » 1,040 Group 3 - iSmall 1.080 :• i j I • ••• ... ••• •i • • i 1 •• •; ! Group 4 - Very Small • ... j • ----- • • 1.060 .#•i ^ * . - ■# |. -r .*«i»... 1..- # • 1 •• i • 1.040 0 ........ • ;■ • ! i 20 40 0 20 40 Percentage of Volume of Starch Grain Figure 1&: Scatter diagrams of variety means between percentage of volume of starch grains and specific gravity obtained from potato tubers grown at Montcalm County in Michigan, 1955 > crop. 63 G r o u p 1 -1 Large 1 Group 2 - Medium • 7-0 • ' • \ •< • 3.0 ------ • • • • 3.0 • • • • • Chip Color Rating • • • • • •• • • • • • G r o u p 3 - Small ■ Group 4 - Very Small • - ... 7.0 • . • • 5.0 • # . # W W • • • • • 0 • • •• • • •• • 3.0 • 20 40 C) 20 40 P ercen t a g e of Volume of Starch Grains Figure 19: Scatter diagrams of variety means between percentage of volume of starch grains and chip color rating obtained from potato tubers grown at Montcalm County in Michigan, 1955 crop. 64 signi.ficant • On volume basis, as the percentages of large and medium starch grains increased in the tubers of different varieties, the specific gravity also increased and as the percentages of small and very small starch grains increased, the specific gravity decreased. The same type of trend was noticed in the relationship with chip color rating (Figure 19). The variety correlation between percentage of volume of large starch grain and chip color was negative and highly significant, r -0.6$9. The correlation between percentage of volume of medium size grains and chip rating was negative but not significant. The correlation between percentage of volume of small and very small starch grains and chip ratings were positive and significant. The higher the percentage of volume of starch grain of the two groups above 50 microns in potato, the lighter the chips, while the percentage of volume of less than 50 microns size, starch grains increased, the darker will be the chips (Figure 19). Variety Partial Correlation Between Specific Gravity, Percentages Of Starch Grains and Chip Rating The variety partial correlation, between specific gravity (x).and percentage of starch grain (y) and eliminat­ ing chip rating (z), rxy*z> was significant only in one case (Table XVllI). The higher the percentage of large, medium and small starch grain, the higher the specific gravity as 65 TABLE XVIII COEFFICIENTS OF PARTIAL CORRELATION FOR VARIETIES BETWEEN SPECIFIC GRAVITY (x), PERCENTAGE OF STARCH GRAINS (y J AND CHIP RATINGS (z) BY LOCATIONS AND ALL LOCATIONS COMBINED Starch Grain Size r Montcalm Emmet Bay Arenac +0.356 -O.468 -0.088 xy. z +0.406 Group 2-Medium 75 to 50 microns xz.y -0.25^ vz.x -0.467. +0 #480 -0.164 +0.467 -0.480 -0.534* -0.529* +0.083 .-Jl.,8.16*-;-0. 298 xy.z +0.508* -0.132 +0.285 +0.249 Group 3-Small 50 to 25 microns xz.y -0.531* -0.526* -0.537* -0.596* yz .X -0.0.80. _ -0^203 .-0.537* * ** 1 1 All Locations -0.138 +0.224 +0.194 +0.001 -0.530* -0.682** -0.3&7 -0.710** -0.787** -0.269 .. -0.58.1* -0.607** . xy.z +0.202 Group 1-Large Above 75 microns xz.y -0.334 vz.x -0.57'3l Group 4-V.Small xy.z -0.465 Below 25 microns xz.y -0.150 juux, .+0.572* Allegan -0.481 +0.103 -0.385 -0.859-*—0.489* -0.570* -a..017 +0.826**:+.Qj 316 +0.185 -0.290 +0.306 -0.402 >'*-0.574* +0.022 +0.528 4—0 •63 5** -0.627*-I 0_«-0-2L_. +OlfcQHl___ -0.254 -0.243 -0.020 -0.439 s+0. 588* +0.,7_4I*iI Exceeds 5$ level of significance Exceeds 1% level of significance The coefficients were obtained fromthe two-way tables of^ variety x location rather than from averages of theindivid­ ual location correlations# 66 seen by the simple (rXy) and partial (rX y #z) correlations, whereas the higher the percentage of very small starch grain, the lower the specific gravity (Table XIX). In partial correlation of rXz.y3 fourteen values were significant* In general the small size starch grain gave stronger partial correlation values than the other sizes (Table XVIII). From Table XIX, it is clear that the higher the percentage of large, medium and small starch grains.the lov/er the chip rating from both simple (ryZ) and partial (r y z * x ) correlations, whereas the higher the percentage of very small grains, the higher the chip rating. Out of twenty-four partial correlation values for ryZ#x, eleven values were significant, three in large size group, three in medium size group, one in small size and four in very small size group (Table XVIII). In general the higher the specific gravity, the lower the chip rating in both simple (rx z ) and partial (rxz#y) correlations. 57 TABLE XII A V E R A G E C O E F F I C I E N T S OF SIMILE A N D PARTIAL GOftuELATIONS F O R V A R I E T I E S B E T N E E N SPECIFIC GRAVITY ( x ) , PERCENTAGE OF S T A R C H GRAINS (y) , AND CHIP R a TINGS (z) REGAR D L E S S OF SIGN Correlation Group 1 Group 2 Group 3 Group 4 Large .. Medium . Small.. .V. Small 0.421 0.28? 0.134 Simple - x y Partial - x y . z Difference 0.517 0.136 0.331 0.606 0.335 0.2.73. _ Simple - yz Partial - y z . x Difference 0.639 O .464 0.155 0.667 0.391 0.693 0.510 0.209 0.494 0.173 _. 0.182. . .Q.183 0.652 0.652 0.652 Simple - xz 0.575 Partial - x z . y Difference ... .. Oit13.4_. ..Q.J3.L __._Qx.Q72_ 0 . 5 1 8 0 . 4 1 6 0.623 0.332 0.291 Average 0.542 0.285 ,,2.25.7, 0.598 0 . 4 2 4 .Q..17A 0.652 0.421 0.231 . Q.17.00 . 6 5 2 0 . 4 8 2 DISSCUSSIQN Specific Gravity From the data obtained in the study of the seventeen varieties at the five locations individually or combined, it is evident that there is a varietal difference in the specific gravity of the potato tubers. Early Gem, Redburt, Redkote and Waseca had lower specific gravity than the aver­ age at all locations whereas Irish Gobbler, Cherokee and Merrimack had higher specific gravity. It can be concluded that specific gravity is a varietal character. This is in accordance with the findings of Akeley and Stevenson (1,2). Highly significant differences in specific gravity were found between tubers from the various locations. There was no difference in specific gravity averages of tubers grown on mineral and muck soils. The potatoes from the Emmet County (mineral soil) plots were highest in specific gravity, followed in order by Arenac (muck), Allegan (muck), Montcalm (mineral) and Bay (mineral). There was also sizeable difference- in the specific gravity within a variety which shows that the specific gravity of a potato tuber is influenced not only by the var­ ietal characteristic but also the environmental conditions. 63 69 Percentage Of Sizes Of Starch Grain The starch consent of a tuber is in granule form and these granules are in various proportions of different sizes. In this experiment, these sizes were classified into four groups - large - above 75 microns, medium— between 75 to 50 microns, small - between 50 to 25 microns and very small less than 25 microns. It was found comparatively easy to obtain consistent readings of percentage of large and of very small starch grains whereas with the both intermediate sizes estimate were loss reliable. The proportions of the above four sizes vary among the different varieties as shown by the data, (Tables VII to XII). Other workers, Johnson and Boyle (2$), Fitch and Barnet (21) and Barham et al (5) reached the same conclusion that starch grain size varied in potato varieties. Varieties could be classified into two grouj)s. The first group had a large percentage of large and medium starch grains and a low percentage of very small grains* Tns other group had a large percentage of very small starch grains. Osage, Pungo, la $03-3, la 961-1, Cherokee, Rushmore and Merrimack can be classified in the first group while Early Gem, Dazoc, Redburt, Waseca, Red LaSoda and Sheridan were in the group with a high percentage of very small starch grains. Thus the findings show that the proportions of these different starch ^rain sizes could be consxdered a varietal characteiistic, which is in agreement with the findings of Veselovsky (44). 70 There were differences in the percentages of large, medium and very small starch grains due to the effects of location but only the variation in large starch grains was significant* There were also noticeable differences in the percentages of large, medium and very small starch grain sizes in tubers within a variety. It may be concluded that the percentages of different starch grain sizes are Influenced not only by the varietal characteristics but also by the en­ vironmental conditions. Chip Color Rating From the observations of seventeen potato varieties from five locations it is evident that the color of potato chips was a varietal characteristic (Tables VII to XII)* This re­ sult is in accordance with those of Wright and Whiteman (50), Wright, et al (51) and Denny and Thornton (15). duced the lightest color potato chips* Osage pro­ Chips from Irish Cob­ bler, Osage, la £03-3, la 961-1, Cherokee, Rushmore, Sebago and Merrimack potato tubers were desirable where as Early Gem, Redburt, M.S. 1363, Redkote, Waseca, Red LaSoda and Sheridan made undesirable chips from color point of view* Smith (37) is of the opinion that the color of potato chips is a large factor In the equality of chips. Hence, the aoove potato varieties could be classified as satisfactory or un­ satisfactory for potato chip manufacture. 71 Hignly significant/ differences in chip color ratings wore found between locations. The average chip color pro­ duced from potato tubers of varieties on muck soil was light­ er than that from tubers produced on mineral soil. There were sizeable differences in the color of chips from tubers of any one variety taken from one location. Hence, it could be inferred that the chipping quality of a potato tuber de­ pends upon the variety of the potato and the environmental condition where it is grown. Relationship Of Percentage Of Sizes Of Starch Grains To Specific Gravity The percentages of the three larger - size groups, (those above 25 microns) showed.positive correlations between the percentage of starch grains and the specific gravity of the tuber. As the percentage of starch grains above 25 mi­ crons in size increased in the tuber, the specific gravity increased, irrespective of location. There was a negative correlation between percentage of very small starch grains, less than 25 microns in size, and specific gravity of the tuber. This shows that as the percentage of very small starch grains increases in the tuber, the specific gravity decreases in the potato varieties. It is evident from this that the specific gravity of the tubers ws.s related to the proportions of sizes of starch grains in the tuber, and that both are varietal characteristics as discussed previously. 72 The tnree different sizes of starch extracted from Cherokee potato tubers, showed different starch densities. It is evident from the data (Table XIV) that as the starch grains increase in size, their density also increases. Previous investigations by Burton (10) have shown high correlation (+0,947) between specific gravity and starch con­ tent. Since the starch content is in the form of discrete starch grains. The present results Indicate that the pro­ portions of different sizes of starch grains could be one of the factors influencing specific gravity. Comparatively speaking, tubers from Emmet County plots had a high specific gravity but not a high percentage of large starch grains. (Figure 9)* From Figure 20, it may be seen that Emmet County experi­ enced a dry summer. When compared to other counties It had the lowest precipitation (£.45 inches) during the growing season (Appendix 1). It had half normal the rainfall coupl­ ed with a higher average temperature than normal years. The correlation within varieties showed highly signifi­ cant coefficients as was true'in the case of variety means. This Indicates that even after the effects of varieties were taken out, the within variety residuals of both factors were positively associated. This relationship indicates that within a variety, apart from varietal influence, the higher the percentage of large starch grains in t-he tuber the signer the specific gravity of the tuboi. Precipitation in Inches 73 June Figure 20: Weekly precipitation during five months in 1955 at five locations in Michigan. 74 ior purposes of observation it was convenient to esti­ mate the proportion of the area occupied by starch grains of vaiious sizes* If one will assume that the layer of starch grains was one grain deep in each case, the proportionate volume in any grain size could be obtained by multiplying the area by the average thickness of the grains of that parti­ cular size* In general the correlations between a propor­ tionate volume of starch grain and specific gravity and chip quality were virtually the same as when the area of starch grains was used rather than the calculated volume* The correlations of amounts of large and medium starch grains with specific gravity were positive whereas negative correlations were found with chip color rating* The correla­ tions were opposite in the case of two smaller grain sizes with these quality factors. This could be a more understand­ able relationship than a positive correlation between large, medium and small starch grains with specific gravity, as was found when area was used as the measure of quantity of any starch grain size. Relationship Of Percentage Of Size Of Starch Grain To Chip Color Rating The potato tubers having a. large percentage of starch grains from the three larger—size groups, produced lighter chips, whereas tubers having large percentages of very small g^^irch grains produced undesirably daik colored chips* ihis 75 is logical as chip color also depends on specific gravity (46, 51, 29) and in turn specific gravity is related to the percentage of larger starch grains* In general, the relationship between starch grain sizes and chip color within a variety was similar to the relation­ ship between varieties. Relationship Of Specific Gravity And Chip Color Rating In all locations, the generalization may be made that the higher the specific gravity of the tuber, the lighter the chip color. This is in accordance with the findings of Wheeler and Salunkhe (46), Wright and Whiteman (50), and Kunkel, et al (29)* Simple And Partial Correlations From the data it may be seen that out of seventy-two variety partial correlations, in sixty-five cases values of partial correlations were less than simple correlations and only three changed signs. This shows that when the effect of the third factor was eliminated, the correlation of the other two factors became weaker as compared to that when the effect was not taken out. In the partial correlation of rxy#z> ^*n percentages of large, medium and very small starch grains, the effect of 76 chip color is considerable but less in small starch grain size; the greater the difference between simple and partial correlation, the greater the effect on chip color (Table XIX)# In partial correlation of ryZ#x, the effect of specific gravity is about the same in percentages of medium, small and very small starch grains but slightly less in large size starch grains. In general the signs of yz are opposite to tnose of xy. When the correlations of rxz and rX2#y were compared, no explanation could be found for high drop in percentages of medium and very small starch grains as compared to large size and specially to small size grains. However, there was very little effect of percentage of small starch grains on xz and on x as seen in xy. All signs were negative. On the average, regardless of sign, specific gravity of the potato tuber and color of the potato chip are more close­ ly related than either percentage of starch grain sizes with chip color or specific gravity with percentage of starch grains, whether, comp.ring simple or partial correlations. The weakest partial correlation is ^xy.z large size group. Regarding sign, large, medium and small size groups tend to react alike but opposite to very small size group in relationships of specific gravity with percentage of starch grains with chip color rating. This shows that the 77 percentages of starch grains above and below 25 microns have a great effect on specific gravity and chip rating* This agrees with the findings of size and density (Spe­ cific gravity) of starch grains* SUMi-iAKX AND CONCLUSIONS 19^5 seventeen varieties of potatoes were grown in four replicated plots at five locations in Michigan, Five tubers of about the same size (U.S. Grade No. 1) were taken from each plot at harvest. These constituted the samples used for the studies on specific gravity, percentage of four sizes of starch grains and chip color rating. Approximately 1,700 tubers were analyzed in. these in­ vestigations. 1. At the five locations, each variety, in general, assumed a characteristic rank, high, medium or low, in speci­ fic gravity. There was, however, great variability in the specific gravity of individual tubers of a variety at any location, and considerable variation in the average specific gravity between locations. 2. Starch grains in potato tubers were classified into four size groups, large - above 75 microns, medium - between 75 to 50 microns, small - between 50 to 25 microns, and very small - less than 2 5 microns# At the five locations, each variety, in most cases, had a specific pattern of starch grain sizes. Some varieties throughout ranked high in large and medium sized grains and low in very small# proportions. Other varieties had precisely the opposite Still others were intermediate in rank in all sizes. 7$ 79 However, ohere was a wide variability in the proportions of the four sizes in individual tubers from any given plot and considerable difierence between location averages* 3# At the five locations, each variety had, in general, a charact :ristic rank among the seventeen varieties, in potato chip color, some ranking consistently light, others consis­ tently dark. There was considerable variability in the color of chips from tubers of any one variety taken from any location, and a moderate to small (although highly significant) variation between location averages. 4. The proportions of the four sizes of starch grains in a potato tuber were related to specific gravity. The higher the proportion of large, medium and small starch grains, the higher the specific gravity. The higher the percentage of very small starch grains (less than 25 microns) the lower the specific gravity of potato tuber. 5. Starch grains extracted from potato tubers and se­ parated into three sizes (above 60 microns, between 60 to 30 microns, less than 30 microns) differed in densities, the larger sizes being denser than the smaller. 6. The potato tubers, having a large percentage of largo - medium - small - starch grains, produced light colored potato chips. The tubers which hod a large percentage of very small starch grains — less than 25 microns — produced dark colored potato chips. 30 7* At all the five locations, varieties having tubers with a high average specific gravity produced potato chips lighter in color than those with a low average specific gravity. 3. The percentages of large, medium and small starch grains tend to react alike but opposite to percentage of very small starch grains in relationship with specific gravity and with chip color rating. This means that the percentages of starch grains above and below 25 microns in size have a great effect on specific gravity and chip quality. LITERATURE CITED 1. Akeley, R. V. and F. J# Stevenson. Yield, Specific Gravity and Starch Content of Tubers In a Potato Breeding Program. Amer. Potato Jour. 20:203-217, 1943 • 2. Akeley, R. V. and F. J. Stevenson. The Inheritance of Dry Matter Content in Potatoes. Amer. Potato Jour. 21:#3-89,■ 1944* 3. Alsberg, C. L.Studies Upon Starch. 18 :190-, 1926. Ind. Eng. Chem. 4* Ashby, S. F. A Contribution To The Study of Factors Affecting The Quality and Composition of Potatoes. Jour. Agr. Sci. 1:347-357, 1905. 5. Barham, H. N., J. A. Wagoner, B. M. Williams, and G. N. Reed. A Comparison of the Viscosity and Certain Microscopic Properties of Some Kansas Starches. Jour. Agr. Res. 68:331-345, 1944. 6. Barmore, M. A. Potato Mealiness and Changes in Soft­ ness In Cooking. Food Res. 2:377-383, 1937. 7. Brautlecht, C. A. Starch - Its Sources, Production and Uses. Reinhold Pub. Corp. New York, p 39, 1953. 8. Briant, A. M., J. P. Catherine, and E. G. Cassel. Physi­ cal Properties of Starch From Potatoes of Different Culinary Quality. Food Res. 10:437-444, 1945. 9. Burton, V. G. The Characteristics of Certain Varieties of Potato With Special Reference to Their Suitability For Drying. Ann. Appl. Biol. 31:69-96, 1944. 10. Burton, V. G. The Potato. Chapman and Hall Ltd. Publi­ cation London, p 284-287, 1948. 11. Clark, C. F., P. M. Lombard, and E. F. Whiteman. Cooking Quality Of The Potato As Measured By Specific Gravity, Amer. Potato Jour. 17:3 8-45, 1940. 12. Cochram, F. D., C. L. McCombs, and J. C. Taylor. Study of Specific Gravity and Storage Temperature As Re­ lated to Chip Manufacture in Early Summer White Po­ tatoes. Potato Assoc. Amoi'. Meet. Abs., p 2, 1952. 81 32 13. Coughlin, i1. J. Quality Control in Potato Chip Manu­ facturing Proc. of Prod. & Tech. Div. Meet., National Potato Chip Inst., 1954. 14. Denny, P. n., and N. C. Thornton. Factors For Color In The Production of Potato Chips. Contr. Boyce Thompson Inst. 11:291-303, 1940. 15. Denny, F. E., and N. C. Thornton. Potato Varieties: Sugar Forming Characteristics of Tubers in Cold Storage and Suitability for Production of Chips. Contr. Boyce Thompson mst. 12:217-252, 1941. . 16 Dexter, S. T., and D. K. Salunkhe. Chemical Treat­ ment of Potato Slices in Relation to The extrac­ tion of Sugars and Other Dry Matter and Quality of Potato Chips. Mich. Agr. Exp. Quart. Bull. 35: 102-109, 1952. 17. Dunn, L. E., and R. E. Nylund. The Influence of Ferti­ lizer on The Specific Gravity of Potatoes Grown in Minnesota. Amer. Potato Jour. 22:275-233, 1945. IS. East, E. M. A Study of The Factors Influencing The Im­ provement of The Potato. 111. Agr. Exp. Sta. Bull. 127:375-456, 1903. 19. Ezekiel, M. Methods of Correlation Analysis. Wiley and Sons Publ. p 373, 1930. 20 . 21 . 22 . John Freeman, M. E. Measurement of Texture in Baked Potato Tissue. Food Res. 7:451-453, 1942. Fitch, C. L., and E. R. Bennett. The Potato Industry of Colorado. Agr, Exp. Sta. Col. Agr. Coll. Bull. 175, P 14, 1910. Garner, W. 1932. Industrial Microscopy - 339 Illus. London, 23. Gilmore, J. A Study of Quality In Potatoes. Present Estimates Of Quality. Com. Univ. Agr. Exp. Sta. Bui:-. 230, 1905. 2km Glvnne M. D. and V. G. Jackson. The Distribution of Dry Matter and N in The Potato Tuber. Jour. Agr. Sci. 9:237, 1920. 25. Goldthwaite, N. a. Variations In The_Composition of Co]orado Potatoes# Colo# Agr# Exp# ota# Bull# 296, 1925. J 26. Janicke, J. Abstract From Jour. Ayr. Res. 66:331 (Hecz. Chem. 12:361-402), 1932. 27* Johnson, T., and C. Boyle. The Industrial end Nutritive Value of The lotato in Ireland. Jour. Dept. Agr. Ire. 16:443-471, 1916. 26. Johnson, T., and C. Boyle, Observations On The Indust­ rial and Nutritive Value of Potato in Ireland. Dept. Ayr. and Tech. Instr. Ire. Jour. 19:416-429, 1919. 29. Kunkel, R,, J. Gregory, and A. M. Burkley. Mechanical Separation of Potatoes into Specific Gravity Shows Promise for Potato Chip Industry. Amer. Potato Jour. 26:690-696, 1951. 30. Meiss, P. E., R. H. Treadway, and F. A. Krantz. White Potato Starches. Ind. Eng. Chem. 36:159-163, 1964* 31* Metzer, C. H., J. V. Tobiska, E. Douglas, and C. E. Vail. Some Factors Influencing the Composition of Colorado Potatoes. Amer. Soc. Hort. Sci. Proc. 35:635-643, 1937. 32. Mikuljskil, A. A. 1953* 33* Nash, L. B. Potato Quality IV - Relation of Variety and Environment Condition to Partial Composition and Cooking Quality. Amer. Potato Jour. 19:91-99, 1941. 34. Radley, J. A. Starch and Its Derivatives. man and Hall, London p 346, 556, 1943* 35. Shutt, F. T. Influences of Early and Late Planting and Sprouting onYield and Dry Matter Content of Potatoes. Dept. Agr. Cannon Dept, p 42, 1925* 36. Sjostrom, 0. A. fications. 37 Smith 36 Stevenson. F. J. Starch Content of Potatoes: Amer. Po­ tato Jour. 15:356-357, 1936* Field Crops. Abs. Vol. 6, No. 1, 40, 2nd Ed. Chap­ Microscopy of Starches and Their Modi­ Ind. Eng. Chem. 26:63-64, 1936. 0. Research Needs of the Potato Chip Industry. Amer. Potato Jour. 27:116-122, 1950. 84 39. Stevenson, F. J., and E. F. Whiteman. Cooking Quality 01 Certain Potato Varieties as Influenced by Envir­ onment. Amer. Potato Jour. 12:41-47, 1935. 40. Stuart, Wm. ^ The Potato: Its Culture, Uses, History and Classification, p 513 - Lippincott Co. Philadelphia, 1923. 9 41 • Sweetman, M. D. Factors Affecting the Cooking Quality of Potatoes. Maine Agr. Exp. Sta. Bui. 383, 1936. 42. Szego, E. Abstract - Jour. Agr. Res. 6o:331. (Assoc, des chim de Suer et Distill. Bui. 48:263-274, 193D. 43# Vanasse, N. A., I. D. Jones, and H. L. Lucas. Specific j Gravity - Dry Matter Relationship in Potatoes. / Amer. Potato Jour. 23:731-791, 1951. 44. Veselovsky, I. A. Biochemical and Anatomical Properties of Starch of Different Varieties of Potatoes and Their Importance for Industrial Purposes. Amer. Potato Jour. 17:330-339, 1940. 45. Vilikovski, Quoted from Starch and Its Derivatives by Radley, p 558, 1943* 46. Vi/heeler, E. J. and D. K. Salunkhe. Specific Gravity and Date of Planting As It Influences the Color of Potato Chips. Potato Assoc. Amer. Meet. Abs. Papers p 3, 1952. 47. Whitehead, T., T. P. McIntosh, and W. M. Findlay. The Potato in Health and Disease. Oliver & Boyd. Edinburgh, p 400, 1945* 48. Willaman, J.U. and R. M. West. Composition of Potato Tubers. Rep. Minn. Agr. Exp. Sta. p 44, 1922. 49. 50. Whittenberger, R. T. and G. C. Nutting. Effect of Phytohormones on Potato Growth and the Size of the Starch Granules. Plant Phys. 24:278-284, 1949. Wright, R. C. and T. M. Whiteman. Varieties and H a n d l ­ ing of Potatoes for Chip Manufacture. Potato Chipper 10:50, 1951. 35 51. Wright, R. C., M. M. Davis, and C. Mendel. Making of Potato Chips. U.S. Agr. Yearbook, 136-139, 1951. 52. Zika, M. Reported from Plant Phys. 1945. (Plants 30:151-159, 1939) 2/f:2'/S-279, 86 APPENDIX 1 WEEKLY PiiSCIPIT AT10N IN INCHES AT FIVE COUNTIES IN MICHIGAN DURING MAY TO SEPTEMBER Month Montcalm Emmet Edmore Pellston 6 12 18 24 31 May __T.at.al__ 6 12 18 24 30 June Total __ July 6 12 18 24 31 Total August 6 12 18 24 31 Total September 6 12 18 24 30 Grand Total 0#31 0.13 0.0 1.30 2.34 ____it-08 0.06 0.69 0.06 0.10 0.01 0.0 0.14 1.06 0.9.8 .__ 1.48 1.88 2.70 0.0 4.75 0.02 0.30 0.71 0.08 0.0 0.74 D..06 . .0.0 .1.53 .... 5.13 . 0.68 0.11 0.26 0.16 0.13 1-3.7.. 0.01 0.30 0.82 0.0 0.77 1.90. 0.94 0.0 0.85 0.08 3.73 ___ 5-.60. 0.59 0.0 0.0 0.29 0 .94 1.82L. 0.0 0.03 0.56 0.0 0.37 0.96 17.14 Bay Bay City 0.10 1.50 0.0 0.38 0.0 .... 1 .98 0.85 0.0 1.0 0.0 0-0 1 •8_5 . 0.92 0.0 1.04 1.12 ...1*11 __3.93_ 0.0 0.0 0.36 0.40 0.26 0.40 0.12 0.0 0.52 ... 1.32.. _. Q.8£_. 11.28 8.45 Arenac Standish 0.0 0.15 0.0 0.92 3.19 ___4.26 . . ... Allegan Gull Lake 0.03 0.38 0.0 0.51 0.99 1.91 0.03 2.08 0.0 0.26 0.0. 2.37 0.25 3*51 0.0 0.07 . __ 0..92 . _ 4.7.5 0.20 0.65 0.0 1.72 0.69 1.13 0.20 0.0 0.01 _ . 0.67 .... 3.48___ 1 -79_ _ 0.70 1.13 0.0 0.13 0.12 1.26 0.01 0.44 , . -1*61...... . 1.89.. A*OJL_. . . 3.28 _ . 0.0 0.0 0.58 0.08 0.0 0.29 0.20 0.0 0*7-5__ . Q.QSL . 0.4.6 ... ..1.5.3 . 14.95 14*93 57 ArPENDIX 2 SPECIFIC GiUVITX, PERCENTAGE OF FOUR STARCH GRAINS AND AND CHIP COLOR RATINGS OF INDIVIDUAL TUBER FROM FOUR POTATO VARIETIES GROtfN AT MONTCALM COUNTY IN 19$5 (Varieties were selected in which the data shows the degree of regularity or divergence that may be ex­ pected in five tuber samples of four replications) Percentage of Starch Variety Irish Cobbler Early Gem Plot No. Potato No. Specific Gravity ______ fiEains___ Gr. Gr. Gr. Gr. Chip Color Rating. 115 1 2 3 4 5 210 6 303 7 5 9 10 11 12 13 14 15 415 16 114 17 15 19 20 1 2 3 4 5 216 6 305 7 5 9 10 11 12 13 14 15 1.060 1.066 1.073 1.072 1.063 1.053 1.052 1.056 1.053 1.056 1.053 1.060 1.064 1.053 1.053 1.064 1.067 1.060 1.066 1.067 1.059 1.054 1.061 1.060 1.061 1.056 1.061 1.056 1.051 1.060 1.055 1.056 1.063 1.050 1.056 20 20 30 30 25 10 45 10 0 5 0 20 10 0 0 25 30 20 30 30 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 30 20 25 20 30 25 25 25 25 35 20 30 30 20 30 30 25 30 20 25 20 20 20 15 15 15 10 10 5 10 15 10 20 0 10 20 25 25 20 20 25 15 25 20 20 25 20 25 25 20 20 20 20 25 20 15 10 20 20 20 25 25 20 20 20 25 25 20 25 25 30 35 20 30 25 40 15 40 55 40 55 30 35 55 50 25 25 30 25 25 65 70 60 65 65 60 65 70 75 70 60 65 60 75 65 5 5 4 6 5 5 4 5 7 6 7 6 6 7 6 4 3 3 3 4 6 / 6 7 6 5 7 7 7 8 7 5 5 4 5 4 33 (continued) Plot No. Potato No. 413 1 Specific Gravity 1.054 1.048 1.054 6 17 13 19 1 2 0 1.057 112 1 2 3 4 5 2 0 8 6 1 3 0 1.064 1.053 1.059 1.071 1.061 1.066 9 1.063 1.049 1.051 1.054 0 11 4 1 1.062 1.060 7 8 1 2 4 - 0 5 2 13 1.066 14 15 19 1.078 1.055 1.065 1.052 1.049 1.050 20 1.066 0 1 6 17 1 8 1 1 0 1 2 3 4 5 2 1 2 6 7 1 1 0 3 0 11 7 7 6 1.059 1.052 1.057 . l 1.059 1 0 6 1.070 1.067 1.059 1.045 12 1.030 13 14 1.030 1.043 1.051 1 *°|5 1 5 411 0 1.062 8 9 . 16 17 1 1 8 1.071 1 1 9 ?n . . 0 0 6 6 8 2 1.051 Percentages of Starch Grains Gr. Gr. Gr. Gr* 2 1 4 3 0 0 0 0 0 25 30 40 30 30 50 30 25 50 0 0 20 30 45 5 30 0 0 25 30 35 25 20 15 15 20 15 35 20 10 0 0 0 0 15 0 30 35 30 15 5 0 10 5 15 30 30 30 30 25 30 20 30 30 30 30 30 30 30 35 30 35 20 20 25 25 20 20 20 30 30 25 25 25 25 10 0 0 15 20 0 25 25 25 20 _ 30 15 25 20 20 20 20 15 20 25 10 25 20 10 20 20 20 20 15 25 20 25 25 20 20 20 20 20 20 20 20 20 20 25 20 20 0 0 20 20 0 25 20 20 20 65 35 65 75 65 25 20 15 20 20 10 25 25 10 50 50 30 20 10 35 20 40 55 35 25 20 35 40 45 35 30 40 20 30 45 70 100 100 65 45 100 20 20 25 45 . hi] lO] tij 6 7 7 7 6 3 3 3 3 3 2 3 3 3 4 4 4 3 2 3 4 3 5 3 3 6 4 5 6 4 5 4 4 3 7 9 9 3 7 7 9 4 5