PHYSIOLOGICAL AND GENETIC STUDIES ON TETRAPLOID AND HAPLOID POTATO (SOLANUM TUBEROSUM L.) Thesis for the Degree of Ph. D. MICHIGAN STATE UNIVERSITY MARTA T. MORALES ‘ ”1968‘ hiichigml State University This is to certify that the thesis entitled PHYSIOLOGICAL AND GENETIC STUDIES ON TETRAPLOID AND HAPLOID POTATO ‘(SOLANUM TUBEROSUM L.) presented by Marta T. Morales has been accepted towards fulfillment of the requirements for Ph. 0. degree in Crop Science Date Dec. 27. 196 I 0-169 ' —_—_—.—.-.____. ._ _, ABSTRACT PHYSIOLOGICAL AND GENETIC STUDIES ON TETRAPLOID AND HAPLOID POTATO (SOLANUN TUBEROSUH L.) by Marta T. Morales The physiological relationship between leaf area distribution and dry matter of potato tubers is considered for both tetraploid varieties and haploid derivatives. The genetics of the physiolo- gical characters is investigated by diallel cross techniques; this is confined to the haploid plants. Broadly speaking, there was good agreement between the phy- siological patterns for haplOids and tetraploids. The accumula- tion of dry letter in the tubers was not only dependent on abso- lute leaf area, attained by a variety (or group) but was also affected by the pattern of leaf area distribution over the growing season. It was suggested that leaf distribution was primarily influenced by the point where senescence starts and the speed of senescence, coupled with the'tine at which tuber naturity takes place. The preceding remarks applyto the results from three tetra- ploid varieties and three groups of haploids. However, more detail- ed physiological studies on the diallel cross (5 x 5) between hap- Marta T. Morales lolds confirmed the above statements. Total dry matter of the parents and crosses was linearly related to leaf area. Generally the ratio of tuber dry matter to total dry matter was constant. however, two crosses did not conform to this pattern, one placing more substrate in the tubers, the other in the rest of the plant. The genetics of the physiological characters indicated that the most important genetic component was specific combining abi- lity. This finding would probably not be an obstacle to breeding, since potato varieties are clonally prOpagated. PHYSIOLOGICAL AND GENETIC STUDIES ON TETRAPLOID AND HAPLOID POTATO (SOLANUM TUBEROSUM L.) By OVDQ Marta T. Morales A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Department of Crap Science I968 ACKNOWLEDGMENTS I am indebted to Dr. N. R. Thompsom for his advice and guidance throughout the course of this study. I would like to thank Drs. R. H. Chase, C. E. Cress, S. T. Dexter and H. T. Magee for their help and critical comments on. the drafts of the thesis. My gratitude goes to Dr. C. M. harrison for his encourage- ment and review'of the final draft, to Dr. J. E. Grafius for his concern and to Ors. N. R. Thompson and R. L. Thomas for their help in the revision of the draft. I wish to acknowledge the Rockefeller Foundation for giving me a travel grant and to MC 84 for financing the project. Finally, I must mention Mr. R. Kitchen who was of great help with the technical aspects of planting, harvesting, etc. TABLE or CONTENTS Page INTRODUCTION e --------------------- I REVIEW OF LITERATURE ------------------ 2 MATERIALS AND METHODS __ ---------------- 7 Experiment I ------------------- IO a. l966 Experiment --------------- II b. l967 Experiment --------------- ll Experiment 2 ------------------- l2 Experiment 3 ------------------- l3 RESULTS AND DISCUSSION ----------------- l7 Experiment I ------------------- l7 8. l966 Experiment ---------------- 17 b. l967 Experiment ---------------- l9 Experiment 2 ------------------- 25 Experiment 3 ------------------- 27 a. Physiology ------------------ 27 b. Genetic studies with haploids --------- 39 SUMMARY AND coucwsnous ---------------- 1+7 LIERATURE CITED __ _ ------------------ A9 52 APPENDIX I ----------------------- LIST OF TABLES Table Page I. Means and standard deviations of leaf area (LA), yield, tuber dry matter (DMT), starch (S) and economic photosynthetic efficiency (EPE) on a‘ per plant basis of 25 plants for the three varieties. 2. Correlation coefficients within varieties for leaf area and each of yield, dry matter of the tubers, and starch (1966 data). -------------- 3. Means of maximum leaf area, day at which maximum leaf area was attained, total photosynthetic leaf area day, maturity, total dry matter, tuber dry matter, net assimilation and economic photosynthe- tic efficiency per plant of Onaway, Katahdin and Russet Burbank (I967 data). - - 7 ........ h. Means and standard deviations for leaf area, yield, tuber dry matter, starch and economic photosyn- thetic efficiency per plant of three groups of haploids (I966 data). -------------- 5a. Means of cumulative photosynthetic leaf area days at different time intervals and totals for the parental types and the diallel cross Fl' 5. 30 5b. Means of yield, plant dry matter, tuber dry matter, total dry matter, net assimilation and economic photosynthetic efficiency per plant for the pa- rental types and diallel cross Fl's. ------- 3l 6. Regression and correlation coefficients of total dry matter, tuber dry matter, plant dry matter, economic photosynthetic efficiency and the per- centage of dry matter in the tubers with ZPLAD, 3PLAD, and TPLAD of the parental types and the F 's derived from diallel series, with and with* out RI and R2. iv Table Page 7. Analyses of variance for lPLAD, ZPLAD, 3PLAD, TPLAD, tuber dry matter, yield, starch, net assimilation and economic photosynthetic efficiency of parental types and diallel cross Fl's. ----------------------- 42 8. Estimates of genetic and environmental parameters of IPLAD, ZPLAD, 3mm, TPLAD, tuber dry matter, yield, starch, total dry matter, net assimilation and economic photosynthetic efficiency. ------ Ah Figure LIST OF FIGURES Page Sum of the dadly photosynthetic leaf area measured at different stages of growth in Russet Burbank, Katahdln and Onaway. ----- 2i Typical growth patterns of different genotypes of haploids. ----------------- 28 3a, b, S c. Total dry matter per plant of parental haploid types and their diallel F 's plotted against ZPLAD, 3mm and TPLAD, rdspectively - 32 ha, b, a c. Plant dry matter per plant of parental types 5a,b, 6. and F 's plotted against ZPLAD, 3PLAD and TPLAD, respeEtlvely. ------------------ 3A 8 c. Tuber dry matter per plant of parental types and F 's plotted against 2PLAD, 3PUAD, and TPLAD, respectively. ------------- 35 The percentage of dry matter accumulated in the tubers of parental types and Fl's plotted against TPLAD. ------------------ 37 vi INTRODUCTION The advancement in potato processing demands more emphasis on dry matter content rather than fresh weight of tubers. As a con- sequence, the efficiency of potato leaves becomes of primary im- potence in the utilization of solar energy for the production of dry matter through photosynthesis. There has been only limited study of the genetics of leaf efficiency in the production of dry matter, total leaf area at different stages of growth and their relationship to total dry matter production in the tubers. This research is primarily concerned with the establishment of the relationship of physiological patterns between tetraploid potato varieties (2n - #8) and haploids (2n - 2k) and a genetic study of inheritance of these physiological characters in haploids. --_;W LITERATURE REVIEW Potato (Solanum tuberosum L.) varieties grown under the same environmental conditions differ in yield. To paraphrase Hatson (l956), the material a farmer harvests is the end product of the photosynthetic process accumulated throughout the life of the crop in the particular plant organ harvested. Thus, photosynthesis may be regarded, economically as a yield-determining process (Gaastra, I959). The obvious and general truism that leaves are the chief organs of photosynthesis has been stated by Watson (I956). The area of the leaf is usually assumed to be the size-attribute that best mea- sures its capacity for photosynthesis. Chapman and Loomis (I953) found that under maximum hydration, rates of carbon dioxide absorption per unit leaf area were nearly equal in all parts of the leaf plane. This was supported by the work of Carraway (I963) using radioactive lh carbon dioxide (C 02), who showed that healthy leaves of potatoes fix carbon dioxide from the air uniformly on their entire surface. Goncharik (1963) found that the absorption of growth substances from the stem proceeds at equal rates in the right and left halves of the potato leaf. Uatson (l9h7)lshowed that in spite of the variation in leaf structure, the net amount of carbon dioxide utilized per unit leaf area is the same in any region of the plane. 2 The amount of photosynthetic activity on the whole or part of a plant may be measured at basic levels by techniques of gas ex- change. According to Pallas, £3. 21. (l967) the theoretical measure of net photosynthesis is the carbon dioxide difference between in- coming and out-going air. Further, Chapman (l95l) demonstrated that '3 IEM'AHW 1.4- - a. V . carbon dioxide absorption by potato leaves is a direct measure of photosynthesis and is free from error due to leaf shrinkage and carbohydrate translocation. Thorne (1959) in his studies on barley leaves, found that the rate of growth of a plant measured by dry weight increase depends on its photosynthetic capacity and total leaf area. Me measured photosynthetic activity by the difference of carbon dioxide concentration of air before and after passage over the leaf. However, Chapman and Loomis (l953) and Chapman (I95I) did not find any difference in the rate of carbon dioxide absorption per unit leaf area under field conditions, in spite of the fact that potato varieties differ greatly in total yields of dry matter, vine size, date of maturity and leaf type. This method of measuring pho- tosynthetic activity in the field is very difficult and impractical. A more practical and easily obtained measure of the end pro- ducts of photosynthetic activity is the increase in dry weight per unit leaf area or net assimilation on a comparative basis between varieties, treatments, etc. This may be regarded as a measure of photosynthetic efficiency (Watson, I956). This method has been used by several workers in different crops. Williams, 33. 21, (I965) in their study on corn, used net assimilation rate as an indication of mean photosynthetic efficiency which Is the net gain of dry matter of a community of plants relative to their leaf area. In alfalfa, Thomas and Hill (I937) used this method to measure pho- tosynthetic efficiency. Leaf area may be regarded as a limiting factor for total dry matter accumulation. This, however, does not mean that greater yield might result from a greater leaf area since the yield of seed, tubers, etc. may not be where the increase is concentrated. Indeed, it has been shown that greater leaf area does not necessarily re- sult in a higher yield of potato tubers. Harper (I963) for instance, found that when there was excess foliage which shaded the lower leaves, the plant could only produce sufficient carbohydrate to meet its own requirements for respiration and did not form any sto- rage organs. There should be an optimum leaf area that produces maximum yield. In kale, Brassica oleracea, Watson and French (I962) actually obtained an optimum leaf area by a thinning procedure. Blackman and Black (I959) found that maximum production of dry matter per unit leaf area under optimal conditions of temperature, nutrient and water supply was limited by the leaf area index and the amount of solar radiation. Optimum leaf area index for dry matter product- ion was dependent on the species under consideration. Breeding and selection for a greater photosynthetic efficiency could be a feasible means of increasing yield of existing varieties. According to Watson (1956) the total annual photosynthesis by a crop depends not only on the size of the photosynthetic system, but also on its efficiency and the time during which it is active. Watson (I952) in his studies on leaf growth in relation to yield showed that agricultural yields could be improved by increasing the photosynthetic efficiency of the species presently cultivated. He found significant differences in the net assimilation rate bet- ween potatoes and sugar beets and also between varieties of potatoes. he concluded that since the net assimilation rate differs between and within species, new crop types may be found with a higher net assimilation rate than those now grown; or an increase in the net assimilation rate of existing crops by breeding and selection, would increase yields. Further advances in crop breeding by the manipulation of pho- tosynthetic efficiency is to some degree dependent on the awareness of geneticists to the importance of physiological characters (Loomis, ._t.'_l., l967). At the present time, such measurements are not usually carried out in breeding programs, although, Kumakov (I958) included photosynthetic efficiency as a breeding character in wheat. In the potato, research on the genetics of photosynthetic efficiency particularly, leaf area at different stages of growth and its effects on total dry matter and dry matter in the tubers, is at best minimal. Swaminathan and Howard (I953) POIDtOd out reasons for lack of information on the genetics of economic and non-economic characters in the potato. Some of the reasons were: (I) tetraploid potato varieties are usually asexually prepagated and thus, highly heterozygous (often no attempt is made to obtain homozygosity); (2) in seedlings derived fro. selfing a variety, there are usually varying percentages of degenerate individuals which may affect the values of variances and give 'biased' estimates of genetic parameters; (3) there is the difficulty that among offspring, many may not flower, or if they do, may have pollen and/or ovule sterility; and (h) the polyploid constitution of the potato means that segre- gations are often conplex. flaploids (2n - 2%) from autotetraploid potatoes (2n 3 #8) function as diploids in their inheritance and offer an aid to genetic studies of this crop (flougas and Peioquin, l958). MATERIALS AND METHODS Economic photosynthetic efficiency and other characters were studied on three tetraploid potato varieties (2n - 48) and groups of haploids (2n - 24). The experiments considered fell into three groups: i) Experiment l - PhysiOIOgical observations on three tetra- ploid varieties grown in two years. ii) Experiment 2 - Physiological observations on a large group of haploids grown for one year. iii) Experiment 3 - Physiological and genetic studies on five haploid parents and their Fl's from a diallel series of crosses. Measurements taken I. Leaf area - The method used in measuring the leaf area was that devised by Epstein and Robinson (1965) for potatoes, that is, leaf area is based on leaf length alone. The leaf area was estimated by the formula: Log 9 - -o.uo + l.78LOg x where ‘? - estimated leaf area (in square cm.) X - length of compound leaf (in cm.). The compound leaf is measured from the base of the petiole to the tip. Epstein and Robinson derived the equation after fitting regression lines of four well known potato varieties, Russet Bur- bank, Katahdin, Kennebec and lrish Cobbler, in different environ- mental conditions. The applicability of this equation was found to be general over a wide range of environmental conditions. They found this measure to be a more reliable method of estimating leaf area than that based on length times width and it is less time consuming. In general, on any one plant in the present work, the lengths of ten (l0) compound leaves taken at random from the main stems and five secondary stems were measured. The average of these measure- ments was the value of X in the formula. The total leaf area per plant was estimated by: 9 times the average number of leaves per stem times the number of stems per plant. The arrangement of leaflets in the compound leaves of the haploids was very irregular. Moreover, the leaflets were much smaller and more numerous than those of the tetraploid varieties. Due to these factors, the method used for the varieties could well be a less accurate estimate for leaf area of the haploids. Therefore, the method used by Ludwig, £5. 31. (1965) in their estimation of leaf area in cotton was employed for the leaflets of the haploids. Samples of leaflets covering the range of shapes and sizes of the experimental plants were collected and the leaf outline traced on graph paper. The area of each leaflet sampled was measured in squarecentimeters. These different standard sizes and shapes with corresp0nding leaf area in sq. cm. were numbered from i to lo. Leaf area measurements were made by comparing leaflets of the sampled compound leaves with the standards. Stratified sampling of the stems and leaves was done. Stems were divided into two groups: main and secondary. Each stem*was divided into three parts: base, middle and tip positions. The leaves in each position were counted and leaf was randomly chosen from each position and measured. The total leaf area of the plant was estimated by: CA - (}.‘.bicmi + libidmiwxbiemi + Zbidsi.s) (H) where bi - area in sq. cm. of standard i cmi - no. of leaves in position i (base) of standard i dmi - no. of leaves in position 2 (middle of standard i em, - no. of leaves in position 3 (tip) of standard i dsi - no. of leaves in secondary stem of standard i s - ave. no. of secondary stems per main stem H - no. of main stem per plant i =1, 2, ..., l0. 2. Yield - the fresh weight of the tubers of each plant was recorded. 3. Tuber dry matter (DHT) - was estimated by taking the speci- fic gravity of the tubers and by the use of the table of conversion to percentage of dry matter (Burton, l9h8). 10 h. Plant dry matter (POE) - all parts of the potato plant other than the tubers were phced in the dryer at 65.5 C for B-li days to insure complete dryness. 5. Total dry matter (we) - the sum of tuber dry matter (our) weight and plant dry matter (PDH) weight. 6. Leaf area index (LAI) - the leaf area per unit area of ground area beneath that plant. Since the plant spacing is constant within the experiment, the pattern of LAI will then follow that of LA. Indeed, the planting distance is more or less constant from experiment to experiment and this enables us to directly compare estimates of LA (or LAI) fromrexperiment to experiment. The results are not included in the discussion but will be presented and dis- cussed in Appendix l. Cultural techniques Fine mist irrigation pipes were set between rows to insure an adequate supply of water and to keep the air and soil temperatures reasonably low. Fertilizer was applied at planting. A regular spray schedule controlled insects and diseases. Heads were well controlled by a chemical herbicide. Experiment l The plant materials were taken from three well known varieties: Russet Burbank, Katahdin and Onaway. Russet Burbank is a late maturing variety with high specific gravity. Katahdin is medium in maturity and specific gravity. Onaway is early with low specific ll gravity. Twenty five plants were taken at random from a seed-increase plot. All the measurements were taken from these 25 plants for each variety. Data were collected in l966 and l967. a. l266 Experiment - The first-year experiment was conducted at Michigan State University Branch Experiment Station at Lake City in 1966. The plants were spaced 86 x 35 cms. in the field. Leaf area was measured only once - just before the plants reached full maturity. Specific gravity of the tubers was taken. Visual ob- servations on growth habit were made. b. 1967 Experiment - The second-year experiment was conducted at Michigan State University Branch Experiment Station in Montcalm County in l967. The plants were spaced 9i x 38 cms. in the field. The leaf area was measured 60 days after planting and every twenty days thereafter until the majority of the leaves were yellow or fully matured. The summation of the daily leaf area was estimated by plotting the measurements taken at 60 days, 80 days, l00 days and l20 days against number of days. The points were connected by a smooth curve. Since growth was fairly uniform between points, measuring many points would probably not greatly increase the accu- racy of estimating the summation of daily leaf area. The area under the curve for each particular case is the sum of the daily leaf area for the number of days in each particular i time interval. That is, the amount of leaf area for the first 60 days of growth was that estimated from the area covered by the curve i2 from 0 to 60 days. The leaf area was measured at more than one growth stage: twice in Onaway and three times in Katahdin and Russet Bur- bank. As soon as the plants showed full maturity the tops were pulled and dried. However, after l2D days, all were pulled regardless of maturity. Specific gravity of the tubers and fresh weight were taken for each plant. Tuber dry matter per plant was estimated by the method previously described. Economic photosynthetic efficiency (EPE) in the first experi- ment was the tuber dry matter per unit leaf area (g/cmz) (i.e., the estimated LA for the single measurement). Hhile in the second experiment, EPE was the ratio between the tuber dry matter per plant and the total leaf area days (i.e., the total area of the curve as described above). All the raw data were punched on IBM cards. Analyses were done by the MSU Computer CDC 3600. Means, standard deviations, correlation coefficients and regression coefficients were evaluated. Experiment 2 Haploid tubers of Solanum tuberosum were originally obtained from the Wisconsin Experiment Station. In this experiment, the plants were grouped according to their parental source. This ex- periment was conducted at Lake City in l966. Group i had 25 individuals, groups 2 and 3 had A and 5 indi- viduals, respectively. These individuals cloned into l0 plants. fl. The 34 clones were planted in randomized-block design with two replications - five plants in each plot. Leaf area was measured only once - just before full maturity by the same method as that used in the varieties. Specific gravity and fresh weight of the tubers were deter- mined for each plant and the dry matter in the tubers (DMT) was calculated. Economic photosynthetic efficiency (EPE) was calcu- lated by DMT/LA. Experiment 3 This experiment was primarily for an estimation of genetic parameters. Haploids of different sources including those tested in the field the previous year were planted in the greenhouse in the winter of l966 and induced to flower. All possible crosses were made. Because of sterility and incompatibility problems, not all combinations were successful. However, a complete set of a S x S diallel series without reciprocals was available. The five parental types of the diallel cross were Parent I (5283-h), Parent 2 (528l-6), Parent 3 (5279-23), Parent h (5279-2I) and Parent 5 (5287-l). The number of FI seeds varied from cross to cross. The seeds were shown in the greenhouse and the plants formed tubers in the summer of l966. One tuber from each seedling was harvested in the fall of l966. All the tubers from each cross were bulked and stored in refrigerated conditions (h C) until the spring of l967 when they were planted at the Station in Montcalm County. Parents and PI tubers were planted #5 centimeters between hills and ICC cms. between rows in a randomized block with two replica- tions and four plants in each plot. Two crosses (2 x h and 3 x 5) failed due to the fact that they came from very small tubers. Generally, the Fl's had smaller tubers than the parents. The leaves were measured ho days after planting and subsequent measurements were made at intervals of 20 days until the leaves were dead or the majority had turned yellow. The averages of the estimated leaf areas at each date were plotted on graph paper. The curve was smoothed, cut, and weighed. These values were converted to leaf areas in sq. meter days. The estimated total photosynthetic leaf area days for each particular interval (in this case no for the first and 20 days for the rest) is the area under the curve OVer this particular time interval. That is, the photosynthetic leaf area days from 0 to ho days after planting was the area under the curve from D to the leaf area measured #0 days after planting which was the sum of the daily photosynthetic leaf area for the first ho days of growth. The estimated photo- synthetic leaf aree days for #0 to 60 days was the area under the curve from the point at 40 to the leaf area measured 20 days after which was the sum of the photosynthetic leaf area for the next 20 days of growth. The total cumulative photosynthetic leaf area days for the entire growing season was the area under the whole curve. The plants were pulled the latter part of September, placed [Er-“‘85 '5 i" th‘ dryer 't 65-5 C for 3 to 9 days to insure complete dryness and weighed to obtain the dry matter in the portions other than the tubers. Genetic parameters were estimated by employing Method h, Model II of Griffing (I956) and Analysis III of Gardner and Eberhart (I966) on the analysis of variance of general and specific combining abi- lities in a diallel cross. This model assumes that parental geno- types are chosen at random, i.e., genotyplc effects were consi- dered random. The gene frequencies of the parental types were ar- bitrary. The specific combining ability gives an estimate of the non- additive genetic variance and the general combining ability an estimate of the additive and non-additive genetic variance. The estimate for environmental variance was the mean square error term in the analysis of variance. Gardner (l966) mentioned that mean square of varieties versus crosses reflects average heterosis and is attributable entirely to non-additive genetic effects. The analysis of variance for Model II Method A of Griffing (1956) and Analysis III of Gardner and Eberhart (l966) giving expected mean square is shown below. The genetic parameters were estimated as follows: oz -(MSg - MSs)/(n - 2) - variance of general combining 9 ability o2 - (MSs - MSe) - variance of specific combining s ability 2 - additive genetic variance 2 GA 269 l6 2 2 ”MA - cs - non-additive genetic variance 2 2 2 ac - UA‘+ UNA - total genetic variance 2 - ‘2 +'e2 - h i UP G . p enotyp c variance of - MSe - environmental variance h: - tile: - heritability in the narrow sense h: - Gila: - heritability in the broad sense SOURCE OF MEAN SQUARE EXPECTED MEAN SQUARE PARENTS n-I MSp PARENTS VS. CROSSES I MSpc CROSSES (n(n-l)/2) - I MSc GCA n-l M59 0: +ro§ + (n-2)o§ 2 SCA n(n-3)/2 M55 0; +'os 2 ERROR MSe o RESULTS AND DISCUSSION Experiments I, 2 and the first part of 3 were conducted to ' determine the similarity of physiological patterns between the tetraploid potato varieties (2n - #8) and the haploids (2n - 2h) derived from tetraplolds. The second part of Experiment 3 was a genetic study of inheritance of physiological characters in haploids involving diallel analysis. The tetraploid varieties used were Russet Burbank, Katahdin and Onaway. Experiment l: a. [966 Experiment - Means and standard deviations of the characters under consideration in Onaway, Katahdin and Russet Bur- bank are presented in Table l. Onaway was the lowest in all the characters studied except yield (962 g. per plant) in which It was the median of the three varieties. Katahdln had the medium leaf area of 5299 sq. cm. but had the highest fresh yield (l0l9 g. per plant) and dry matter (2l0 9.). Russet Burbank had the highest leaf area (6790 sq. cm.), but lowest yield. Tuber dry matter of 206 g. in Russet Burbank ' was about that of Katahdin (2l0 9.). Starch content follows the pattern for dry matter. I7 18 Table l. Means and standard deviation of leaf area (LA), yield, tuber dry matter (DMT), starch (S) and economic photo- synthetic efficiency (EPE) on a per plant basis of 25 plants for the three tetraploid varieties. “ME" :(quAcn-l "(5)0 2:) <31 :(s/sfle-n.) 0mm 32 5050 962 18k 129 0.0361: 32 2l50 356 52 33 KATAHOIN 32 5299 1019 210 151 0.0396 s2 2190 3I7 54 36 RUSSET BURBAK SE 6790 9M 206 152 0.0196 si 3000 210 42 3o If we assume that the difference In mean leaf area measured at one point in time may be regarded as a reliable measure of var- ietal difference and that this is a valid estimate of active leaf area over the life of the plant, we can proceed to the consideration of the economic photosynthetic efficiency (EPE) Table I. The results show that Katahdin and Onaway have high EPE, 0.0396 and 0.0369 grams per sq. cm. of leaf area, respectively, and Russet Burbank had the lowest, 0.0I96 grams per sq. cm. No standard errors were attached to EPE since this observation was obtained from a calculation based on the mean leaf area and tuber dry matter per plant. The investigation of the association between leaf area, dry matter of the tubers, starch and EPE was extended to the inter- 19 relationships of these characters within varieties. In this case, it is possible to examine numerical relationships by means of corre- lation coefficients (Table 2) rather than verbal associations, since the number of paired comparisons (multiple observations on individual plants) is much larger within than between varieties. Table 2. Correlation coefficients within varieties for leaf area and each of yield, dry matter of the tubers, and starch (1966 data). CHARACTERS CORRELATED : CORRELATION COEFFICIENTS HITH LEAF AREA OMAUAY : KATAMDIN : RUSSET BURBAMK YIELD O. 77“ 0.78“ 0.09" TUBER DRY MATTER o. 76“ 0.78“ 0.1m" STARCII 0. 713* o. 77“ min" * Significant at 5% level **Significant at 1% level From Table 2, all characters were positively and significantly correlated with leaf area within these three varieties. Moreover, within any one variety the degree of correlation of yield, DMT, and starch is almost the same. This indicated that these characters could have a high internal relationship between them, i.e., a change in one affects the other two characters. b. 1262 Experiment - A more comprehensive study of the pho- tosynthetic efficiency of these three varieties was carried out in 1967. Duncan (1967) suggested that in a study of photosynthesis, .20 the time factor should be considered because the product a farmer harvests is not simply a rate per day but an accumulation over a certain time. Also, the 1966 results for these varieties indicate that there‘was a definite drawback in considering only one measure- ment of leaf area and in neglecting consideration of maturity times. Accordingly, the leaf area was measured at more than one growth stage: twice in Onaway and three times in Katahdin and Russet Burbank. Onaway had matured before the third measurement. 'The first measure- ment was made 60 days after planting and the subsequent measure- ments were made at 20-day intervals until plants were fully matured. The average (25 plants) leaf area at these intervals for each of the varieties is indicated by the points on the graphs in Fig. i. From Fig. 1, five main characteristics of the curves, which show differences between the varieties, are apparent: - (l) The maximum LA obtained differs; (2) the point (day) at which the maximum was reached is slightly different; (3) the area under the curve differs in bulk, i.e., the integral under the curve, which is termed as photosynthetic leaf area day (PLAD) (the term is derived from the naming of the x and y axes and was calculated by weighing out the total graphed area and converting it to sq. m. days); (A) the shapes are different; (5) the end point, i.e., the time of maturity varies. However, the harvested yield and tuber dry matter changed only slightly from variety to variety (Table 3). This table includes measures of points 1, 2, 3, and S, AVERAGE LEAF AREA PER PLANT IN 1000 cm2 10~ I 84 64 44 2b 4. 2. 16H 144 12‘ 10‘ 21 £3£pggp4l. Sum of the daily photosynthetic leaf area measured at different stages of growth in Russet Burbank. Ketahdin and Onaway 2 (10,141 cmz) (9532 cm ) (a) RUSSET BURBANK (8693 cm. 2) \\ \\ (b) KATAHDIN (5840 cm2) (5318 cm!) (3937 cmz) \\ '\ ‘x \ \. (15,454 cmz) (c)ONANAY (8 514 cm2) \ \ \ \ \ \ \ \ \ \ 1O 20871 30 4b 50 60 8o 90 160 lib 1Z0 NUMBER OE DAYS 22 mentioned above, and also estimates of total dry matter (TDH), i tuber dry matter (ONT), net assimilation (NA), and economic pho- tosynthetic efficiency (EPE). Figure l and Table 3 should be examined to account for the lack of differences in tuber dry mat- ter: - (i) The maximum LA was highest in Onaway, median in Russet Burbank and lowest (about ill of Russest Burbank) in Katahdin. These large differences in maximum levels obviously did not result in differences in yield dry matter. (2) There was a difference in the time when maximum LA was attained. (3) The area under the curve (TPLAD) did not follow the level of maximum LA in the two varieties Onaway and Russet Burbank. They were, in fact, reversed. However, it was again lowest in Katahdin. Since there was no substantial difference in the tuber dry matter content it must be concluded that TPLAD by itself cannot account for dry matter accumulation in the tubers. It is necessary to emphasize that although TPLAD (and/or maxi- mum LA) are the most likely factors which might affect dry matter accumulation - neither did so. The explanation is thought to lie in the next two considerations: (A) Shape of the curve and (5) end point or maturity. The pattern of leaf area development is quite different from variety to variety (Fig. l). The most striking difference is bet— ween Russet Burbank and Katahdin and Onaway. All three varieties accumulated leaf area at a rapid rate during the early growth stages. Onaway and Katahdin attained maximum LA at approximately 23 the 60-day point. While Russet Burbank attained its maximum LA at the loo-day point the increase after the 60-day point was very small. After this point the first two varieties (Russet Burbank and Katahdin) more or less leveled off. The third variety (Onaway) decreased in LA until all the leaves senesced at the loo-day point, at which time 'maturity', if defined as the complete laying down ‘f’ of substrate in the tubers, has been reached. Nevertheless, there were less striking differences in pattern between Russet Burbank g; . and Katahdin. After th 60-day point, LA of Russet Burbank increased slightly, then leveled off and decreased very little by the time the experiment was terminated. 0n the other hand, Katahdin started a slow almost imperceptible decrease in LA and all the leaves had senesced completely by the end of the experiment. Leaf area alone whether measured as TLA or TPLAD does not seem to account for ONT. It would seem logical to suppose that the distribution of leaf area over the growing season, the onset of senescence, and the time of maturity are modifying forces. Fur- ther, the critical time for the accumulation of dry matter in the tubers is the period after maximum leaf area has been attained. This could be a function of senescence/maturity and could be due to variation in efficiency of leaf areas at any given time. For example, too much leaf area could decrease photosynthesis and in- crease respiration. The results of the estimated LA of the three varieties in relation to each other did not entirely agree in both years. in 2A the l966 results Katahdin had the medium LA among the three varieties studied and Russet Burbank had the highest, while the l967 results showed that Katahdin had the smallest LA both in the total and at any time interval of measurement. Russet Burbank had the highest TPLAD because of the longer growing period. Onaway had the median TPLAD with a very short growing period. Table 3. Means of maximum leaf area, day at which maximum leaf area was attained, total photosynthetic leaf area day, maturity, total dry matter, tuber dry matter, net assimilation and economic photosynthetic efficiency per plant of Onaway, Katahdin and Russet Burbank (l967 data). . VARIETY CHARACTERS ' : ONAUAY : KATAHDIN : RUSSET BURBANK (l) MAXIMUM LA (sq. cm.) 15,45h 5,840 l0,lhl (2) MAX. LA ATTAINED (DAY) 60 60 lOO (3) TPLAD (sq. m. days) 5|.h3 32.l9 60.l5 (5) MATURITY (DAYS) 100 120 120 TDM (grams) 3l8 3h2 325 DMT (grams) 209 223 227 MA (grams/sq. m. day) 6.17 l0.63 5.110 EPE (g/sq. m. day) 4.06 6.92 3.77 The discrepancy in the LA measurements could be that Katahdin had its maximum LA between the second and third measuring time and] or the measurement in Onaway in the l966 experiment had been made 25 so late in the season that the leaf area had already decreased due to the onset of leaf senescence or tuber maturity. Another reason could be that the l967 LA was presented as the cumulative photo- synthetic leaf area days while in the l966 results, LA was the ac- tual estimation at one particular time of measurement. The other characters followed the same pattern for the two years' experiments. That is, Katahdin had the highest TDM, NA and EPE, although, MA and EPE for the l967 experiment are not compa- rable with those of l966 because the latter was based on LA while the former was based on PLAD. However, the trend was the same. Dry matter of the tubers was almost the same as that of Russet Burbank. Net assimilation (MA) was the ratio of TDM and EPLAD and economic photosynthetic efficiency (EPE) was DMT/TPLAD in the l967 experiment. 0f the three varieties studied, Katahdin had the highest MA and EPE. The data suggested that plants which had moderate LA during the early stage of growth and remained that way for a period of time before maturity, stored most of the photosynthate in the tubers. Uhen leaf area continued to increase, much of the photo- synthate was used in the production of more leaves. If there are too many leaves, there is a possibility of shading, thus, these plants will not be as efficient as those with fewer leaves. This suggestion would be compatible with the results of Watson (i958). Experiment 2: The main object of this experiment was to determine whether 26 similar physiological patterns exist between the tetraploids and the haploids. Means and standard deviations were calculated bet- ween individual clones within the three groups (progenies), Table A. The standard deviations for LA for each of the three groups were very large, but were not significant between groups. It seems pointless, therefore, to discuss the influence of LA on tuber dry matter, yield, etc. for this experiment particularly since it is felt that the large errors were duefto errors in measurements arising from the inability of the method of Epstein and Robinson (l965) to deal with the different morphological type of the haploids. This situation was corrected in the main experiment with haploids, Ex- periment 3. The results, however, showed a pattern of the relation- ships between LA and yield, DMT, starch and EPE similar to that obtained in the varieties (Expt. l). Table A. Means and standard deviations for leaf area, yield, tuber dry matter, starch and economic photosynthetic efficiency per plant of three groups of haploids (l966 data). GROUPS :(sq.L:m.: : (I) i 2;) g (z) : (gisszcm.) Group l (25 plots)?! 32 4211 493 90 65 0.0214 53" #797 “0] 72 #7 Group 2 (h plots) 2 6b27 729 lZS 84 0.0l95 Si hl9l 325 A5 29 Group 3 (5 plots) 2 #506 756 l29 86 0.0286 5; 328i 769 l20 76 .2/ number of progenies in each group. 27 Experiment 3: More intensive observations were made on the haploids. The parental haploids, 5283-h, 5279-23, 5279-2l, 5287-l and 5281-6 and the F"s of the diallel cross were evaluated. The experiment was broken down into two parts: (a) Physiological and (b) Genetic investigations. a. Physiology - It was apparent in the results of Expt. 2 that there was a very high variation in leaf area measurement. One of the causes might be that the method used in measuring LA was the same as that used in the varieties. All the parental types matured in l00 days. Parent l (5283-h) consistently had the greatest PLAD followed by Parents 3 and h (5279-23 and 5279-2l, respectively) with the smallest PLAD found in Parents 2 and S (S28l-6 and 5287-l). Maximum LA was attained by all the parental types at the 60-day measurement. This agreed with Onaway and Katahdin varieties and the results of Carolus (l937). The Fl's of the diallel cross had variable maturity. Crosses (l x A), (l x S), (2 x 3) and (l x 3) were not fully matured af- ter l20 days when they were all harvested. Maximum LA or PLAD of the Fn's was obtained at different stages of growth. For in- stance, cross (l x h) had its maximum PLAD during the 80-]00 day interval, (2 x 5) on the AO-60 day interval and (2 x 3) on the 100-120 day interval. The last measurement on the (2 x 3) FI might not have been the maximum LA because all were harvested after l20 days regardless of maturity. All the other crosses reached maxi- 28 mw§n ho mMMZDz Cad 00H om ow 0m 00 on ca om ON OH roH (zma 0001) .LNV'Ia 113a mv JVH'I 29 mum PLAD during the 60-80 day interval. Typical growth patterns are shown in Fig. 2. The results are summarized in Tables 5a and Sb. It was shown by the parental types and the Fl's that there was a direct relation- ship between lPLAD and ZPLAD with the TPLAD. However, if the plant matured early even if it had higher lPLAD and 2PLAD it did not have as high TPLAD as the one with a longer growing period of moderate lPLAD and 2PLAD. The parental types were generally more vigorous than the Fl's. In the potato, the interest is in the proportion of the pho- tosynthate that is translocated to the tubers from the leaves. The values of 2PLAD, 3PLAD and TPLAD for both parents and F"s are plotted against total dry matter (TDM) in Figs. 3a, b, and c, res- pectively. In general, there is a linear increase in TDM with in- crease in leaf area (PLAD) for all three measurements of PLAD. in the earlier stages the increase is steeper, i.e., a given increase in PLAD at stage 2 (ZPLAD) gave a greater increase in dry matter than a similar increase at the later stages. It may be seen from the fitted values that there is a decrease in regression slopes, i.e., b (ZPLAD) - 0.2l6 b (3PLAD) - 0.lh6. Photosynthetic ef- ficiency (as defined by the TOM/TPLAD) tended to decrease with plant age. To obtain a clearer idea of the relationship of PLAD and dry matter distribution in the plant, ZPLAD, 3PLAD, and TPLAD were graphed against both tuber dry matter (DMT) and dry matter of the 30 Table 5a. Means of cumulative photosynthetic leaf area days at different time intervals and totals for the parental types and the diallel cross Fl's. , CUMULATIVE PHOTOSYNTHETIC LEAF AREA DAYS TYPES ‘ : O-AO :90-60 : 60-80 :80-100 : 100-1203T0TAL : days ; days : days : 4215, : days : 9411:1111 ‘ 4.34 16.74 24.32 14.54 0 58.50 PARENT 2 1.30 4.40 6.82 3.59 0 15.59 PARENT 3 1.98 11.55 15.98 8.0A 0 36.16 PARENT A 3.96 12.03 16.85 11.30 0 “2.51 PARENT 5 1.35 4.09 5.88 2.97 0 13.66 1 x 2 2.13 3.48 3.89 1.35 0 8.88 l x 3 2.55 5.62 6.8h 5.35 3.77 21.92 1 x 4 3.15 8.15 12.18 13.52 12.63 48.09 1 x 5 3.25 10.37’ 13.19 6.03 1.19 33.18 2 x 3 2.06 4.37 5.65 5.76 5.90 22.31 2 x 5 2.72 3.13 2.29 0.45 O 6.83 3 x A 1.59 2.73 3.45 1.68 0 7.60 4 x 5 2.70 5.62 9.61 6.63 0 22.95 31 Table 5b. Means of yield, plant dry matter, tuber dry matter, total dry matter, net assimilation and economic photo- synthetic efficiency per plant for the parental types and diallel cross Fl's. TYPES : YIELD : PDM : DMT : TDM : NA :EPE:(DMT/TDM)100 :(g/plt.):(g/plt.):(g/p1t.) :(g/plt.): : : per cent PARENT 1 1354 140 282 422 7.33 4.92 66.82 PARENT 2 554 58 106 164 11.05 7.47 64.63 PARENT 3 1106 132 '207 339 9.35 5.68 61.06 PARENT 4 942 116 179 295 7.99 5.04 60.68 PARENT 5 410 32 92 124 9.55 6.93 74.19 1 x 2 244 60 63 123 13.87 7.08 51.22 1 x 3 422 95 96 191 8.63 4.51 50.26 1 x 4 360 226 76 303 6.73 1.63 25.08 1 x 5 644 104 133 236 7.81 4.44 56.36 2 x 3 364 108 84 192 8.37 3.63 43.75 2 x 5 248 41 59 100 14.40 8.40 59.00 3 x 4 162 63 45 108 14.33 5.93 41.67 4 x 5 474 49 106 155 7.67 5.33 68.39 32 2.8 .13 «a. as). :3 2.1.3389... .32. .26.. «a. a»... sec- ..ee. Belgians... n 75 «a. .5 e2. .3. 0.85.533... « (sum) Jenni ‘10 10301 am mm 3 g OH “R an Du Pu D“ w_ Np b W nu Hm ON mm NM m Q c Om 0_ N— U w u _ . . .. 8— o e 28— .. cu. . on. . 3. . 3. . 8. . 3. . 3. . 3. . 8m .03 I. .03 w .. on" u a .3N a .2...N m e. =8 n .62 J v ) 1 has SW 03 . 8n ( L can . 8n «n 3.; + 2 .3 u u . 3n . 3n . 3n . 3n ton Kn..o+mn.ooam .oan m.~h 0 queen-..— m . co: . . 8.. h 0 o §~.o+e~.nmum x A v Tun: cocoa-m x 2.. ON: .a. ..c .3338?! so»; me..- eee. 9313:3393. n was me..- eee. 02225.39! .33 :53. ece :3 «one pee. 0.35.5333 N unfam- venue—e .330... 3.02.... u use 3:93.. .3 use... tee Leonel P... .30.. .un 953; 3.0.3.. a use 339.... ace... ..ee ceuuae Co .30... .e 33 plant (leaves, stems, etc.) (PDM) in Figs. 5a, b, and c and 4a, b, and c, respectively. It can be seen from all 6 figures that generally, there was a linear increase both in DMT and PDM with an increase in PLAD. It may be seen that the pattern for the 3 measure- ments of PLAD was similar for both DMT and PDM*within the qualifi- cation stated in the preceding paragraph, i.e., there were decreas- ing regression slepes as the plant ages. In this case, it is better to concentrate on the differences in the patterns between DMT and PDM from Figs. 4c and 5c. The components of total dry matter (TDM), DMT and PDM are not as clear as the TDM. Consider first Fig. 4c. Generally, there seems to be a liner response to increase in PLAD. However, there are two points designated as RI and R2 (encircled on the graphs) which are off the trend (Fig. 4c). At this point, consider also Fig. Be. There is also a general linear response, i.e., DMT in- 'creases as PLAD increases, but one of the two points (R2) which was off the trend in Fig. 4c also disturbed the trend in Fig. 5c (encircled as R2 which corresponds to the R2 in Fig. 4c). By considering the two points in Fig. 4c, the plants belonging to RI were least efficient in the production of taps while those in R2 were most efficient. In Fig. 5c, Rl plants were more efficient in accumulating photosynthate in the tubers and R2 plants were less efficient. It would appear, therefore, (Figs. 4c and SC) that R] plants are more economically efficient, i.e., a greater prOportion of the photosynthate was accumulated in the tubers and R2 plants Ana-e «I. amen eeu< use; uuuezusmeooosm dough «ammo «no mace see. u_uezue>n0uo£m n Aux-v «no eeee see. u.ue:uc>e0uoge u 34 «n we ea ca on an as an as o. w. o e c on an on o. N. o a o as w. n. o a o a . on w m ca 6 co .om .oo. .4 n. Loud w .oe. a 3 u iced a was.“ + on..~ n m .8. m. m x3... + on... n > ( x86..o:.» 18" .8“ .o- .o- N¢ 0 g e m .3 3a . 9: 2. e e 3: e a queen-m x a..u . «acute; a .>.es.uueeaec .eece mes. ..3. .3- u..2.§.32a n a... L. .8. 0:22.332... u :58. no a a o e e a eat-e o to as >c .AIMIMMqumMII amen ouueaumseouosm nave» accumu- veuuonm evuoummn tea _ v. — m: u a: u m an t ace—m .u e.—m one momma ueuaeuee no use"; use menu-I hue uoeum .ue eumuum Jen-w Ma 30014 (smeafl) 35 .53 «a. $3 8:. ...,. 0.02afiwoast .36.— ?er «I. 058 eeu< nee.— m n Ass-w «I. 058 00.3 «004 m u enumSSSIAm—iono.2oco 12:832....832... . on . 3 .3 u a Q .8 . 8. I. n a .3. J o u .3. q u 0 J .00. x-.n+o~.nnn> fl: .3. m . com I .ONN .SN .SN 2 . .08 a. .. . .. no..o + ~o.~« a » unu.o + n~.n~ I u 3:0..- a L A“; SH any .5 ...u . cones-m a .43 .050 .00. 032.25.391 .33 ups-me 0030... 3.0.9.. 5 0:0 3:0»! e0 ...qu .Cv seas.— .qula... ..u. massages-em .50.. 09—0 use. 0305050000.... n 100 u used-me 1030: 0301.2. ..m 000 309—0.. no use: use menu-I mum men-F blag“ on om co can can Sn can 63 SN con 103311 m 80101. (emu!) 36 were not econonically efficient. This is amplified in Fig. 6 where the ratio (DHT/TDH) tines lOO is plotted against TPLAD. The ratio seems to be constant for both parents and Fl's (the line through the points appears to be hori- zontal) except again for the two points, RI and R2 (encircled). If these points RI and R2 be examined closely considering the na- turity of these plants, the differences may be explained. Plants in RI (cross h x 5) matured in lOO days and plants in Rz (cross l x h) matured in l20 days. ‘Plants in RI were more econo- uically efficient because they matured earlier than those in Rz. In fact, R2 plants were not fully natured when harvested. Had these plants been allowed to reach full maturity, they might have had greater DHT and therefore might have had higher efficiency. However, in field plots the growing season is limited by frost. Therefore, R plants may be considered the ideal with an optinuu l TPLAD of approximately 23 sq. m. days at lOO-day maturity. The PLAD during the attainment of the maximum LA and before full natu- rity, however, must be considered. The amount of photosynthetic leaf area at the 60-day and 80-day period have a greater influence on the total leaf area and DHT, i.e., 2PLAD and 3PLAD, respectively. To return to a more statistical treatment of Figs. kc and 5c, regression and correlation coefficients were calculated with and without the points RI and R2. These are shown in Table 6. Percentage Tuber Dry Matter (1) 100 ' 80* 60, 50, 40- 37 Figure 6. The percentage of dry matter accumulated in the tubers of parental typea and P1 haploids plotted against total photosynthetic leaf area days. x Parents 0 171's . Y - 57.18 - 0.06X A J A A J L J l L 12 16 20 24 28 32 36 40 44 48 52 Total Photoaynthetic Leaf Area Daya (m2 daya) ¢~+ a: 38 Table 6. Regression and correlation coefficients of total dry matter, tuber dry matter, tops dry matter, economic photosynthetic efficiency and the percentage of dry matter in the tubers with 2PLAD, 3PLAD and TPLAD of the parental types and the F '5 derived from diallel series, with and without 11l 6nd 112. CHARACTERS i—iLLAD = 3w : 1mm 3 r 3 b __i. r 3 b : r : b * .8 TD“ (VI/0 R, 9 R2) 0.97 0.216 0.97 0.1116 0.98 6.171. (w/ a] 5112),“095 0.220 0.95 0.1118 0.96 5.862 DHT * 0.97 0.149 0.98 0.102 0.96 4.199 ** 0.94 0.146 0.93 0.098 0.79 3.221 PDH * 0.85 0.070 0.84 0.046 0.90 2.088 ** 0.62 0.078 0.62 0.052 0.83 2.738 EPE * -0.47 -0.001 -0.46 -0.001 -0.59 -0.053 ** -0.39 -0.002 -0.42 -0.001 -0.66 -0.072 (DHT/TDH)100 * 0.39 0.008 0.42 0.006 0.34 0.200 ** 0.19 0.006 0.21 0.004 -0.07 -0.060 A much better relationship is obtained between both DHT and PDH with TPLAD when these two points were omitted. It seems logical, on the basis of biological considerations, to accept the better fit as describing the general relationship and to consider, RI and R2 as special cases. Plant breeders would, however, be interested in the special cases. The physiological patterns for both tetraploids and haploids were discussed in detail under their separate headings, however, 39 general similarities are summarized here. (1) The distribution of LA over the growing season, the 6nset of senescence and the time of maturity are modifying forces in the accumulation of ONT. (2) The critical time for the laying down of dry matter in the tubers is the period after maximum LA is attained. Leaf area at the 60- and 80-day periods has the greatest influence on the ac- cumulation of dry matter in the tubers. (3) Plants with moderate maximum LA which senece slowly and mature in reasonable time are more economically efficient than those with more LA, long maturity and rapid senescence. On this basis the genetic action of the physiological characters under consideration in the genetic expe- riment with haploids would apply to the tetraploid potato. b. igenetic_stgdies with haploids: To attain the objective of maximum production it is necessary to have strains or varieties that have highly efficient leaves. Blackman and Black (1959) concluded that optimum LAl for dry mat- ter production is dependent on the Species. According to Watson and French (1962) a better way to remedy the inefficiency of the kale crop in dry matter production when LAI was high would be to decrease the leaf-density dependence of net assimilation rate by breeding and selection. Breeding and selection can be utilized effectively by know- wing the genetics of the characters under consideration. In this experiment the diallel set was utilized to study the genetic be- haviour of the different characters. To test the null hypotheses that there are no genotypic differences among the parents and Fl progenies, a randomized-block analysis of variance for each cha- racter was performed. The analyses showed that all the characters under study had highly significant values of F. This means that the null hypotheses were rejected and it can be assumed that genotypic differences exist. The potato is an autotetraploid plant. It is asexually pro- pagated and thus highly heterozygous. in this study, haploids de- rived from autotetraploids were used. Haploidy provides a means of obtaining a high degree of homozygosity. Hougas and Peloquin (1958) stated 'The haploids in themselves as initially derived from an autotetraploid closely approximate, assuming random chro- mosome segregation and not more than two alleles for any one locus, the degree of homozygosity obtained following three generations of selfing the autotetraploid. If one assumes random chromatid seg- regation the degree of homozygosity would be slightly less.‘ The analyses of general and specific combining abilities for the different characters under consideration are given in Table 7. The methods of analyses of Griffing (1956) were performed by least squares as described by Gardner and Eberhart (1966). The analyses of the parental types were separated from the progenies due to the differences in their physiological behavior. The parental types were more vigorous than the crosses. This could be due to the fact that parental types were grown from larger 41 seed pieces while the F 's were from small, some very small, tubers. The parental types had higher PLAD at any time than their Fl's. Host of the Fl's had lower PLAD than their mid-parents. However, some of the Fl's had yield and DHT lower than their mid-parents. Host approached their mid-parents in NA and EPE. The parental types showed significant differences for lPLAD, 2PLAD, 3PLAD, and TPLAD. There were also significant differences between parents and crosses in all the traits mentioned above except for lPLAD. The non-significance between parents and crosses for lPLAD could be that the plants were starting to develop. The photosynthetic leaf area at early deve10pment, lPLAD, 2PLAD and 3PLAD among the crosses. Table 7) did not show any signi- ficant differences at the 5 percent level in general and specific combining abilities. The non-significance of the general and specific combining abilities for lPLAD, 2PLAD, and 3PLAD indicates that the ability of the parents to transmit these characters was very low or non- existent. Specific combining ability for TPLAD was significant at the one percent level. This character then, can be improved through breeding and selection by using parental lines that combined or nick well. However, it did not show any significant additive ge- netic variance (0%) but very high non-additive genetic variance (“:A)' it may be possible that the genes for lPLAD were different from those for 2PLAD or for 3PLAD and that there might have been 42 .~.m mmm.o_ ans. m_: o_._. m~.m o..: m_.o :N «exam .o._ f . -. . a -. .. . . . . a... maaum m. as. m_ «sauna moo «moo mma :m m. a. m ON 6 m >p_4_m< az_z_mzoo u_a_ouam «m:.m m~.m mom._~ anew mm. .m.om_ _o.m_ ...o o:.o : >._s_m< az_z_mzou 4<¢uzmu mm.~ mo.m :...m_~ «mm:— nmm. .m.omm o_.mo om.m~ m:._ N mammogo m .N . . . . I . . . a «N sesame mamaammsmaaamn_mmaae musaamm mawaqe mm _o a _ mummoau ms mhzm¢ do mugsom m¢<2mm zoeu_u.mmo o_uo;uc>mouo;a 0.50:000 use :o_um._e_umm use £6.66. u_o_> .cuubme >66 268:6 .a .6 moas_~=< .. 6.66. 43 gene interaction within a locus and between loci, giving the total effect of very high 03A, thus lowering the estimate of heritability in the narrow sense. It is also possible that this leaf area days (lPLAD, etc.) is not the best physiological measure of genetic difference. The analysis showed that there was a highly significant difference in the tuber yield between the parental types. The difference bet- ween parents and crosses was significant at the one percent level. However, this character did not show significance in general and specific combining abilities of the parents. The USA was about three times that of the oi, thus giving a heritability percentage of 11.7 per cent, Table 8. The differences in tuber dry matter in the parental types was significant at the one percent level. There was also high signi- ficance between parental types and crosses. The parents did not show any significant difference in general and specific combining abilities for this trait. The ofiA was about 4 times as much as the 6A. Heritability percentage was 8.4 percent which is very low. This might be due to the high 6:A and 0:. it could mean that this trait had an overdominance effect. Total dry matter included all the dry matter produced by the plant throughout its life, i.e., DHT and PDH. The analysis showed that there were significant differences of TDH among parents and between parents and crosses. There was a significant difference among parents in specific combining ability for TDH. Total dry o o:._m ...m o..: o..: o no._ mam o mm.~m ~m.m_ m~.m_ m~.m_ o .N.m <2 oo.m am.om mm. on. mm _m oNN m o ma... cum» .mm: .mm: o m.:.. tap a“... mm.m: . ammo: _o~o_ mam. m_:~ mmm.c_ > o:.m an.~: ma.w~. m:..om mm.o:~ mo._m mo.m_: are c ::.~. oo.mm~ om.om_ om.mw_ o o_._. o60uoze 6.26:666 6:6 co_u6__e.mma no: ..onume see .6.6» .gutmsa .u_o_> .touome >tn .683. .w 6.66. .aco 6:6 6_uocom mo moums_umm ' 45 matter appeared to be a complex character as exhibited by its lack of 6% and very high 03A, i.e., zero a: and 4,881 oi“. The heri- tability in the broad sense was 77.23 percent compared with zero percent heritability in the narrow sense. The non-additivity could be accounted for by gene interaction within a locus or bet- ween loci. Like TPLAD, this trait may be improved through breeding and selection by using parental lines that combined well and taking advantage of the non-additive effects. The efficiency of the plant to utilize the radiation energy for the production of usable energy is the ultimate factor to con- slder. It was divided into two categories, viz.: (l) the production of dry matter of the whole plant per unit leaf area (NA) and (2) the dry matter stored in the tubers per unit leaf area (EPE). These two were considered but the latter was the more important. The analyses showed that in these two characters, there were no significant differences among the parental types or between parents and crosses. However, the parents showed highly signifi- cant specific combining abilities for both NA and EPE. The 63A for each trait was high but zero 0:. The heritability percentages in the broad sense were 82 and 81 for MA and EPE, respectively. Both had zero heritability in the narrow sense because of the lack of additivity, i.e., zero a:- One of the possible explanations for the non-additivity in these traits is that there must have been a very high frequency of dominant genes. It could also be that the distribution of genes 4.6 for the transport of photosynthate to the tubers, and of the genes for the process of photosynthesis was probably unequal between the parents, since the parents were not homozygous at all loci. It was assumed that a majority of the loci are homozygous. Overdominant or epistatic effects may be reSponsible for the large non-additive variances. In either case the best genetic combination must be specifically evaluated. For the traits measured in this study, it would appear that mass selection, or other se- lection methods which depend on additive genetic variance, would be ineffective with this gene base. However, in the potato, over- dominant or epistatic effects can be an aid to improvement, since the potato is an asexually prOpagated crop. Superior characteris- tics can be prOpagated and maintained without the problem of loss through sexual generations. SUMMARY AND CONCLUSIONS A comparison of physiological patterns of growth within and between tetraploid potato (2n - 48) varieties and haploids (2n - 24) were studied in three experiments. The first experiment was a physiological study of tetraploids using three well known varieties, Russet Burbank, Katahdin and Onaway. The second experiment was a physiological study of haploid groups, grouped according to paren- tal source. The third experiment was the physiological and gene- tical study of the haploids. Five parental types and their Fl's derived from diallel series were used. The following conclusions may be stated: (1) The varieties and haploids examined showed similar physiological patterns (i.e., DHT, TDH, etc., increased as LA increased with only two exceptions which were considered as special cases). (2) The amount of DHT produced dependedupon the total leaf area distribution through- out the life of the plant and is discussed in terms of the size, shape, and end point of the growth curve. (3) There are some plants that are very efficient in producing and accumulating photosynthates in the tubers, while others used a greater proportion of the pho- tosynthate in the production of more tOps and maintenance of the normal metabolic processes. (4) Accumulation of photosynthate in 41 1.3 the tubers occurred after the maximum LA was attained. Maximum LA occurred in most plants at the 60- and 80-day measurements. Hoderate LA and slow senescence produced more DHT than large LA and rapid senescence or too much LA and too long a maturity. The cause of less accumulation of DHT was due to a limited growing season, the problem of shading or a very short period of accumu- lation, thus resulting in less efficiency. Plant Breeders will be interested in plants which have (a) moderate maximum LA attained around 60 or 80 days after planting, (b) that senesce slowly to take full advantage of the accumulation of dry matter in the tubers and that mature within the normal growing season. (5) All the traits studied appeared to be complex with low heritability. Thus, the breeder must plan selection systems to take advantage of the non-additive variance, if this population is representative, or devise a better evaluation of the genetic differences. (6) Host of the traits studied showed overdominance or epistatic effects. Non-additive effects can be an aid rather than a hindrance to breeding and selection for the improvement of the potato, since this crop is asexually propagated. LITERATURE CITED Anderson, A. K. 1960. Essentials of physiological chemistry. Fourth Ed. John Hilley and Sons. Inc. H. Y, Lond. Blackman, C. E. and J. H. Black. 1959. Physiological and ecolo- gical studies in the analysis of plant environment. XII. The role of the light factor In limiting growth. Ann. Bot. H. S. 23: 13]. Burton, H. G. 1948. The Potato. Chapman 5 Hall Ltd. 37 Esses Street v.c.2. 319 pp. Carolus, R. L. 1937. Chemical estimations of the weekly nutrient level of a potato crop. Amer. Potato J. 14: 141-153. Carraway, Michael 0. 1963. Movement of the products of photosyn- thesis in potato plants infected with leaf blight. Phyto- protectlon 44 (I): 60 Abst. Chapman, H. H. 1951. Absorption of carbon dioxide by leaves of ‘ potato. Amer. Potato J. 28: 602-615. and H. E. Loomis. 1953. Photosynthesis in the potato under field conditions. Plant Physiol. 28: 702-716. Duncan, William G. 1967. Model building in photosynthesis. Har- vesting the Sun. Symp. Photosynthesis in Plant Life. Ed. A. San Pietro, F. A. Greer and T. J. Armey. Acad. Press, N.Y., London. 309-314. Epstein, E. and R. R. Robinson. 1965. A rapid method for deter- mining leaf area of potato plants. Agron. J. 57: 515-516. Gaastra, P. 1959. Photosynthesis of crop plants as influenced by light, carbon dioxide, tempeature and stomatal diffusion resistance. Hededelingen van de Landbouwhogeschool te Ha- geningen, Hederland. 59 (13): 1-68. 1962. Photosynthesis of leaves and field crops. Repr, Neth. J. Agric. Sci. 10 (5): 311-324. us 50 Gardner, C. 0. and S. A. Eberhart. 1966. Analysis and interpreta- tion of the variety cross diallel and related populations. Biometrics 22(3): 439-451. Goncharik, H. N. 1963. The method of halves in photosynthesis measurement. Biological Abst. 24896 (44). Griffing, B. 1956. Concept of general and specific combining ability in relation to diallel crossing systems. Australian J. Biol. Sci. 9: 463-493. Harper, Peter. 1963. Optimum leaf area index in the potato crop. Nature (London) 197: 917-918. Hougas, R. W. and S. J. Peloquin. 1958. The potential of potato haploids in breeding and genetic research. Amer. Potato J. 35: 701-707. Ivins, J. D. and P. H. Brem ner. 1965. Growth, development and yield in the potato. Outlook in Agric. 4: 211-217. Kumakov, V. A. 1958. Photosynthesis indices as a breeding cha- racter in wheat (Sel'skohoz. Biol. 1967. 2: 551-558 (Russian)). Plant Breeding Abst. 415. 38(1): 53. Loomis, R. S., W. A. Williams and W. G. Duncan. 1967. Community architecture and the productivity of terrestial plant commu- nity. Harvesting the Sun. Symp. Photosynthesis in plant life. Ed. A. San Pietro, F. A. Greer and T. J. Army. Aca- demic Press. H.Y., London. 291-308. Ludwig, L. J., T. Saeiki, and L. T. Evan. 1965. Photosynthesis in artificial communities of cotton plants in relation to leaf area. Australian J. Biol. Sci. 18: 1103-1118. Pallas, J. E. Jr., B. E. Hikel and D. G. Harris. 1967. Photosyn- thesis, transpiration, leaf temperature and stomatal activi- ty of cotton plants under varying water potentials. Plant Physiol. 42: 76-88. Swaminathan, H. S. and H. W. Howard. 1953. The cytology and ge- netics of the potato (Solanum tuberosum L.) and related species. Repr. Bibliographia Genetica XVI: 1-192. Thomas, H. D. and G. R. Hill. 1937. The continuous measurement of photosynthesis, respiration and transpiration of alfalfa and wheat growing under field conditions. Plant Physiol. 12: 285-307. 511 Thorne, Gillian N. 1959. Photosynthesis of lamina and sheath of barley leaves. Ann. Bot. N. S. 23: 365-370. Watson, 0. J. 1947). Comparative physiological studies in the growth of field crops. Ann. Bot. N. 5. 11(41): 41-76. - 1952. The physiological basis of variation in yield. Advan. Agron. 4: 101-145. 1956. Leaf growth in relation to crop yield. Proc. Third Easter School Agric. Sci. Univ. Nottingham, Lon. Butter- worths Scientific Publ. 1958. The dependence of net assimilation rate on leaf area index. Ann. Bot. Lond. N. S. 22: 37-54. and G. A. W. French. 1962. An attempt to increase yield by controlling leaf area index. Ann. Appl. Biol. 50: l-lO. Williams, W. A., R. S. Loomis, and C. R. Lepley. 1965. Vegeta- tive growth of corn as affected by population density. 11. Components of growth, net assimilation rate and leaf area index. Crop Sci. 5: 215-219. APPENDIX 1 Some leaf area estimates (only one was used, maximum LA) from Experiments 1 and 3 are presented in the table below along with the correSponding leaf area index (LAI) calculated as described in the Materials and Hethods Section. : EXPERIMENT Ia (1966) : EXPERIMENT lb (1962) VAR'ET'ES : LA : LAI :HAX. LA : HAX. LAI ONAWAY 5050 1.64 15,45u n.4u KATAHDIN 5299 1.72 5,840 1.68 RUSSET BURBANK 6790 2.21 10,1u1 2.91 HAPLOIDS :____§g§§ginsur 3 (HAPLQIDS, 196]) .. HAXIHUH fiLA : HAXIHUH;LA1__ P] (5283-4) 16,246 3.61 P, (5281-6) '#,349 0.97 P3 (5279-23) 10,994 2.4a P4 (5279-21) 10,808 2.40 95 (5287-1) 3,840 0.85 1 x 2 2,570 0.57 l x 3 45657 1.03 1 X ('1 9,39“ 2.09 1 x 5 9,604 2.13 2 x 3 5,155 0.92 2 x 5 1,567 0.35 3 x 4 2,178 0.48 4 x 5 6,293 1.40 52 53 Since the experiments have virtually the same spacing, any LAI may be computed by multiplying LA by the constant (.0003). The trend of LA is thus, exactly followed by LAI. The term LAI could have been substituted for LA in the discussion of results, thus needs little further consideration here. It is included in the above table mainly, so that other authors may compare these results with those obtained in other crops. Nevertheless, it may be briefly noted that the LAI results are not in agreement with Watson (1958) with kale and Harper (1963) on potato who stated that the optimum LAI should be about 3.5, whereas, the most effi- cient variety here (Katahdin) and haploid cross (4 x 5) had much lower LAI's. It was suggested that the reasons for the efficiency of these two low LAI types lie in their pattern of growth, which was fully discussed in the results and discussion section. “.11. Ill- Ill "i H "il Rm H VII“ N11“ 3196 2685 111 3 1293 11111111IIIWIHH