Showing papers in "Crop Science in 1962"

Heterosis and Genetic Diversity in Variety Crosses of Maize1

Abstract: Our limited understanding of the cause of heterosis does not provide a basis for deducing the relative amount of heterosis expected in crosses of parents with varying degrees of genetic diversity. Other experimental findings reported in the literature indicate that crosses of unrelated inbred lines of corn show greater heterosis than crosses of related lines (4, 5, 7, 8, 9, 13). These earlier experiments involved lines derived from locally adapted material and represent a limited range of genetic differences. Gilbert (6) has recently expressed the opinion that increased heterozygosis is not always advantageous. The question of the association of heterosis and genetic diversity over a wider range has become particularly important with increasing interest in exotic corns for breeding programs. The study to be reported here involves a wide range of varietal material to examine further this question. Genetic differences between....

Performance Level as Criterion for the Choice of Maize Testers1

Abstract: IT HAS been generally accepted that broad gene base testers are more efficient than narrow gene base testers for the evaluation of general combining ability in inbred lines of maize (Matzinger (7), Grogan and Zuber (4), and others). The importance of performance level or, by inference, gene frequency of the tester as a criterion for choice of testers, however, has never been as clearly established. Hull (5) stated that theoretically the most efficient tester would be homozygous recessive at all loci and that homozygosity for the dominance alleles at any locus should be avoided. These conclusions were based on considerations of the constant parent regression method of analysis of single crosses. The regression of performance of offspring on the performance of the variable parents for a particular constant parent was shown to be largest when the gene frequency of the character for the constant parent was zero. The regression was zero when the gene frequency was at one for complete dominance or at equilibrium gene frequency for overdominance. A strong positive regression would be desirable as this would allow more discrimination among the variable parents. Green (2) tested Hull's hypothesis with respect to lodging resistance. A lodging resistant double cross and a lodging susceptible open-pollinated variety were used as testers for the F2 progenies of three single crosses. When considerable lodging occurred, there was little difference between the testers. With little lodging, however, the lodging susceptible tester gave a much greater range for standability within all the F;2 progenies than the lodging resistant tester. Keller (6) reasoned that if Hull's hypothesis were correct, the component of variance due to the interaction of lines with testers would be less for high combining testers than for low combining testers. Separate estimates of the line X tester component of variance were obtained for the high and low yielding groups in 22 single cross experiments. The averages of these estimates were essentially the same for the two groups. It was concluded that the data disagreed with Hull's hypothesis. The purposes of the study reported herein were to consider further the role of average gene frequency of the

Carbohydrate Root Reserves in Alfalfa, Red Clover, and Birdsfoot Trefoil under Several Management Schedules 1

Abstract: carbohydrates by perennial legumes is fundamental to an understanding of management responses. Carbohydrates are of prime importance since they are the most readily available source of energy for growth and other metabolic processes. Cutting perennial legumes at near maturity is considered generally to be favorable to the accumulation of high carbohydrate reserves and to the maintenance of plant vigor and productivity. Cutting during a period of low carbohydrate reserves is considered to be detrimental to the plant. For perennial legumes, these principles derive mainly from the extensive studies of food reserve trends made on alfalfa by Graber et al. (3), Grandfield (4), Graumann et al. (5) and others. It is noteworthy, however, that studies of food reserve trends in red clover, a widely grown legume, have been few (11, 14), while such studies for birdsfoot trefoil have been found in the literature. In the present investigation, the trends of total available carbohydrates in the roots of alfalfa, red clover, and birdsfoot trefoil were studied and compared under three management systems during the 1960 season.

Diallel Crosses in Nicotiana tabacum 1

Abstract: COMPARISONS of parent and F1 hybrid performance in tobacco are numerous in literature and a review of this early work was given by Ashton (1). The objective most previous studies has been to assess the amount of heterosis and to determine if it was sufficient to justify the use of F1 hybrids on a commercial scale. Even though tobacco is naturally self-fertilized, crossing can be accomplished with ease and seed yields are high. In some cases workers have advocated the use of F1 hybrids commercially, e.g., Bawolska et al. (2), however, most authors refer \"fixing of heterosis\" in later generations, e.g., Rave and Bolsunov (3). The resolution of the question of whether heterosis can be maintained only in the F1 generation, or whether transgressive segregates can be isolated in pure lines equal or superior to the F, depends upon the types of predominant gene action for each character in the population under study. Very little has been done to relate the amount of heterosis obtained in tobacco crosses with estimates of types or amount of genetic variability. As the first step in a program to obtain quantitative genetic information in fluecured tobacco and to relate this information to breeding methodology, the present experiment was planned with the following objectives: (1) to estimate the amount of heterosis and inbreeding depression in flue-cured tobacco crosses, (2) to test for differences between reciprocal F hybrids, (3) to obtain estimates of variances of general and specific combining ability, and (4) to measure the stability of general and specific effects with respect to environmental differences. The material used will form the foundation for extensive statistical genetic studies to determine more clearly the genetic mechanism governing the inheritance of a number of characters and their response to selection.

Photosynthesis Under Field Conditions. IV. Light Studies with Individual Corn Leaves1

Abstract: The shape of the light response curve of individual leaves has recently become important in models for light absorption by field crops. Studies of the light response of individual corn leaves under sunlight is discussed. A leaf chamber technique for the continuous measurement of net assimilation of CO/sub 2/ by a leaf or corn ear was developed. Uptake rates of corn leaves under optimum light were of the order of 45 mg. of CO/sub 2/ per square decimeter leaf area per hour. Corn ear temperature and percent dry matter were found to have a marked effect on the respiration rate. Corn ear husks photosynthesized approximately 30 mg. CO/sub 2/ per ear per hour under midday sun. 20 references, 5 figures, 3 tables.

Trend of Carbohydrate Reserves in Alfalfa, Smooth Bromegrass, and Timothy Grown Under Various Cutting Schedules 1

Abstract: LFALFA, one of the most important forages grown in A the northern United States, is sown usually with a grass, principally bromegrass or timothy. Therefore, when managing an alfalfa-grass mixture, one must consider the growth characteristics of both the legume and the grass in order to maintain a desired proportion of each species in the mixture. A close relationship of herbage production and persistence with the level of organic food reserves has been demonstrated in alfalfa by Graber et al. ( I ) , Grandfield (2), Graumann et al. (3), Nielsen and Lysgaard ( 7 ) , Smith ( 8 ) , and others. Studies of the trend of food reserves in the storage organs of bromegrass and timothy are few. Tee13 has indicated that available fructose in the shoot bases of bromegrass was at a low level when internode elongation began in the spring, increased during internode elongation until heading, decreased during flowering, and then increased to the ripe seed stage. Kust4 found that carbohydrate reserves in bromegrass rose somewhat in the early spring, decreased until emergence of the heads, and then increased to anthesis. Carbohydrates usually decreased following cutting. Harper and Phillips (4) and Kust4 found that carbohydrate reserves in timothy decreased in the spring and then increased to a peak near full bloom. Harper and Phillips ( 4 ) also found that the carbohydrate reserves in timothy decreased very little following cutting at near full bloom, but Kust found some decrease. Troughton ( 9 ) and May

Grain Protein Content and Its Relationship to Other Plant and Seed Characters in the Parents and Progeny of a Cross of Triticum aestivum L

Abstract: RESULTS of several studies concerning variability of grain protein content in segregating populations of wheat are reported, in the literature. Some of the earlier studies indicated that phenotypic variability of protein in the Fe of a cross of two wheat varieties was no greater than that found in the p~,rental populations although the parental varieties differed in protein content (1, 2, 3). While numerous investigations showed that high grain protein content is correlated with low yield, occasional exceptions were reported (5, 7, 8). Heritability of wheat grain protein has been considered to be low, but Haunold et al. (6) and Davis et al. (4) reported moderately high heritability estimates of 0.65 and 0.67, respectively.

Estimates of Genetic Variance in Open-Pollinated Varieties of Cornbelt Corn 1

Abstract: THE choice of method to be used for the genetic improvement of crop plants is dependent upon the type of gene action involved. In the case of a quantitatively inherited character such as grain yield, only the mass action of all the genes involved can be studied. However, generalizations can be drawn as to the important types of gene action taking place through a study of genetic variation. Total genetic variance can be divided theoretically into additive genetic, dominance, and epistatic variance (Fisher, 3; Wright, 15). The relative magnitude of these three genetic variances is of importance to the plant breeder in order to plan the most effective breeding scheme. Comstock and Robinson (1) presented theoretical derivations together with an experimental procedure applicable to corn which permits the estimation of additive genetic and non-additive genetic variance (including dominance variance) portions. Robinson et al. (9, 10) and Gardner et al. (5) presented results from advanced generations of hybrids from inbred lines of southern prolific origin and in general obtained estimates of appreciable dominance variance relative to additive genetic variance for grain yield. Genetic linkages as well as epistasis were considered to be possible sources of bias in these results. Robinson et al. (11) in studying open-pollinated southern prolific varieties estimated that additive genetic variance constituted the major portion of the total genetic variance for grain yield, with the conclusion that overdominant loci were not the single important source of genetic variability in the material studied. Sprague and Tatum (14) obtained estimates of the variances associated with combining ability for grain yield in corn. In previously selected material, the variance for specific combining ability (related to dominance variance) was found to be larger than the variance for general combining ability (related to additive genetic variance). In unselected

Quantitative Interrelations of Protein and Nonprotein Constituents of Soybeans 1

Abstract: T HE increasing use of high-protein feeds since World War II has resulted in an expansion in the demand for soybean meal because of its high protein content (8). spite of a great increase in the production of soybeans, still more soybean protein is needed, but the demand for fats and oils has not kept pace with the increased production. For this reason, interest has increased in the possibility of breeding soybeans for high protein content. If the percentage of protein increases the percentage of other constituents must decrease correspondingly. It is important to know whether the protein gained is more valuable than the materials which would be lost. The inverse relation between percentages of protein and oil is well known (3, 5). The increase in protein generally averages 1.6 to 2.0 times the decrease in oil. The purpose of this study was to determine what .changes in the proportions of other constituents accompany Increase or decrease in the percentage of protein.

Effect of Epistasis on Grain Yield in Maize 1

Abstract: \"pPISTASIS may be broadly defined as any interaction -*-' between alleles at nonhomologous loci. This is a common type of gene action among qualitative traits. The first statistical treatment of epistasis was presented by Fisher (5) in 1918. Since that time additional reports dealing with the partitioning of epistatic variances have been presented by Wright (12), Cockerham (3, 4), Kempthorne (11), Horner (9), Anderson and Kempthorne (1), Hayman and Mather (6), Horner and Kempthorne (8), Horner et al. (7), and others. An additional report by Horner (10) is somewhat more pertinent to the present paper. The majority of mathematical models in current use for estimating gene action conditioning quantitative traits assume epistasis to be of no importance or absent. A few models have been developed which permit the estimation of epistasis if certain limiting assumptions are satisfied. These assumptions include linkage equilibrium and randomness of mating. In cases where statistical estimates of epistasis are possible, values so obtained tend to be minimal in a classical genetic sense since the portion of the effects which can be accounted for on an additive basis is allocated to the additive effects estimate.

Triallel Analysis 1

Abstract: The term three-way hybrid, symbolized by A (BC), refers to the cross of a line with an unrelated F^ hybrid. The ancestral control, and for purposes of reference, is the parent line on one side of the pedigree and the two grandparent lines on the other side of the pedigree. The number of combinations of 3 lines from p lines is PC3 = ppjp.j/6, where p[ denotes (p—i). Three different hybrids may be formed from each combination of lines by letting each of the three lines appear as a parent, giving altogether 3 PC3 3-way hybrids from p lines when reciprocal crosses are omitted. For the analysis of variance of these hybrids, it is assumed that the lines have an arbitrary degree of inbreeding which is equal for all lines. No reciprocal differences or maternal effects are assumed although these effects may be taken into account when reciprocal crosses are available. The basic model for a replicated experiment in which the treatments are the three-way hybrids is

A Comparative Study of Seven Methods of Measuring Earliness of Crop Maturity in Cotton1

Abstract: T. R. Richmond and Sami R. H. Radwan L^CK of agreement among cotton breeders on the meaning of the term earliness of crop or boll maturity and on methods of measuring or estimating earliness in cotton is due in great part to the fact that the genus Gossypium is characterized by an indeterminate flowering and fruiting habit. The practical interest of cotton growers, as well as breeders, is in the relative time required to set and mature a crop of bolls. The analysis of methods of measuring earliness of maturity in experimental stocks of American Upland cotton, G. hirsutum L., given here was part of a more comprehensive experiment designed to determine the inheritance of earliness as well as to study the relation of earliness to certain agronomic characters and to identify genetically some of thechromosomes on which genes for earliness might be located. REVIEW OF LITERATURE

Breeding Corn with High Provitamin A in the Grain 1

Abstract: ORN (Zed mays L.) undoubtedly has greater diverc gence among its cultivated varieties than any other cultivated species. Agronomic characters have myriad variations which are susceptible for selection. Variability in the chemical composition of the grain is no exception. In the classical Illinois ear-to-row work, selections for 50 years changed the original content of oil of Burr White with 4.7070 oil to the Illinois High Oil Selection with about 15% oil and to the Illinois Low Oil selection with about 170 oil. A single recessive gene (wx wx) produces “waxy” starch with 100%amylopectin and no amylose. The waxy grain is used in industrial production for adhesives and food specialties. On the other hand, intensive research is being carried on to produce a high percentage of amylose in corn starch which is to be used for valuable industrial products such as transparent films and fibers. About 40 years ago Steenbock ( 9 ) discovered that yellow corn contained a fat-soluble vitamin needed to promote normal growth in rats whereas white corn in the diet produced stunted rats which died prematurely. During the 1920’s many investigators proved that hogs in the dry lot gained weight faster with yellow corn than with white corn. Widespread publicity was given this conclusion and as a result the Cornbelt farmers increased their use of yellow varieties. About the same time the northern corn breeders developed the then new production of hybrid corn and emphasized the yellow hybrids. Aurand et al. (1) reported on the analyses of the grain of corn in 1946, 1947, and 1948. In each year the produce of all-combination single crosses among 10 yellow inbred lines was grown and analyzed for crude carotene and protein content. There is no mention of hand-pollinating the ears so that, no doubt, there was a xenia effect of the pollen from the adjacent plots, but the different yellow inbred lines transmitted definite inherent differential capacities to produce carotene.

Fatty Acid Composition of the Oil in Crossed Seed of Flax 1

Abstract: I.N R.ECIPROCAL crosses between varieties of flax differmg in percentage of oil content of the seed and iodine value of the oil it was founda that while samples of selfed and crossed seed developing on the same homozygous plant had the same oil content, they did not have the same iodine value. This was considered as evidence that the amount of oil in the seed is determined by the genotype of the sporophyte on which the seed is developing, but that the kind or quality of oil produced is determined largely by the genotype of the seed itself. This xenia-like4 genetic phenomenon i relation with the inheritance of the iodine value has not been described in the literature. In view of its theoretical and practical significance the following experiments were undertaken to obtain additional information on it by using more refined experimental techniques. In planning these experiments it was felt that the quality of an oil should be specified in terms of its fatty acid composition rather than by its iodine value. The iodine value is determined by the number of conjugated double bonds in the unsaturated fatty acids of an oil. It does not reveal the identity or the proportion of each of the unsaturated fatty acids in the oil. Thus, oils differing rather widely in their unsaturated fatty acid composition may still have the same iodine value. Furthermore, the iodine value does not provide any information on the occurrence or the relative proportions of the saturated fatty acids, whose synthesis is very likely related both qualitatively and quantitatively to that of the unsaturated fatty acids. Ignoring the saturated fatty acids might lead to loss of valuable information for the interpretation of gone action in the inheritance of the fatty acids in general. Therefore, it was concluded that a study of the inheritance of each one of the major fatty acids would provide a much more informative approach in evaluating the relative degree of genetic control exercised by the genotypes of the seed and the sporophyte in determining oil quality than the study of the inheritance of the iodine value. Furthermore the iodine value can be computed theoretically if the fatty acid composition is known. To make such detailed fatty acid determinations possible all oil samples in this experiment were analyzed by gas chromatography. An additional advantage of this method is that it can be used for the analysis of very small amounts of material; in this case a technique was developed for the analysis of single seeds of flax. It should be noted that if the fatty acid composition of the oil is indeed determined by the genotype of the seed, then seed developing on an F1 plant would actually represent an F2 segregating generation as far as the quality of the oil is concerned. Thus

Inheritance and Heritability of Seed Weight and Its Components in Oats1

Abstract: A COMMON objective of small grain breeding programs is to improve grain yield. With oats, as with other crops, grain yield variation is due to an interaction of environmental and genetic effects. One method proposed to circumvent this problem is to select for characteristics associated with or composing yield, i.e., yield components. Primary components of grain yield are number of panicles per plant, number of seeds per panicle, and weight per seed. It is conceivable that if heritability percentages for and correlations among yield components were used to construct an optimum selection index, the efficiency of selection might be greater than when yield performance was used. Since seed weight can be subjected to component analysis and measured relatively precisely with small sample size, this character was selected to study the theory and application of character component analysis.

Mode of Pollination and Factors Affecting Fruit Set in Piper nigrum L. in Puerto Rico 1

Abstract: T HE source of black and white pepper is Piper nigrum L., a tropical woody perennial vine of the family Piperaceae. It is the most important spice imported in the U. S., accounting for about half the ~tollar value of all imported spices. The availability of pepper to the western world has varied considerably, reaching a low during the years of World War II when supplies were unavailable at any price. Its culture has been largely restricted to India, Indonesia, and neighboring countries, where it has been grown for hundreds of years in close association with related wild species. However, the selection and multiplication by cuttings of superior strains has resulted in the establishment of well-recognized clonal varieties.

Inheritance of Flower Color of Soybeans1

Abstract: SOYBEAN flowers have been described by Piper and Morse (3) as being either purple or white. -In some cases shades of purple have been recognized, but under most field conditions shades of purple are difficult to classify. A new flower color, herein designated dilute-purple, was observed in the purple-flowered Tanner variety in 1946. At first glance, flowers appeared to be white but examination of the standard separated from the intact flower proved the base to be distinctly purple. This area of the standard is normally darker in purple flowers. A similar flower marking was found later in the Laredo variety. Varietal descriptions of Laredo reported it to have both purple and white flowers. Inspection of plants from several seed lots of Laredo revealed only purpleand dilutepurple-flowered plants. The reference to white-flowered plants in Laredo is believed to have resulted from failure to detect the purple coloration of the base of the standard in the dilute-purple types. The study herein reported was conducted to gain information on the inheritance of this newly recognized flower color.

Influence of Environment on Amylose Content of Maize Endosperm1

Abstract: T HE development of corn containing proportionately large quantities of amylose starch initiated considerable interest during the past decade. Starch in commercial dent hybrids consists of two components, amylopectin and amylose. The amylose component is a straight-chain, or linear-type, compound formed by the chemical dehydration of a large number of glucose or dextrose units. In contrast, the amylopectin component has a branched, or nonlinear molecular, structure. The total endosperm starch of commercial dent hybrids consists of approximately 27% amylose and 73% amylopectin. Several genetic factors have been identified (1, 4, 8, 9, 12) which are associated with an increase in the amylose-starch synthesis of corn endosperm. In the amylose breeding program at Missouri, experimental hybrids which contain as much as 70% amylose have been developed. Previous information from the breeding of high-amylose corn suggested that variation in amylose content of relatively homozygous lines was environmentally induced. For example, at the Missouri Agriculture Experiment Station it was found that high-amylose lines grown in the Florida winter nursery were higher in amylose content than the same lines grown in Missouri the following summer. The present study was subsequently initiated to evaluate the possible influence of environment on the amylose content of corn endosperm. Experiments were designed to determine whether differences in amylose content within relatively homozygous inbred lines might be due to climatic and edaphic factors associated with various geographical regions, as well as these factors associated with year effects. Affirmative results would be in general agreement with numerous earlier studies on the influence of environment on the chemical components of other crop plants.

The Seedling Establishment of Rice Under Water in Relation to Temperature and Dissolved Oxygen 1

Abstract: to keep the fields flooded to this depth until the crop is near maturity. Where the aerial sowing of presoaked seed is practiced in the southern U.S., it is considered necessary, at least on some soils, to drain the water from the fields soon after sowing to get satisfactory stands. In British Guiana good stands of rice are obtained by broadcasting pregerminated seed into water. The fields may be drained