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• 1. [Article] Compensating effects and gene action estimates for the components of grain yield in winter wheat (Triticum aestivum, L. em Thell)

  Five winter wheat cultivars and their diallel crosses were evaluated for plant height, harvest index, deading-maturity duration, the components of yield, (spikes per plant, spikelets per spike, kernel ...

  Citation × Citation Citation Abstract Copy Title: Compensating effects and gene action estimates for the components of grain yield in winter wheat (Triticum aestivum, L. em Thell) Author: Abi-Antoun, Michel Five winter wheat cultivars and their diallel crosses were evaluated for plant height, harvest index, deading-maturity duration, the components of yield, (spikes per plant, spikelets per spike, kernel weight and kernels per spikelet)and total plant yield. Two diverse locations, Moro, a dryland site (250 mm annually) located in central Oregon and the Hyslop Agronomy Farm, a high rainfall site (over 1000 mm annually) located in the Willamette Valley, were utilized for one and two cropping seasons, respectively. Three rates of seeding were used as main plots in a split-plot design that was replicated four times. A modified blend method of seeding was used to simulate solid seeding conditions. Experimental seeds were planted 30.5 centimeters apart within the row over a filler cultivar in equally spaced (30.5 centimeters) rows. The data were analyzed by analysis of variance, Griffing's diallel analysis (Method 4, Model 1), correlation, path-coefficient analysis and by parent progeny regression. The correlation between grain yield, its components, harvest index, maturity-duration and plant height was dependent on the particula. r environment of the test. The re waspoorcorrelationbetween yield, tiller number and seed size under all the conditions of these studies. Negative associations between the components of yield indicated the sequential compensatory behavior of these characters under all environments. It would be very hard to select for large grain and short stature wheat because of the positive correlation between plant height and seed size within this population. The low correlations of yield with tiller number and seed size were mainly caused by indirect negative effects through one or more of the other yield components. Harvest index, maturity-duration and plant height had very small direct or indirect influences on grain yield. It was concluded that maximum yield would be obtained from a plant type which produces enough tillers to cover a particular unit of field area with large, fertile spikes, having medium to large kernels and semi-dwarf stature. No significant differences existed between parents and single crosses in the expression of the yield components. Nevertheless, hybrids outyielded their parents in grain yield and demonstrated that heterosis for complex traits was a consequence of multiplicative relationships among the components of these traits. Significant interactions between the genotypes and locations, seeding rates and years were observed in the expression of all characters studied. These interactions indicated that using data from non-competitive conditions to assess performance under competitive conditions could not be justified. Also, limiting the number of testing sites may lead to unsound generalizations and erroneous recommendations regarding gene action estimates of yield and the components of grain yield and three associated characters. Under non-competitive conditions, estimates of the additive type of gene action were more significant and contributed larger effects than the non-additive type for all traits. As competition increased at higher seeding rates, the effects of specific combining ability became more important in the expression of yield, number of spikes, spikelets per spike, and plant height. Heritability estimates confirmed these results except for yield. Of the agronomic characters, harvest index, maturity-duration and plant height, only harvest index showed some promise as a selection criterion under noncompetitive conditions. A breeding procedure utilizing the component approach consisted of selecting early generations under spaced planting with emphasis on avoiding extreme values in any of the components of yield. The balanced combinations of the components of yield should be tested under solid seeding conditions. Title: Compensating effects and gene action estimates for the components of grain yield in winter wheat (Triticum aestivum, L. em Thell) Author: Abi-Antoun, Michel Five winter wheat cultivars and their diallel crosses were evaluated for plant height, harvest index, deading-maturity duration, the components of yield, (spikes per plant, spikelets per spike, kernel weight and kernels per spikelet)and total plant yield. Two diverse locations, Moro, a dryland site (250 mm annually) located in central Oregon and the Hyslop Agronomy Farm, a high rainfall site (over 1000 mm annually) located in the Willamette Valley, were utilized for one and two cropping seasons, respectively. Three rates of seeding were used as main plots in a split-plot design that was replicated four times. A modified blend method of seeding was used to simulate solid seeding conditions. Experimental seeds were planted 30.5 centimeters apart within the row over a filler cultivar in equally spaced (30.5 centimeters) rows. The data were analyzed by analysis of variance, Griffing's diallel analysis (Method 4, Model 1), correlation, path-coefficient analysis and by parent progeny regression. The correlation between grain yield, its components, harvest index, maturity-duration and plant height was dependent on the particula. r environment of the test. The re waspoorcorrelationbetween yield, tiller number and seed size under all the conditions of these studies. Negative associations between the components of yield indicated the sequential compensatory behavior of these characters under all environments. It would be very hard to select for large grain and short stature wheat because of the positive correlation between plant height and seed size within this population. The low correlations of yield with tiller number and seed size were mainly caused by indirect negative effects through one or more of the other yield components. Harvest index, maturity-duration and plant height had very small direct or indirect influences on grain yield. It was concluded that maximum yield would be obtained from a plant type which produces enough tillers to cover a particular unit of field area with large, fertile spikes, having medium to large kernels and semi-dwarf stature. No significant differences existed between parents and single crosses in the expression of the yield components. Nevertheless, hybrids outyielded their parents in grain yield and demonstrated that heterosis for complex traits was a consequence of multiplicative relationships among the components of these traits. Significant interactions between the genotypes and locations, seeding rates and years were observed in the expression of all characters studied. These interactions indicated that using data from non-competitive conditions to assess performance under competitive conditions could not be justified. Also, limiting the number of testing sites may lead to unsound generalizations and erroneous recommendations regarding gene action estimates of yield and the components of grain yield and three associated characters. Under non-competitive conditions, estimates of the additive type of gene action were more significant and contributed larger effects than the non-additive type for all traits. As competition increased at higher seeding rates, the effects of specific combining ability became more important in the expression of yield, number of spikes, spikelets per spike, and plant height. Heritability estimates confirmed these results except for yield. Of the agronomic characters, harvest index, maturity-duration and plant height, only harvest index showed some promise as a selection criterion under noncompetitive conditions. A breeding procedure utilizing the component approach consisted of selecting early generations under spaced planting with emphasis on avoiding extreme values in any of the components of yield. The balanced combinations of the components of yield should be tested under solid seeding conditions. Close

• 2. [Article] A study of methods of parental evaluation using testers to predict subsequent progeny performance in winter wheat (Triticum aestivum L.)

  The major objective of this study was to determine why certain winter wheat cultivars, when hybridized, will produce a greater proportion of desirable plants in subsequent, segregating generations. Three ...

  Citation × Citation Citation Abstract Copy Title: A study of methods of parental evaluation using testers to predict subsequent progeny performance in winter wheat (Triticum aestivum L.) Author: Alexander, William Larry The major objective of this study was to determine why certain winter wheat cultivars, when hybridized, will produce a greater proportion of desirable plants in subsequent, segregating generations. Three winter wheat parents were chosen as the experimental material, based on their known performance as parents. Yamhill and Pullman Selection 101 are recognized as cultivars with good combining abilities for grain yield. Crosses with Nugaines have been disappointing, even though the cultivar itself is high yielding. Each parent was crossed to a series of five testers. These testers were chosen on the basis of their genetic diversity, especially for the components of yield. This parent x tester crossing scheme was analyzed as a 3 x 5 factorial, where the main effects due to parents and testers were their general combining ability effect estimates. The interactions of these main effects were their specific combining abilities. F₁ hybrids were evaluated for two years and F₂ populations for one year to characterize the parents' capacity to transmit selected attributes to their resulting progeny. These generations were evaluated on a per plant basis for their grain yields and the primary components of yield, tillers per plant, kernels per spike, and 1000 kernel weight. The four methods of evaluating parents assessed were parental performance, midparent-progeny correlations, examination of individual crosses, and combining ability analysis. Midparent-progeny correlations usually were not significant within the progeny of each parent. Significant differences were not found for grain yields among the parents in either year. However, significant differences existed for their expressions of yield components. Parental expressions of the yield components were generally more erratic than those of their F₁ progenies. Significant differences occurred for estimates of general combining ability effects in both years and for each generation in all traits. These estimates for a particular parent were relatively consistent. Specific combining ability was not found to be a dependable means of identifying superior combinations. Associations between the parental general combining ability effect estimates for kernels per spike and 1000 kernel weight were positive. Relationships between other yield component combinations were negative with regard to general combining ability effects. Trends observed in single crosses reflected the relative general combining abilities of the parents. Crosses involving Yamhill generally had fewer tillers with a higher number of kernels per spike, heavier kernel weights, and superior grain yields to those of the other parents. Progeny of Pullman Selection 101 were usually high in tillering, intermediate for number of kernels per spike, low in kernel weights, and intermediate for grain yields. The progeny of Nugaines were characterized by high tillering, a low number of kernels per spike, low kernel weights, and also low grain yields. The parent x tester crossing scheme was found to be an effective way of determining the potentials of the three parents by estimating their general combining abilities, as well as minimizing the number of crosses required. If, as found in this study, the general combining ability effect estimates of the parents for grain yield accurately predict performance of later generations, this parent x tester crossing scheme would be an efficient method of assessing the potentials of prospective parents in breeding programs. Title: A study of methods of parental evaluation using testers to predict subsequent progeny performance in winter wheat (Triticum aestivum L.) Author: Alexander, William Larry The major objective of this study was to determine why certain winter wheat cultivars, when hybridized, will produce a greater proportion of desirable plants in subsequent, segregating generations. Three winter wheat parents were chosen as the experimental material, based on their known performance as parents. Yamhill and Pullman Selection 101 are recognized as cultivars with good combining abilities for grain yield. Crosses with Nugaines have been disappointing, even though the cultivar itself is high yielding. Each parent was crossed to a series of five testers. These testers were chosen on the basis of their genetic diversity, especially for the components of yield. This parent x tester crossing scheme was analyzed as a 3 x 5 factorial, where the main effects due to parents and testers were their general combining ability effect estimates. The interactions of these main effects were their specific combining abilities. F₁ hybrids were evaluated for two years and F₂ populations for one year to characterize the parents' capacity to transmit selected attributes to their resulting progeny. These generations were evaluated on a per plant basis for their grain yields and the primary components of yield, tillers per plant, kernels per spike, and 1000 kernel weight. The four methods of evaluating parents assessed were parental performance, midparent-progeny correlations, examination of individual crosses, and combining ability analysis. Midparent-progeny correlations usually were not significant within the progeny of each parent. Significant differences were not found for grain yields among the parents in either year. However, significant differences existed for their expressions of yield components. Parental expressions of the yield components were generally more erratic than those of their F₁ progenies. Significant differences occurred for estimates of general combining ability effects in both years and for each generation in all traits. These estimates for a particular parent were relatively consistent. Specific combining ability was not found to be a dependable means of identifying superior combinations. Associations between the parental general combining ability effect estimates for kernels per spike and 1000 kernel weight were positive. Relationships between other yield component combinations were negative with regard to general combining ability effects. Trends observed in single crosses reflected the relative general combining abilities of the parents. Crosses involving Yamhill generally had fewer tillers with a higher number of kernels per spike, heavier kernel weights, and superior grain yields to those of the other parents. Progeny of Pullman Selection 101 were usually high in tillering, intermediate for number of kernels per spike, low in kernel weights, and intermediate for grain yields. The progeny of Nugaines were characterized by high tillering, a low number of kernels per spike, low kernel weights, and also low grain yields. The parent x tester crossing scheme was found to be an effective way of determining the potentials of the three parents by estimating their general combining abilities, as well as minimizing the number of crosses required. If, as found in this study, the general combining ability effect estimates of the parents for grain yield accurately predict performance of later generations, this parent x tester crossing scheme would be an efficient method of assessing the potentials of prospective parents in breeding programs. Close

• 3. [Article] Evaluation of parental performance for grain yield in two populations of wheat (Triticum aestivum Vill., Host)

  Six winter wheat cultivars were evaluated for their breeding value in transmitting superior genetic factors for grain yield to subsequent progeny. The cultivars were selected on the basis of their potential ...

  Citation × Citation Citation Abstract Copy Title: Evaluation of parental performance for grain yield in two populations of wheat (Triticum aestivum Vill., Host) Author: Alcala de Stefano, Maximino Six winter wheat cultivars were evaluated for their breeding value in transmitting superior genetic factors for grain yield to subsequent progeny. The cultivars were selected on the basis of their potential grain yield and divided into two populations. Population I was comprised of three cultivars which have been in commercial production for several years and are regarded as intermediate for grain yield. Population II was represented by three recently developed cultivars which have superior grain yielding potential. Each of the three parents within each population were crossed in a diallel manner Hence, the parents and subsequent F₁, F₂, and BC progeny made up the experimental populations. These populations were grown at two environmentally diverse sites within the state of Oregon. Morphological characters measured were: (1) tillers per plant; (2) kernels per spike; (3) plant height; (4) weight of 300 kernels; and (5) grain yield. To detect which parental combination had the greatest potential for transmitting superior performance to the subsequent progeny for the components of yield and grain yield, the following parameters were determined for both populations: (1) the amount and nature of the genetic variance associated with each population; (2) average combining ability of each parent within the populations; (3) estimates of heterosis and heterobeltiosis in the F₁ and (4) the possible influence of the genotype-environmental interactions on the parameters measured. Also information concerning the desirability of using top crosses and double crosses rather than single crosses was obtained. In an effort to compare the relative performance between the populations, Pullman Selection 101, which is a good general combining winter wheat cultivar, was used as a tester for both populations. The values obtained in this investigation reflect the properties of the populations studied and should not be interpreted as applying to all wheat populations. Considerable genetic variability was found within both populations for the characters studied. This variability was largely due to genetic factors which were additive. Tillers per plant and grain yield were influenced by both additive and nonadditive genetic variance. The higher yielding parents in Population II were found to be higher in their average combining ability for kernels per spike and grain yield per plant whereas the lower yielding parents in Population I were higher for tiller number, weight of 300 kernels and plant height. Parental combinations identified as being promising, for grain yield in a conventional program, where nearly homozygous lines are desired, were also the same parental combinations which resulted in a maximum expression of heterobeltiosis and would be of most interest in a hybrid program. The desirability of using multiple crosses to maximize the number of favorable factors need further study inctuding additional parents and different combinations plus an evaluation of the performance of such crosses in later generations. In this investigation, the single crosses appeared to be the most promising; however, inbreeding depression due to segregation within top and double crosses influenced the values obtained. Also, the population sizes should be increased to measure the total potential of such crosses. Significant genotype-environmental interactions were observed between locations for plant height and weight of 300 kernels. The estimates obtained for average combining ability, heterosis and heterobeltiosis for the other characters measured also suggested that it will be necessary to identify the most promising hybrid combinations based on the performance of the parents at the specific location. To make the most rapid progress in developing high yielding cultivars in either conventional or hybrid programs, the wheat breeder needs to emphasize crosses between unrelated high yielding cultivars. However, the need to provide superior parental lines which include such factors as disease resistance, should be evaluated. The development of elite germ plasm by geneticists will be mandatory if plant breeders are to continue to improve grain yield. Title: Evaluation of parental performance for grain yield in two populations of wheat (Triticum aestivum Vill., Host) Author: Alcala de Stefano, Maximino Six winter wheat cultivars were evaluated for their breeding value in transmitting superior genetic factors for grain yield to subsequent progeny. The cultivars were selected on the basis of their potential grain yield and divided into two populations. Population I was comprised of three cultivars which have been in commercial production for several years and are regarded as intermediate for grain yield. Population II was represented by three recently developed cultivars which have superior grain yielding potential. Each of the three parents within each population were crossed in a diallel manner Hence, the parents and subsequent F₁, F₂, and BC progeny made up the experimental populations. These populations were grown at two environmentally diverse sites within the state of Oregon. Morphological characters measured were: (1) tillers per plant; (2) kernels per spike; (3) plant height; (4) weight of 300 kernels; and (5) grain yield. To detect which parental combination had the greatest potential for transmitting superior performance to the subsequent progeny for the components of yield and grain yield, the following parameters were determined for both populations: (1) the amount and nature of the genetic variance associated with each population; (2) average combining ability of each parent within the populations; (3) estimates of heterosis and heterobeltiosis in the F₁ and (4) the possible influence of the genotype-environmental interactions on the parameters measured. Also information concerning the desirability of using top crosses and double crosses rather than single crosses was obtained. In an effort to compare the relative performance between the populations, Pullman Selection 101, which is a good general combining winter wheat cultivar, was used as a tester for both populations. The values obtained in this investigation reflect the properties of the populations studied and should not be interpreted as applying to all wheat populations. Considerable genetic variability was found within both populations for the characters studied. This variability was largely due to genetic factors which were additive. Tillers per plant and grain yield were influenced by both additive and nonadditive genetic variance. The higher yielding parents in Population II were found to be higher in their average combining ability for kernels per spike and grain yield per plant whereas the lower yielding parents in Population I were higher for tiller number, weight of 300 kernels and plant height. Parental combinations identified as being promising, for grain yield in a conventional program, where nearly homozygous lines are desired, were also the same parental combinations which resulted in a maximum expression of heterobeltiosis and would be of most interest in a hybrid program. The desirability of using multiple crosses to maximize the number of favorable factors need further study inctuding additional parents and different combinations plus an evaluation of the performance of such crosses in later generations. In this investigation, the single crosses appeared to be the most promising; however, inbreeding depression due to segregation within top and double crosses influenced the values obtained. Also, the population sizes should be increased to measure the total potential of such crosses. Significant genotype-environmental interactions were observed between locations for plant height and weight of 300 kernels. The estimates obtained for average combining ability, heterosis and heterobeltiosis for the other characters measured also suggested that it will be necessary to identify the most promising hybrid combinations based on the performance of the parents at the specific location. To make the most rapid progress in developing high yielding cultivars in either conventional or hybrid programs, the wheat breeder needs to emphasize crosses between unrelated high yielding cultivars. However, the need to provide superior parental lines which include such factors as disease resistance, should be evaluated. The development of elite germ plasm by geneticists will be mandatory if plant breeders are to continue to improve grain yield. Close