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• 1. [Article] Nature of inheritance, genotype-environment interaction and association of selected agronomic characters in crosses of winter X spring wheats (triticum aestivum L. em Thell)

  This investigation was motivated by the apparent increase in genetic variability resulting from the systematic combining of gene pools represented by winter and spring types of wheats. It was the objective ...

  Citation × Citation Citation Abstract Copy Title: Nature of inheritance, genotype-environment interaction and association of selected agronomic characters in crosses of winter X spring wheats (triticum aestivum L. em Thell) Author: Brajcich, P. This investigation was motivated by the apparent increase in genetic variability resulting from the systematic combining of gene pools represented by winter and spring types of wheats. It was the objective of this study to provide information regarding the nature of this genetic variability for nine agronomic characters in populations resulting from winter x spring crosses. Evaluations were made for: 1) the amount of total genetic variability; 2) the nature of the gene action making up this genetic variability using parent-progeny regression and combining ability analysis and 3) possible direct and indirect associations for traits which influence grain yield. Experimental populations which involved parents, Fl, F2 and backcross generations were grown at two locations where a spring and a winter environment could be utilized. At the winter site, the research was evaluated over a two year period. When the two experimental sites were compared, greater genetic diversity was observed at the spring site for maturity date, plant height, tillers per plant, kernel weight and grain yield. At the winter site, heading date, grain filling period, harvest index and kernels per spike were found to have more total genetic variation. From the expected mean square values, it would appear that the winter parents contributed more to the total genetic variation for most traits measured at both locations. A large genotype-location interaction was also noted suggesting that estimates of gene action and selection for adapted plant types can be done only at the specific winter or spring site. A large portion of the total genetic variation controlling the traits measured was due to additive gene action. However, at the winter site there was also a large influence of non-additive gene action associated with heading date, plant height, harvest index, tillers per plant, kernel weight, kernels per spike and grain yield. Of special interest was that at the winter site the most promising parental combinations could be predicted based on the general combining ability effects of the individual cultivars for each trait studied. Such data were not available for the spring site. Consistent and high correlations were observed between tillers per plant, kernels per spike and, to a lesser extent, kernel weight and grain yield at the winter location. Some negative associations were observed at the spring location between these traits and grain yield suggesting that yield component compensations were involved in the final expression of grain yield. The other characters measured did not reflect significant correlations with yield. When the correlation values were considered in terms of direct and indirect effects for specific traits, a large direct effect was noted for the three components and grain yield. The other traits exhibited small or no direct effects on grain yield but did have a slight influence on grain yield through tillers per plant, kernels per spike or kernel weight. Title: Nature of inheritance, genotype-environment interaction and association of selected agronomic characters in crosses of winter X spring wheats (triticum aestivum L. em Thell) Author: Brajcich, P. This investigation was motivated by the apparent increase in genetic variability resulting from the systematic combining of gene pools represented by winter and spring types of wheats. It was the objective of this study to provide information regarding the nature of this genetic variability for nine agronomic characters in populations resulting from winter x spring crosses. Evaluations were made for: 1) the amount of total genetic variability; 2) the nature of the gene action making up this genetic variability using parent-progeny regression and combining ability analysis and 3) possible direct and indirect associations for traits which influence grain yield. Experimental populations which involved parents, Fl, F2 and backcross generations were grown at two locations where a spring and a winter environment could be utilized. At the winter site, the research was evaluated over a two year period. When the two experimental sites were compared, greater genetic diversity was observed at the spring site for maturity date, plant height, tillers per plant, kernel weight and grain yield. At the winter site, heading date, grain filling period, harvest index and kernels per spike were found to have more total genetic variation. From the expected mean square values, it would appear that the winter parents contributed more to the total genetic variation for most traits measured at both locations. A large genotype-location interaction was also noted suggesting that estimates of gene action and selection for adapted plant types can be done only at the specific winter or spring site. A large portion of the total genetic variation controlling the traits measured was due to additive gene action. However, at the winter site there was also a large influence of non-additive gene action associated with heading date, plant height, harvest index, tillers per plant, kernel weight, kernels per spike and grain yield. Of special interest was that at the winter site the most promising parental combinations could be predicted based on the general combining ability effects of the individual cultivars for each trait studied. Such data were not available for the spring site. Consistent and high correlations were observed between tillers per plant, kernels per spike and, to a lesser extent, kernel weight and grain yield at the winter location. Some negative associations were observed at the spring location between these traits and grain yield suggesting that yield component compensations were involved in the final expression of grain yield. The other characters measured did not reflect significant correlations with yield. When the correlation values were considered in terms of direct and indirect effects for specific traits, a large direct effect was noted for the three components and grain yield. The other traits exhibited small or no direct effects on grain yield but did have a slight influence on grain yield through tillers per plant, kernels per spike or kernel weight. Close

• 2. [Article] Estimates of heterosis for five agronomic traits in selected winter x spring and winter x winter wheat crosses (Triticum aestivum L. em Thell)

  Concern regarding the lack of genetic variability and the apparent yield plateau reached in wheat breeding have prompted this investigation. The systematic crossing of spring and winter wheat types which ...

  Citation × Citation Citation Abstract Copy Title: Estimates of heterosis for five agronomic traits in selected winter x spring and winter x winter wheat crosses (Triticum aestivum L. em Thell) Author: Brajcich, P. Concern regarding the lack of genetic variability and the apparent yield plateau reached in wheat breeding have prompted this investigation. The systematic crossing of spring and winter wheat types which have evolved to form somewhat different gene pools, may provide a source of additional usable genetic variability for future yield increases. Five winter and five spring wheat cultivars with different degrees of genetic similarities in their pedigrees were crossed to obtain F1's and F2's. The parents plus winter x spring F1's were planted in two growing seasons at Hyslop Agronomy Farm near Corvallis, Oregon. During the second season the winter x spring F2 and winter x winter F1 crosses were also included. Agronomic traits were measured on an individual plant basis. These traits were plant height, number of tillers per plant, 100 kernel weight, number of kernels per spike and grain yield. Analyses of variance were conducted for each trait. Estimates of the amount of usable genetic variation were determined by heterosis values, inbreeding depression and parent-progeny standard regressions. Possible interactions between years and the above five characters were determined for the winter x spring F1's. Evidence of non-additive gene action was found in the expression of heterosis and subsequent inbreeding depression which depended on the specific trait measured and the parents involved in the cross. The greatest heterosis values were noted for grain yield per plant. Crosses with the winter parent, Weique Red Mace, resulted in the highest estimates for grain yield. This was due to the late maturity of these hybrids and to the diverse genetic background of this winter parent compared to the five spring parents. Parent-progeny regressions indicated that a large amount of additive genetic variance was present for plant height, 100 kernel weight and grain yield an intermediate amount for kernels per spike and tillers per plant. Winter x spring F1 crosses resulted in higher heterosis estimates and a wider range of values between crosses than winter x winter F1 crosses. Parent-progeny regression estimates were similar in value for the two types of F1 populations. Thus, these results indicate that the systematic crossing between winter and spring wheats will produce greater total genetic variability for further wheat improvement. This is true for the development of hybrid wheat (non-additive) and may also be promising for conventional breeding programs when only the additive portion of the total genetic variance can be used. The data support the general conclusion that the amount of heterosis is a function of genetic diversity between the two parents. Those breeders working on hybrid wheat may wish to look at winter x spring crosses as a means of maximizing heterosis. However, since a significant interaction between years x F1's was noted for the traits measured, more than one year of evaluation will be necessary if winter x spring crosses are employed. Title: Estimates of heterosis for five agronomic traits in selected winter x spring and winter x winter wheat crosses (Triticum aestivum L. em Thell) Author: Brajcich, P. Concern regarding the lack of genetic variability and the apparent yield plateau reached in wheat breeding have prompted this investigation. The systematic crossing of spring and winter wheat types which have evolved to form somewhat different gene pools, may provide a source of additional usable genetic variability for future yield increases. Five winter and five spring wheat cultivars with different degrees of genetic similarities in their pedigrees were crossed to obtain F1's and F2's. The parents plus winter x spring F1's were planted in two growing seasons at Hyslop Agronomy Farm near Corvallis, Oregon. During the second season the winter x spring F2 and winter x winter F1 crosses were also included. Agronomic traits were measured on an individual plant basis. These traits were plant height, number of tillers per plant, 100 kernel weight, number of kernels per spike and grain yield. Analyses of variance were conducted for each trait. Estimates of the amount of usable genetic variation were determined by heterosis values, inbreeding depression and parent-progeny standard regressions. Possible interactions between years and the above five characters were determined for the winter x spring F1's. Evidence of non-additive gene action was found in the expression of heterosis and subsequent inbreeding depression which depended on the specific trait measured and the parents involved in the cross. The greatest heterosis values were noted for grain yield per plant. Crosses with the winter parent, Weique Red Mace, resulted in the highest estimates for grain yield. This was due to the late maturity of these hybrids and to the diverse genetic background of this winter parent compared to the five spring parents. Parent-progeny regressions indicated that a large amount of additive genetic variance was present for plant height, 100 kernel weight and grain yield an intermediate amount for kernels per spike and tillers per plant. Winter x spring F1 crosses resulted in higher heterosis estimates and a wider range of values between crosses than winter x winter F1 crosses. Parent-progeny regression estimates were similar in value for the two types of F1 populations. Thus, these results indicate that the systematic crossing between winter and spring wheats will produce greater total genetic variability for further wheat improvement. This is true for the development of hybrid wheat (non-additive) and may also be promising for conventional breeding programs when only the additive portion of the total genetic variance can be used. The data support the general conclusion that the amount of heterosis is a function of genetic diversity between the two parents. Those breeders working on hybrid wheat may wish to look at winter x spring crosses as a means of maximizing heterosis. However, since a significant interaction between years x F1's was noted for the traits measured, more than one year of evaluation will be necessary if winter x spring crosses are employed. Close