|Abstract or Summary
- The purpose of this study was to determine the nature and amountof genetic variation and possible associations between winterhardinessand earliness in winter x spring wheat crosses.Four winter wheat cultivars selected for differences in earlinessand winterhardiness were crossed with a nonhardy
- The purpose of this study was to determine the nature and amountof genetic variation and possible associations between winterhardinessand earliness in winter x spring wheat crosses.Four winter wheat cultivars selected for differences in earlinessand winterhardiness were crossed with a nonhardy, day length insensitivespring wheat cultivar. The following year, experiments containing parents, F₁, BC, and F₂ populations were planted at twoenvironmentally diverse sites located at the Sherman Branch ExperimentStation, Moro, Oregon (250 mm of moisture) and the HyslopAgronomy Farm, Corvallis, Oregon (1000 mm of moisture).The amount and nature of genetic variation involved were determinedby obtaining broad and narrow sense heritability estimates,evaluating the degree of dominance and estimating the number of genes influencing both earliness and winterhardiness. Also frequency distributionswere developed for each of the populations.Both broad and narrow sense heritability estimates for earlinesswere higher than those observed for winterhardiness. Both winterhardinessand earliness appeared to be conditioned by both additive andnonadditive gene action. Degree of dominance estimates for the fourwheat crosses grown at two locations differed for each cross andlocation. Earliness was influenced by one to six genes while winterhardinessappeared to be controlled by two genes. The estimation ofgenetic advance indicated that the crosses with high narrow senseheritability estimates and high phenotypic variance in F₂ generationwould result in greater gains under selection for both traits.Based on the results of this study, it seems that Moro is aproper site to select for winterhardiness and Corvallis for earliness.However, it might be better to select for both traits at the same timeat another site such as Pendleton, Oregon, where a realistic selectionpressure can be applied for winter survival and drought would notinfluence the selection procedure. Such a site could also provide anopportunity to evaluate earliness at the same time. Correlationcoefficient estimates showed the presence of a positive associationbetween earliness and winterhardiness. The possibility of using leafdamage readings to measure the winterhardiness levels in wheat populationsalso appears promising.