Inheritance studies in four New Zealand wheat cultivars

Inheritance and correlations of yield, yield components, and morpho-physiological and agronomic characters involving four parent diallel crosses of F₁ and F₂ generation were studied in Kopara, Ruru, Hilgendorf and Oroua. Three environments in terms of different sowing dates were imposed in the Fl generation in order to study the stability of the genetic system. Dominance variation was important in governing the inheritance of yield, and significance of specific combining ability from a combining ability analysis was established. Additive genetic variation was significant for two yield components, that is, number of spikelets on the main stem and number of grains per ear, and all morpho-physiological and agronomic characters, except maximum tiller production, tiller survival, and tiller mortality. Dominance variation was significant for 1000 grain weight. Epistasis was present for number of ears per plant and yield in the F₁ and F₂ generations respectively. (Wr, Vr) graphical analysis indicated the presence of over-dominance for yield, 1000 grain weight, ear area, and maximum tiller production in F₁ generation, and number of ears per plant and tiller survival in F₂ generation. Partial dominance was present for other characters in both generations. Narrow sense heritability was high for number of spikelets on the main stem, number of grains per ear, and all morpho-physiological and agronomic characters, except maximum tiller production, tiller survival, and tiller mortality. Positive genotypic correlations between yield and number of spikelets on the main stem, number of grains per ear, 1000 grain weight, and all morpho-physiological and agronomic characters, except tiller characters, were indicated. Combining ability analysis suggested that Ruru and Kopara gave consistently high general combining ability effects for yield, number of spikelets on the main stem, number of grains per ear, and all morpho-physiological and agronomic characters, except tiller characters. Based on spaced planting of F₁ and F₂ generations, bulk population breeding for yield would be a more efficient method to use in early generations and the pedigree method may be best applied in later generations. In early generations, selection for number of spikelets on the main stem, number of grains per ear, and all morpho-physiological and agronomic characters, except tiller characters, should give good response. Analysis of genetic-environmental interactions indicated instability of additive effects for number of spikelets on the main stem, flag leaf area, ear area, anthesis date, plant height, spikelets 12 fertility, and flag leaf angle under different environments. Dominance effect was quite stable for all characters. Epistasis which controlled the inheritance of number of ears per plant and flag leaf angle was also quite stable.