EPISTATIC BIAS IN ADDITIVE AND DOMINANCE VARIATION AND GENETIC ASSOCIATIONS BETWEEN TWO QUALITY TRAITS IN BREAD WHEAT

Abstract

Grain protein and Pelshenke value in 8 × 8 diallel crosses and after eliminating the interacting arrays were genetically analysed. All the dominance variation for grain protein was due to epistatic interactions. The dominance component for Pelshenke value was considerably inflated by epistasis. For both characters, the dominance component was affected more by the epistatic bias than the additive component of genetic variance, resulting in considerably low narrow-sense heritability estimates. Covariance between grain protein and Pelshenke value was primarily due to additive gene effects and was attributed to pleiotropic relationships in the absence of genetic linkage. An ambidirectional trend of dominance with an asymmetric distribution of dominant and recessive alleles among the cultivars was observed for grain protein, whereas preponderance of the dominant decreasing genes with more isodirectional gene distribution was operative for Pelshenke value. Correlated responses of these quality traits to selection due to high additive genetic correlation and degree of co-inheritance in relation to their gene action is stressed.