GENETIC CONTROL OF YIELD AND ITS COMPONENTS IN BREADWHEAT

Abstract

Genetic control of tillers/plant, grains/spike, 1000-grain weight, grain weight/spike and yield/plant in nine generations (Pt, P:z, Fl, F:z, Fs, BCt, BC:z, F2 XP:z, and F2 biparental crosses) were investigated in an intervarietal cross of breadwheat involving NI 5439 and PH 663, having higher number of spikelets/spike, grains/spike and grain weight/spike. Biparental progeny excelled their corresponding F3 and F2 for tiller number, spikelets/spike, IP'ains/spike, grain weight/spike, 100o-grainweight and yield/plant. Considerable additive genetic variance was observed for tillers/plant and grain weight/spike while additive and dominance genetic variance was predominant for 1000-grain weight. The additive-dominance model was adequate for tillers/plant, grain weight/spike and yield/plant. Epistatic effects of additive X additive, additive x d.ominance and dominance x .dominance were observed for 100o-grain weight. The digenic: epistatic model was inadequate to explain the nature of gene action for spikelets/spike and 1000·grain weight. Thus, nonallelic interactions should not be ignored in formulating breeding programmes and the biparental approach would be extremely useful for enhancing genetic variability and creation of transgressive segregates.