Genetic control of yield and its components in breadwheat

Genetic control of tillers/plant, grains/spike, 1000-grain weight, grain weight/spike and yield/plant in nine generations (P₁, P₂, F₁, F₂, F₃, BC₁, BC₂, F₂ X P₂, 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 grainweight/spike. Biparental progeny excelled their corresponding F₃ and F₂ for tiller number, spikelets/spike, grains/spike, grainweight/spike, 1000-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 dominance and dominance x dominance were observed for 1000-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.