Diallel analysis to study the genetic makeup of spike and yield contributing traits in wheat (Triticum aestivum L.)

Five wheat genotypes were crossed in complete diallel fashion for gene action studies of spike length, spikelets per spike, grains per spike, grain weight per spikeand grain yield per plant. Analysis of variance reveals significant differences for all the traits. The significant deviation of joint regression value “b” from zero and non significance of “t” square value, suggested the absence of epistasis for all traits which in turn attested fitness of the data for simple additive dominance model. Additive genetic component (D) proved to be significant for all traits under consideration except grain weight spike per spike, but dominant component H1 and H2 was higher in magnitude than additive (D) for spike length and grain yield per plant, illustrating the prevalence of dominance genetic effects. The additive genetic component was more imperative for genetic manipulation of number of spikeletsper spike and number of grains per spike. Dominant genes at most of the loci were in excess than recessive genes for spike length and grain yield per plant which was firmly supported by the positive value of F and further strengthened by the value of (4DH1)0. 5+F/ (4DH1) 0. 5-F which was greater than unity for these two traits. The component that was strongly influenced by the environment was spikelets per spike. High magnitude of narrow sense heritability (h2n.s) was noticed for spikelets per spike (79%), and grains per spike (88%) thus illustrated fixable and additive heritable variation for these traits. The operation of over dominance was observed for spike length, grain weight per spike and grain yield per plant, whereas, spikelets per spike and grains per spike were under additive type of gene action with partial dominance, implying that spikelets per spike and grains per spike can significantly be improve by pursuing pedigree method while heterosis can be exploited for spike length, grain weight per spike and grain yield per plant. Key words: Wheat, gene action, genetic parameters, heritability, yield.