Study on genetic components of grain yield and its contributing characters in bread wheat (Triticum aestivum L.)

This study was conducted at Crop Research Farm, Nawabganj, C. S. Azad University of Agriculture and Technology, Kanpur (U. P.) during rabi 2021-22 for estimating the components of variance and other genetic parameters through 8 x 8 parent diallel cross excluding reciprocals for 11 characters in bread wheat. The variance component analysis indicated significant role of additive (D̂) and dominant (Ĥ1 and Ĥ2) genetic components for all the traits viz., days to 75% heading, days to maturity, plant height (cm), number of productive tillers per plant, spike length (cm), number of grains per spike, biological yield per plant (g), harvest index (%) and grain yield per plant (g) except additive component for 1000-grain weight (2.60) and dominant component for number of spikelets per spike (2.91 and 2.53). The estimates of dominant components (Ĥ1 and Ĥ2) were mostly greater than additive component (D̂) for all the characters indicating the greater role of non-additive gene action in the expression of attributes. The relative magnitudes of Ĥ1 component were higher than Ĥ2 component for all the characters except spike length (0.39) indicating unequal distribution of positive and negative alleles in the parent. Over dominance expression for all the attributes was due to the involvement of asymmetrical distribution of dominant genes with positive and negative effects in the parents for all the characters except spike length. Based on study, it was revealed that both additive and non-additive genes were responsible for expression of almost major of the traits.