Estimation of genetic parameters in the F1 and F2 generations of diallel crosses of bread wheat [Triticum aestivum L.]

ABSTRACT

A half diallel analysis of crosses among seven bread wheat varieties were usedto estimate combining ability, genetic components of variation and carry outgraphical analysis for days to heading, plant height, number of spikes/plant,main spike length, number of spikelets/spike, grain weight/spike, 1000-grainweight and grain yield/plant in the F1 and F2 generations. Highly significantdifferences among genotypes, parents and crosses were observed for all traitsin both generations. General and specific combining ability variances werehighly significant for all traits in the two generations indicating theimportance of both additive and non additive gene effects in the inheritanceof the traits studied. The estimated values of dominance components [H1 andH2] were found to be highly significant for all traits studied and higher inmagnitude in the F2 than in the F1. The three long spiked varieties [Sids 5,Sids 7 and Sids 8] were good general combiners for earliness, plant height,main spike length, grain weight/spike and number of spikelets/spike in the twogenerations, except Sids 8 in the F2 for the latter trait. Gimmeza 3 and Sids7 were the best general combiners for 1000-grain weight. The best generalcombiner for grain yield/plant and some of its components was the selectedline followed by Gimmeza-3. Estimates of F values revealed an excess ofdominant alleles in the parental lines for days to heading and grainweight/spike in the two generations. The best specific combinations for grainyield and some of its components were detected in both generations in ninecrosses. Graphical analysis revealed that partial dominance was found fordays to heading, plant height, main spike length and grains weight/spike inboth generations. Overdominance played an important role in the inheritanceof grain yield in both generations. The distribution of parental arrays alongthe regression line were widely scattered for all traits studied indicatinggenetic diversity among the parents. The relative order of the points of theseven parents along the regression line were different from one generation toanother. The results recommended using the two wheat varieties Gimmeza 3 andSids 7 and the best five hybrid combinations Giza 157 x Sids 5, Sakha 69 xSids 5, Gimmeza 3 x Sids 8 and the selected line with each of Sids 5 and Sids8 as the most promising genotypes in a future breeding program for developingnew bread wheat cultivars possessing high yielding potentiality