Genetic Variability and Heterosis in F1 and F2 Generations of Diallel Crosses among Seven Wheat Genotypes

Abstract

In order to study the effect of heterosis and nature of genetic on plant height and yield traits were studied in a 7x7 diallel cross without reciprocals and their F 2 generation in wheat to define and select an efficient and prospective material for immediate use in hybridization programs to improve grain yield of wheat in Egypt. Parents, F 1 and F 2 were evaluated for quantitative traits in 2016/2017 season. Significant genotype mean squares and its components (parents and crosses) were obtained for all traits in both generations. Significant heterosis in F 1 generation was obtained for all studied traits. Heterosis of grain yield/plant relative to mid parent varied from 4.64 to 75.50% in F 1 crosses. The P2xP3, P1xP4 and P2xP5 were the best crosses for grain yield heterosis. General (GCA) and specific (SCA) combining ability mean squares were significant for all traits. MS (GCA)/ MS (SCA) ratios indicated the relative importance of additive and non-additive gene action in their inheritance for all the traits. The nine crosses i.e. P1xP2, P1xP6, P2xP5, P2xP6, P4xP5, P4xP6, P5xP6 and P5xP7 had significant and positive ij S ^ effects in F 1 and F 2 generations and contained Inter-and intera-allelic interactions. Generally, no wide differences in the genetic parameters in F 1 and F 2 generations were detected. Highly significant and larger (in magnitude) values of dominance component (H2) than additive were obtained for all studied traits resulting in more values of (H1/D) 0.5 which were more than unity in both generations. High heritability values (in a broad-sense) along with medium or low ones in narrow-sense were exhibited in both generations, indicating that most genetic variances were due to non-additive genetic effects. The regression line passed through the origin in spike length and No. of spikes/plant in F 1 generation and 1000-grain weight in F 2 generation, revealed a presence of complete dominance. Meanwhile, it intersects the Wr axis above the origin in plant height in both generations,1000-grain weight in F 1 , No of spike/plant and Spike length in F 2 , reflecting partial dominance.