Genetic Control for Some Traits Using Generation Mean Analysis in Bread Wheat (Triticum aestivum L.)

In order to study the inheritance and genetic analysis of drought tolerance indicators a six generations of P1, P2, F1, F2, Bc1 and Bc2 of two wheat crosses i.e., Sakha 94xTokwie (C1) and Giza 168xTokwie (C2) under normal irrigation (N) and drought stress (D) were studied using generation mean analysis at Faculty of Agriculture, Sohag University, Egypt. Genetic variation was found for No. of spikes/plant (NS), 100-seed weight (SW), grain yield (GY), biological yield (BY), relative water content (RWC) and chlorophyll content (CC) (N&D) in two crosses. High heterosis was observed for all studied characters (N&D) except CC in two crosses. Genetic analysis showed over dominance in the inheritance of all studied characters (N&D) in two crosses. High to moderate heritability values in broad sense were detected for all characters in both crosses. Narrow-sense heritability (C1&C2) ranged from 0.18 for CC (D) to 0.37 for RWC (D) in C1. The genetic advance (C1&C2) was high (more than 40%) for GY (N&D), while NS, BY, RWC and CC (N&D) were moderate (14-40%), indicating the importance of direct selection for these characters. The genetic models fitted for all studied characters (N&D) in two crosses except RWC (D in C1), indicated dominance and additive x additive gene effects. Both additive x additive and dominance x dominance effects were significant for all studied characters (N&D) in two crosses except RWC (D in C1), supporting the presence of duplicate type of epistasis. Since several important characters are influenced by dominance and non-allelic gene interaction, it is advisable to delay selection to later generation with increased homozygosity.