Generation mean analysis in wheat (Triticum aestivum L.) under drought stress conditions

The six populations (parents, F1, backcrosses and F2) of the two wheat crosses, Gemmeiza 9 · IL1 (C1) and Sids 1 · IL2 (C2) were grown under normal irrigation (N) and drought stress (D) at the farm of Faculty of Agriculture, Sohag University, Egypt to study the genetic background of drought stress tolerance. 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) under normal and drought stress environments in the two crosses. High heterosis was observed for all studied characters under both water treatments in the two crosses except RWC and CC in the first cross. Genetic analysis showed dominance in the inheritance of all studied characters under both water treatments in two crosses except BY, RWC and CC under normal irrigation in cross 1 and RWC under drought in cross 2 were controlled by the additive type of gene action. Narrow-sense heritability in the two crosses ranged from 0.20 for GY (D) to 0.57 for CC (N) in C1. The genetic advance in the two crosses 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 NS, SW, BY, GY, RWC (D) and CC (D) in C1 and NS, BY (N), GY, RWC and CC in C2 indicated dominance and additive · additive gene effects. Both additive · additive [i] and dominance · dominance [1] effects were significant for NS, BY, GY, RWC (D) and CC (D) in C1 and NS, BY (N), GY, RWC and CC in C2, 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.