General and Specitic Combining Abilities of Some Crosses in Bread Wheat at Normal Watering and Moisture Stress Conditions

In order to determined of 6 bread wheat varieties representing different traits were crossed in a half-diallel in 2013/2014 season. The 6 parents and its15 F₁ crosses were evaluated under normal watering and water stress conditions in 2014/2015 season the objective of this investigation was aimed to study the combining ability and mode of gene action for some wheat traits under normal and stress conditions.  Mean squares of genotypes were highly significant for all the studied traits. Both GCA and SCA variances were found to be highly significant for most traits under investigation at both conditions, indicating the importance of additive and non-additive effect in determining the performance of these characters. The ratio of  GCA/SCA at the two conditions were more than unity for all studied traits, except heading date and flag leaf area under normal condition, and biomass yield per plant at water stress condition. This indicates that these traits are predominantly controlled by additive gene action, and it could be concluded that selection based on the accumulation of additive effects would be more effective in the early generations. P5 (Sids 14) at normal, P6 (Misr 2) under stress and combined data showed the highest biomass yield /plant. Among crosses, cross No. 12 (P3 x P6) under normal and combined data and cross No. 14 (P4 x P6) under stress showed the highest biomass yield /plant. P1 (Giza 168) and P2 (Sakha 93), at both normal and stress conditions were the best combiners for days to heading (earliness). P6 (Misr 2) was the best combiners for biomass yield per plant under both conditions. The best cross combinations for heading date (earliness) were crosses No. 1 (P1xP2), No. 6 (P2xP3) No. 10 (P3xP4) and No. 15 (P5xP6) at normal condition, crosses No. 5 (P1xP6) and No. 9 (P2XP6) under stress condition, and cross No. 2 (P1xP3) under both conditions. Also, the best cross combinations for biomass yield per plant were crosses No. 3 (P1xP4), No.8 (P2xP5) and No.15 (P5xP6) at both conditions, No. 10 (P3xP4) at normal watering condition, and No. 4 (P1xP5) and No. 14 (P4xP6) at water stress condition.