Performance, correlation and path coefficient analysis for grain yield and its related traits in diallel crosses of bread wheat under normal irrigation and drought conditions.

摘要

Seven parents of bread wheat namely; Giza 168 (P1), Cham 6 (P2), Line 1 (P3), Line 2 (P4), Sakha 94 (P5), IB 18 (P6) and Maryout 5 (P7) were crossed in 2008/2009 season in a half diallel pattern. In 2009/2010 season, the 7 parents and their 21 F1 crosses were grown under two different water regimes, i.e. normal irrigation (plants gave 5 irrigations during growth season) and water stress (plants gave 3 irrigations where the 2nd and 4th irrigations were prevented during vegetative and anthesis stages, respectively). A field experiment was devoted for each irrigation treatment and laid out in a randomized complete blocks design with three replicates. Performance, phenotypic correlation coefficient and path coefficient were evaluated for grain yield/plant and its contributors under target environments. The results revealed that wheat genotypes greatly differed in there responses under both irrigation treatments for the studied traits. Drought caused great reduction in grain yield and its contributors, i.e. flag leaf area, plant height, spike length, number of spikes/plant, number of spikelets/spike, number of kernels/spike and 1000-kernel weight as well as days to heading and relative water content. The genotypes; P2, P3, P4, P7, P1 x P4, P2 x P7, P4 x P7 gave the highest values for the most traits under both water regimes. At the same time, the parents P2, P6, P1 and P3 and the crosses; P1 x P2, P1 x P4, P1 x P6, P2 x P3, P2 x P5, P3 x P6, P4 x P6, P4 x P7 and P5 x P7 were the best drought tolerant according to their drought susceptibility index. Significant and positive phenotypic correlation coefficients were found between grain yield/plant and each of flag leaf area, relative water content, number of kernels/spike, 1000-kernel weight and number of spikes/plant under the two levels of irrigations. Results of path coefficient analysis illustrated that flag leaf area, relative water content under both water regimes followed by number of spikes/plant under drought treatment proved to be the major contributors in grain yield variation. Thus, these traits should be considered as selection criteria in wheat breeding programs for yield improvement under the target treatments.