This investigation was carried out at Sakha Agricultural Research Station, ARC, Egypt during the two growing seasons (2010/2011 and 2011/2012). Seven lines and three testers were used to develop barley hybrids for earliness and vegetative traits under normal and water stress conditions. Data revealed that most of the variances due to genotypes, parents, crosses, parents x crosses, lines, testers and line x testers were highly significant for most studied traits under both conditions and their combined data. The water stress treatment decreased the mean of days to heading for parents and their hybrids. The parental Line-1, Tester-1 under all conditions and top cross no. 7 under normal and combined and cross no. 1 under stress were the earliest parents and crosses for days to heading. The stressed genotypes for water, matured earlier than genotypes grown under normal condition. The ratios of GCA/SCA were lesser than unity for all studied traits under all conditions, which mean that non-additive gene effects played an important role in the inheritance of these traits. In such cases, a bulk method would be fruitful to eliminate the effect of dominance in the advanced generation. Desirable significant GCA effects were showed by Line-1 under water stress and Tester-1 under all conditions for days to heading; Tester-1 under normal and combined for days to maturity; Line-2 under stress and Line-7 under normal condition for grain filling period; Line-4, Line-6 under both conditions and combined, Line-3 under normal, Line-7 under water stress, Tester-3 under both conditions and combined data for grain filling rate; Line-4 under both conditions and their combined data, Line-7 under water stress and combined data, Tester-2 under stress and combined data for flag leaf area; and Line-3 under normal, Line-2 and Line-7 under water stress for total chlorophyll content. Moderate phenotypic and genotypic coefficients of variability were obtained for grain filling rate and total chlorophyll content, and high for flag leaf area. Small differences between genotypic and phenotypic coefficients of variability were found for all studied traits under all conditions, indicating the presence of sufficient genetic variability for these traits, which may facilitate selection. Broad sense heritability percentages ranged from moderate to high with percentages ranged from 10.82% for days to maturity at combined data to 97.30% for grain filling rate under normal condition. These results indicate that genotypic variances played the major part of phenotypic variances. Narrow sense heritability percentages varied from low to moderate with percentages ranged from 0.92 % for grain filling period at combined data to 18.92% for grain filling rate under normal condition. The expected genetic advance (Δg) ranged from 0.02 for grain filling period at combined data to 0.36 for total chlorophyll conten under normal condition. While, the estimates of predicted genetic advance (Δg %) ranged from 0.04% for grain filling period at combined data to 7.41% for grain filling rate under stress condition. Generally, traits that showed high values of narrow sense heritability and expected genetic advance from selection should be used in breeding program where selection in the early segregating generations will be useful because additive gene action is more important than non-additive genetic components.
Mapping dynamic QTL dissects the genetic architecture of grain size and grain filling rate at different grain-filling stages in barley
