Heterosis and combining ability in wheat

This investigation was carried out at EI-Giza Agricultural Research Station of the Agricultural Research Center (ARC) during two successive seasons 2008-2009 and 2009-2010. The main objective was to study performance, heterosis, combining ability and interrelationships among traits for earliness, grain filling and grain yield and its attributes in bread wheat (Triticum aestivum L.). Seven bread wheat genotypes viz., Sids 12(P1), Giza 168(P2), Sakha 93(P3), Gemmeiza 9(P4), Line 109(P5), Line 147(P6) and Line 172(P7) were crossed in a half diallel mating design to produce 21 F1 hybrids in 2008-2009. Parents and 21 F1 hybrids were evaluated in 2009-2010. Significant mean squares due to genotypes, parents and crosses were detected for all traits. The parents VS. crosses mean squares as indication average of heterosis were highly significant for all characters. A verage desirable heterotic effects relative to better-parent across all studied hybrids were detected for all traits, except grain filling period and harvest index. \\ Significant positive heterobeltiosis for grain yield/plant was recorded for 10 crosses where the highest cross P3 x P6 (37.83%). Analysis showed that both general combining- ability (GCA) and specific combining ability (SCA) variances were highly significant for all studied traits except the mean square of GCA for number of spikelets/spike. The ratio of GCA/SCA mean squares was more than unity for all traits except number of spikelets/spike, number of kernels/spike and grain filling rate. Additive gene effects were more important and played a major role in the inheritance of all studied traits. However, non-additive gene effects played a major role in the inheritance of number of spikelets/spike, number of kernels/spike and grain filling rate. Line 147 was the best general combiner for grain yield/plant, grain filling rate and number of spikes/plant. The cross PI x P3 showed superiority in SCA effects for number of kernels/spike, grain filling rate and grain yield/plant. Grain yield/plant showed highly significant phenotypic correlation with all studied traits except plant height.