GENETIC SYSTEM CONTROLLING THE YIELD AND ITS COMPONENTS IN THREE BREAD WHEAT (TRITICUM AESTIVUM, L.) CROSSES

Abstract

This investigation was carried out at El. Gemmeiza Agric. Res. Station , A.R.C, Egypt, during the three successive seasons, 2009/2010, 2010/2011 and 2011/2012 to study genetic variance, gene action, heterosis, inbreeding depression, heritability and genetic advance for grain yield and its components and some agronomic characters. Six populations (P1, P2, F1, F2, Bc1 and Bc2) for three crosses were used in this study coming from (P1x P3), (P2 x P4) and (P3 x P4). Analysis of variance showed significant differences among the studied generations' means for all studied traits. Scaling test showed that most studied characters were significant indicating the presence of non-allelic interaction.. Additive type of gene effect was significant either positive or negative for no .of spikes / plant, 100-kernel weight and grain yield /plant in the first and second crosses. Meantime, dominance gene effects was significantly positive for all studied traits except plant height, no. of spikes /plant and grain yield /plant in the second cross .Additive x additive and additive x dominance type of gene actions were significantly positive or negative for all studied traits in the three crosses except for no .of spikes / plant in the first and second crosses and 100- kernel weight in the second and third crosses. On the other hand dominance x dominance type gene effect was found to be significant for all studied traits except plant height and 100-kernel weight in the first and third crosses, respectively. Heritability for days to heading in narrow sense was high and nearly equal to its corresponding in broad sense. High estimates for hertibility in broad sense were accompanied bymoderate value of narrow sense for no. of kernels /spike, 100 –kernel weight and grain yield plant in the three crosses.The third cross gave the highest heterotic effect towards earliness for number of days to heading and number of days to maturity with moderate heritability in narrow sense and with genetic advance being 1.59 and 1.98 days for both characters , respectively .Significant positive heterotic effects relative to better parent was obtained for no . of kernels / spike , 100 kernel weight and grain yield in the second and third crosses .