GENERATION MEAN ANALYSIS OF TWO BREAD WHEAT CROSSES UNDER NORMAL AND LATE SOWING DATE CONDITIONS

Abstract

Parents (P1&P2), F1, F2 and first generation of backcrosses (BC1&BC2) of two bread wheat crosses i.e., Sids 12 x Gemmeiza 11 (C1) and Misr 2 x Sids 1 (C2), were grown in two experiments {normal sowing date 20th Nov. (N) and late sowing date 20th Dec. (L)}. This study was conducted at the Experimental Farm of Shandaweel Agric. Res. Station, ARC during 2015/2016, 2016/2017 and 2017/2018 seasons. The study aimed to estimate non-allelic interaction, scaling tests (A,B,C and D), coupled with three and six types of gene action and to determine the adequacy of genetic model controlling the genetic system of the inheritance for seven economic traits of bread wheat. Scaling test showed the presence of non-allelic interactions for all studied taits, except number of spikes/plant in cross 1 under late sowing. The relative importance of dominance and additive effects differ for traits and crosses under normal and late sowing conditions. Dominance effects were generally more important than additive for all studied traits in both crosses under the two sowing dates, except for days to heading in cross 2 under late sowing, number of spikes/plant in cross 1 under late sowing and biological yield in cross 1 under normal sowing. This explains that dominant genes play a major role in the inheritance of these traits beside the additive one. Dominance × dominance gene interaction was higher in magnitude than additive × dominance and additive × additive in most traits, indicating that these traits are greatly affected by dominance and non-allelic interactions. Therefore, it is advisable to delay selection to late segregating generations with increased homozygosity. Positive highly significant heterosis over better parent values was observed for all studied traits in both crosses under the two sowing dates, except for plant height in cross 1 under late sowing and cross 2 under normal sowing, number of kernels/spike in cross 1 under both sowing dates and grain yield/plant in cross 1 under normal sowing. Broad and narrow sense heritabilities and genetic advance ranged from moderate to high in most cases. These results indicated that selection in segregating generations could be effective to develop early maturing lines that have high yielding ability under heat stress conditions (late sowing date).