Heterosis and Combining Ability Studies for Grain Yield and some Contributing Traits in Bread Wheat (Triticum aestivum L.) under Normal and Late Sowing Conditions.

Abstract

Seven parental cultivars of bread wheat (Triticum aestivum L.) were used in a half diallel mating design at the Experimental Farm of Faculty of Agriculture, Sohag University, Egypt, during the two successive seasons of 2013/2014 and 2014/2015 to study combining ability and heterosis and their interactions under two sowing dates , 15 th November (normal sowing date) and 15 th December (late sowing date) in two adjacent experiments, for days to heading, No. of spikes/plant, 1000-grain weight and grain yield/plant. Sowing dates mean squares was highly significant for all studied traits. Genotypes mean squares was highly significant for all studied traits at the two sowing dates and their combined. The overall means of genotypes were (88.98, 83.76 and 86.37days) for days to heading; (13.87, 10.00 and 11.94) for No. of spikes/plant; (47.26, 35.41 and 41.34g) for 1000-grain weight and (39.43, 24.58 and 32.01g) for grain yield/plant on the normal, late sowing dates and their combined, respectively. Late sowing date (heat stress) caused reduction for days to heading (5.87%), No. of spikes/plant (27.90%), 1000-grain weight (25.07%) and grain yield/plant (37.66 %), compared with normal sowing date (favorable). Interaction of sowing dates with genotypes was highly significant for all studied traits. General combining ability (GCA) and specific combining ability (SCA) mean squares was significant for all studied traits at the both sowing dates and their combined, except general combining ability mean squares for 1000grain weight and grain yield/plant for the combined data. Genetic analyses of these traits confirm the participation of both additive and non-additive gene effects in controlling their inheritance. The interactions of sowing dates with general combining ability were found to be not-significant for all studied traits, whereas the interactions of sowing dates with specific combining ability were found to be significant for all studied traits. The ratio of GCA to SCA variance (predictability ratio) was closer to 1 for all studied traits, except for No. of spikes/plant and grain yield/plant at normal sowing date that revealed the predominance of additive gene action in the inheritance. The parental line (P 5) proved to be the good general combiner for grain yield/plant at the two sowing dates and their combined. Hybrid combination (P 1 × P 4) showed highly significant desirable SCA effects for days to heading, No. of spikes/plant, 1000-grain weight and grain yield/plant. Six cross combinations (

Half Diallel Analysis and Heat Stress Tolerance Indices for Grain Yield in Bread Wheat

“…This may be due to the negative effect of high temperature on pollen grains that caused reduction in number and size of spike grains. These results are in line with those reported by Motawea (2017) and Fouad (2019 a and b).…”

Analysis of Genetic Architecture for Ten Genotypes of Bread Wheat Using Half Diallel Crosses Under Nitrogen Stress

“…It is noted from the foregoing from table (4) that the effects of the special combining ability were significant and in the desired direction in hybrids (1 × 9) for all studied traits with sufficient and insufficient nitrogen , followed by hybrids (4 × 8) also for all studied traits except for number of spikes plant -1 Insufficiency nitrogen , followed by hybrids (2×4), (2×8), (3×7), and (6×9) The effects of the special high combining ability of any hybrid in general indicate the high value of the performance of this hybrid and its superiority, and are attributed to the non-additive effects of genes. [20,19,10]. Table 4.…”