Genetic Analysis of Grain Yield and its Components Under Heat Stress Conditions in Bread Wheat (Triticum aestivum L.) | ||
| Assiut Journal of Agricultural Sciences | ||
| Volume 56, Issue 4, October 2025, Pages 120-143 PDF (2 M) | ||
| Document Type: Original Article | ||
| DOI: 10.21608/ajas.2025.400090.1512 | ||
| Authors | ||
| Ayat S. Mohammed S. Mohammed Mohammed; Mohamed I. Hassan* ; Mahmoud A. El-Rawy; Mohamed M. El-Defrawy | ||
| Department of Genetics, Faculty of Agriculture, Assiut University, Assiut, Egypt . | ||
| Abstract | ||
| This investigation aimed to study the genetic system of grain yield and related traits in a half diallel cross of bread wheat, involving eight parents and their 28 F₁ hybrids, under optimal and heat-stressed field conditions. The traits assessed included plant height (PLH), spike length (SPL), grain yield per plant (GYP), number of tillers (NOT), number of spikelets per spike (NSP), and 1000-kernel weight (TKW). Under heat stress, significant variation was observed among genotypes for all traits except TKW. Heat stress caused substantial reductions in the performance of parental lines and F₁’s. Several hybrids exhibited notable heterosis. The general combining ability (GCA) was significant for all traits, whereas specific combining ability (SCA) was significant for SPL, GYP, NOT, and NSP. The predominance of GCA over SCA effects observed suggested a major role in additive gene action. These findings are further supported by the significance of both additive (a) and non-additive (b) gene actions, with a predominance of additive gene action under heat stress. Regression analysis supported the adequacy of the additive-dominance model for PLH, SPL, and TKW, while the model was non-adequate for NOT and NSP, and partially adequate for GYP. CIMMYT-9 (P4), followed by CIMMYT-10 (P5) exhibited the highest and significantly positive (P<0.01) GCA for GYP and most traits. The hybrid P4×P8, followed by P5×P7 and P3×P6, exhibited the largest and significantly positive (P<0.01) SCA for GYP. Cluster analysis using SSR markers successfully distinguished between parents based on heat tolerance. These results highlight the potential of identified superior genotypes for developing heat-tolerant wheat varieties. | ||
| Keywords | ||
| Bread wheat; Combining ability; Diallel analysis; Grain yield; Heat stress | ||
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