Combining Graphical and Diallel Analyses to Identify Elite Bread Wheat (Triticum aestivum L.) Genotypes for Grain Yield and Its Component Traits

Enhancing grain yield and its components through understanding of genetic parameters remains a central challenge in wheat breeding due to the complexity of improving multiple agronomic traits simultaneously. This study utilized numerical and graphical Hayman diallel analyses to investigate the inheritance of grain yield and related traits in seven bread wheat ( Triticum aestivum L.) genotypes and their F₁ progenies, evaluated under a randomized complete block design with three replications. Morley–Jones analysis revealed significant differences ( p < 0.05 or 0.01 ) for grain yield and most traits. Inheritance was predominantly governed by both additive and dominant gene effects, with nonadditive action, particularly overdominance, playing a substantial role in grain yield per plant (GY/P) and most traits. Parental genotypes exhibited higher frequencies of dominant than recessive alleles, and favorable alleles outnumbered unfavorable ones. Regression analysis indicated the absence of nonallelic interactions for plant height (PH), spike length (SL), spike weight (SW), number of grains per spike (NGS), spike grain weight (SGW), and number of spikelets per spike (NSP), while epistatic interactions were detected for number of tillers (NT), number of spikes (NS), and GY/P. Low Wr + Vr values suggested that dominant alleles primarily controlled SD, SGW, SW, and SL. Graphical analysis revealed partial dominance for PH, SL, NT, NS, and GY/P; overdominance for SGW, SD, NGS, and SW; and complete dominance for NSP. Genotypes P6 and P7 carried more recessive alleles, whereas P2 and P3 had higher dominant allele frequencies, suggesting potential hybridization to develop superior lines. GGE biplot analysis identified P2 (Sakha 93) as the top performer for SD, NS, NT, and NSP, while P2, P3, and P5 combined high stability and grain yield, positioning them near the ideal genotype.