Hayman’s diallel analysis for yield-related traits in F1 and F2 durum wheat (Triticum durum Desf.) progenies

Overview

This investigation applied Hayman's diallel analysis to characterize the genetic architecture underlying agronomic traits in durum wheat across two filial generations. Using a 4 × 4 half-diallel mating design, eight yield-related traits were evaluated in F1 and F2 progenies derived from field trials conducted at the INRAA experimental station in Sétif, Algeria, during the 2021-2022 and 2023-2024 growing seasons. The study aimed to elucidate inheritance patterns, gene action modes, and heritability estimates to inform breeding strategy optimization for durum wheat improvement under semi-arid Mediterranean conditions. Significant genotypic variation was observed across all traits, with inheritance mechanisms differing substantially between generations. The research addresses the imperative to enhance durum wheat productivity and resilience in regions where the crop serves as a cornerstone of food security and economic stability.

Methods and approach

The experimental design comprised a 4 × 4 half-diallel cross involving durum wheat parental lines, with progeny evaluated across F1 and F2 generations in field trials at Sétif, Algeria. Eight agronomic traits were assessed, including plant height, spike length, number of grains per spike, spike weight, number of spikes per plant, and grain yield. Hayman's diallel analysis methodology was employed to partition genetic variance into additive and dominance components, estimate the degree of dominance, assess allele distribution asymmetry among parents, and calculate broad-sense and narrow-sense heritability. The analytical framework relies on assumptions including the absence of epistasis, maternal effects, and multiple allelism, with diploid segregation and homozygous parental lines. Both graphical and numerical implementations of Hayman's method were used to visualize gene action patterns and quantify genetic parameters. The study specifically examined generational shifts in inheritance patterns to identify recombination effects on heterotic expression and additive genetic variance.

Key Findings

Plant height exhibited predominantly additive gene action across both generations, indicating heritable genetic control amenable to early-generation selection. Spike length and number of grains per spike displayed a marked shift from overdominance in F1 to partial dominance in F2, reflecting enhanced additive effects following recombination events. Yield components, specifically spike weight, number of spikes per plant, and grain yield, demonstrated persistent non-additive inheritance and overdominance across generations, suggesting limited selection efficiency in early generations for these traits. Dominance effects were significant in F1 but diminished substantially in F2 for most traits, consistent with a recombination-mediated breakdown of heterotic patterns. Allele distribution among parental lines was asymmetric, indicating unequal parental contributions and potential for heterosis exploitation. The ratio of genetic variance components indicated that most traits were controlled by a single gene or a closely linked gene block. Broad-sense heritability was consistently high across traits, whereas narrow-sense heritability varied substantially, underscoring the differential contribution of additive versus non-additive genetic variance to phenotypic expression.

Implications

The distinct inheritance patterns observed between generations necessitate generation-specific breeding strategies for durum wheat improvement. Traits governed by additive gene action, such as plant height, are suitable for pedigree selection in early generations, enabling efficient fixation of desirable alleles. Conversely, yield components exhibiting persistent overdominance and non-additive inheritance require recurrent selection or advanced-generation selection approaches to capitalize on heterotic effects and achieve genetic gains. The recombination-mediated increase in additive variance for certain traits between F1 and F2 generations suggests that delaying selection until later generations may enhance selection efficiency for these characters. The asymmetric allele distribution among parental lines provides opportunities for strategic parent selection to maximize heterosis in hybrid breeding programs. High broad-sense heritability coupled with variable narrow-sense heritability indicates that realized genetic gain will depend on the relative importance of additive effects for specific traits. These findings contribute to optimizing durum wheat breeding methodologies for semi-arid Mediterranean environments, addressing regional imperatives for enhanced productivity, quality, and environmental resilience in a crop central to food security and economic stability.