Combining Ability Analysis, Estimation of Heterosis and Some Genetic Parameters Using Half Diallel Cross in Bread wheat (Triticum aestivum L)

Abstract

This research was conducted at the Agricultural Scientific Research Center in Idlib during the 2022–2023 and 2023–2024 growing seasons. The study aimed to evaluate heterosis relative to the mid-parent (MP) and better-parent (BP), and to assess general and specific combining abilities (GCA and SCA) for several traits, including: number and weight of grains in the main spike, thousand-kernel weight, grain yield per plant, and grain crude protein content (%).

A comparison of the trait means among the parental lines revealed sufficient variability across most traits, qualifying them for use in breeding and hybridization programs. This was evident in the hybrids derived from half-diallel crosses, which showed notable differences in most studied traits. Analysis of variance for combining ability indicated that (δ²GCA < δ²SCA) for traits such as number and weight of grains in the main spike, grain yield per plant, and grain crude protein content—suggesting a predominance of non-additive genetic effects. However, for thousand-kernel weight, the relationship (δ²SCA = δ²GCA) indicated the involvement of both additive and non-additive gene actions.

Several parental lines exhibited significant and favorable general combining ability effects for grain yield and its components, qualifying them for inclusion in wheat breeding programs due to their potential to transmit desirable traits to their progeny. Notably, cultivars Wafiya, Douma 4, and Golan 2 demonstrated such potential.

Moreover, high and significant heterosis values relative to MP and BP were observed in several hybrids for various traits. These hybrids also showed desirable specific combining ability effects, typically resulting from at least one parent with favorable GCA, including: Douma 4× Golan 2, Odessa × Douma 4, Jihan 99 × Douma 4, Golan 2× Sham 12, Wafiya × Sham 12, and Odessa × Jihan 99. These hybrids are promising candidates for further selection in segregating generations and may serve as a basis for the development of high-yielding and protein-rich soft wheat lines.