Genetic analysis of rust resistance in barley through diallel cross approach

Abstract:

Leaf rust alone can cut barley grain yield by up to 62 percent in epidemic years across Central Europe, yet most commercial Polish varieties carry only one or two known resistance genes—a narrow genetic base that invites pathogen adaptation. This research used a 6 × 6 half-diallel cross among six barley genotypes differing in rust resistance to dissect the genetic architecture of resistance to Puccinia hordei at the Mazovia Institute of Agricultural Sciences, Warsaw, during 2021-22 and 2022-23. Parents and 15 F₁ crosses were evaluated for infection type, disease severity, and latent period under artificial inoculation. Griffing's Method 2, Model I analysis revealed that general combining ability (GCA) variance was 3.4 times larger than specific combining ability (SCA) variance for infection type, indicating predominantly additive gene action. Parents P1 and P3 showed the most favorable (negative) GCA effects for all three resistance traits. The cross P1 × P3 exhibited the best SCA effect (−2.87 for infection type), combining additive resistance from both parents. Narrow-sense heritability estimates were 0.71 for infection type and 0.64 for severity. These findings suggest that recurrent selection exploiting additive effects would be the most efficient breeding strategy, with P1 × P3 and P1 × P5 progeny recommended as base populations for rust resistance improvement in Polish barley.