Molecular marker aided characterization of race specific and non-race specific rust resistance genes in elite wheat (Triticum spp.) germplasm

Among wheat diseases, leaf (brown) rust caused by Puccinia triticina Eriks. causes more damage to the crop than any other rust. The pathogen is very dynamic and renders rust-resistant wheat cultivars susceptible by evolving new pathotypes. To counter such threats, developing wheat cultivars using diverse germplasm carrying rust resistance genes effective at different growth stages is required. Forty elite wheat genotypes were selected for characterizing race specific (Lr19/Sr25, Lr24/Sr24) and non-race specific (Lr34/Yr18/Pm38/Sr57, Lr46/Yr29/Pm39) rust resistance genes using Sequence Tagged Site (STS) markers Sr24#12, Gb, csLV34 and SSR marker wmc44. The marker analysis revealed the presence of Lr24/Sr24 genes in 47% of the wheat genotypes, whereas 22.2% possessed Lr24/Sr24 and Lr34/Yr18/Pm38/Sr57 gene combination. Two genotypes G16 and G12 were confirmed to have Lr19/Sr25, Lr24/Sr24, Lr34/Yr18/Pm38/Sr57 and Lr24/Sr24, Lr34/Yr18/Pm38/Sr57, Lr46/Yr29/Pm39 gene combinations, respectively. Genetic diversity analysis based on the dissimilarity indices indicated the presence of huge genetic diversity among the wheat germplasm. The presence of Lr24/Sr24 using Sr24#12 marker was confirmed in HS545, which showed monogenic control of leaf rust resistance against pathotype 77-5 (THTTM). Leaf rust and stem rust resistance present in this set of diverse germplasm could be used as potent donors for durable rust resistance breeding in wheat. The molecular markers utilized in this study would also be useful in pyramiding or transferring the R genes into the rust susceptible agronomically superior wheat germplasm. Genotypes G12 and G19 resistant to rusts and also had significant grain yield superiority over HS490 could be a better choice for their use in rust resistance breeding.