Molecular mapping of Triticum monococcum derived leaf rust resistance gene in durum wheat

Key message: A putatively novel leaf rust resistance gene, introgressed from Triticum monococcum into durum, temporarily named as LrTm64-8 and mapped on chromosome 2AS will aid in broadening the genetic base of rust resistance in wheat. A leaf rust resistance gene, tentatively named as LrTm64-8 was introgressed into durum wheat from diploid species Triticum monococcum (2n = 2x = 14, genome AA) by direct hybridization. The Introgression Line DTM648 showed wide spectrum of resistance against a panel of 18 pathotypes of leaf rust pathogen Puccinia triticina Eriks. Genetic analysis of leaf rust resistance in DTM64-8 was performed using F1, F2 and F2:3 generations derived the cross DTM64-8/Malvi Local. The results showed a single dominant gene for leaf rust resistance. The resistance gene LrTm64-8 was mapped on short arm of chromosome 2A using both SNP-based PCR markers and SSR markers. Initially, polymorphic SNPs in Bulked Segregant Analysis (SNP) were identified and primers were designed to convert SNPs into PCR-based markers. Additionally, polymorphic SSR markers were identified in the putative genomic region carrying the leaf rust resistance gene. The final map was constructed using one SNPbased PCR marker and three SSR markers spanning a distance of 33.4 cM. LrTm64-8 was flanked by SNP AX94756068 and Xwmc522 on chromosome 2AS. SSR marker Xwmc522 was closest at 3.7 cM proximal to the resistance gene. The resistance gene LrTm64-8 was distinguished from other leaf rust resistance genes mapped on short arm of chromosome 2A by molecular markers and rust response. While all other leaf rust resistance genes identified on chromosome 2AS are mapped in hexaploid wheat, the resistance gene LrTm64-8 was introgressed and mapped in tetraploid durum wheat and may be useful in broadening the genetic base of rust resistance in both durum and bread wheat.