Phenotypic and molecular dissection of all-stage and adult-plant leaf rust resistance in Iranian Aegilops tauschii

Leaf rust caused by Puccinia triticina (Pt) is the most prevalent disease of wheat, which threatens its production worldwide. The most viable strategy to control this disease is genetic resistance, which can be achieved through deploying new resistance genes. Hence, we studied a collection of 117 Iranian Ae. tauschii along with 31 near isogenic lines lines of the wheat cultivar Thatcher at the seedling stage using 12 Pt pathotypes to postulate leaf rust resistance (Lr) gene(s). Nine specific markers for the genes Lr1, Lr19, Lr21, Lr22a, Lr24, Lr32, Lr37, Lr39, and Lr42 were also utilized to investigate the presence of corresponding Lr genes in the germplasm and validate the phenotyping results. Fifty-two accessions produced high infection types (ITs) of '3-' to '3+' to at least one pathotype, while the remaining 65 showed low ITs (0;= to 2+) against all pathotypes. Resistant accessions often belonged to the southeastern shores of the Caspian Sea and the strangulata subspecies. Based on phenotyping results and molecular markers the genes Lr1, Lr15, Lr19, Lr22a, Lr32, Lr37, Lr39, and Lr42 in addition to unknown Lr gene(s) were present either individually or in combinations in 112 accessions of Ae. tauschii, while the remaining five accessions probably did not carry any detectable Lr gene. The presence of the all-stage resistance genes Lr1 and Lr32 was confirmed in all accessions postulated to carry them. Adult plant resistance (APR) was also evaluated where 19 accessions were found to possess potentially novel APR gene(s). Overall, this study identified genotypes with possibly new genes, which could be used in wheat breeding programs, and are valuable for genetic analysis of their resistance gene(s). Moreover, the environment and subspecies in which higher resistance levels are more common, were identified.

Automated summary

This study investigated the presence of leaf rust resistance (Lr) genes in a collection of Iranian Ae. tauschii and near isogenic lines of the wheat cultivar Thatcher. The results identified multiple Lr genes, including potentially novel ones, and provided valuable insights for wheat breeding programs and genetic analysis of resistance genes.