A novel leaf rust resistance gene introgressed from Aegilops markgrafii maps on chromosome arm 2AS of wheat

Abstract

A new leaf rust resistance gene tentatively named LrM was introgressed from the diploid non-progenitor species Ae. markgrafi (2n=2x=14, genome CC) into common wheat using the nulli-5B mechanism. The introgression line ER9- 700 showed a high degree of resistance against a wide spectrum of Puccinia triticina pathotypes. Genetic analysis was performed using the F1, F2, F2:3 and BC1F1 generations derived from the cross ER9-700/Agra Local. The results showed a single dominant gene for leaf rust resistance. The resistance gene LrM was mapped on chromosome arm 2AS using SSR- and SNP-based PCR markers. Preliminary mapping with SSR markers in the F2:3 population from the cross ER9-700/Agra Local identifed two SSR markers fanking the LrM. SNPs were identifed in the genomic region fanked by SSR markers, and SNP-based PCR markers were developed to construct the fnal map. Three SNP-based PCR markers co-segregated and mapped closest to the resistance gene at a distance of 2 cM. The gene LrM was distinguished from all the other genes designated and mapped on chromosome arm 2AS by molecular markers and rust reaction. All fve markers used in the mapping amplifed identical alleles in the donor Ae. markgrafi accession and introgression line ER9-700. The chromosomal location and rust reaction suggest that LrM is a novel leaf rust resistance gene that may be useful in broadening the genetic base of leaf rust resistance in wheat.