Genetic mapping of the wheat leaf rust resistance gene Lr2a and its importance in Canadian wheat cultivars.

population developed from the cross Chinese Spring/RL6016. Seedlings were tested with the Lr2a avirulent Pt races 74-2 MGBJ (Superb/BW278) and 12-3 MBDS (Superb/86ISMN 2137 and Chinese Spring/RL6016) in greenhouse assays and were genotyped with 90K wheat Infinium SNP and kompetitive allele-specific PCR (KASP) markers. Lr2a was mapped to a collinear position on chromosome arm 2DS in all three populations, within a 1.00 cM genetic interval between KASP markers kwm1620 and kwm1623. This corresponded to a 305 kb genomic region of chromosome 2D in Chinese Spring RefSeq v2.1. The KASP marker kwh740 was predictive of Lr2a in all mapping populations. A panel of 260 wheats were tested with three Pt isolates, which revealed that Lr2a is common in Canadian wheats. The KASP markers kwh740 and kwm1584 were highly associated with resistance at the Lr2 locus, while kwm1622 was slightly less correlated. Genetic mapping of the leaf rust resistance gene Lr2a and DNA markers developed here will facilitate its use in wheat breeding programs.