The Alien VPM1 Segment in Jagger Wheat Has Lr37 and the Orthologous Gene Lr17N

Winter wheat cultivar ‘Jagger’ was recently found to have an alien chromosomal segment ‘VPM1’ that should carry Lr37, a gene conferring resistance against leaf rust caused by Puccinia triticina, and this cultivar was also reported to have the wheat gene Lr17 against leaf rust. Both Lr17 and Lr37 were reported to reside on the short arm of chromosome 2A in wheat. In this study, two fungal pathogen races, THBJG and BBBDB that are avirulent to Lr17 at the seedling stage, were used to precisely map this gene by inoculating the population of Jagger × ‘2174’ recombinant inbred lines. As a result, a major quantitative trait locus (QTL) for THBJG and BBBDB was coincidently mapped to chromosome 2AS, and the QTL alone accounted for 62.2 % of total phenotypic variation in reaction to THBJG, and 64.4 % to BBBDB. However, it was found that Jagger did not have the wheat Lr17 but had an orthologous Lr17N present in the VPM1 segment that conferred resistance against both THBJG and BBBDB. Further analysis of IWGSC Chinese Spring genome sequences showed that the VPM1 segment translocated into a region starting from the telomere of 2AS and its physical length was approximately 24 Mb. The Lr17N gene was delimited to a genomic region of 4.4 Mb, where several candidate genes encoding RGA, WRKY and LRR conserved domains were identified. In addition, Jagger was found to have a resistant allele at another three minor QTLs that were mapped associated with reaction to both THBJG and BBBDB.