Fine mapping of PmL270, a new powdery mildew resistance gene on chromosome 7AL in wheat.

: Wheat (Triticum aestivum) is one of the most important cereal crops, providing essential food and nutrition for humans. Wheat powdery mildew, caused by the biotrophic fungal pathogen Blumeria graminis f. sp. tritici (Bgt), seriously threatens wheat production by reducing yield and quality. Utilizing effective powdery mildew resistance (Pm) genes to develop resistant cultivars is a powerful means for controlling this disease. In this study, we identified a new resistance gene, PmL270, from the wheat line L270. By means of bulked segregant RNA‑Seq (BSR‑Seq) and molecular marker analysis, we fine-mapped PmL270 to a 0.1-cM interval on chromosome 7AL, flanked by the markers X7AL07 and X7AL09. This interval corresponds to a 630-kb region in the reference genome of Chinese Spring. Comparative analysis showed that PmL270 is distinct from other Pm genes previously reported on the same chromosome arm. A co-dominant marker, X7AL08, developed from a candidate NLR gene, co-segregated with PmL270 in the mapping population and showed high specificity for this gene. The mapping and development of co-segregation marker will facilitate the cloning of PmL270 and contribute to its rapid utilization in wheat resistance breeding. The online version contains supplementary material available at 10.1007/s11032-025-01574-0.