Identification and Precise Mapping of , a Novel Recessive Powdery Mildew Resistance Allele from Wheat Landrace Heshangmai.

Common wheat ( L.) is the world's primary food crop, and ensuring its safe production is of utmost importance for global peace and human development. However, the continuous threat of fungal diseases, including Fusarium head scab, rusts, sharp eyespot, and powdery mildew (PM), poses a significant challenge to production. PM caused by f. sp. causes substantial yield losses. Heshangmai (HSM), a wheat landrace originating from Sichuan Province, possesses high levels of resistance to PM. A comprehensive study using a large segregating population of a cross between HSM and Ningmaizi119 (NMZ119) revealed a single recessive allele conferring resistance. The gene, provisionally designated , was located on the long arm of chromosome 4A (4AL). Molecular marker analysis, a PM response array, and an allelism test indicated that is a novel recessive resistance gene that shares an allelic relationship with . Thirteen simple sequence repeat markers were developed using the sequence information of the 4AL region in the Chinese spring reference sequence version 2.1. was flanked by the markers and at genetic distances of 0.11 and 0.18 cM, respectively, and cosegregated with the markers //.