Identification and fine mapping of PmNJ3946 for powdery mildew resistance in einkorn wheat

Powdery mildew caused by Blumeria graminis f. sp. tritici (Bgt) is a destructive wheat disease. Although it can be easily overcome by deployment of resistance genes, the resistance is often quickly compromised by pathogen virulence. Thus, exploration and characterization of new resistance genes is always ongoing. Line NJ3946 derived from a cross of einkorn wheat accessions TA2032 and M389 showed resistance to powdery mildew. Inheritance analysis of an F2 population derived from a cross of NJ3946 and M389 suggested that the resistance was conferred by a dominant allele. With polymorphic markers identified through bulked segregant analysis (BSA), this gene was mapped to a novel locus on chromosome 3A, and was designated as PmNJ3946. Bulked segregant RNA-seq analysis (BSR-seq) was conducted to obtain more closely linked markers, which allowed delimitation of the PMNJ3946 locus to a 0.9 cM interval covering a physical distance of less than 1 Mb. PMNJ3946 was flanked by Xwgrc5153 and SNP-derived marker CHS21_3A008915069, and co-segregated with SNP-derived markers CHS21_3A008939814 and CHS21_3A008943175. The PmNJ3946 discovery expands the diversity of powdery mildew resistance genes and is useful for wheat breeding.