An NLR pair in the Pm68 locus confers powdery mildew resistance in durum and common wheat.

Abstract

Common wheat and durum wheat are widely cultivated cereal crops, both of which are infected by the obligate biotrophic pathogen Blumeria graminis f. sp. tritici (Bgt), causing powdery mildew. Recently, Pm68 gene was identified on the short arm of chromosome 2B in the Greek durum wheat line TRI 1796, conferring resistance to this disease. Here, we have cloned Pm68 from TRI 1796 using an integrated approach of genetic mapping, association analysis and PacBio sequencing. Transgenic assays demonstrate that Pm68 mediated resistance is controlled by a pair of genetically linked nucleotide-binding leucine-rich repeat (NLR)-encoding genes, Pm68-1 and Pm68-2. Transient expression assays in Nicotiana benthamiana leaves reveal that the activation of Pm68-1 is positively modulated by Pm68-2, likely through its N-terminal coiled-coil (CC)-like domain. Evolutionary analysis traces the origin of Pm68 to a specific wild emmer subpopulation. The introgression and transgenic wheat lines carrying this gene show no significant negative effects on major agronomic traits, highlighting the potential value of Pm68 for disease-resistant breeding programs of both durum wheat and common wheat.