Identification of Novel Powdery Mildew Resistance Sources in Wheat

Genetic resistance plays an important role in managing powdery mildew of wheat (Triticum aestivum L.), a disease of global importance. The objectives of this study were to evaluate powdery mildew resistance and the underlying genes in US wheat breeding lines and identify novel resistance sources from a worldwide collection of winter wheat germplasm. Our results suggested that 37.5% of powdery mildew resistant breeding lines recently developed in the United States carry the Pm3a gene, indicating the abundance of Pm3a in US cultivars. Among a worldwide collection of 1,297 landraces and 874 early cultivars or breeding lines, 59 and 68 accessions showed high (HR) and moderate resistance (MR), respectively. In addition, highly resistant plants were identified in 41 heterogeneous accessions. These resistant accessions were further screened for the presence of Pm3a, Pm3b, Pm3c, Pm3d, and Pm3f genes as well as the 1RS translocation segment. Among them, 13 accessions had a Pm3 allele, and another seven accessions possessed the 1BL/1RS translocation fragment with the Pm8 gene. Genetic diversity analysis based on a set of 5,011 single-nucleotide polymorphism (SNP) markers identified genetically similar accessions. The deployment of resistance sources identified in this study in wheat breeding may greatly broaden the genetic base of powdery mildew resistance.