Evaluation and genetic dissection of the powdery mildew resistance in 558 wheat accessions

Powdery mildew, a widespread and destructive wheat disease caused by the fungal pathogen Blumeria graminis f. sp. tritici (Bgt), results in significant yield losses globally. Employing host resistance is the most cost-effective and environmentally sustainable approach to managing this disease. Assessing the resistance levels of wheat germplasms and understanding the genetic underpinnings of this resistance is crucial. In this study, we evaluated the seedling resistance to powdery mildew in 558 wheat accessions, along with the presence of resistance genes Pm1, Pm2, Pm4, Pm5, Pm6, Pm8, Pm12, Pm21, Pm24, Pm41, Pm42, Pm45, Pm47, Pm60, and Pm69 using various Bgt isolates and associated diagnostic markers. The study revealed that out of 558 wheat accessions tested, only 25 showed resistance to the Bgt isolate E09, highlighting a general lack of powdery mildew resistance among the evaluated accessions. Furthermore, these 25 accessions exhibited a significantly different resistance spectrum to 25 additional Bgt isolates. Notably, seven of these accessions were resistant to all the tested isolates, indicating they possess Pm genes with broad-spectrum resistance. Molecular analysis using closely linked or diagnostic markers revealed diverse resistance gene profiles: 249 accessions harbored a single tested Pm gene, 75 accessions possessed combinations of Pm genes, and 234 accessions lacked any of the tested genes. Pm8 was the most frequently detected gene, present in 27.42% of accessions, whereas Pm5, Pm12, Pm24, Pm41, Pm42, Pm45, Pm47 and Pm69 were not detected. Among the seven accessions resistant to all 26 tested isolates, Pm21 was detected in four accessions (HengS29, Chang 4640, Xinong 556, and ML728). Pm2 and Pm60 were identified in Emai 18 and Xinmai 296, respectively. Interestingly, none of the tested genes were detected in Emai 16, suggesting the presence of potentially novel Pm gene(s) conferring broad-spectrum resistance. These findings offer valuable insights for the strategic dissemination of these resistant accessions and for targeted breeding programs aimed at combating powdery mildew.