China is a significant wheat producer and consumer in the world. It is very important for our food security to making sure the stable wheat production. Wheat powdery mildew is an important leaf disease to affect the global wheat yield. Breeding resistant wheat varieties is one of the most economically and environmentally effective way to manage this disease. Identification of new adult plant resistant loci is very important for breeders to develop durable powdery mildew-resistant wheat varieties.
The CIMMYT-derived common wheat (Triticum aestivum L.) Arableu#1, showed susceptibility to powdery mildew at the seedling stage, but exhibited a high level of resistance to this disease at the adult plant stage in the field. In order to understand the genetic basis of powdery mildew resistance in this line, we made an F5 recombinant inbred line (RIL) population between Arableu#1 and the susceptible line Apav#1 and genotyped by genotyping-by-sequencing (GBS) platform. We obtained 4 298 polymorphic molecular markers between the parents and analyze the 142 RILs. Joinmap 4.1 and IciMapping 4.1 were respectively used to construct the linage maps and identify the powdery mildew resistance QTL in this study.
Four adult plant resistance loci from Arableu#1 were identified on wheat chromosome arms 1BL, 5BL, 6BS and 7BL, while two loci from Apav#1 on chromosomes 2DS and 4BL, which can explain the powdery mildew disease severity variation from 3.1% to 28.5%. The MFDS of RIL reached the lowest level when it carried all six detected resistance loci, while RILs combing QPm.hzau-1BL, QPm.hzau-4BL, QPm.hzau-5BL, and QPm.hzau-7BL also showed lower disease severity over multiple environments.
KASP markers KASP-5B-1 and KASP-7B-2 for QPm.hzau-5BL and QPm.hzau-7BL, respectively, were developed in the present study. The two loci showed varying degrees of resistance to powdery mildew when present individually or in combination based on the genotype and phenotype of 570 wheat germplasm collections. Additionally, the frequency of these two loci in Chinese wheat materials is lower compared to CIMMYT's wheat germplasm. A line combining 6 QTLs was found and it showed near-immune resistance to powdery mildew in the field. This material will be an important germplasm resource for breeders to develop powdery mildew-resistant wheat varieties.