Dynamic QTL for adult plant resistance to powdery mildew in common wheat (Triticum aestivum L.)

Agriculture will benefit from a rigorous characterization of genes for adult plant resistance (APR) since this gene class was recognized to provide more durable protection from plant diseases. The present study reports the identification of APR loci to powdery mildew in German winter wheat cultivars Cortez and Atlantis. Cortez was previously shown to carry all-stage resistance gene Pm3e. To avoid interference of Pm3e in APR studies, line 6037 that lacked Pm3e but showed field resistance from doubled-haploid (DH) population Atlantis/Cortez was used in two backcrosses to Atlantis for the establishment of DH population 6037/Atlantis//Atlantis. APR was assessed in the greenhouse 10, 15, and 20 days after inoculation (dai) from the 4-leaf stage onwards and combined with single-nucleotide polymorphism data in a genome-wide association study (GWAS) and a linkage map-based quantitative trait loci (QTL) analysis. In GWAS, two QTL were detected: one on chromosome 1BL 10 dai, the other on chromosome 2BL 20 dai. In conventional QTL analysis, both QTL were detected with all three disease ratings: the QTL on chromosome 1BL explained a maximum of 35.2% of the phenotypic variation 10 dai, whereas the QTL on chromosome 2BL explained a maximum of 43.5% of the phenotypic variation 20 dai. Compared with GWAS, linkage map-based QTL analysis allowed following the dynamics of QTL action. The two large-effect QTL for APR to powdery mildew with dynamic gene action can be useful for the enhancement of wheat germplasm.