Identification of molecular markers associated with adult plant resistance to powdery mildew in common wheat cultivar Massey

Powdery mildew, caused by Blumeria graminis (DC.) E.O. Speer f. sp. tritici Em. Marchal (syn. Erysiphe graminis f. sp. tritici), is one of the major diseases of wheat (Triticum aestivum L.) worldwide. Race-specific resistance has been extensively used in wheat breeding programs, even though it is ephemeral. Adult plant resistance (APR) to powdery mildew is more durable than race-specific resistance. The APR to powdery mildew in winter wheat cultivar Massey has remained effective since its release in 1981. A cross was made between Massey and a powdery mildew susceptible cultivar Becker. Powdery mildew severity on F-2 leaves (the second leaf below the flag leaf) of 180 F-2:3 lines was rated under natural disease pressure in the field. Among 213 RFLP and 139 microsatellite markers surveyed, 88 (41%) and 90 (65%) markers, respectively, detected polymorphism between Becker and Massey. Bulked segregant analysis (BSA) was used to facilitate the identification of molecular markers associated with APR to powdery mildew. Three quantitative trait loci (QTLs), designated as QPm.vt-1B, QPm.vt-2A, and QPm.vt-2B, were identified with interval mapping. They are located on wheat chromosomes 1B, 2A, and 2B, and, respectively, explained 17, 29, and 11% of the total variation of F-2:3 lines for powdery mildew resistance. The three QTLs associated with APR to powdery mildew were derived from Massey, and displayed additive gene action. QPm.vt-2B also fits a recessive model for APR to powdery mildew. In a multi-QTL model, the three QTLs explained 50% of the total variation of F-2:3 lines for APR to powdery mildew. The presence of the three QTLs was confirmed with 97 recombinant inbred (RI) lines, tested for APR to powdery mildew under natural powdery mildew pressure over 3 yr (F-5:6-F-7:8 generation). The molecular markers identified in this study have potential for use in marker-assisted selection and pyramiding of genes for resistance to powdery mildew.