Identification of molecular markers associated with adult plant resistanceto 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 d iseases of wheat (Triticum aestivum L.) worldwide. Race-specific resistance has been extensively used in wheat breeding programs, even though it is ep hemeral. Adult plant resistance (APR) to powdery mildew is more durable tha n race-specific resistance. The APR to powdery mildew in winter wheat culti var Massey has remained effective since its release in 1981. A cross was ma de 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 2 13 RFLP and 139 microsatellite markers surveyed, 88 (41%) and 90 (65%) mark ers, respectively, detected polymorphism between Becker and Massey. Bulked segregant analysis (BSA) was used to facilitate the identification of molec ular markers associated with APR to powdery mildew. Three quantitative trai t loci (QTLs), designated as QPm.vt-1B, QPm.vt-2A, and QPm.vt-2B, were iden tified with interval mapping. They are located on wheat chromosomes 1B, 2A, and 2B, and, respectively, explained 17, 29, and 11% of the total variatio n of F-2:3 lines for powdery mildew resistance. The three QTLs associated w ith 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 milde w. In a multi-QTL model, the three QTLs explained 50% of the total variatio n 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 powd ery mildew under natural powdery mildew pressure over 3 yr (F-5:6-F-7:8 gen eration). The molecular markers identified in this study have potential for use in marker-assisted selection and pyramiding of genes for resistance to powdery mildew.