Mapping Adult Plant Resistance to Powdery Mildew in Soft Red Winter Wheat.

The soft red winter wheat cultivar USG3209 contains adult plant resistance (APR) to powdery mildew (PM), Blumeria graminis (DC.) E.O. Speer f. sp. tritici.  Due to its quantitative nature, APR to PM can be difficult to assess phenotypically.  Yet, its durability compared to that of single race-specific major genes makes it very desirable to wheat breeders especially in the eastern and southern US soft wheat region where favorable environmental conditions create substantial PM losses.  A quantitative trait loci (QTL) analysis for PM resistance was completed on a USG3209/Jaypee recombinant inbred line mapping population in 7 field environments and one greenhouse environment from 2002 to 2007.  The preliminary genetic linkage map of the USG3209/Jaypee population identifies QTL for APR to PM on chromosomes 1B, 2B, and 2A.  The QTL on chromosome 1B is located in the same region as the APR leaf rust gene, Lr46 near molecular marker Xgwm259.  The QTL located on the long arm of chromosome 2A is located in the same region as the single major PM resistance gene Pm4.  The QTL located on chromosome 2B is located in the same region as the single major stem rust gene Sr36 near molecular marker Xgwm501 and the single major PM resistance gene Pm6.  An updated genetic linkage map of the QTL for APR to PM contained within this population will be presented in the poster. The genetic linkage map contains both microsatellite markers and diversity array technology (DArT) markers.