Molecular Characterization of Quantitative Trait Loci for Powdery Mildew Resistance in US Soft Red Winter Wheat

Powdery mildew (Pm) has caused increasing damage on wheat production in southeastern USA. To combat the disease, there is a continuing need to discover new genes or quantitative trait loci for Pm resistance and promptly adopt those loci in breeding program. Pioneer^® variety 26R61 (shorten as 26R61) and AGS 2000 have been used as checks in Uniform Southern Soft Red Winter Wheat Nursery for decade, and perform good resistance to Pm across regions. In the present study, genetic analysis of Pm resistance was conducted in a RIL population from a cross between the two cultivars 26R61 and AGS 2000. Phenotypic evaluation was conducted independently in the field in Plains, GA and Raleigh, NC in 2012 and 2013 with the total of four environments. Three QTL of major effect were consistently detected and assigned to 2BL, 4A and 6BL, respectively; the 2BL QTL contributed by the parent 26R61 was different from Pm6, a widely used gene in these wheat growing regions; the other two QTL from AGS 2000 might both represent new loci for Pm resistance and the 6BL locus has been characterized as a Mendelian locus in our previous study and temporarily designated as PmA2K. The R² explained by these loci ranged from 6 to 30% but varied with different environments. QTL on 2BL from 26R61 played a key role for Pm resistance in Raleigh, NC; while QTL on 6BL from AGS 2000 contributed significantly in Plains, GA; the QTL on 4AL was a major determinant in both locations. The information provided here will be useful for breeding Pm resistant cultivars in the soft red winter wheat growing regions.