Powdery mildew of wheat (Triticum aestivum L.), caused by Blumeria graminis DC f. sp. tritici Em. Marchal, occurs annually in eastern North America resulting in reduced grain yield and end-use quality in susceptible cultivars. The objectives of this study were to determine the inheritance, chromosomal location, and linkage with molecular markers of powdery mildew resistance genes in the two recently released germplasm lines NC96BGTA4 and NC99BGTAG11. Between 99 and 194 F(2:3) progenies plus parents in two populations, 'Saluda' x NC96BGTA4 and Saluda x NC99BGTAG11, were evaluated in greenhouse and field nurseries for reaction to powdery mildew infection. Results indicated that the germplasm lines each contained a different, partially dominant, major resistance gene. The two segregating populations were subjected to amplified fragment length polymorphism (AFLP) and simple sequence repeat, or microsatellite (SSR) analyses. Both resistance genes were located on the long arm of chromosome 7A. The most likely locus order indicated that the resistance gene in NC96BGTA4 was flanked by the SSR loci Xbarc292 and Xwmc525. The resistance gene in NC99BGTAG11 was most likely flanked by the AFLP markers XE38M54-196 and XE36M55-126, and the SSR loci Xgwm332 and Xwmc525. Both genes mapped to a chromosome arm that contains the powdery mildew resistance loci Pm1 and Pm9. The resistance genes in the two germplasms are different from the Pm1a allele. Our mapping results suggested that the resistance genes were not alleles at the Pm1 or Pm9 loci, but further allelism tests are necessary to determine the relationships both between the two genes themselves and between the two genes and named Pm loci on chromosome 7AL.
