Quantitative Trait Loci Identified for Resistance to Stagonospora Glume Blotch in Wheat in the USA and Australia

Abstract

Resistance to stagonospora nodorum blotch (SNB) in glumes of hexaploid wheat (Triticum aestivum L.), caused by Phaeosphaeria (Stagonospora anamorph) nodorum was investigated in a recombinant‐inbred (RI) population. The Purdue University winter wheat breeding lines P91193D1 and P92201D5, unrelated by parentage but both exhibiting partial SNB resistance, were crossed to develop 254 RI lines by single‐seed descent (SSD) from a random population of F2 plants, to identify quantitative trait loci (QTLs) controlling SNB resistance in wheat glumes. The RI population, together with parent lines, was phenotyped for glume resistance to SNB under field conditions in F8:10 at Evansville, Vincennes, and Lafayette, IN, in 2003; in F7:9 at South Perth, Australia, in 2004; and in F8:10 in greenhouse‐grown inoculated tests at Lafayette in 2003 and 2004. Two QTLs for resistance to SNB in glumes were identified: QSng.pur‐2DL.1 from P91193D1 and QSng.pur‐2DL.2 from P92201D5. The QTL QSng.pur‐2DL.1 explained from 12.3% of the phenotypic variation for resistance in southern Indiana (Evansville and Vincennes) to 38.1% at South Perth; QSng.pur‐2DL.2 accounted for 6.9 and 11.2% of the phenotypic variation in Indiana and South Perth, respectively. This study is the first report of SNB glume blotch resistance in which the same QTLs were identified in tests on different continents where Stagonospora nodorum populations are probably genetically diverse.