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.

New Quantitative Trait Loci in Wheat for Flag Leaf Resistance to Stagonospora nodorum Blotch

“…Both Snn2 and Tsn1 co-locate with a QTL for flag leaf resistance from a Brazilian genotype, BR34, indicating a role for toxin-host interactions. In other studies, however, QTL for flag leaf and glume resistance were not associated with any known loci for toxin insensitivity (25,27,28), indicating that either different genes or alleles control toxin insensitivity or mechanisms different from the compatible toxin-host interactions are responsible for adult plant resistance in spring and winter wheat accessions.…”

“…The key to developing germplasm with adult plant resistance will be to assess which QTL from different sources are consistently detected across multiple and relevant field environments, deploy them in appropriate genetic backgrounds, and identify which QTL combinations provide significant improvements in SNB resistance. The QTL for flag leaf resistance and associated markers identified in this study can be combined with other QTL (3,13,27,28) to develop new germplasm with improved flag leaf resistance to SNB. The use of molecular markers will be an important tool to track and select QTL combinations in germplasm development and commercial breeding.…”

“…QTL for seedling resistance on chromosomes 6A and 7A were recently identified in association mapping studies (2). QTL for flag leaf resistance were identified on chromosomes 1B, 2A, 2D, 5A, 5B, and 7A (3,13,27) and glume resistance on 2D, 3B, 4B, and 5A (3,25,27,28). The majority of QTL for seedling, flag leaf, and glume resistance from these studies contributed a small proportion (usually <20%) of phenotypic variation.…”

“…Therefore, there is a greater emphasis on developing flag leaf and glume resistance in commercial cultivars. Two QTL for glume resistance on chromosomes 2D and 4B have shown to be effective in Western Australian environments (27,28) and are suitable for deploying in genetic backgrounds. However, only one QTL for flag leaf resistance has been identified on sunlight with a shade cloth bag (84 to 90% cover factor).…”

Quantitative Trait Loci for Seedling and Adult Plant Resistance to Stagonospora nodorum in Wheat

“…Similarly, QTL for glume blotch resistance were identified on 2B, 3B, 5B, and 5D in addition to nine other chromosomal regions (30) in another winter wheat population, but most were not consistently detected across different environ-ments and their effect in seedling resistance has not been determined. More recently, the same QTL for glume blotch resistance on the long arm of chromosome 2D (2DL) was detected in a winter wheat accession in the United States and Australia even though extreme environmental conditions and genetically distinct isolates are likely to exist across continents (35). However, the lack of disease rating for seedlings in the same populations precluded the identification of alternative or similar QTL interacting between seedling and adult plant resistance.…”