Molecular markers for glume blotch resistance in wheat

Stagonospora nodorum blotch (SNB) is a fungal disease of wheat causing leaf and glume blotch. The disease occurs in many wheat growing regions worldwide and is considered to be among the major diseases of wheat in humid temperate climates, resulting in significant losses in grain quality and yield. The development of resistant cultivars is the most efficient and environmentally sustainable means of controlling SNB. However, incorporation of resistance to SNB into wheat using conventional methods is difficult because resistance appears to be inherited as a quantitative character in the majority of cultivars. Furthermore, agronomic traits such as plant height, earliness, and winter growth habit also influence the development of the disease. The complexity of resistance mechanisms has made it difficult to assess resistance in new wheat cultivars. The use of quantitative resistance in breeding programs would be greatly facilitated by marker-assisted selection. During the 2002-2003 growing season (FWF, Lise Meitner Program, project no: M696-B07), two mapping populations of recombinant F1-derived doubled haploid (DH) lines from two crosses between two partially resistant (Frontana and CM 82036) and one susceptible wheat cultivar (Remus) were evaluated for leaf and glume blotch resistance at the adult stage in the greenhouse and in the field. No significant QTLs for leaf blotch resistance were detected in both mapping populations. However, three QTLs were significantly associated with glume blotch resistance in each mapping population in the greenhouse. The multiple QTL model explained 33.5% and 16.3% of the total phenotypic variation in the Frontana/Remus, and CM82-036/Remus populations, respectively. In the field, three, and seven QTLs were identified as contributing to glume blotch resistance in the Frontana/Remus, and CM82-036/Remus populations, respectively, collectively accounted for 30.1 and 29.4% of the phenotypic variance, respectively. Because of the complex nature of genetic resistance to glume blotch, QTL identification is not always very robust and is subject to genotype x environment interactions. Therefore, the aim of this proposal is to repeat the resistance screening in an independent season for verification of results, and to complete the molecular mapping in promising QTL regions. Validation of these QTLs is important before implementing marker-assisted selection in a breeding program.