Identification of molecular markers linked to Fusarium head blight (scab) resistance genes in wheat

Fusarium head blight (FHB, scab) is a fungal disease of wheat that has attracted increasing concern during the past decade almost worldwide. FHB may cause relevant yield and quality losses, but the most serious threat is the contamination of cereal food and feed with toxic secondary metabolites of the fungus, known as mycotoxins. Cereal products, which are contaminated with mycotoxins, may enter the food chain. As these substances are heat stable they can be found even in processed food like bread and pasta. Fusarium mycotoxins may cause or promote human diseases and have a serious implication on livestock productivity. Chemical or agronomic measures to control the disease are either not available or not feasible. Breeding resistant cultivars is the method of choice for FHB control. Conventional breeding for FHB resistance is hampered by several constraints, e.g. field selection is tedious and biased by the environment, and the resistant genotypes are of exotic origin and have many undesirable characters. The application of molecular markers could complement classical plant breeding. Aim of this proposal was therefore to characterize the inheritance of FHB resistance in two resistant sources and to identify molecular markers linked to FHB resistance genes for use in marker-assisted selection. Populations were created from crosses between two different resistant and one susceptible spring wheat line. More than 200 lines per cross were evaluated for resistance in replicated field experiments using artificial inoculation methods. A subset of the lines was used to develop linkage maps using different types of molecular markers. The molecular marker data together with the resistance data allowed the detection of those chromosomal segments, which harbor resistance genes. In one population two quantitative trait loci (QTLs) with large effects were found in the other population several QTLs with small individual effects were detected. For the significant QTLs we were able to find flanking PCR (polymerase chain reaction) markers. The application of these markers appears feasible in a practical breeding program and should allow the transfer of FHB resistance into locally adapted lines in a much shorter time than before. Several plant breeders in Europe and beyond have begun to apply these new findings in their cultivar development. It is anticipated that improved cultivars with enhanced resistance to FHB and reduced vulnerability to mycotoxin contamination will enter the markets in the years to come.