Genetic mapping of quantitative trait loci conditioning Fusarium head blight resistance in hard winter wheat

Doctor of PhilosophyDepartment of AgronomyGuihua BaiAllan K. FritzFusarium head blight (FHB), also known as ‘scab’, incited by Fusarium graminearum (Schw), is one of the most damaging fungal diseases in wheat. FHB reduces grain yield drastically, but also grain quality due to shriveled kernels, protein damage, and mycotoxin contamination caused by the fungal infection. Host plant resistance is the most effective and environmentally safe approach to combat this disease. To identify resistance genes from locally adapted cultivars, a population of 178 recombinant inbred lines (RILs) from Overland × Everest was genotyped using single nucleotide polymorphism (SNP) markers derived from genotyping-by-sequencing (GBS). The RIL population was phenotyped for resistance to the initial infection (type I), fungal spread within a spike (type II), mycotoxin (DON) accumulation in grains (type III) and Fusarium damaged kernel (type IV) in repeated greenhouse and field experiments. Seven QTLs were identified on chromosome arms 1AL, 3BL, 4BS, 4BL, 6AL, 6BL 7AS and 7BL for type I resistance. Hard winter wheat cultivar Everest contributes all the resistance alleles except two on chromosome arms 4BS and 6BL, which are contributed by hard winter wheat cultivar Overland. Six QTLs on chromosome regions of 1BL, 4A, 4BS, 5AL, 6BL and 7AS confer type II resistance with the resistance QTLs on 1BL, 4BS, 6BL and 7AS from Everest and on 4A, 4BS, and 5AL from Overland. The type II QTL on chromosome 4BS is overlapped with the reduced height gene Rht-B1. QTLs for type III resistance were mapped on 4BS and 5AL while QTLs for type IV resistance were mapped on chromosome 4BS, 5AL and 7AS and they overlapped with type II resistance in the corresponding chromosome regions. The haplotype analysis showed that genotypes containing multiple QTLs showed significantly higher resistance than those with fewer or no QTLs, indicating that these QTLs have additive effects on FHB resistance. Type I FHB resistance was poorly characterized in the literature. The current study demonstrated that Everest carries several QTLs for type I resistance, thus is a useful native source for type I resistance. Some SNP markers tightly linked with the QTLs for different types of resistance were successfully converted into Kompetitive allele-specific polymerase chain reaction (KASP) assays and could be used in marker-assisted breeding for FHB resistance in wheat