Abstract
Fusarium head blight (FHB) is one of the most damaging wheat (Triticum aestivum L.) diseases in humid and semihumid regions around the world. Breeding efforts have focused on resistance mechanisms that limit the spread once a spike is infected-type II resistance. But resistance to initial infection, type I resistance, is an important trait that could be combined with other modes of resistance. The objective of this project was to identify and map the locations of previously unknown quantitative trait loci (QTL) that reduce the incidence of initial infection. A mapping population of 198 recombinant inbred lines (RILs) was evaluated for type I resistance in both the field and greenhouse. A two-enzyme genotyping-by-sequencing (GBS) approach was applied to construct a 1883-cM linkage map yielding single-nucleotide polymorphism (SNP) markers. Composite interval mapping analysis detected a QTL on chromosome 1AS under greenhouse conditions and three other QTL on chromosomes 1BL, 2BL, and 3AS in field environments. Each QTL explained between 7.44 and 12.20% of the total phenotypic variation. Sixteen RILs were identified with markers for all three QTL on chromosomes 1BL, 2BL, and 3AS exhibiting significantly improved type I resistance (a mean of 33.06% improvement) over RILs with none of the three markers in field experiments. Our results also confirmed that types I and II FHB resistance were controlled by different loci in the wheat RIL population and could be used in combination to provide multiple layers of defense for cultivar development through marker-assisted selection.