Combining and mapping qtl for fusarium head blight (FHB) resistance in wheat

Fusarium head blight (FHB) has become one of the most damaging wheat diseases in humid and semi-humid regions around the world. Single gene resistance to FHB in wheat provides only partial resistance and also the disease severity is highly influenced by environment. Consequently multiple genes are required for effective resistance. Our hypothesis is that identifying DNA markers for type I resistance will be very beneficial for selection, and combining type I and type II FHB resistance will be more effective than either type alone. The objectives of this project are to 1) combine type I resistance from cultivars Goldfield, INW0412, Bess, 99751, and Truman; and type II resistance of Fhb1 and Qfhs.pur-7EL backcrossed into adapted soft winter wheat lines and quantify augmentation of FHB resistance and 2) characterize a RIL population from the cross INW0412 (type I resistance)/992060G1 (susceptible) for frequency of initial infection and map QTLs for type I resistance. For objective 1, QTL from Sumai3 on chromosome 3B (Fhb1), from tall wheatgrass on 7EL (Qfhs.pur-7EL), and from Goldfield together provided high resistance, whereas epistatic interactions among those three QTL resulted in lower resistance than expected. QTL from Sumai3 and from tall wheatgrass on 7EL (Qfhs.pur-7EL) each significantly improved type II FHB resistance. No effect on increasing type I FHB resistance was detected in the presence of the QTL on 2B in these lines, which may be overshadowed by other potential genes controlling type I resistance that presented. Combining cultivars with type I and type II FHB resistance provided lines with high FHB resistance that will be beneficial to improve wheat cultivars. For objective 2, a population of 198 RILs and the two parents were characterized for FHB incidence at Lafayette, IN in 2011 and 2013 and in the greenhouse 2012 and 2013. A two-enzyme genotyping-by-sequencing (GBS) approach was applied to construct a 1,883 cM linkage map. Composite interval mapping analysis detected a QTL on chromosome 1AS under greenhouse conditions, and three other QTL on chromosomes 1BL, 2BL, and 3AS under field environments. Each QTL explained between 7.44% and 12.20% of the total phenotypic variation. RILs with all three QTL on chromosomes 1BL, 2BL, and 3AS significantly improved type I resistance by 33.06% in the field experiments. Our results also confirmed that type I and type II FHB resistance were controlled by different loci in wheat