Fine mapping Fhb1, a major gene controlling fusarium head blight resistance in bread wheat (Triticum aestivum L.)

A major fusarium head blight (FHB) resistance gene Fhb1 (syn. Qfhs.ndsu-3BS) was fine mapped on the distal segment of chromosome 3BS of spring wheat (Triticum aestivum L.) as a Mendelian factor. FHB resistant parents, Sumai 3 and Nyubai, were used as sources of this gene. Two mapping populations were developed to facilitate segregation of Qfhs.ndsu-3BS in either a fixed resistant (Sumai 3*5/Thatcher) (S/T) or fixed susceptible (HC374/3*98B69-L47) (HC/98) genetic background (HC374 = Wuhan1/Nyubai) for Type II resistance. Type II resistance (disease spread within the spike) was phenotyped in the greenhouse using single floret injections with a mixture of macro-conidia of three virulent strains of Fusarium graminearum. Due to the limited heterogeneity in the genetic background of the crosses and based on the spread of infection, fixed recombinants in the interval between molecular markers XGWM533 and XGWM493 on 3BS could be assigned to discrete "resistant" and "susceptible" classes. The phenotypic distribution was bimodal with progeny clearly resembling either the resistant or susceptible parent. Marker order for the two maps was identical with the exception of marker STS-3BS 142, which was not polymorphic in the HC/98 population. The major gene Fhb1 was successfully fine mapped on chromosome 3BS in the same location in the two populations within a 1.27-cM interval (S/T) and a 6.05-cM interval (HC/98). Fine mapping of Fhb1 in wheat provides tightly linked markers that can reduce linkage drag associated with marker-assisted selection of Fhb1 and assist in the isolation, sequencing and functional identification of the underlying resistance gene.