Development and verification of wheat germplasm containing both Sr2 and Fhb1

Fusarium head blight (FHB) and stem rust are two devastating fungal diseases of common wheat prevalent worldwide. Fhb1 is a well-known major quantitative trait locus effective against FHB, and Sr2 is the most widely characterized and deployed wheat stem rust adult plant resistance gene. These genes are linked in repulsion phase, approximately 3 cM apart, on chromosome 3B. To obtain wheat germplasm containing both Fhb1 and Sr2 genes, we developed and screened two F-2 populations using tightly linked DNA markers, Xgwm533 and csSr2 for Sr2, and UMN10, and a newly designed marker UMN10(v2) for Fhb1. Among 1949 F-2 plants, 43 were identified with Fhb1 and Sr2 in coupling phase. After screened with vernalization gene markers, 59 F-3 spring wheat lines with homozygous Fhb1 and Sr2 were obtained. All these lines showed significantly lower FHB severity than susceptible checks (P < 0.01) and similar FHB severity to the resistant checks (P > 0.61) in the field. And these lines were susceptible as seedlings in greenhouse assays, but resistant as adult plants to race QTHJC in the stem rust nursery. Field disease resistance evaluation verified that all these recombinant lines showed moderate or high levels of resistance to both FHB and stem rust. This germplasm would benefit efforts to breed for resistance to FHB and stem rust, and the procedure to obtain recombinants is adaptable to other wheat breeding programs.