Development and validation of diagnostic markers for the wheat Fusarium head blight resistance gene Fhb7

Fusarium head blight (FHB), mainly incited by Fusarium graminearum Schwabe, has caused great losses in grain yield and quality of wheat globally. Fhb7, a gene with a major effect on FHB resistance, was recently cloned and shown to be a GST encoding glutathione S-transferase. Fhb7 originated from the 7E chromosome of Thinopyrum ponticum and confers broad resistance to Fusarium species. However, high-throughput diagnostic markers are not available for wider deployment of Fhb7 in breeding programs. To develop such DNA markers for high-throughput screening of Fhb7, we designed two kompetitive allele specific polymerase chain reaction (KASP) markers (Fhb7-KASP1 and Fhb7-KASP2) based on the promoter and coding sequences of GST homologs and tested their cosegregation with Fhb7 FHB resistance in a recombinant inbred population. As a validation of their usefulness in marker-assisted selection in breeding programs, Fhb7-KASP1 and Fhb7-KASP2 were shown to be diagnostic for Fhb7 status in a set of RWG34-near-isogenic lines (NILs) and a natural winter wheat population (RGON2020). Haplotype analysis of Thinopyrum accessions using the two markers and GST homolog sequences identified only six accessions with the Fhb7 resistance marker alleles and the Hap I-R haplotype, and five of them were cytologically confirmed to be Th. ponticum, the species in which Fhb7 was originally identified. The development of the diagnostic markers in this study will facilitate the deployment of Fhb7 in wheat breeding programs to improve FHB resistance.