Fhb9, a major QTL for Fusarium head blight resistance improvement in wheat

Fusarium head blight (FHB), mainly caused by Fusarium graminearum, is one of the most devastating diseases of wheat worldwide. Identification and validation of major quantitative trait loci (QTLs) for FHB resistance without negative effects on agronomic traits is critical to success in breeding FHB-resistant cultivars. In this study, a stable major QTL on chromosome arm 2DL was identified by evaluating a recombinant inbred line (RIL) population derived from Shi4185×Shijiazhuang 8 in both field and greenhouse experiments. QTL mapping and pedigree analyses indicated that the 2DL QTL is the same as QFhb-2DL previously identified in Ji5265; therefore, it was designated Fhb9. Four kompetitive amplicon sequence polymorphism (KASP) markers were developed based on exome capture sequencing data to enhance marker density in the Fhb9 region, and it was delimited to an interval between single nucleotide polymorphism (SNP) markers KASP-12056 (533.8 Mb) and KASP-525 (525.9 Mb) explained 26.0–30.1% of the phenotypic variation. Analysis of the geographic distribution of the Fhb9 resistance allele suggests that it originated from the Huang-Huai winter wheat region in China. The very low frequency of Fhb9 in modern Chinese cultivars reveals that it has not been widely deployed in breeding programs. Field and greenhouse evaluations of yield-related traits in near-isogenic lines (NILs) contrasting in Fhb9 alleles reveal that the Fhb9 resistance allele have no adverse effects on these traits. Fhb9 showed an additive effect on enhancing FHB resistance with Fhb1. Therefore, Fhb9 is a valuable major QTL for improving FHB resistance in wheat, and the near-diagnostic markers developed in this study will facilitate its deployment in wheat breeding programs.