Identification and validation of a major QTL, QFhb-6AL, for Fusarium head blight resistance on chromosome 6AL in wheat.

A novel major QTL, QFhb-6AL, accounting for 34.6% phenotypic variation for FHB resistance, was identified in the Chinese cultivar Xunong 029, and a near-diagnostic marker was developed for marker-assisted selection. Fusarium head blight (FHB) is a destructive disease in wheat (Triticum aestivum L.) that seriously threatens global wheat production and food safety. Host resistance is the most effective strategy for reducing FHB damage. The Chinese wheat cultivar Xunong 029 possesses desirable agronomic traits and demonstrates stable FHB resistance in multiple environments. A population of 190 F6 recombinant inbred lines (RILs) was developed by crossing Xunong 029 with Xumai 35 to identify quantitative trait loci (QTLs) for FHB resistance. The RIL population was genotyped by a low-coverage whole-genome sequencing (lcWGS) technology and evaluated for FHB symptom spread within a spike (Type II resistance) in both greenhouses and field experiments. A stable major QTL, designated as QFhb-6AL, was mapped to a 3.0 cM interval between markers lcWGS613.5 and lcWGS616.5 on the long arm of chromosome 6A, and it explained up to 34.6% of the phenotypic variation for FHB Type II resistance. QFhb-6AL was validated using near-isogenic lines (NILs) and another RIL population derived from the cross Xunong 029 and Xumai 33. Four kompetitive amplicon sequence PCR (KASP) markers which tightly linked to QFhb-6AL were developed. Haplotype analysis of the target QTL region showed a low frequency distribution of QFhb-6AL in Chinese cultivars, indicating that the QTL has not been widely deployed in wheat breeding programs. The QFhb-6AL has great potential for improving wheat FHB resistance, and the tightly linked markers developed in this study will facilitate its deployment in wheat breeding programs.