Pre-breeding to establish Fhb7 in winter wheat using marker-assisted, modified backcrossing

Fusarium head blight (FHB) is a destructive disease of wheat (Triticum aestivum L.) that causes major grain yield and quality losses. Improving host resistance remains an important strategy for managing FHB; however, resistance is quantitatively inherited and is often strengthened by combining multiple complementary resistance loci. The recently released wheat-Thinopyrum elongatum translocation line WGC002 carries Fhb7 in a Chinese Spring-derived spring wheat background, but this resistance source has not been established in the hard winter wheat (HWW) germplasm. The objective of this study was to introgress Fhb7 into diverse HWW backgrounds using marker-assisted modified backcrossing while simultaneously selecting for additional FHB resistance loci. WGC002 was crossed with HWW germplasm, and three modified backcrosses were made using seven genetically diverse HWW genotypes. The recurrent and backcross parents contributed additional resistance sources, including Fhb1, Qfhb.rwg-5A.1, Qfhb.rwg-5A.2, and native background resistance from ND Noreen. A total of 322 BC₃F₂ plants were evaluated for resistance-marker alleles, Type II FHB disease severity, and plant phenotype, from which 32 BC₃F₂ families were selected for further evaluation. Twenty-two segregating BC₃F₂:₃ families were re-tested for marker genotype and agrotype, resulting in the selection of 94 BC₃F₂:₄ families carrying different resistance-locus combinations involving two or more of Fhb1, Fhb7, Qfhb.rwg-5A.1, and Qfhb.rwg-5A.2. The remaining 10 selected families were homozygous for one or more resistance-locus combinations, including Fhb7 alone, Fhb7 plus Qfhb.rwg-5A.1, Fhb7 plus Qfhb.rwg-5A.2, and Qfhb.rwg-5A.1 plus Qfhb.rwg-5A.2, and showed strong Type II resistance. Overall, this study developed diverse HWW pre-breeding materials carrying Fhb7 alone or in combination with additional FHB resistance loci. These selections provide promising pre-breeding candidates for future HWW breeding efforts, aiming to enhance FHB resistance by pyramiding complementary resistance sources.