Cytogenetic and genomic characterization of a novel tall wheatgrass-derived Fhb7 allele integrated into wheat B...

We identified and integrated the novel FHB-resistant Fhb7^The2 allele into wheat B genome and made it usable in both common and durum wheat breeding programs without yellow flour linkage drag. A novel tall wheatgrass-derived (Thinopyrum elongatum, genome EE) Fhb7 allele, designated Fhb7^The2, was identified and integrated into the wheat B genome through a small 7B-7E translocation (7BS·7BL-7EL) involving the terminal regions of the long arms. Fhb7^The2 conditions significant Type II resistance to Fusarium head blight (FHB) in wheat. Integration of Fhb7^The2 into the wheat B genome makes this wild species-derived FHB resistance gene usable for breeding in both common and durum wheat. By contrast, other Fhb7 introgression lines involving wheat chromosome 7D can be utilized only in common wheat breeding programs, not in durum wheat. Additionally, we found that Fhb7^The2 does not have the linkage drag of the yellow flour pigment gene that is tightly linked to the decaploid Th. ponticum-derived Fhb7 allele Fhb7^Thp. This will further improve the utility of Fhb7^The2 in wheat breeding. DNA sequence analysis identified 12 single nucleotide polymorphisms (SNPs) in Fhb7^The2, Fhb7^Thp, and another Th. elongatum-derived Fhb7 allele Fhb7^The1, which led to seven amino acid conversions in Fhb7^The2, Fhb7^Thp, and Fhb7^The1, respectively. However, no significant variation was observed in their predicted protein configuration as a glutathione transferase. Diagnostic DNA markers were developed specifically for Fhb7^The2. The 7EL segment containing Fhb7^The2 in the translocation chromosome 7BS·7BL-7EL exhibited a monogenic inheritance pattern in the wheat genetic background. This will enhance the efficacy of marker-assisted selection for Fhb7^The2 introgression, pyramiding, and deployment in wheat germplasm and varieties.