A novel assembly of Thinopyrum ponticum genes into the durum wheat genome: pyramiding Fusarium head blight resistance onto recombinant lines previously engineered for other beneficial traits from the same alien species

Abstract

Favoured by climate changes, Fusarium head blight (FHB) has recently become a threat also in unusual environments, including those where durum wheat is largely cultivated. Since current durum wheat cultivars are mostly susceptible to FHB, new germplasm is needed, capable of maintaining yield capacity and grain quality under the disease pressure. To achieve this goal, a sustainable approach relies on transfer of resistance from related Triticeae species by means of chromosome engineering. We resorted to this cytogenetic strategy, efficiently complemented with advanced selection systems, to transfer into durum a QTL for FHB resistance (here, temporarily designated Fhb-7el2) previously mapped on the 7el2L arm of the wild Thinopyrum ponticum. A bread wheat 7DS.7el2L translocation line was employed as donor of Fhb-7el2 in crosses with previously developed durum wheat 7AS.7AL–7el1L recombinant genotypes, carrying genes for rust diseases (Lr19 + Sr25) as well as for quality- and yield-contributing traits, deriving from a different Th. ponticum accession. In pentaploid F1s, the largely homologous 7el1L and 7el2L arms showed considerable reduction in pairing and recombination frequency as compared to what observed in a parallel experiment we carried out in a hexaploid context. Nevertheless, pyramiding into durum of target genes/QTL from the two Th. ponticum accessions was successfully achieved. The selected 7el1L + 7el2L tetraploid lines exhibited 70–85 % reduction in FHB severity following Fusarium inoculation, and a parallel decrease in fungal biomass in kernels of infected spikes. Similar effects were detected in bread wheat lines carrying the same target gene assembly on 7DL instead of 7AL. Preliminary evidence of good agronomic performance of the novel 7el1L + 7el2L recombinant lines paves the way for their straightforward exploitation in breeding.