A major locus for resistance to different Fusarium diseases was mapped to the most distal end of Th. elongatum 7EL and pyramided with Th. ponticum beneficial genes onto wheat 7DL. Perennial Triticeae species of the Thinopyrum genus are among the richest sources of valuable genes/QTL for wheat improvement. One notable and yet unexploited attribute is the exceptionally effective resistance to a major wheat disease worldwide, Fusarium head blight, associated with the long arm of Thinopyrum elongatum chromosome 7E (7EL). We targeted the transfer of the temporarily designated Fhb-7EL locus into bread wheat, pyramiding it with a Th. ponticum 7elL segment stably inserted into the 7DL arm of wheat line T4. Desirable genes/QTL mapped along the T4 7elL segment determine resistance to wheat rusts (Lr19, Sr25) and enhancement of yield-related traits. Mapping of the Fhb-7EL QTL, prerequisite for successful pyramiding, was established here on the basis of a bioassay with Fusarium graminearum of different 7EL-7elL bread wheat recombinant lines. These were obtained without resorting to any genetic pairing promotion, but relying on the close 7EL-7elL homoeology, resulting in 20% pairing frequency between the two arms. Fhb-7EL resided in the telomeric portion and resistant recombinants could be isolated with useful combinations of more proximally located 7elL genes/QTL. The transferred Fhb-7EL locus was shown to reduce disease severity and fungal biomass in grains of infected recombinants by over 95%. The same Fhb-7EL was, for the first time, proved to be effective also against F. culmorum and F. pseudograminearum, predominant agents of crown rot. Prebreeding lines possessing a suitable 7EL-7elL gene/QTL assembly showed very promising yield performance in preliminary field tests.

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-7el 2 ) previously mapped on the 7el 2 L arm of the wild Thinopyrum ponticum. A bread wheat 7DS.7el 2 L translocation line was employed as donor of Fhb-7el 2 in crosses with previously developed durum wheat 7AS.7AL-7el 1 L recombinant genotypes, carrying genes for rust diseases (Lr19 ? Sr25) as well as for quality-and yieldcontributing traits, deriving from a different Th. ponticum accession. In pentaploid F 1 s, the largely homologous 7el 1 L and 7el 2 L 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 7el 1 L ? 7el 2 L 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 7el 1 L ? 7el 2 L recombinant lines paves the way for their straightforward exploitation in breeding.

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