Hybrids between durum wheat and Thinopyrum junceiforme:: Prospects for breeding for scab resistance

Tetraploid wheatgrass, Thinopyrum junceiforme (2n = 4x = 28; J(1)J(1)J(2)J(2)), a wild relative of wheat, is an excellent source of resistance to Fusarium head blight. Intergeneric F-1 hybrids (2n = 4x = 28; ABJ(1)J(2)) between durum wheat (Triticum turgidum; 2n = 4x = 28; AABB) cultivars Lloyd or Langdon and Th. junceiforme were synthesized. Most of the pairing in F-1 hybrids was between the J(1)- and J(2)-genome chromosomes. Some pairing occurred between wheat chromosomes and alien chromosomes, resulting in segmental exchange that was confirmed by fluorescent in situ hybridization (FISH). The F-1 hybrids were largely male-sterile and were backcrossed, as the female parent, to the respective durum cultivar. Backcrosses from Lloyd x Th. junceiforme hybrids yielded fertile partial amphiploids (2n = 6x = 42; AABBJ(1)J(2)) as a result of functioning of unreduced female gametes of the hybrid. Lloyd proved to be a more useful durum parent than Langdon in crosses with Th. junceiforme designed to transfer scab resistance genes. Pairing in the amphiploids was characterized by preferential pairing, which resulted in bivalent formation. However, some intergeneric pairing also occurred. Several fertile hybrid derivatives were produced by further backcrossing and selfing. The introduction of alien chromatin into the durum complement was confirmed by FISH. Hybrid derivative lines had significantly lower mean infection scores (p = 0.01), the best showing 10.93% infection, whereas the parental durum cultivars had 70.34% to 89.46% infection. Hybridization with wild relatives may offer an excellent means of introducing scab resistance into durum wheat.