Submitted to: Euphytica
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/10/2000
Publication Date: 2/15/2001
Citation: Jauhar, P.P., Peterson, T.S. 2001. Hybrids between durum wheat and thinopyrum junceiforme: prospects for breeding for scab resistance. Euphytica 118:127-136. Interpretive Summary: Fusarium head blight (FHB) or scab is a serious fungal disease of wheat. The fungus infects wheat heads from flowering through grain fill, causing huge losses in grain yield and quality. There is no reliable source of scab resistance in the current wheat cultivars. We found a wheatgrass (a distant relative of wheat) to be a very good source of scab resistance. To transfer this resistance to durum wheat, we crossed two commercial cultivars (Langdon and Lloyd) with the wheatgrass and produced sterile hybrids. After backcrossing these hybrids to the parental cultivar Lloyd and subsequent selfing, we produced several fertile hybrid derivatives with all the chromosomes (rod-like structures that contain genes for different traits) of durum wheat and one or a few chromosomes of the wild grass parent. Some of these hybrid derivatives showed high resistance to scab; the best hybrid line had only 10.93% infection. Using a specialized technique, fluorescent in situ hybridization (FISH), we confirmed the introduction of wild grass chromatin into the durum genome. This work shows that wide hybridization offers a promising means of introducing scab resistance into durum wheat.
Technical Abstract: Tetraploid wheatgrass, Thinopyrum junceiforme (2n = 4x = 28; J1J1J2J2), a wild relative of wheat, is an excellent source of resistance to Fusarium head blight. Intergeneric F1 hybrids (2n = 4x = 28; ABJ1J2) between durum wheat (Triticum turgidum; 2n = 4x = 28; AABB) cultivars Lloyd or Langdon and Th. junceiforme were synthesized. Most of the pairing in F1 hybrids was between the J1- and J2-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 F1 hybrids were largely male-sterile and were backcrossed, as the female parent, to the respective durum cultivar. Backcrosses from Lloyd Th. junceiforme hybrids yielded fertile partial amphiploids (2n = 6x = 42; AABBJ1J2) 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 integration of alien chromatin into the durum complement was confirmed by FISH. Hybrid derivative lines had lower mean infection scores, the best showing 10.93% infection (p = 0.01), 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.