Cytogenetic and molecular characterization of a durum alien disomic addition line with enhanced tolerance to Fusarium head blight.

Current durum wheat (Triticum turgidum L. subsp. durum (Desf.)) cultivars have little or no resistance to Fusarium head blight (FHB), a ravaging disease of cereal crops. A diploid wheatgrass, Lophopyrum elongatum (Host) A. Löve (2n = 2x = 14, EE genome), is an excellent source of FHB resistance. Through an extensive intergeneric hybridization using durum cultivar Langdon, we have developed a disomic alien addition line, named DGE-1 (2n = 28 + 2), with a wheatgrass chromosome pair. We used a unique method for isolating the addition line taking advantage of unreduced gametes functioning in Langdon x L. elongatum F1 hybrids in their first backcross to the Langdon parent, resulting in 35-chromosome plants from which we derived DGE-1. The addition line DGE-1 has a plant type similar to its Langdon parent, although it is shorter in height with narrower leaves and shorter spikes. It is meiotically and reproductively stable, generally forming 15 bivalents with two chiasmata each. The alien chromosome pair from the grass confers FHB resistance to the addition line, which has less than 21% infection on the visual scale, mean = 6.5%. Using various biochemical and molecular techniques (Giemsa C-banding, fluorescent genomic in situ hybridization (fl-GISH), chromosome-specific simple sequence repeat (SSR) markers, targeted region amplified polymorphism (TRAP) markers, and sodium dodecyl sulfate - polyacrylamide gel electrophoresis (SDS-PAGE)), we have shown that the extra chromosome involved is 1E of L. elongatum. This is the first time that FHB resistance has been discovered on chromosome 1E. We have established a chromosome-specific marker for 1E that may be used to screen fertile hybrid derivatives and durum addition lines for this chromosome that confers FHB resistance.