Fusarium head blight reaction of langdon durum - Triticum dicoccoides chromosome substitution lines

Fusarium head blight (FHB), caused by Fusarium graminearum Schwabe, is a serious disease problem on durum wheat (Triticum turgidum L. var. durum) in the USA. To date, the resistance to FHB available in hexaploid wheat (T. aestivum L.) sources has not been transferred successfully to tetraploid durum. In the 1980s, USDA geneticist L.R. Joppa produced a set of disomic lines [LDN(DIC)] derived from wild emmer (T. turgidum L. var. dicoccoides). Each line had a different pair of chromosomes from T. dicoccoides substituted for the corresponding 'Langdon' durum chromosomes. The purpose of this study was to determine if any of the LDN(DIC) lines showed useful levels of resistance to FHB. We tested these lines for FHB response by inoculation with F. graminearum in the greenhouse. Inoculation was accomplished via the single spikelet method, in which a droplet of conidiospore suspension is placed into one spikelet per spike followed by mist-high humidity for 3 d to establish infection. After 21 d, spikes were scored for extent of FHB symptoms and the average disease severity of the lines compared. A low disease severity score in this test indicated the presence of resistance to FHB in that line. Each test was replicated and the tests were done five times. In each test, some lines differed significantly. One line, LDN(DIC-3A), was consistently less susceptible and another line, LDN(DIC-2A), was consistently more susceptible than the parent Langdon durum, which itself showed an intermediate FHB reaction. Several other LDN(DIC) lines showed a trend either for increased or reduced susceptibility to FHB. Since each line differs by a single chromosome pair, the results suggest that genes affecting FHB resistance are present on several different T. dicoccoides or Langdon durum chromosomes.