205wheat. The QTL on 3B and 6B were coincident with Fhb1 and Fhb2. The 4B QTL
collocated with a major QTL for plant height and the 7B QTL overlapped with a
QTL for fl owering time. A complete series of T. dicoccoides substitution lines were
produced in Langdon durum by L.R. Joppa of USDA, Fargo ND (Joppa and
Williams 1988 ). After point inoculation with FHB it was found that the substitution
line LDN (DIC-3A) was consistently less susceptible than Langdon and another
line LDN (DIC2A) was more susceptible (Stack et al. 2002 ). Several other substitu-
tion lines such as 2A and 6B also showed lower percentages of infected kernels
indicating that these chromosomes also carried QTL for FHB resistance. The QTL
on T. dicoccoides chromosome 3A was found to account for 37 % of the phenotypic
variability plus occupied a 29.3 cM region between the marker Xmwg14 to Xbcd828
(Otto et al. 2002 ). Using the Langdon substitution lines produced by Leonard it was
found that T. dicoccoides substitution lines LDN (DIC 3A) and LDN (DIC 3B) had
about the same level of FHB resistance as the parental cultivar Langdon. However
the substitution line for chromosome 3A completely suppressed the bleaching of
the heads caused by F. graminearum. It was concluded that chromosome 3A of
T. dicoccoides carries gene(s) for resistance to head bleaching following Fusarium
infection. In none of the studies did any accessions approach the level of Sumai3 for
FHB resistance. However the FHB resistance in durum cultivars is so low, that some
of the variability observed in the screening mentioned above, might be useful in
providing limited incremental improvements in FHB resistance. Despite the paucity
Fig. 8.4 FHB resistance QTL from T. carthlicum mapping population. The 6B QTL is from T.
carthlicum and 2BL from Strongfi eld, the other parent in the mapping population
8 Alien Introgressions from wild Tr it icu m species, T. monococcum...