203wheat and mapped to a gene-rich region on chromosome 5BL (Xue et al. 2012 ). An
incompletely dominant powdery mildew resistance gene that gave resistance at the
seedling and adult plant stages was detected in T. dicoccoides (Liu et al. 2012 ).
It was mapped to the distal region of chromosome 2BS. According to Dhaliwal
et al. ( 1993 ) the powdery mildew resistance genes Pm4a , Pm5 and Pm16 from
T. dicoccum were transferred to cultivated wheat. As were Pm 46 from T. carthli-
cum , Pm10 & Pm11 from T. spelta , Pm15 from T. compactum , and Pm36 from
T. sphaerococum. The emmer wheats are a good source of resistance to powdery
mildew. For example, 233 T. dicoccoides accessions were collected at ten sites in
Israel and inoculated with four cultures of the fungus (Moseman et al. 1984 ).
It was determined that 49 % of the accessions were resistant. The conclusion was
that the number of resistance sources in T. dicoccoides was unlimited. It has been
stated (Huang and Röder 2004 ) that up to that time, 32 loci with 48 genes/alleles
for mildew resistance have been identifi ed and located on various chromosomes.
Eleven of those resistance genes are shown in Table 8.5.
8.2.2.5 Fusarium Head Blight Resistance
Although wild emmer wheats , T. dicoccoides are good sources of resistance to such
diseases as stem rust, there is limited variability for resistance to Fusarium head
blight in this species. For example, 151 T. dicoccoides genotypes originating from
16 habitats in Israel and one habitat in Turkey were screened by point inoculation
in greenhouse conditions. Most of the accessions proved to be highly susceptible
and only a few were moderately resistant (Buerstmayr et al. 2003 ). Similar results
were obtained by several other labs when screening T. dicoccoides accessions for
FHB resistance. Wan et al. ( 1997 ) screened 21 T. dicoccoides accessions and found
that fi ve were moderately resistant while the remainder were susceptible to highly
susceptible. Among 97 tetraploids screened by Gilbert and Tekauz ( 2000 ), six were
rated as moderately resistant. A total of 282 T. dicoccoides accessions were screened
by Miller et al. ( 2006 ) and most were found to be highly susceptible, with only a
few lines rating as moderately resistant.
In another study, 416 accessions of T. dicoccoides were screened over multiple
seasons and environments (Oliver et al. 2005 , 2007 ). Two accessions PI 481521
and PI 478742 had consistently low FHB scores across four seasons. Substitution
lines were developed with chromosomes from these lines in a Langdon background.
QTL for resistance in the latter were located on chromosomes 7A and 7B (Stack
et al. 2002 ) while in the former, resistance QTL were located on chromosome 1A,
3A, 5B, and 7A (Stack et al. 2003 ). In continued screening of tetraploid wheat for
FHB resistance (Oliver et al. 2008 ) a total of 376 accessions of fi ve subspecies of
T. turgidum including subsp. carthlicum , subsp. dicoccum , subsp. polonicum ,
subsp. turanicum , and subsp. turgidum were evaluated. Point inoculation was
applied for three seasons and grain inoculation at two locations. Sixteen T. turgidum
subsp. c arthlicum and four subsp. dicoccum accessions consistently gave resistant
or moderately resistant reactions. It was shown that the main FHB resistance QTL
8 Alien Introgressions from wild Tr it icu m species, T. monococcum...