197FHB resistance was also sought in Ae. speltoides. In this case, 50 accessions
were screened and line S184 selected (Fedak et al. 2004 , 2006 ). It has been previ-
ously shown that different accessions of Ae. speltoides can lead to different levels of
meiotic chromosome pairing in F1 hybrids with wheat. The hybrid between wheat
and the resistant selection in our studies showed 3–4 bivalents at meiosis, i.e., an
accession that induced fairly high meiotic chromosome pairing. Despite this, three
backcrosses were required to restore fertility in the progeny. The agronomic charac-
teristics of line S184 are shown in Table 8.2. For most agronomic traits such as
yield, plot yield, plant height, protein content, and even fl our yield, the values for
S184 compare favorably to the check cultivars. This may be attributed to the fact
that large populations were screened at each backcross generation and the most
vigorous plants were selected. Probably the most important attribute of this line is
the lower DON content following inoculation.
8.1.2.6 Karnal Bunt Resistance
Karnal bunt resistance genes have been identifi ed in T. monococcum , transferred to
hexaploid wheat and subsequently tagged with molecular markers (Vasu et al.
2000 ).
8.1.3 Other Traits
8.1.3.1 Virus Resistance
A large number of diploid and tetraploid wild wheat accessions, currently being
maintained at the University of California Riverside, and Kansas State University
were screened for resistance to a number of insects and fungal diseases. Nine of 233
accessions of T. boeoticum screened showed resistance to Hessian fl y and nine of
237 accessions were resistant to wheat streak mosaic virus.
8.1.3.2 Cold Hardiness
A cluster of 11 CBF genes have been mapped to the frost hardiness locus ( Fr.A m^2 )
on chromosome 5A (Miller et al. 2006 ) of T. monococcum. CBF genes (C-repeat
binding factor) are transcription factors that activate cold-regulated genes, whose
proteins confer cold resistance to plants. Fr A m^2 is a complex locus that contains
genes for whole plant frost survival plus controls transcript levels of cold induced
genes (Knox et al. 2008 ). Orthologous loci have been identifi ed in barley and wheat.
The locus in T. monococcum is being used to dissect the components of frost hardi-
ness in plants.
8 Alien Introgressions from wild Tr it icu m species, T. monococcum...