201One dominant major gene from this accession ( Yr15 ) was subsequently transferred
to durum and hexaploid wheat (Gerechter-Amitai et al. 1989 ). Some of the acces-
sions of wild emmer carried genes that were temperature sensitive in their reaction
to the fungus; for example the resistance in 10 of 26 lines was temperature sensi-
tive (Gerechter-Amitai and Van Silfhout 1984 ).
The gene bank at the Punjab Agricultural University, Ludhiana, India maintains
about 1000 accessions of wild Triticum species (Dhaliwal et al. 1993 ). After
screening, resistance to stripe rust, leaf rust and karnal bunt was found in accessions
of durum, T. urartu , T. boeoticum , T. dicoccoides , and T. araraticum. They provide
a summary of the genes that were transferred to cultivated wheat from T. dicoccoi-
des. Yr15 and at least 8 other Yr genes were transferred. More than 60 genes for
stripe rust resistance have been identifi ed in wheat and its wild relatives.
Unfortunately most of the genes have now been defeated by new races of the patho-
gen. In the last 10 years, more than 140 QTL have been identifi ed for Yr resistance;
many of these could be identical genes. 850 samples of wild emmer populations
collected in Israel were evaluated for resistance to stripe rust. About 10 % of the
collection was resistant to Israeli isolates of the pathogen (van Silfhout et al. 1989a , b ).
Fifty eight accessions of T. dicoccoides from 32 collection sites in Israel were
screened with 21 races of the stripe rust fungus. Two accessions G7 and G25 were
found to be resistant to all 21 races (Gerechter-Amitai and Stubbs 1970 ). A single
dominant gene for resistance was identifi ed in accession G25 and transferred to
durum wheat (Gerechter-Amitai and Grama 1974 ). A total of 541 accessions of
T. dicoccoides from 32 locations in Israel were screened with one accession of each
of stripe rust, stem rust, and leaf rust (The et al. 1993 ). Stripe rust resistance showed
a wide range of variability indicative of a number of genes for resistance. Only
moderate levels of stem rust resistance were observed. This level of resistance was
not considered adequate to transfer to commercial cultivars. Yr15 was assigned by
aneuploid analysis to chromosome 1BS and found to be linked to Yr10 (McIntosh
et al. 1996 ). Flanking markers were defi ned for Yr15 (Sun et al. 1997 ).
It has been shown that a relatively small number of microsatellites can be used to
estimate genetic diversity in wild accessions of T. dicoccoides (Fahima et al. 1998 ).
In this case 20 stripe rust resistant accessions were screened with 23 microsatellites
to obtain estimates of variability within the sample. In total, 230 alleles were
detected located on 14 different chromosomes and 23 chromosome arms. A further
refi nement of the screening is the application of GWAM (Genome-wide association
mapping). In this way three putative new Yr gene regions were identifi ed (Sela et al.
2014 ) after screening 128 accessions of T. dicoccoides. Genome-Wide Association
mapping (GWAM) using the wheat 9K Infi nium chip was used on 128 accessions of
T. dicoccoides to fi nd association with stripe rust resistance loci (Sela et al. 2014 ).
The model produced signifi cant association with putative resistance loci on chro-
mosome 1BS, 1BL, and 3AL. The 1BS locus was located in a region known to
contain stripe rust resistance genes. In one mapping effort, the gene YrH52 derived
from T. dicoccoides was mapped to chromosome 1B (Peng et al. 1999 ).
8 Alien Introgressions from wild Tr it icu m species, T. monococcum...