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Wheat Information Service
Number 83: 28-30 (1996)
II. Research Information
Screening of spontaneous major translocations
in Israeli populations of Triticum dicoccoides
Korn.
T. Kawahara1 and E. Nevo2
1Plant Germ-plasm Institute, Faculty of Agriculture,
Kyoto University, Mozume, Muko 617, Japan
2Institute of Evolution, University of Haifa, Mt. Carmel,
Haifa 31905, Israel
Triticum dicoccoides Korn. is a wild tetraploid species with
AABB genome. It is the ancestral species of cultivated Emmer wheats
and the progenitor of all hexaploid common wheats. Several studies
have shown that spontaneous translocations are common in this
species. Kawahara (1987) reported 8 translocations among 46
dicoccoides strains from Iran, Iraq, Turkey, Syria and Israel,
which have been preserved at the Plant Germ-plasm Institute, Faculty
of Agriculture, Kyoto University. Thus, overall frequency of
translocations is 0.174 in these samples. Recently, Joppa et
al. (1995) studied translocations in 17 populations, 16 from
Israel and one from Turkey, and reported a high overall frequency of
0.70. In the present paper, our results on the screening of major
translocations in Israeli populations are reported to obtain
different estimation of translocation frequency in natural
populations.
Total of 127 genotypes representing 10 populations (10 to 16
each) and two genotypes from Mt. Gilboa were examined for presence or
absence of translocations. Each genotype was established from the
original seed sample by controlled selfing for two or three
generations. They were then crossed with tetraploid testers with the
standard chromosome structure or hexaploid Chinese Spring that also
has the standard AABB genome structure together with the DD genome
(Kawahara 1988). Chromosome pairing at meiosis in F1
hybrids were observed by ordinary squash method stained by
aceto-orcein. In most of the hybrids, 33 cells or more were examined
but 19 to 21 cells were available in four hybrids.
Of129 hybrids examined, 70 formed no quadrivalent. 34 hybrids formed
quadrivalents at a low frequency, 0.03 to 0.09 per cell, one had a
frequency of 0.16 and 23 showed high frequencies from 0.64 to 1.03
(Table1) Since we found a gap in the
frequency of quadrivalents, we determined that a genotype is
homozygous for a 'major' translocation when a hybrid with testers
forms a quadrivalent at a frequency higher than 0.50. Thus, each of
23 genotypes was regarded to have one spontaneous translocation
relative to the standard. The remaining one hybrid formed a
quadrivalent and a sexivalent (IV+VI) or a quadrivalent and a
quinquevalent (IV+V) per cell. Multivalent frequencies of this hybrid
were 0.11 III + 0.84 IV + 0.21V + 0.79VI. This was regarded to be
heterozygous for three translocations. In conclusion, one genotype
had three translocations in homozygous condition, 23 had one
translocation and the remaining 105 had standard chromosome
arranements.
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