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Wheat Information
Service
Number 72: 83 (1991)
Further
analysis of Cs chlorosis observed in hybrids between the Emmer
and the Timopheevi group of tetraplold wheats
Taihachi Kawahara
Plant Germ-plasm Institute, Faculty of Agriculture, Kyoto
University, Mozume, Muko, Kyoto 617, Japan
Necrosis and chlorosis are hybrid weakness most commonly observed in
intra- and inter- specific hybrids of wheat. In hybrids between the
two groups of tetraploid wheats, the Emmer and the Timopheevi,
chlorosis is reported by Tsunewaki and Hamada (1968) and by Tsunewaki
and Nakai (1973). It is caused by two complementary genes; Cs1
caried by wheats of the Emmer group and Cs2 by the Timopheevi
group. Later, Kawahara (1985) found three types of chlorosis, weak,
medium and strong chlorosis, in several hybrids between wheats of the
Timopheevi group and a Cs1 tester. The present report deals
with genes responsible to these three types of chlorosis. In order to
study the gene(s) carried by the Timopheevi group, hybrids within
Timopheevi group was pollinated by a Cs1 tester strain, KU-123
of Triticum dicoccum. In total, 14 hybrid combinations were
observed. Segregation of normal and chlorotic plants and of plants
showing different types of chlorosis fitted well to 1 : 1 ratio.
Kawahara (1985) already found that Cs1 interact with gene(s)
carried by the Timopheevi group irrespective to the degree of
chlorosis. The present results indicate that the gene carried by the
Timopheevi group consist of four alleles instead of the two, Cs2
and cs2, reported earlier. Therefore, they were designated
as Cs2w, Cs2m, Cs2s and cs2. Further, it
was confirmed that Cs2 of the earlier reports correspond to
Cs2w in the present study. Distribution of Cs genes was
examined by crossing the Emmer wheats with a Cs2w tester and
the Timopheevi wheats with a Cs1 tester. In wild Emmer,
T. dicoccoides, 56 strains were examined but no
Cs1 was found. In cultivated Emmer wheats, Cs1 allele was
found in 3 strains and cs1 in 24 strains. Over-all frequency
of Cs1 in the Emmer group was very low (3.6%) as was reported
by Tsunewaki and Nakai (1973). In T. araraticum, wild
Timopheevi wheat, 155 strains were examined. Of these, 87 strains
(56.1%) had cs2, 29 (18.7%) had Cs2w, 32 (20.6%) had
Cs2m and Cs2s was found in 7 strains (4.5%). Two
alleles was found in cultivated T. timopheevi,. 7
strains had Cs2w and 2 had Cs2m. In contrast to the
Emmer group, about half (47.0%) of the strains of the Timopheevi
group had either Cs2w, Cs2m or Cs2s.
References
Kawahara T (1985) New types of Cs chlorosis found in
hybrids between the Emmer and the Timopheevi group of the tetraploid
wheats. Wheat Inf Serv 60: 38-39.
Tsunewaki K and Hamada J (1968) A new type of hybrid chlorosis found
in tetraploid wheats. Jpn J Genet 43: 279-288.
Tsunewaki K and Nakai Y (1973) Considerations on the origin and
speciation of four groups of wheat from the distribution of necrosis
and chlorosis genes. Proc 4th Int Wheat Genet Symp: 123-129.
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