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Results
The D genome in the special Chinese hexaploid landraces
Table 2
shows the meiotic
configurations at MI in the PMCs of the hybrids involving Aegilops
tauschii. The chromosome pairing at MI of the PMCs of the
F1 hybrids of Ae. tauschii with the TW, SW
(including CS, Chengdu-guang-tou, Pen-an White, Xinjin White Wheat
and Langzhong White Wheat) were all normal (Table
2 and
Fig.1a and
b): Seven
bivalents, most of which were ring, and no multivalent was observed
in these hybrids. These results suggested that TW and SW had a quite
primitive D genome which were structurally unchanged in comparison
with the D genome of Ae. tauschii. In comparison with the
F1 hybrids of the SW with Ae. tauschii, the number
of rod bivalents were reduced 50% in the F1 hybrid of TW x
Ae. tauschii. Therefore, the D genome in the TW might be
closer to the genome of the Ae. tauschii than the D genome of
the Sichuan Wheat complex was.
In the F1 hybrid of SP X
Ae. tauschii,
0.04 trivalents and 0.01 quadrivalents were observed. Cells which
had both trivalent and quadrivalents were also observed
(Fig.1c and
d). These results
might indicate pairing between the D genome chromosomes and the A or
B genome chromosomes and, therefore, confirm the translocation
between these chromosomes in SP reported by Riley et al (1967). Our
results suggested that one to three D genome chromosomes might be
involved in these translocation.
Chromosome pairing in the hybrids involving the special Chinese
hexaploid wheat landraces
The four special Chinese hexaploid wheat landraces were crossed
with each other and with SP. Meiotic configurations
at
MI
of the
PMCs
varied among these
F1 hybrids (Table
3,
Fig.1e-h).
Pairing in the CS x Chengdu-guang tou was nearly normal. No
multivalents were observed in this hybrid and the numbers of
univalents and rod bivalents were very close to those observed in CS.
It seems that there is no constructive difference between these two
landraces. Since these two landraces are morphologically alike, CS is
certainly a strain of the Chengdu-guang-tou landrace. In this study,
the CS x Chengdu-guang-tou hybrid was used as a check.
In comparison with their meiotic configurations at MI of the PMCs to
those of the check, the remaining nine hybrids can be grouped into
three types. Type
1
consists the hybrids
of CS with YH and TW. In these hybrids, the numbers of univalents and
rod bivalents were a little bit higher than those in the check and
only few multivalents were observed (Table
3). These results
indicated that the genomes of TW and YH are very similar to that of
CS though small differentiation has occurred.
Type 2 contains the hybrids of SP with CS, TW and YH. Two univalents
were usually observed at MI of the PMCs of the hybrids in this group.
The number of multivalents in the hybrids of this group were higher
than the check (Table
3). This means
that SP differs from CS, TW and YH by two chromosomes.
Type 3 includes the hybrids of XR with CS, TW, YH and SP. At the MI
of PMCs of the hybrids in this group, 3-4 univalents were usually
observed, and the number of multivalents were
also higher than the
check. This result indicated that XR differs from CS, TW, YH and SP
by 3-4 chromosomes. Univalents were
observed
to be formed
usually by satellite chromosomes in the hybrid of XR with CS, TW and
YH (Fig.
1e-g). This kind
of univalents were found in 53.3%, 45.2% and 55.1% of the PMCs
observed in the hybrids involving CS, TW and YH, respectively.
Morphologically, these satellite chromosomes seem to be chromosome
6B.
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