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In the two. subsequent generations, the amphiploid displayed high
cytological instability. The chromosome number varied from 46 - 66
and averaged 52 in 24 plants derived from the 70-chromosome
amphiploid. It is evident that the high ploidy amphiploid always
presented continuous decrease of chromosomes after its
polyploidization. Spetsov et al. (1993) stated that a 70 chromosome
amphiploid between a winter wheat and Ae. variabilis exhibits
a high level of aneuploidy. But the present amphiploid produced
aneuploid at a high level, which may have resulted from the effective
gene ph1b of its wheat parent.
Though interspecific and intraspecific C-banding pattern
polymorphisms is present in genus of Aegilops (Teoh 1983), it
does not prevent the identifications of their chromosomes in wheat
background, after the establishment of standard karyotypes of
corresponding genome (Friebe et al. 1996). In the present study, the
C-banding of Sv genome of Ae. variabilis accession
13E is the most similar to that of the B genome in wheat. But these
strong telomeric bands in Sv chromosomes allows for their
identification. Moreover, the band patterns together with their
length and arm ratio make Uv genome chromosomes easily
distinguishable from those of wheat chromosomes. Giemsa C-banding
patterns of the Ae. variabilis chromosomes in the amphiploid
and its selfed progenies were similar to those of its diploid state.
In C-banded chromosomes. of a F3 plant of amphiploid
(2n=48), eight Ae. variabilis chromosomes were observed
(Fig. 4). It can be concluded that the
chromosomes from wheat or Aegilops parents may have
opportunity to be lost when the amphiploid is selfed, which further
confirms the cytological instability of the amphiploid. Moreover, the
cytological instability together with the effectiveness of ph
gene may be beneficial for creating the desirable gene recombination
between wheat and Aegilops chromatin.
Seed storage protein analysis: APAGE of seed gliadin revealed that
the strong bands of Ae. variabilis 13E existed in w, r and b
zone (Fig. 5B). Ae. variabilis
contained quite strong and some aggregated bands in w zone. These are
totally expressed in amphiploid. The additive electrophoresis
patterns of gliadin permit the genetic identification of amphiploid
and chromosome markers for directed genetic manipulation. By using
the different band patterns as biochemical markers including seed
gliadin, Williams and Mujeeb-Kazi (1996) and Spetsov et al. (1998)
identified a wheat-Ae. variabilis amphiploid and Wheat-Ae.
kotschyi substitution lines, respectively.
The composition of glutenin was analyzed by SDS-PAGE (Fig.
5A). The high molecular weight glutenin subunits (HMW-GS) of
J-11ph1b contained null subunit of Glu-Al, and
subunits 7 + 8 of Glu-B1, as well as subunits 2+12 of
Glu-D1. Ae. variabilis also exhibited two strong
slower-migrating bands. The slowest band with electrophoretic
mobility as the subunit 2.2 of Glu-D1 can also be observed in
the amphiploid selfed plant. Other faster-migrating group of two
closely located bands of Ae. variabilis were between subunit 8
and subunit 12 of wheat. However, those two bands were modified in
amphiploid selfed plant. The faster-moving one was absent, and a new
band moving slightly slower than subunit 8 emerged. Furthermore, the
amphiploid selfed plant lost the glutenin subunits of both
Glu-B1 and Glu-D1 from wheat parent, indicating the
corresponding chromosomes or segments were lost. This also
demonstrated that the wheat chromosomes were lost or modified in the
selfed amphiploid background. In addition, the other bands in HMW and
LMW regions of the amphiploid are mostly from its Aegilops
parent.
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