Materials and
methods
The ph1b mutants of a common wheat cultivar Chinese Spring
(abbreviated to CS ph1b) was kindly provided by the
Cytogenetic Laboratory of Sichuan Agricultural University. Professor
Z.L. Ren proved the authenticity of the mutant ph by
cytogenetic method (personal communciation). The euploid Chinese
Spring (CS) was kept at the Triticeae Research Institute, Sichuan
Agricultural University,
Psathyrostachys huashanica Keng (2n=14, genomes NN) is an
endemic species of Huashan mountain, Shaanxi Province, China. All
materials were grown in the field at the Triticeae Research
Institute.
The euploid Chinese Spring and ph1b mutant were used as female
parents. Their spikes were emasculated, covered with cellulose bags,
and few days later, artificially pollinated with P.
huashanica. Well-developed 14 to 16 day-old embryos were excised,
and cultured on N6 basic medium. When the hybrid seedings
had three leaves, they were transplanted into sand-pot and kept in an
airconditioned room to survive the hot summer.
Young spikes of the hybrid were fixed in Carnoy's solution (95%
ethanol:glacial acetic acid=3 : 1) for 24hr, transferred to 70%
ethanol, and stored at 4C in a refrigerator. The 1% aceto-orcein
smear method was used for the cytological study.
The F1 hybrid was backcrossed with the Ph1b
mutant.
Results
1. Production of intergeneric hybrid: The result of the crosses is
shown in Table
1. The cross CS
ph1b x P. huashanica produced 5 embryos out of 286
pollinated florets. One well-developed seedling was obtained by means
of embryo culture. No hybrid embryo was obtained from the cross
between CS and P. huashanica. The previous studies (Chen et
al. 1991; Sun et al. 1992) and the present result showed that the
crossibility of P. huashanica with different common wheat
cultivars varies 0 to 2.81% (Table
1).
2. Cytology: The chromosome pairing at metaphase 1 of the pollen
mother cells (PMCs) of the hybrid CS ph1b x P. huashanica
is shown in Table
2. The hybrid (2n=28)
had 22 to 28 univalents, 27.14 on an average. Of 58 PMCs examined, 38
PMCs had 28 univalents (Fig.
1-1). Twenty PMCs
contained 1 to 3 rod bivalents (Fig.
1-2). No ring bivalents
and multivalents were observed. The average number of bivalents was
0.43 per cell. The chiasma frequency was 0.43 per cell. There were
lagging chromosomes at anaphase I and II and micronuclei were found
at the tetrad stage.
3. Fertility of F1 hybrid: The
hybrid had yellowish white anthers, which did not dehisce. Staining
of the pollen grains with Iodine-KI solution showed that the hybrid
plant was completely male sterile. The F1 hybrid plant was
back crossed with CS ph1b, and three well-developed embryos
were obtained from 210 pollinated florets.
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