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Materials and methods
The species used for morphological analysis and intergeneric
hybridizations in the present study were collected in 1987. The
experimental materials are listed in Table
1.
Roegneria tsukushiensis (Honda) Lu B. R., Yen et J. L. Yang
was used as male parent. The spikes of Kengyilia gobicola Yen
et J. L. Yang and K. zhaosuensis J. L. Yang, Yen et
Baum were emasculated and covered with cellulose bag. The
hand-emasculated spikes were pollinated two days later by brushing
maternal stigmas with newly broken anthers of the paternal species.
Caryopses showing enlargement at 14 days were excised for embryo
culture. Seedlings at the three leaves stage were transplanted into
sand culture pots, watered with complete nutrient solution, and kept
in low temperature room over summer.
Morphological characters were compared between the the parents and
their F1 hybrids.
For cytological observation, the young spikes were fixed in Carnoy's
I solution (alcohol:acetic acid = 3:1), and stored in a refrigerator.
Chromosome pairings were observed at the MI of the pollen mother
cells (PMCs) using the aceto-carmine smear method. Photographs were
taken by Olympus AD-10 camera system.
Voucher specimen of the parents and the F1 hybrids have
been kept in the nursery and the herbarium of Triticeae Research
Institute, Sichuan Agricultural University.
Results
Production and morphology of F1 hybrids: K.
gobicola and K. zhaosuensis were used as female parents
in crossing with R. tsukushiensis. The results are shown in
Table
2. One well
growing seedling was obtained by means of embryo culture for
K. gobicola x R. tsukushiensis and K.
zhaosuensis X
R. tsukushiensis,
respectively.
Eighteen morphological characters of the parents and the hybrids were
observed and measured as shown in Table
3. Number of
spikelets per spike and florets per spikelet in R. tsukushiensis
are more than those in K. gobicola and K.
zhaosuensis. Lengths of spike, spikelet, awn on lower and
upper glumes, lemma and awn on lemma, and palea of R.
tsukushiensis were longer than those of K. gobicola and
K. zhaosuensis. The lower and upper glumes of R.
tsukushiensis are as long as those of K. gobicola, while
shorter than those of K. zhaosuensis. The lemmas and rachis of
K. gobicola were pubescent, while those of R.
tsukushiensis were glabrous. The lemmas of K. zhaosuensis
was pubescent. The F1 hybrids of K. gobicola
x R. tsukushiensis and K. zhaosuensis x
R. tsukushiensis were intermediate between their parents in
morphology. Since K. gobicola and K. zhaosuensis
are distributed in and area of Xinjiang, they could not endure
the summer of subtropic climate of Dujiangyan city, Sichuan, while
R. tsukushiensis and its hybrids crossed with K.
gobicola and K. zhaosuensis could adapt to this
condition.
Cytology: The data of chromosome pairings at metaphase I of PMCs in
the two cross combinations are shown in Table
4. The chromosome
configurations are shown in Figures
1 to 10.
Both of the hybrids of K. gobicola x R. tsukushiensis,
and K. zhaosuensis x R. tsukushiensis had 42
chromosomes. They had similiar meiotic pairing patterns. A large
number of univalents were found in the two cross combinations, i. e.,
on average, 18.69 univalents per cell for K. gobicola x R.
tsukushiensis, and 18.56 univalents per cell for K.
zhaosuensis x
R. tsukushiensis.
The average number of bivalents were 11.56 with the range of 7 to
14 for K. gobicola x R. tsukushiensis, and 11.73
with the range of 8 to 14 for K. zhaosuensis x R.
tsukushiensis. A low frequencies of trivalents were also observed
in both combinations with the average of 0.04 per cell. The chiasmata
frequencies in K. gobicola x R. tsukushiensis
and K. zhaosuensis x
R. tsukushiensis
were 17.44 and 17.41, respectively. The lagging chromosomes at
anaphase I and II, and tetrads with micronuclei were observed in both
combinations. Chromosome bridges at anaphase I and II were found in
the hybrid of K. zhaosuensis x
R.
tukushiensis.
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