Discussion
Fan et al. (1992) reported that PMCs of the hybrids between
ph1b and Aegilops ovata, and between CS and Ae.
ovata had 12.88 and 0.94 chiasmata at metaphase I, respectively.
A similar result was reported with the hybrids of Ae. umbellulata
with CS and ph1b (Fan et al. 1993). These show that the
ph1b gene has a strong effect on inducing homoeologous pairing
in the hybrids of Ae. ovata, Ae. umbellulata with common wheat
(Fan et al. 1992, 1993). In the present study, only the F1
hybrid between ph1b and P. huashanica was
obtained. However, Chen et al. (1991) and Sun et al. (1992)
reported successful hybridizations of common wheat cultivars
7182-09-11-1 and J-11 with P. huashanica, respectively
(Table
2). The scarce
chromosome pairings in the hybrids confirmed the non-homology between
the genomes of T. aestivun (ABD) and P.
huashanica (N). Miller and Chapman (1976), and McGuire and
Dvorak (1982) reported 0.24 and 0.27 chiasmata per cell in CS haploid
plants, respectively. The low chiasma frequency of the hybrid between
ph1b and P. huashanica (0.43), which was lower
than those of the hybrids of common wheat cultivars with P.
huashanica (Table
2), indicated that
ph1b gene did not induce homoeologous chromosome pairing in
the hybrid.
Wang and Hsiao (1984) suggested that the existence of a diploidizing
genetic system in Leymus (JN genomes), which is similar to the
Ph gene system found in T. aestivum. Dovrak
(1981) demonstrated that some species of Thinopyron (J genome)
promoted heterogenetic pairing in hybrids involving T.
aestivum. Our data implied that the N genome of P.
huashanica had a Ph-like gene. If so, the high level of
auto-alloploidy of Leymus angustus (2n=84, containing several
N and J genomes), which forms bivalents, would be explained.
Acknowledgements
The authors thank Mrs. B.H. Wu for her technical assistance. This
work was supported by the Sciences and Technology Council of Sichuan
Province.
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