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Discussion
Embryoid induction from anther culture of the DT lines for
chromosomes 4B and 4D was not significantly differed from CS euploid.
Only DT 4DL showed a comparatively high response in the first
replicate, suggesting a suppressing effect of the short arm of
chromosome 4D. Shimada et al. (1991) found that a removal of either
4DS or 4DL of CS largely promoted embryoid induction. In the present
study, embryogenesis of CS euploid was similar (about 6-7%) but no
lines with remarkably increased response were detected. Thus, factor
on chromosome 4D influencing embryogenesis in anther culture should
be further examined.
In experiment 2, there were no semidwarf lines that decrease embryoid
induction. Moreover, the Rht1 + rht2 lines were
superior to the tall controls in embryoid induction in both the TD
and Itana set. This would be supported by the high response of
Haruyutaka, used as a check because this cultivar has a semidwarf
stature controlled by the Rht1
gene (Miura, unpublished data). These results may lead to
conclusion that there are no problems in Improving cultivars carrying
the Rht1 and Rht2
genes by means of anther culture in breeding programs.
In addition to genotype of the anther donor plants, the physiological
stage or the growing conditions of donor plants is a major
determinant of anther culture response (Duyang et al. 1987; Bjornstad
et al. 1989). Three experiments in the present study were designed to
have two or three replicates with different conditions. The first
replicate in the CS DT lines and the TD experiments, in which plants
were raised at the experiment field showed striking superior response
to other replicates in a glasshouse or growth cabinet. These results
confirm importance of environments in which donor plants grow.
Moreover, anther culture response consist of three different and
independently inherited traits: embryoid induction, regeneration
capacity and albino frequency (Henry and De Buyser 1985; Ekiz and
Konzak 1994a). Hence examinations for regeneration of green plant and
albino frequency are indispensable for much more practical study to
determine the influence of the Rht1 and Rht2
genes on the production of DH.
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