Vergara - 1976 - Physiological and morphological adaptability of ri

86 CLIMATE AND RICE
not really sure how‘ we could really improve wide adaptability this way, although the
example I mentioned is being used by many farmers.
Okn: As to the first point, I have no particular objection to your definition. As to the
second point. everybody‘ agrees with your idea that genetic heterogeneity may be a factor
in adaptability. There are many different kinds of evidence in different organisms,
but my question is what kind of particular evidence have you in rice‘?
Iergara: There is none except for the example that I showed. We have no evidence on
this. nor on pie-sowing hardening. nor on the therapeutic method. I am pointing out
the possibility of increasing adaptability by this method. But no work is being done
that I know,
FRANKELI As far as I know, Mr. Chairman, there is no convincing evidence in any
crop. including rice. I think all recent work on mixed populations in high-yielding eonditions
has shown that multi-lines. from the point of view of yield increase. have
neither helped to stabilize yields nor to increase them.
VENKATESAVARLIJ: Between the two traits. "shattering oli grains" and "donnancyz"
which do you consider more important for rice areas under monsoonic conditions?
lbrjgara: In areas where rice is harvested panicle by panicle, as in parts of Indonesia
and Philippines. grain shattering is very" important. In areas where irrigation water is
available. farmers may want the seeds of the recently harvested crop for use in the succeeding
crop. and short dormancy’ is important. In areas where rainfall is still relatively
high during the ripening stage. strong dormancy is definitely needed to prevent the
grains from germinating on the panicle.
VENKATESWARLLII I think we should be more concerned with situatiomoriented
varietal improvement than with wider adaptability due to multiple-stress situations
that confront us.
Vernsco: By attempting to breed high adaptability into the rice plant. at the same
time having high yield. are we not hoping to cat our cake and to keep it too‘?
Verjgara: Actual field planting of IR8 or Taichung Native I in tropical areas all
over the world have shown that high adaptability and high grain yields are possible.
Even at low nitrogen levels. the high~yelding varieties like 1R8 have shown higher
grain yields than the traditional varieties.
Nnnuzv: Should research be directed toward developing a super-adaptable variety
or several ‘rarieties which are more geographically specific‘?
Vergara: A super-adaptable variety would be a big mistake and certainly dangerous
Since there are many adverse environmental condilinn, developing a variety adapted
to all these conditions would entail an enormous amount of time. effort. and money.
CHANDLERI What causes the yellow color (apparent loss of chlorophyll) in rice plants
subjected to above-freezing temperatures?
Iergara; We do not know why the leaves become yellow, and I am not aware of any
publication on rice regarding the explanation of this phenomenon. We have several
Japanese experts in this symposium. perhaps they would care to comment.
TIDRIYAA-tfiti If we have enough knowledge for specific adaptability to climatic factors.
I suppose wide adaptability may be broken down into several specific adaptabilities.
Therefore. it is very difticult to imagine a term of wide adaptability‘. The relation
between wide and specific adaptability’ should be clarified.