Chestnut Hill, Massachusetts
Boston College
More studies of day length effect on cloning gene in tetraploid maize
--Ting, YC and Tran, L
In order to find out how short-day illumination (12 hrs or less) affects
the expression of cloning gene in tetraploid maize (Zea mays L.),
several tests were conducted in the last few years. Descriptions of these
tests follow:--In July of 1999, a short-day treatment was applied to 11
adult plants heterozygous for the cloning gene (Clg clg clg clg),
by covering them with black plastic barrels from 6:00 PM to 10:00 AM the
next day. At that time, those plants were a little over three months old
and their male inflorescences just began to initiate. The treatment continued
for three months. One month after the treatment was discontinued, contrary
to expectation, none of the treated plants responded positively by regenerating
tassel plantlets. However, three of the control-plants having the same
genetic background manifested a weak expression of plantlet regeneration
by growing out three to five plantlets per tassel. It was intriguing! When
those control-plants showing regeneration were sib-crossed, many well developed
kernels were obtained. Therefore, it was deemed necessary to make another
test on the transmission of the cloning gene. Subsequently, in early November
of the year 2000, 12 selected kernels of one of the above parental plants
were sown in the greenhouse. In the first week of February of this year,
the same number of kernels of another parental plant were sown next to
the first planting. Last May, it was observed that six adult plants of
the first planting were healthy and well developed, and four of the second
planting did as well. About three weeks later, it was surprising to find
that only one of six of the first group and two of the second responded
respectively by regenerating vigorous tassel plantlets. Figure 1 depicts
one of the tassels bearing many plantlets. This plant was one of the pedigree
plants of the fifth generation of cloning gene transmission. In the middle
of last June, a further test on the behavior of the cloning gene was carried
out. Of each of the above positive respondents, 10 plantlets were detached
and planted in the summer experimental plot. The plantlets were at the
three- to four-leaf stage in development. In the first week of July, it
was found that one of the plantlets grew to about two feet tall and regenerated
plantlets. However, in contrast, all of the other plantlets continued to
develop into normal adult plants and, on average, they reached about six
feet in height two months later. They all failed to regenerate plantlets.
The above plantlet transmission experiment was conducted under long-day
(more than 12 hrs) condition, from the time of their initiation to the
stage of their seed maturation. Up to the present, it appears that a tentative
conclusion can be drawn on the inheritance of the cloning gene in the tetraploid,
starchy and semiperennial maize. It is dominant. The expression of its
phenotype was more likely to be affected by day length; short day was more
effective in the induction of plantlet regeneration than long day. Nevertheless,
under a short day regime, the stage of plant growth may play a certain
role in the sensitivity of the cloning gene to day length.
Figure
1.
Please Note: Notes submitted to the Maize Genetics Cooperation Newsletter may be cited only with consent of the authors.
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