--Y. C. Ting and Stephen Schneider
In the last summer, 78 out of 182 plantlets derived from anther culture in vitro grew into adult plants. Those plants developed both female and male inflorescences, even though some of those inflorescences were very small.
Male inflorescences of all the above plants were collected and fixed in an alcohol and acetic acid fixative. Up to the present, meiotic observations were performed for 31 plants. It was found that among them, 15 plants were diploid (20); nine haploid (10); three triploid (30); and two aneuploid (one extra chromosome). The remaining two plants had only a very small amount of inflorescences and chromosome studies were not adequate.
Of the above progeny plants about 50 percent (15 plants) were identified
to be diploid with 20 chromosomes in spite of the expected 10 chromosomes.
It is significant. This high frequency of spontaneous chromosome doubling
in the microspore plants is different from several previous studies. These
doublings may be accomplished either by fusion of adjacent nuclei or by
endomitosis. The latter is a process by which a doubled number of chromosomes
was achieved by a successful nuclear division but without cytokinesis.
Even though this is a preliminary observation, it immediately suggests
that for future corn breeding mediated by anther culture in vitro, chromosome
doubling by colchicine could be eliminated. If this can be realized, it
would save not only lots of tedious labor but also a great deal of money.
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