--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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