Gamma-ray induced meiotic chromosome stickiness in tomato.

In gamma-ray treated populations of tomato, one of the plants showed stickiness of chromosomes at meiosis. At diakinesis, some of the bivalents tended to fall apart as univalents, and at about the same time or a little later, the bivalents and/or univalents congregated into groups. At metaphase I, the number of such groups varied from 1 to 14 and the groups were of various sizes; the masses of chromatin in which the individuality of chromosomes seemed to be completely lost were spherical, oval or irregular in outline and freely dispersed in the cytoplasm. Some of the masses were so small that they might possibly represent fragments of chromosomes. As the stage passed to anaphase I, the masses dissolved into individual chromosomes, even though stickiness was still persistent but less intense. Laggards in varying numbers were also found. At completion of meiosis, in some proportion of telophase II cells, persistent laggards were found. Pollen fertility and seed set were low. The selfed M2 progeny of the sticky plant contained a few yellow seedlings which died at the cotyledon stage. Cytological examination of meiosis of some of the individuals of this progeny revealed stickiness again in a majority of plants. Sticky as well as normal plants in M2 were selfed and the M3 generation raised. In progenies of both kinds, yellow lethals were found in proportions that gave a good fit with three green to one yellow seedlings in many cases. The occurrence of a sticky plant in M1 and many such plants in M2 was assumed to be due to a dominant mutation induced by gamma irradiation. This, besides causing sticky meiosis, also produced recessive yellow lethal mutations.