Clayberg, C. D.
In order to obtain new translocation stocks in tomato, mature pollen from a single plant clone of the variety Valiant (Harris Seed Co.) was irradiated with 4,000 r at Yale University in summer 1958 and applied to emasculated flowers of this clone. The pollen was collected, irradiated, and used in the same day. An X\1 generation of 199 plants was grown in the field during the summer of 1959. Preliminary estimates of pollen abortion in this family gave an interplant range of from 5 to 80% abortion with 80% of the plants having no greater than 20% aborted pollen. There were 23 plants in the range of 40-80% abortion. Meiotic studies of diakinesis in 20 of these latter plants revealed only four reciprocal translocations, the remaining 17 plants having 12 bivalents. Except for one plant with a translocation involving the nucleolar chromosome, no pachytene studies were made. Consequently no deficiencies were seen, nor were the chromosomes involved in the other three translocations identified. It is possible that translocation heterozygotes having less than 40% pollen abortion in the field might have occurred and thus been missed in this study. This is not considered to be particularly likely on the basis of comparative pollen abortion rates observed here (Mt. Carmel, Conn.) in translocation heterozygotes induced by Barton (1954). Barton, who also used a dosage of 4,000 r in his studies, obtained eight reciprocal translocations in a random sample of 48 plants for an induction rate of 17% as compared with that of 2% in the present material --an almost ten-fold difference.