Effects of chronic irradiation upon a self-incompatible clone ofLycopersicum peruvianum.

Flovering plants from a self-incompatible clone ofLycopersicum peruvianum were exposed during 90 days to different dose-rates of gamma-rays ranging from 2 to 17 rad perhour. Irradiation was continuous, except for a daily interruption of 7 hours.Whereas irradiation at dose-rates higher than 7.50 rad per hour seriously inhibited bud formation and floral development, chronic exposure at dose-rates ranging from 3 to 7 rad/hour increased the number of seeds per plant. This stimulation is not due to a higher number of seeds per fruit but to a very significant rise in the number of fruits per plant. As irradiation treatment did not significantly increase the number of flowers per plant and did not appear to stimulate pollen tube germination in the styles, it is concluded that the recorded increase in fruit-setting essentially resulted from a radio-induced inhibition of the processes which control floral abscission in the absence of cross-pollination.Three plants with reduced self-incompatibility and one completely parthenocarpic individual were observed in theM 2 progeny but no evidence was obtained that irradiation could induce a permanent type of self-compatibility inL. peruvianum.