The effects of exposure dose and dose rate of gamma radiation on in vitro shoot-forming capacity of cotyledon explants in red pepper. (Capsicum annuum L. cv. Yatsufusa).

Abstract

The effect of exposure dose and dose rate of gamma radiation on shoot-forming capacity of cotyledon explants of red pepper were investigated. The twelve-day-old seedlings were irradiated by gamma radiation with varying exposure doses of O, 0.5, 0.75, 1.0, 1.25, 1.5, 1.75, 2.0 and 2.5 krad delivered at the dose rates of l, 5 and 10 krad/ hr. After irradiation, cotyledons were excised from the seedlings and cultured on MURASHIGE and SKOOG medium supplemented with benzyladenine at the concentration of 3 mg/l to induce shoot formation. It was found that the percentage of shoot-forming explants and the number of shoots per explant were decreased as the exposure dose increased. Moreover, the increase in exposure dose delayed callus and shoot bud formation and inhibited the development of shoot buds into vigorous shoots. At the same exposure dose, the higher dose rate (10 krad/hr) was more detrimental for shoot formation than the lower ones (1 and 5 krad/hr). The exposure dose which caused 50 percent reduction in the number of shoots per explant (RD50) was around 1.0 krad at the dose rates of 1 and 5 krad/hr whereas RD50 was 0.75 krad at the rate of 10 krad/hr.