SENSITIVITY TO GAMMA IRRADIATION OF FUNGI PATHOGENIC TO PEARS

The effect of gamma irradiation at doses of 50-300 krad, on the germination ability of fungi in vitro, and prolongation of the incubation period in vivo, was studied with known spore populations of four fungi pathogenic to stored pears. Rot development and fungal control were examined in cold storage after irradiation of fruit inoculated with two radio-sensitive fungi. Inhibition of spore germination was found to be directly correlated to the strength of the radiation dose and indirectly correlated to the spore concentration. Penicillium expansum was the most sensitive to radiation both in culture and in fruit tissues. Some prolongation of the incubation period of P. expansum and of Botrytis cinerea, the two principal pathogens, occured after irradiation with 100 krad. With increasing dosage, the incubation period was more prolonged and staggered and the percentage of infected fruit began to decrease from 200 krad. Alternaria tenuis and Stemphylium botryosum were radiation-resistant. In spite of a decrease in germination ability at the higher doses, the pathogenicity and incubation period of both these fungi were not significantly affected. © 1969.