Postharvest Control of Botrytis cinerea and Monilinia fructigena in Apples by Gamma Irradiation Combined with Fumigation.

To extend the shelf life of apples in South Korea, we evaluated the effect of gamma irradiation alone or gamma irradiation combined with fumigation on the control of postharvest decay caused by Botrytis cinerea and Monilinia fructigena. An irradiation dose of 1.0 kGy caused the maximal inhibition of B. cinerea and M. fructigena spore germination. The gamma irradiation dose required to reduce the spore germination by 90% was 0.76 and 0.78 kGy for B. cinerea and M. fructigena, respectively. Inhibition of conidial germination of both fungal pathogens occurred at a greater level at the doses of 0.2 to 1.0 kGy compared with the nontreated control; 0.2 kGy caused 90.5 and 73.9% inhibition of B. cinerea and M. fructigena, respectively. Treatment in vitro with the ecofriendly fumigant ethanedinitrile had a greater effect compared with the nontreated control. The in vitro antifungal effects of the gamma irradiation and fumigation treatments allowed us to further study the effects of the combined treatments. Interestingly, when irradiation was combined with fumigation, the percentage of disease inhibition increased more at lower (<0.4 kGy) than at higher doses of irradiation, suggesting that the combined treatments reduced the necessary irradiation dose in phytosanitary irradiation processing under storage conditions.