Postharvest abscission in longkong (Lansium domesticum Corr.) is related to ethylene from fungal growth on the fruit

Abstract

Postharvest fruit abscission from the rachis (fruit drop) is a major problem in longkong. Recent reports showed that 1-MCP or NAA could reduce fruit drop, indicating ethylene involvement in the longkong fruit abscission process. Fungicides were found to give good fungal control and reduce fruit drop in longkong. This suggests that postharvest abscission in longkong is due to ethylene production induced by fungal growth on the fruit. An experiment was conducted by dipping longkong in fungicide solutions with different modes of action, i.e., carbendazim, prochloraz, mancozeb and difenoconazole at 1000 mg L-1 for 3 min, then stored at 25±1°C. It was found that fruit rot was reduced in proportion to the rate of ethylene production and the degree of fruit abscission. When ethylene production was determined in apple and wax gourd tissues, which had been dipped in 500 mg L-1 of all four fungicide solutions for 1 min, it was found that only prochloraz effectively reduced ethylene production in both tissues. The results suggested that the cause of longkong abscission is ethylene simultaneously produced by fungi grown on the fruit and by the fruit induced by the fungal growth. Hence, it is suggested that to prevent longkong fruit abscission pre- and postharvest fungal control is indispensable.