Effect of Continuous Exposure to Low Levels of Ethylene on Mycelial Growth of Postharvest Fruit Fungal Pathogens

Ethylene enhances the ripening and senescence of fruit with increased susceptibility to fungal decay a common feature of such changes. Most studies on the effect of ethylene have been in vivo where it is not possible to determine whether any effect due to ethylene arises from changes in metabolism of produce or from a direct effect on the pathogen. The few in vitro studies, that have been carried out, have been with very high ethylene levels, and did not identify the source of pathogens tested. This study examined the effect of air and ethylene, at 0.1 and 1 mu L L-1, on the growth of fungi isolated from five climacteric fruits (persimmon, pear, tomato, mango and papaya), and three non-climacteric fruits (orange, grape and blueberry). All fungi isolated from climacteric fruits had reduced mycelial growth when held in 0.1 and 1 mu L L-1 ethylene but those from non-climacteric fruits showed no effect of ethylene. The finding was unexpected and suggests that fungi that colonise climacteric fruits are advantaged by delaying growth when fruits start to ripen. Since non-climacteric fruits do not exhibit any marked increase in ethylene, colonising pathogens would not need such an adaptive response.