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

Penta Pristijono,John Golding,Len Tesoriero,Ron Wills

doi:10.3390/horticulturae4030020

Penta Pristijono, John Golding + Show 2 more

Open Access

https://doi.org/10.3390/horticulturae4030020

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Abstract

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 μL 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 μL 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.

Highlights

Ethylene is a gaseous plant hormone that is well known to initiate postharvest ripening of climacteric fruit, and enhance the senescence of non-climacteric fruit and vegetables [1]
Interest in the role of ethylene arose from the commercial postharvest degreening process of citrus fruit where physiologically mature but green skinned fruit are exposed to relatively high temperatures (25 to 30 ◦ C) in the presence of an ethylene concentration of about 5 μL L−1 to accelerate the loss of chlorophyll in the peel and ‘degreen’
Grierson and Newhall [6] found enhanced incidence of stem-end rot due to Diplodia natalensis, and Brown [7] found reduced green mould due to Penicillium digitatum; while Plaza et al [8] found no effect on mould incidence for P. digitatum, and Porat et al [9] showed decreased blue mould due to P. italicum

Summary

Introduction

Ethylene is a gaseous plant hormone that is well known to initiate postharvest ripening of climacteric fruit, and enhance the senescence of non-climacteric fruit and vegetables [1]. Published data on the effect of ethylene on fungal decay development have mostly been in vivo studies, where native or inoculated produce were exposed to atmospheric ethylene at a wide range of concentrations. Interest in the role of ethylene arose from the commercial postharvest degreening process of citrus fruit where physiologically mature but green skinned fruit are exposed to relatively high temperatures (25 to 30 ◦ C) in the presence of an ethylene concentration of about 5 μL L−1 to accelerate the loss of chlorophyll in the peel and ‘degreen’. The findings on the effect of such ethylene concentrations on postharvest decay of citrus fruit are inconsistent. The effect of ethylene on the development of decay in other fruits include Zhu et al [10] who reported that fumigation of 200 μL L−1 ethylene had no effect on grey mould incidence in grapes inoculated with Botrytis cinerea, Palou et al [11] who found that

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