Control of postharvest stem-end rot on mango by antifungal metabolites of Trichoderma pinnatum LS029-3

Abstract

Mango stem-end rot caused by Lasiodiplodia theobromae is a destructive postharvest disease that seriously endangers the mango production process after picking. In this study, the antifungal activities of 10 Trichoderma isolates isolated from mango rhizosphere soil were tested against L. theobromae through dual-culture. To understand the mechanism of antifungal activity, volatile and non-volatile metabolites produced by these 10 strains were also tested. Among ten Trichoderma isolates, the highest antifungal activity was shown by non-volatile metabolites of Trichoderma LS029-3, which was identified as Trichoderma pinnatum by morphological and molecular characteristics. The concentration for 50% of maximal effect (EC50) of the crude extracts extracted by ethyl acetate from the fermentation broth of isolate LS029-3 on L. theobromae was 0.25 ± 0.03 g L−1. Scanning electron microscopy (SEM) showed that crude extracts could destroy the mycelium structure of L. theobromae at the 4 × EC50 concentration. Ten chemical constituents from crude extracts were identified by gas chromatography-mass spectrometry (GC-MS) among which three compounds (Z)-13-docosenamide (ACROS), Hexanedioic acid, bis(2-ethylhexyl) ester (DOA) and (Z)-9-Octadecenamide (MSDS) were the major constituents and could suppress fungal growth significantly. LS029-3 crude extracts significantly reduced severity and lesion area of mango stem-end rot disease, and maintained the hardness and color of the fruit by increasing the activity of mango defense enzyme (polyphenol oxidase, peroxidase, total phenol) and reducing the decline rate of superoxide dismutases enzyme, glutathione enzyme and ascorbic acid content, thereby slowing down fruit rot. Post-harvest treatment of fruits with protective chemicals is a serious concern, that is directly related to human health. This study provides a practical solution to control postharvest of stem-end rot disease on mango through a safe and effective biocontrol strategy. This study firstly reported the biocontrol effect of T. pinnatum metabolites on postharvest mango stem-end rot and maintain the quality of mango fruit.