2-Phenylethyl Isothiocyanate Exerts Antifungal Activity against Alternaria alternata by Affecting Membrane Integrity and Mycotoxin Production.

Miao Zhang,Tingting Zhang,Qian Yang,Yongcai Li,Yang Bi,Yupeng Dong,Tiaolan Wang

doi:10.3390/toxins12020124

Abstract

Black spot caused by Alternaria alternata is one of the important diseases of pear fruit during storage. Isothiocyanates are known as being strong antifungal compounds in vitro against different fungi. The aim of this study was to assess the antifungal effects of the volatile compound 2-phenylethyl isothiocyanate (2-PEITC) against A. alternata in vitro and in pear fruit, and to explore the underlying inhibitory mechanisms. The in vitro results showed that 2-PEITC significantly inhibited spore germination and mycelial growth of A. alternata—the inhibitory effects showed a dose-dependent pattern and the minimum inhibitory concentration (MIC) was 1.22 mM. The development of black spot rot on the pear fruit inoculated with A. alternata was also significantly decreased by 2-PEITC fumigation. At 1.22 mM concentration, the lesion diameter was only 39% of that in the control fruit at 7 days after inoculation. Further results of the leakage of electrolyte, increase of intracellular OD260, and propidium iodide (PI) staining proved that 2-PEITC broke cell membrane permeability of A. alternata. Moreover, 2-PEITC treatment significantly decreased alternariol (AOH), alternariolmonomethyl ether (AME), altenuene (ALT), and tentoxin (TEN) contents of A. alternata. Taken together, these data suggest that the mechanisms underlying the antifungal effect of 2-PEITC against A. alternata might be via reduction in toxin content and breakdown of cell membrane integrity.

Highlights

Alternaria alternata is a filamentous fungus [1] that causes different diseases during the postharvest shelf-life of horticultural products including black rot of cherry tomato [2], moldy core and core rot of apple [3], Alternaria brown spot of citrus [4], black rot of Hylocereus undatus [5], and Alternaria rot of netted melon [6]
The spore germination rate of A. alternata was significantly inhibited after 2-phenylethyl isothiocyanate (2-phenethyl isothiocyanate (PEITC)) fumigation, and a positive correlation (R2 = 0.8979, p < 0.05) was observed between the concentration of 2-PEITC
Results presented in this study showed that 2-PEITC at minimum inhibitory concentration (MIC) efficiently decreased black spot disease severity in pear fruit

Summary

Introduction

Alternaria alternata is a filamentous fungus [1] that causes different diseases during the postharvest shelf-life of horticultural products including black rot of cherry tomato [2], moldy core and core rot of apple [3], Alternaria brown spot of citrus [4], black rot of Hylocereus undatus [5], and Alternaria rot of netted melon [6]. Most Alternaria species produce mycotoxins during growth that pose potential threat to animal and human health [9]. These mycotoxins belong to three classes including dibenzo-α-pyrone derivatives (alternariol, AOH; alternariol monomethyl ether, AME; and alteuene, ALT), tetramic acid derivatives (tenuazonic acid, TeA), and perylene derivatives Inhibiting mycotoxin synthesis or reducing mycotoxin levels are main fields of research interest in controlling postharvest black spot disease in fruit and vegetables. It is necessary to find safe and effective natural alternatives to chemical fungicides to control postharvest diseases of pear fruit

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