Antifungal Agents Based on Chitosan Oligomers, ε-polylysine and Streptomyces spp. Secondary Metabolites against Three Botryosphaeriaceae Species.

Laura Buzón-Durán,José Casanova-Gascón,Pablo Martín-Ramos,Eduardo Pérez-Lebeña,David Ruano-Rosa,M Carmen Ramos-Sánchez,José L Revuelta,Jesús Martín-Gil

doi:10.3390/antibiotics8030099

Abstract

Grapevine trunk diseases (GTDs) are a major threat to the wine and grape industry. The aim of the study was to investigate the antifungal activity against Neofusicoccum parvum, Diplodia seriata, and Botryosphaeria dothidea of ε-polylysine, chitosan oligomers, their conjugates, Streptomyces rochei and S. lavendofoliae culture filtrates, and their binary mixtures with chitosan oligomers. In vitro mycelial growth inhibition tests suggest that the efficacy of these treatments, in particular those based on ε-polylysine and ε-polylysine:chitosan oligomers 1:1 w/w conjugate, against the three Botryosphaeriaceae species would be comparable to or higher than that of conventional synthetic fungicides. In the case of ε-polylysine, EC90 values as low as 227, 26.9, and 22.5 µg·mL−1 were obtained for N. parvum, D. seriata, and B. dothidea, respectively. Although the efficacy of the conjugate was slightly lower, with EC90 values of 507.5, 580.2, and 497.4 µg·mL−1, respectively, it may represent a more cost-effective option to the utilization of pure ε-polylysine. The proposed treatments may offer a viable and sustainable alternative for controlling GTDs.

Highlights

Grapevine trunk diseases (GTDs) have been reported in most grapevine producing regions worldwide, causing a serious decline and loss of productivity
The vibrational spectra of conjugates prepared with six different EPL:chitosan oligomers (EPL):COS mass ratios were examined in order to confirm their secondary structure and to determine the most suitable proportion (Figure 1)
It may be observed that the EC50 values for the treatments presented (Table 1), in particular those of EPL and EPL:COS conjugate, were comparable to or better than those of popular synthetic organic compounds used to control GTDs, and only slightly lower than the excellent activities reported for AgNPs

Summary

Introduction

Grapevine trunk diseases (GTDs) have been reported in most grapevine producing regions worldwide, causing a serious decline and loss of productivity. These diseases include black dead arm, caused by Botryosphaeria dothidea; esca, which includes vascular symptoms and internal white rot in the trunk; eutypiosis, caused by Eutypa lata; Petri disease; black foot; and Phomopsis dieback, being the esca complex the most frequent and increasing syndrome in almost all European countries [1]. Concerns have been raised about both their environmental impact and the potential associated health risks In this context, the use of natural antifungals as a feasible alternative is receiving increasing attention

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