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

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.

On the Applicability of Chitosan Oligomers-Amino Acid Conjugate Complexes as Eco-Friendly Fungicides against Grapevine Trunk Pathogens

“…For the same strains of N. parvum and D. seriata, EC 90 values of 1270 and 1120.7 µg•mL −1 were attained for COS with molecular weight < 2000 Da in [33]. In this case, differences may be tentatively ascribed to slight differences in the molecular weight, polymerization degree or deacetylation degree of COS, which are known to influence its efficacy against phytopathogenic fungi [50,51].…”

“…Regarding analogous polysaccharide-peptide based formulations, little information is available in the literature. The EC 90 values attained with a COS−ε-polylysine conjugate (507.5, 580.2 and 497.4 µg•mL −1 for N. parvum, D. seriata and B. dothidea, respectively [33]) were better than those attained in this work for the COS−Tyr conjugate (1021.4, 672.1 and 707.7 µg•mL −1 , respectively), but-from an economic perspective-the latter formulation would be much more viable (given that the price of ε-polylysine is much higher than that of tyrosine: 245 €/100 mg vs. 58 €/100 g). An additional advantage of the COS-Tyr formulation could be its versatility as a crop protection product: EC 50 and EC 90 values against Fusarium culmorum (320 and 1107 µg•mL −1 , respectively) were of the same order of magnitude as those reported herein [37].…”

“…Chitosan oligomers (COS) were prepared according to the procedure previously reported in [33]. Cysteine (Cys), glycine (Gly), proline (Pro) and tyrosine (Tyr) solutions were obtained by dissolution of the amino acids (with 99% purity) in sterile double distilled water at an initial concentration of 3000 µg•mL −1 .…”

“…[31]; chitosan oligomers/propolis/silver nanoparticles composites have been tested against D. seriata [32]; and ε-polylysine:chitosan oligomers conjugates showed antifungal activity against Neofusicoccum parvum (Pennycook & Samuels) Crous, Slippers & A.J.L. Phillips, Diplodia seriata, and B. dothidea [33].…”

Antifungal Activity of Chitosan Oligomers–Amino Acid Conjugate Complexes against Fusarium culmorum in Spelt (Triticum spelta L.)

“…Chitosan oligomers (COS) were prepared following the procedure described by Buzón-Durán et al [27]. The amino acid-only bioactive solutions were prepared by dissolving the amino acids in distilled water, without further purification, at an initial concentration of 3000 µg•mL −1 .…”