A Coating Based on Bioactive Compounds from Streptomyces spp. and Chitosan Oligomers to Control Botrytis cinerea Preserves the Quality and Improves the Shelf Life of Table Grapes

Abstract

Botrytis cinerea is the most harmful postharvest disease of table grapes. Among the strategies that can be envisaged for its control, the use of coatings based on natural products is particularly promising. The study presented herein focuses on the assessment of the antagonistic capacity of two Streptomyces species and their culture filtrates against B. cinerea. Firstly, the secondary metabolites were characterized by gas chromatography–mass spectrometry, with N1-(4-hydroxybutyl)-N3-methylguanidine acetate and 2R,3S-9-[1,3,4-trihydroxy-2-butoxymethyl]guanine acetate as the main compounds produced by S. lavendofoliae DSM 40217; and cyclo(leucyloprolyl) and cyclo(phenylalanylprolyl) as the most abundant chemical species for S. rochei DSM 41729. Subsequently, the capacity of S. lavendofoliae DSM 40217 and S. rochei DSM 41729 to inhibit the growth of the pathogen was tested in dual culture plate assays, finding 85–90% inhibition. In agar dilution tests, their culture filtrates resulted in effective concentration values (EC90) in the 246–3013 μg·mL−1 range. Upon the formation of conjugate complexes with chitosan oligomers (COS) to improve solubility and bioavailability, a synergistic behavior was observed, resulting in lower EC90 values, ranging from 201 to 953 μg·mL−1. Ex situ tests carried out on ‘Timpson’ and ‘Red Globe’ table grapes using the conjugate complexes as coatings were found to maintain the turgor of the grapes and delay the appearance of the pathogen by 10−15 days at concentrations in the 750−1000 µg·mL−1 range. Hence, the conjugate complexes of COS and the selected Streptomyces spp. culture filtrates may be put forward as promising protection treatments for the sustainable control of gray mold.

Whole Genome Analysis of Streptomyces spp. Strains Isolated from the Rhizosphere of Vitis vinifera L. Reveals Their Role in Nitrogen and Phosphorus Metabolism

“…It promotes plant growth by participating in phosphorus and nitrogen metabolism [8]. Furthermore, it contributes to plant health by producing antimicrobial compounds [9,10] and other bioactive compounds involved in biological control [11][12][13]. Microbial nitrogen and phosphorus metabolism are crucial processes in the dynamics of biogeochemical cycles.…”

Carvacrol Treatment Reduces Decay and Maintains the Postharvest Quality of Red Grape Fruits (Vitis vinifera L.) Inoculated with Alternaria alternata

“…Consequently, grapes hold significant economic worth within the worldwide fruit industry [12]. However, grapes are berries, which are susceptible to mechanical damage and pathogen infection while being picked, stored, and transported [13]. Among them, pathogens such as Alternaria can quickly invade through the wounds or skin of fruits [14].…”