Antifungal activity of volatile organic compounds from Streptomyces sp. strain S97 against Botrytis cinerea

The antifungal activity of volatile organic compounds (VOCs) from 10 Streptomyces isolates was tested using the double-dish chamber method. The VOCs-producing strain S97 exhibited the highest inhibitory effect against Botrytis cinerea mycelium growth. This isolate was identified as Streptomyces sp. with high similarity with Streptomyces lydicus based on morphological and physiological properties, as well as 16S rRNA gene sequence analysis. S97 VOCs analysis was performed by SPME-GC-MS revealing the presence of 14 compounds including three major terpenoids: 3-carene 2,5-dione, geosmin, beta-cubebene and one phenolic compound Phenol, 2-(1,1-dimethylethyl)-6-methyl- representing 43%, 20%, 11% and 9.34% of total produced VOCs, respectively. S97 VOCs inhibited mycelial growth of Rhizoctonia solani and Phoma medicaginis by 95%, Fusarium solani by 69% and Fusarium oxysporum and Sclerotium rolfsii by 20%. The in vivo test carried out on ripe strawberries inoculated by Botrytis cinerea conidia showed that S97 VOCs inhibited the development of grey mould symptoms on fruits by more than 87% compared to untreated control strawberries. Further, light microscope observations revealed 60% swelling and 21% crumbling of B. cinerea conidia when treated with S97 VOCs. Fungal mycelium also showed deep structural alterations with S97 VOCs after 48 h incubation. Strain S97 exhibited strong fumigation potential to control phytopathogenic fungi.