Identification of antagonistic microorganisms associated with strawberry phyllosphere and their evaluation in the biological control of Botrytis cinerea

Gray mold, caused by Botrytis cinerea is one of the most important diseases in strawberry, causing pre– and postharvest fruit rot. One of the safe and healthy ways to reduce this disease is biocontrol and the use of biological control agents. In this study, using culture–based methods, 268 bacterial strains, and 136 fungal isolates, were isolated and purified from the phyllosphere of strawberry plants in the greenhouse and field in Jiroft city. The antagonistic effect of the isolates against the pathogen B. cinerea was investigated using dual culture and investigation of the inhibition zone, and the effect of volatile compounds under in vitro conditions, as well as the antifungal properties of the antagonistic bacteria on strawberry fruit. Identification of the selected bacterial and fungal strains was made by polymerase chain reaction, respectively, by determining the nucleotide sequence of a part of the 16S–rDNA gene and its region. The results showed that among the examined isolates, bacterial isolates UJB1, UJB3, UJB4, UJB10, UJB5, UJB6, UJB7, UJB11, UJB2, UJB8 and UJB9 and fungal isolates UJF1300, UJF1301, UJF1302, UJF1303, UJF1304, UJF1305 had an effective inhibitory effect against B. cinerea and their volatile compounds reduced pathogenic mycelium growth. In evaluating the antifungal impact of bacterial isolates on strawberry fruit, bacterial isolates UJB8, UJB2, UJB11, UJB6, UJB5, UJB10, UJB4, and UJB1 significantly increased the disease index caused by B. cinerea compared to They reduced the witness. According to morphological and molecular data, bacterial isolates belonging to the genera Delftia (isolates UJB1, UJB3, UJB4, UJB10), Bacillus (isolates UJB5, UJB6, UJB7, UJB11, and UJB2) and Stenotrophomonas (isolates UJB8 and UJB9) and fungal isolates belonging to Albifimbria verrucaria, Aspergillus terreus, Leptosphaerulina australis, Pilidium lythri, Pseudozyma flocculosa, and Seimatosporium pistaciae species.