Study of endophytes as biocontrol agents vis-a-vis their compatibility to fungicides in grapes

The present study was conducted at ICAR-National Research Centre for Grapes in Pune, Maharashtra, India during 2021-2022 to study endophytic bacteria as biocontrol agents vis-a-vis their compatibility to fungicides in grapes. Eighteen endophytic bacteria were isolated from nine varieties of grapevine (Vitis vinifera L.) viz. Manjari Naveen (MN), Nanasaheb Purple (NP), Thompson Seedless (TS), Crimson Seedless (CS), Manik Chaman (MC), Maruti Seedless (MS), Fantasy Seedless (FS) and 2A Clone (2A). The distinct colonies were selected, sub-cultured, purified and subjected to analysis of macroscopic and microscopic features followed by screening of bacterial isolates for plant growth-promoting (PGP) traits, extracellular hydrolytic enzyme production, and abiotic stress tolerance assay. Eighteen diverse endophytic bacteria were found to be Gram positive to Gram negative and with white, whitish yellow and whitish red colonies. Different biochemical tests which were needful for the identification of the bacteria were performed. Antibiotic sensitivity and antifungal assays were conducted with five antibiotics and pathogenic fungi Colletotrichum gloeosporioides respectively. Results of dual culture plate assay for antimicrobial activity revealed that 10 isolates showed significant growth inhibition of the test pathogen and were selected for the compatibility studies. The results highlighted that most of the isolates were highly compatible with all the fungicides used for powdery mildew, downy mildew, anthracnose and bacterial leaf spot. The work indicated the importance of the endophytic bacteria which can be used as promising biocontrol agents for grapevine disease management.