Bio-Prospecting Plant Growth Promoting and Antimicrobial Potential of Bacterial Endophytes From Medicinal Plant Rauvolfia serpentina.

Rauvolfia serpentina L. is a plant with medicinal and antimicrobial properties. The coexistence of endophytes inside plants plays a crucial role in their medicinal properties, imparting plant growth potential (PGP) and antimicrobial potential. To explore this, 58 bacterial endophytes were isolated from tissues of Sarpgandha. While screening for in vitro PGP activity, 19 isolates were indole-3-acetic acid producers (≥ 20 μg/mL), whereas 37, 15, and 12 isolates showed siderophore production and, phosphate and zinc-solubilization ability, respectively. Notably, 29, 18 and 9 endophytes showed nitrate reduction, DNase and urease production abilities, respectively. These endophytes also produce hydrolytic enzymes viz. as amylase, cellulase, protease, and lipase. Thirty endophytes showed antifungal activity among which 17, 16, and 18 isolates exhibited antagonism against Sclerotium rolfsii, Fusarium oxysporum and Rhizoctonia solani, respectively. Molecular characterization identified 14 endophytes belonging to phyla Firmicutes and Pseudomonadota representing three genera Bacillus, Pseudomonas and Aeromonas. Lipopeptide genes, namely surfactin and iturin were identified in the endophyte Bacillus velezensis and bacillomycin-D in Bacillus tropicus. In planta PGP evaluation of potential endophytes in chickpea demonstrated significant increase in germination percentage, shoot and root length, and fresh and dry biomass parameters in endophyte-bioprimed plants, particularly Bacillus xiamenensis NIBSM_SgR3. Similarly, during bioefficacy study, endophyte biopriming protects plants significantly from S. rolfsii infection up to 76.11% compared to infected control at 14 dpi, with maximum protection being conferred by Bacillus velezensis NIBSM_SgL59. Thus, promising endophytes especially Bacillus xiamenensis and Bacillus velezensis with multifaceted PGP and antimicrobial potential can be explored to develop bio-stimulants and biocontrol agents.