Multifaceted growth promotion and biocontrol of Agroathelia rolfsii and induction of defense mechanism by Bacillus amyloliquefaciens SS-CR10 on chilli.

Abstract

Plant-growth-promoting (PGP) endophytic bacteria are beneficial microorganisms that can help plants withstand biotic stress caused by fungal phytopathogens. In the present study, 78 endophytic bacterial isolates were isolated from chilli (Capsicum annuum L.). A potent isolate with several PGP attributes and better inhibition against Agroathelia rolfsii was selected and identified as Bacillus amyloliquefaciens using 16S rDNA homologies. Phosphate solubilization (65.9 μg ml^-1), nitrogen fixation, production of IAA (9.77 to 24.45 μg ml^-1), ammonia, ACC deaminase, siderophore, and hydrolytic enzymes were among the PGP traits shown by the strain SS_CR10. Furthermore, the strain demonstrated the ability to colonize roots. It significantly improved the plant's developmental traits, such as fresh and dry weight, photosynthetic pigments, and root and shoot length. LC-MS analysis and PCR amplification of lipopeptide genes also showed that surfactin, iturin, and bacilysin lipopeptides were present. Following treatments with lipopeptide extract and bacterial suspension, A. rolfsii mycelia showed severe deformation and cell death, as seen by live dead staining by fluorescent microscopy and scanning electron microscopy (SEM). Finally, the upregulation of defense-related genes CaPR1, CaPR2, and CaPR4 after bacterial treatment confirmed the induction of systemic resistance. In conclusion, this study shows how strain SS_CR10 might be useful for promoting plant growth in chilli and controlling A. rolfsii in an eco-friendly way, which would protect the health of the soil.