Plant growth promotion and lipopeptide-mediated biological control of chilli pathogen Colletotrichum siamense by endophytic Bacillus sp.

Abstract

Biocontrol is the need of the hour and a necessary replacement for chemical fungicides in controlling pre- and post-harvest crop losses by plant pathogenic fungi. The present study explored an endophytic Bacillus sp. strain (K7) from Jasminum officinale for its plant growth promotion and protection abilities. Bacillus sp. K7 was found to produce IAA, ammonia, siderophores, cellulases, amylases, proteases, and fix atmospheric nitrogen, which promoted seed germination in chilli. Agar cup diffusion assays, MIC and MFC assays, light microscopy, scanning electron microscopy, and infection studies in the chilli fruit model showed that Bacillus sp. K7 possessed strong antifungal activity against Colletotrichum siamense. PCR confirmed that the organism possessed biosynthesis clusters for surfactin biosurfactant lipopeptides. MALDI-TOF-MS of the acid-precipitated extract and whole cells revealed that Bacillus sp. K7 produced at least twelve isoforms of surfactins, iturins, and fengycins. 3D structures of some of the selected lipopeptide molecules were docked against cutinase, a virulence-related protein of C. gloeosporioides species complex, where the docking scores of fengycin, iturin, and surfactin were found to be −6.2, −5.1, −5.1, and −5.8 kcal/mol respectively. The combined in-vitro and in-silico results suggest that Bacillus sp. K7 is a potential biocontrol agent and can be used as a seed protectant, biopesticide, biofertilizer, and anti-food spoilage agent.