Antifungal activity and genome annotation of Bacillus amyloliquefaciens subsp. plantarum SMLR1, a potential biocontrol agent of Rhizoctonia solani

Abstract

The potential use of 172 Solanaceae seed-borne endophytic bacteria strains for biocontrol of Rhizoctonia solani was investigated. Most strains (88.95%) showed an early antifungal effect, but only 27.91% exhibited persistent activity at 14 days via soluble compounds against R. solani. Thirty-two selected strains with high antifungal activity were tested for plant growth promotion on tomato seedlings, hydrolytic enzymes production, phosphate solubilization, and siderophore production. The strain SMLR1 combined high and persistent antifungal activity with the most positive effect on tomato seedlings' hypocotyl and radicle lengths. This strain produced antifungal lipopeptides extracted after 66 h of culture, with an effective concentration 50% (EC50) ranging from 27 to 98 µg/mL against various R. solani strains. Genome analysis of SMLR1 revealed it belongs to Bacillus amyloliquefaciens subsp. plantarum, with diverse biosynthetic gene clusters associated with non-ribosomal peptides (NRPs), lipopeptides (fengycin and surfactin), siderophores, bacteriocins, β-lactones, type III polyketide synthases (T3PKS), terpenes, and antimicrobial compounds. These findings highlight the potential of B. amyloliquefaciens subsp. plantarum SMLR1 as a biocontrol agent for R. solani, with whole genome sequencing offering a cost-effective way for rapid genomic selection of biocontrol agents.

Keywords: Bacillus; Rhizoctonia solani; Antagonistic activity; Lipopeptides; Whole genome annotation.