Identification, genomic analysis, and disease-resistant and plant growth-promoting characterization of a Bacillus velezensis

Abstract:

Crop diseases caused by phytopathogens result in great harm to global agriculture. Biocontrol has garnered increasing attention in plant disease prevention and control because of its effectiveness and environmental friendliness.Objective To identify, analyze the genome, and evaluate the disease-resistant and plant growth-promoting effects of the strains with antagonistic activities that were screened from the culture collection.Methods Antagonistic strains were screened by plate confrontation method. and identified by morphological observation, phylogenetic analysis based on the 16S rRNA gene and genome, comparative analysis of average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values, and physiological and biochemical tests. The whole genome sequence of the target strain was analyzed for the mining of functional genes. The plant growth-promoting effect of the target strain was characterized in terms of the phosphorus-solubilizing, siderophore-producing, and proteinase- and cellulose-producing properties. The inhibition of volatile gas produced by the target strain on phytopathogenic fungi was examined in petri dishes with a septum. The effects of the target strain on tomato growth and diseases were studied by pot experiments.Results Strain MB1019 with obvious inhibitory effects on Ralstonia solanacearum and three phytopathogenic fungal strains was screened out and identified as Bacillus velezensis. The physiological and biochemical tests showed that strain MB1019 tolerated the temperature of 15-50 ℃, 10.0% NaCl, and pH 5.0-9.0. The genome of strain MB1019 was 3.8 Mb in length, with the G+C content of 46.4%. The prediction on antiSMASH suggested that the MB1019 genome had 17 synthetic gene clusters for secondary metabolites. The prediction on dbCAN2 suggested that MB1019 carried 108 genes belonging to 52 types of the CAZy family, among which glycoside hydrolases (GHs) were the richest and most abundant. The volatile gas produced by MB1019 significantly inhibited the growth of phytopathogenic fungi. The results of pot experiments showed that MB1019 promoted the growth and inhibited the diseases of tomato seedlings.Conclusion B. velezensis MB1019 capable of antagonizing R. solanacearum and phytopathogenic fungi has tolerance to high temperatures and saline-alkali and demonstrates plant growth-promoting effects. Its genome contains a large number of functional genes, and the volatile gas produced by this strain can inhibit the growth of pathogenic fungi. The fermentation broth of MB1019 has the effects of promoting the growth and preventing the diseases of tomato seedlings. In summary, B. velezensis MB1019 can be used as an elite strain in the research and development of microbial fertilizers and pesticides, demonstrating promising development and application prospects.