Abstract
The main objective of this study was to evaluate Bacillus velezensis strain CMRP 4490 regarding its ability to inhibit soil-borne plant pathogens and to increase plant growth. The study included evaluation of in vitro antifungal control, sequencing the bacterial genome, mining genes responsible for the synthesis of secondary metabolites, root colonization ability, and greenhouse studies for the assessment of plant growth–promoting ability. The strain was obtained from soil samples in the north of Paraná in Brazil and was classified as a B. velezensis, which is considered a promising biological control agent. In vitro assay showed that B. velezensis CMRP 4490 presented antagonistic activity against Sclerotinia sclerotiorum, Macrophomina phaseolina, Botrytis cinerea, and Rhizoctonia solani with a mycelial growth inhibition of approximately 60%, without any significant difference among them. To well understand this strain and to validate its effect on growth-promoting rhizobacteria, it was decided to explore its genetic content through genome sequencing, in vitro, and greenhouse studies. The genome of CMRP 4490 was estimated at 3,996,396 bp with a GC content of 46.4% and presents 4,042 coding DNA sequences. Biosynthetic gene clusters related to the synthesis of molecules with antifungal activity were found in the genome. Genes linked to the regulation/formation of biofilms, motility, and important properties for rhizospheric colonization were also found in the genome. Application of CMRP 4490 as a coating film on soybean increased from 55.5 to 64% on germination rates when compared to the control; no differences were observed among treatments for the maize germination. The results indicated that B. velezensis CMRP 4490 could be a potential biocontrol agent with plant growth–promoting ability.
Highlights
The use of elite free-living rhizospheric microorganisms has been considered an important strategy for disease management in several crops and has earned strength in the last decade (Chen et al, 2009a; Mizuhara et al, 2011; Rückert et al, 2011; Sibponkrung et al, 2017; Liu et al, 2018)
Genomic analysis has revealed that B. velezensis Coleções Microbiológicas da Rede Paranaense (CMRP) 4490 possesses specific clusters of genes related to the biosynthesis of secondary metabolites, which play significant roles in both pathogen suppression and plant growth promotion, and to genes related to rhizospheric colonization
It was possible to affirm that B. velezensis CMRP 4490 harbors a biotechnological potential because of its high genetic similarity with other strains from the Bacillus genus already used as biocontrol control agents and already established on the market
Summary
The use of elite free-living rhizospheric microorganisms has been considered an important strategy for disease management in several crops and has earned strength in the last decade (Chen et al, 2009a; Mizuhara et al, 2011; Rückert et al, 2011; Sibponkrung et al, 2017; Liu et al, 2018). Among these soil microorganisms, the PGPR (plant growth–promoting rhizobacteria) has gained attention for their root colonization ability, high survivability, and multiplicity in root surroundings, favoring plant growth and inhibition of phytopathogens (Beneduzi et al, 2012). Biofilm formation has been considered as another important property of microbial biocontrol agents (Bais et al, 2004; Fan et al, 2011)
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