Potencial de bactérias do gênero Bacillus para o biocontrole de fitopatógenos de interesse agrícola

Abstract

The genus Bacillus includes species of industrial and biotechnological interest and is the most used for different forms of biological control in agriculture. Thus, the main objective of this study was to evaluate the potential of bacteria of the genus Bacillus for the biocontrol of phytopathogens of agricultural interest. For this, two Bacillus strains (MAD 168 and MPUR 39.2) belonging to the biological collection of the Laboratory of Molecular Biology of Embrapa Western Amazonia-CPAA, were submitted to in vitro evaluation to verify the antagonistic potential against phytopathogens, in plant analysis to test the biological control of Rhizoctonia symptoms in cowpea plants (line MPUR 39.2 only), qualitative analysis of the production of hydrolytic enzymes, genome sequencing to identify genes related to the biosynthesis of secondary metabolites and microscopy and phylogenomic analysis to confirm the species identity. MAD 168 and MPUR 39.2 isolates were able to inhibit over 50% in vitro mycelial growth of 8 and 11 phytopathogenic fungi with indices ranging from 53.3 to 79.5% and 58.1 to 97.1%, respectively. In plant tests using the MPUR 39.2 isolate to control damping off caused by Rhizoctonia sp. in cowpea (cultivar BRS Novaera) there was no decrease in severity. When evaluated for in vitro enzymatic production of amylase, protease, chitinase, lipase, siderophore production and phosphate solubilization, only the MAD 168 strain showed cellulase activity. The phylogenomic analysis indicated that isolate MAD 168 belongs to Bacillus tropicus species (ANIb 95.38%, ANIm 95.89%) and isolate MPUR 39.2 to Bacillus subtilis species (ANIb 97.84, ANIm 98.86). As for the identification of BGC's, the MAD 168 lineage presents 10 clusters for the production of secondary metabolites, of these, three present similarities of 40 to 85% with clusters already known, such as fengycin, bacilibactin (non-ribosomal peptides - NRPS), Turincina H (polyketides synthase - PKS); and the MPUR 39.2 strain has 14 clusters for the production of secondary metabolites, of which twelve have similarities from 7 to 100% with already known clusters, such as bacilibactin, surfactin and plipastatin (non-ribosomal peptides - NRPS); carbapene acid, fengycin and bacillus (polyketides synthase-PKS); carotenoid (terpenes); tallantatin (epipeptide); subtylosin A (sactpeptide); pulcherriminic acid (CDPS).