Bacillus velezensis RC 218 as a biocontrol agent to reduce Fusarium Head Blight and deoxynivalenol accumulation: genome sequencing and secondarymetabolite cluster profiles..

PALAZZINI, J.M; DUNLAP, C.; BOWMAN M.J; CHULZE, S.N

Florianopolis

Congreso; 5th International Symposium on Fusarium Head Blight (ISFHB) and 2nd International Workshop on Wheat Blast (IWWB) Florianópolis, Brazil, 6 a 10 Abril de 2016.; 2016

Embrapa, CAPES

Bacillus subtilis RC 218 was originally isolated from wheat anthers as a potential antagonist of Fusarium graminearum sensu stricto, the causal agent of Fusarium head blight (FHB) in Argentina. In previous studies we demonstrated the ability of B. subtilis RC 218 to reduce disease severity and DON accumulation in vitro, under greenhouse and field trials. The current study extends characterizing B. Subtilis RC 218 under a field trial, genome sequencing and secondary metabolite production. The field trial was conducted in Córdoba province, Argentina, during the 2014 harvest season. The wheat cultivar BioInta 1005 (susceptible to F. graminearum) was used. Application of the biocontrol agent was done at the anthesis stage with the inoculation of B. subtilis RC 218 first and then a mixture of F. graminearum strains. FHB disease incidence and severity were evaluated 21 days after inoculation. The genome of B. subtilis RC 218was sequenced using MiSeq DNA sequencer. Genome comparisons and alignments for phylogenetic trees were made using BIGSdb software. Secondary metabolite clusters were identified with antiSMASH3.0 or direct blasting. Culture supernatants containing secondary metabolites were analyzed by LC-MS. The field study demonstrated that B. velezensis RC 218 could reduce FHB severity by 26 % and the associated mycotoxin (deoxynivalenol) production to undetectable levels. The genome sequencing allowed us to accurately determine the taxonomy of the strain using a phylogenomic approach, which places it in the B. velezensis clade. The genome mining allowed us to identify 9 active secondary metabolites conserved by all B. velezensis strains and one additional secondary metabolite, the lantibiotic ericin, which is unique to this strain. This represents the first confirmed production of ericin by a B. velezensis strain. The genome also allowed us to do a comparative genomics with its closest relatives and compare the secondary metabolite production of the publically available B. velezensis genomes. The biocontrol activity can be related to the ability of the strain to produce several lipopeptides, from the surfactin, fengycin and iturin families since the gene cluster for these compounds were detected. The results showed that the diversity in secondary metabolites of strains in the B. velezensis clade is driven by strains making different antibacterials.