Biocontrol potential of chenodeoxycholic acid (CDCA) and endophytic Bacillus subtilis strains against the most destructive grapevine pathogens

Abstract

A total of 41 endophytic bacterial strains were assessed for antimicrobial activity against indicator organisms in a preliminary screening. Of these, two bacterial strains that showed a strong antimicrobial activity were selected and identified as Bacillus subtilis (Bs1 and Bs2). The activities of Bs1 and Bs2 strains and different bile acids were assessed against Botrytis cinerea and Plasmopara viticola grapevine pathogens using in vitro and in vivo methods. Bs1 and Bs2 strains strongly inhibited Botrytis cinerea growth in vitro. The cell-free filtrates of both strains also reduced Botrytis cinerea growth. Chenodeoxycholic acid (CDCA) inhibited Botrytis cinerea growth in potato dextrose agar medium and suppressed P. viticola development in grapevine leaf discs. Epifluorescence microscopy observations revealed an important restriction of P. viticola development at the vesicle stage. In addition, CDCA markedly reduced the ability of P. viticola sporangia to release zoospores in vitro, confirming the direct fungicidal effect of this bile acid.