In vitro antifungal activity of Pseudomonas synxantha against Monilinia laxa

Abstract

Background: There is globally recognized necessity to find safe alternative for pesticide use. Using microorganisms with antagonistic activity against pathogens is one of the biocontrol strategies. Pseudomonas synxantha belongs to the P. fluorescens group comprising many members with biocontrol abilities. Monilinia laxa is fungal causative pathogen of brown rot disease of stone fruits. Objectives: Evaluation of an isolate of Pseudomonas synxantha for its biocontrol properties. Methods: The antifungal activity of P. synxantha isolate (P4/16_1) was tested in initial screening on 11 M. laxa isolates and in dual culture assay on three selected M. laxa isolates. The antagonistic effect of volatile organic compound from P. synxantha was tested in sealed dishes bioassay. The non-volatile antifungal compounds were isolated by benzene extraction of 5 days old P. synxantha culture in minimal salt medium. The benzene extract dissolved in methanol was tested on three selected M. laxa isolates and inhibition of radial growth (PIRG %) was calculated. Results: In initial screening P. synxantha had activity on all tested M. laxa isolates. The antagonistic activity against selected M. laxa isolates in dual culture assay was in range from 80-87.5% of growth inhibition. The benzene extract exhibited 57.2-63.04% radial inhibition of mycelial growth. The biocontrol activity of this isolate is partly due to the production of volatile compounds that decrease the growth of the tested M. laxa between 15.94 and 29.58% after 14 days of incubation. Isolate P. synxantha showed promising potential for biocontrol of brown rot disease causing pathogen and should be investigated further.