Suppression of Rhizopus fruit rot by volatile organic compounds produced byPaenibacillus polymyxaCF05

Volatile organic compounds (VOCs) from a biocontrol bacteriumPaenibacillus polymyxaCF05 were evaluated for antifungal effects againstRhizopus stolonifer, an important pathogen causing postharvest fruit rot. The aerial mycelial growth and sporangia production ofR. stoloniferwas inhibited after exposure to the bacterial VOCs. Moreover, bacterial VOCs exhibited effective inhibition on Rhizopus rots of cherry, mango and nectarine, resulting 75.88%, 60.64% and 73.13% of suppression ratios at 96 h postinoculation (hpi), respectively. However, the suppression ratios were lower than chemical fungicide imazalil. The main volatile compounds from CF05 were analysed by solid-phase microextraction-gas chromatography tandem mass spectrometry (SPME-GC-MS) and 14 compounds were predominately identified. Among them, the volatile compounds benzothiazole and butylated hydroxytoluene exhibited the highest inhibitory effects onR. stolonifer, resulting 0.03 mu L mL(-1)headspace and 0.04 mu L mL(-1)headspace of 50% effective concentrations (EC50), respectively. Furthermore, the antagonistic effects of bacterial VOCs were dependent on the cultivation medium, which might be attributed to their various amounts and compositions. In conclusion, the antifungal VOCs from strain CF05 could be a promising agent in the integrated management of Rhizopus fruit rot.