Abstract:To study the bioactivity and application potential of antifungal volatile organic compounds (VOCs) from soil bacteria, the volatiles generated by five bacteria were determined by SPME-GC-MS (Solid Phase Microextraction-Gas Chromatography-Mass Spectrometry) and their bioactivity was given further confirmation with commercially available compounds in sealed plates. Further, the application of these volatile-producing bacteria for the biological control of two main diseases on cucumber caused by Sclerotinia sclerrotium and Sphaerotheca fuliginea, respectively treated by soil and direct fumigation, was investigated in greenhouse. In total, 21-31 and 12 compounds were detected from bacterial TSB-YE cultures and TSB-YE medium controls, respectively, which covered a wide range of alkyl, aldehyde, alcohol, ketone, fatty acid, amine, oxime, phenol and heterocyclics. Of the 20 candidate compounds assayed for antifungal activity in sealed plates, furfural, benzaldehyde, 1-octanol, 1-octen-3-ol, 3, 7-dimethyl-1, 6-octadien-3-ol, 2-ethyl-1-hexanol exhibited complete inhibition against S.sclerotiorum at a lowest treatment dosage of 0.01g. Mixing the autoclaved soil with bacteria caused a higher control effect (28.57%-71.43%) on S.sclerrotium than those of bottom layer treatments, and an obvious growth promotion of cucumber seedlings was shown. When applied directly as fumigation, these volatiles could significantly inhibit the disease severity of powdery mildew on the fumigating seedlings.