Effects of volatile substances of Streptomyces globisporus JK-1 on control of Botrytis cinerea on tomato fruit

Volatile substances produced by Streptomyces globisporus JK-1 grown on autoclaved wheat seed inhibited Botrytis cinerea growth and development both on media and in inoculated tomato fruit. The volatiles suppressed mycelial growth of various plant pathogens in vitro, especially that of B. cinerea and Sclerotinia sclerotiorum. Conidial germination and sporulation of B. cinerea were also suppressed. Disease incidence and severity on wound-inoculated tomato fruit (Lycopersicon esculentum) were inhibited when fumigated with 120 g wheat seed culture of S. globisporus JK-1 per liter of airspace in treatment containers. Suppression of the infection process of B. cinerea on tomato fruit was observed via scanning microscopy, showing inhibition of conidial germination and of appressorial formation on tomato fruit, as well as abnormal morphology of appressoria and conidia. The viability of the conidia obtained from the volatile-treated and non-treated disease lesions was tested with the vital stains fluorescein diacetate (FDA) and propidium iodide (PI). Conidia fumigated with 30, 60 or 120 g/L wheat seed culture of S. globisporus JK-1 at 20 °C for 6 days showed 46.0%, 69.8%, or 80.9% reduction in viability, respectively. Transmission electron microscopy of fumigated and untreated B. cinerea showed excessive vesiculation or thickened cell walls in exposed conidia and increased vesiculation or strong retraction of plasma membrane in exposed hyphae. These results provide a better understanding of the mode of action of volatiles from JK-1 on B. cinerea. The inhibition growth of B. cinerea both in vitro and in vivo showed that volatiles from S. globisporus JK-1 have the potential for control of postharvest grey mold of tomato fruits through fumigant action.

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► Streptomyces globisporus JK-1 volatiles inhibited mycelial growth.
► Conidial germination and sporulation of Botrytis cinerea were suppressed.
► Grey mold on tomato fruit was reduced.
► Vital staining showed decreased conidial viability.
► TEM showed excessive vesiculation, thickened walls or retracted membranes.