Spore production in solid-state fermentation of rice by Clonostachys rosea, a biopesticide for gray mold of strawberries

Abstract

Gray mold caused by Botrytis cinerea is an important disease of strawberry. Clonostachys rosea is a mycoparasite of B. cinerea that reduces fruit losses when used as a biocontrol agent. Since spore production by C. rosea has not been optimized, we investigated factors affecting sporulation under aseptic conditions on white rice grains. The greatest spore production in glass flasks, 3.4 × 10 9 spores/g-dry-matter (gDM), occurred with an initial moisture content of 46% (w/w wet basis), inoculated with 1 × 10 6 spores/gDM and hand shaken every 15 days. However, a lower inoculum density (9 × 10 3 spores/gDM) and no shaking also gave acceptable sporulation. In plastic bags 1.1 × 10 8 spores/gDM were produced in 15 days, suggesting that larger scale production may be feasible: with this spore content, 24 m 2 of incubator space would produce sufficient spores for the continued treatment of 1 ha of strawberry plants.