Large-Scale Production of Spores to Botrytise Grapes for Commercial Natural Sweet Wine Production

¹ Department of Plant Pathology, University of California, Davis; Technician, Cresta Blanca Winery, Livermore, California.

A large dependable supply of spores of Botrytis cinerea Pers. was obtained by growing pure cultures of the fungus on sterilized Thompson Seedless grape berries in one-liter Pyrex Roux culture bottles. A 10-ml glass syringe was used to introduce 2-8 ml of a spore suspension through a gauze filter disk covering the bottle opening. The spore suspension was drawn from a 1-2 liter supply through a syphon tube attached to the syringe. One to two-hundred bottles could be inoculated in less than an hour from 2-4 single-spore sporulating test tube cultures. Practically no contamination problems were encountered. A temperature of 20-22°C, a strong source of indirect sunlight and a sterile air supply induced best sporulation. Spores were dry-harvested by a vacuum cyclone separator and could be stored in cotton stoppered flasks at 4°C for at least 10 months without appreciable reduction in viability.

These results make it possible to produce a more economical and dependable supply of spores for inoculating fruit in natural sweet wine production from botrytised grapes. Labor and equipment requirements can be drastically reduced by producing the spores throughout the year and storing them until used.