Mass production of conidia of Penicillium frequentans, a biocontrol agent against brown rot of stone fruits

Conidial production of Penicillium frequentans, a biocontrol agent of the fungal pathogen Monilinia laxa, was tested in liquid and solid-state fermentation. Conidial production of P frequentans in solid-state fermentation was higher than in liquid-state fermentation. Solid-state fermentation was made in specially designed plastic bags (VALMIC(R)) containing peat: vermiculite (1:1 w/w). Addition of nutrients to the peat: vermiculite increased conidial production of P frequentans, especially when lentil meal was added. The number of conidia obtained in this solid-state fermentation was maintained in the range of 10(8)-10(9) conidia g(-1) from 5 to 120 days after inoculation. Germinability of these conidia was > 90% until 90 days of incubation and declined at 120 days. Optimal initial moisture content in the substrate was 30-40% (v/w). At lower moisture contents, significant reductions in conidial production and germinability were observed, particularly at 10% (v/w). Conidial production was similar when the substrate was inoculated with 10(5), 10(6) or 10(7) conidia g(-1) dry substrate. Fresh conidia produced by solid-state fermentation reduced the incidence of brown rot on plums by 75%.