Solid substrate production of Epicoccum nigrum conidia for biological control of brown rot on stone fruits

Production of conidia of Epicoccum nigrum, a biocontrol agent of the fungal pathogen Monilinia laxa, was tested in liquid- and solid-state fermentation. Liquid fermentation was conducted in 250 ml Erlenmeyer flasks containing 50 ml of a mineral medium (containing per litre 20 g lactose, 10 g NO3K, 1 g K2HPO4, 0.5 g MgSO4·7H2O, and 1 ml of a minor-element solution), inoculated with 2×105 E. nigrum conidia ml-1, and incubated at 20-25°C and 150 rpm for 7 days. Solid-state fermentation was carried out in specially designed plastic bags (600 cm3) (VALMIC®) containing either 50 g of peat/vermiculite (11, w/w), or 50 g of peat/vermiculite/lentil meal (111, w/w/w) with 40% (v/w) initial moisture content. Substrate was inoculated with a conidial suspension of E. nigrum to give 105 conidia g-1 substrate, and bags were incubated at 20-25°C for 7 days in darkness. The amount of conidia of E. nigrum obtained in solid-state fermentation with substrate based on peat/vermiculite/lentil meal was 10-fold higher than with substrate based on peat/vermiculite or in liquid fermentation. Conidial production under these conditions was maintained in the range of 108 conidia g-1 substrate from 10 to 150 days after inoculation. Germinability of these conidia was >90%. Addition of other nutrients than lentil meal to peat/vermiculite did not enhance production of conidia. Presence of peat in the substrate was necessary for good conidia production, but change in the kind of peat or vermiculite did not improve conidial production. Conidial production was similar when the substrate was inoculated with 105, 106 or 107 conidia g-1 dry substrate. Incubation of bags in light conditions did not enhance conidial production. Fresh conidia produced in this solid-state fermentation system reduced the incidence and lesion diameter induced by M. laxa on peaches. © 2004 Elsevier B.V. All rights reserved.