IDENTIFICATION OF MYCOTOXIN-PRODUCING FUNGAL STRAINS - A STEP IN THE ISOLATION OF COMPOUNDS ACTIVE AGAINST RICE FUNGAL DISEASES

The simultaneous occurrence of very toxic mycotoxins with other useful fungal metabolites is a major obstacle in assays for new antifungal m olecules. Screening of 67 fungal extracts in ethyl acetate to identify those with high contents of a known mycotoxin, patulin, has been unde rtaken. The extracts were earlier found to inhibit the in vitro growth on solid malt extract medium of three important rice pathogens: Pyric ularia oryzae, Drechslera oryzae, and Gerlachia oryzae. Eupenicillium javanicum, Penicillium cyaneum, Penicillium diversum, Penicillium ducl auxii, Penicillium echinulatum, Penicillium glabrum, Penicillium ligno rum, Alternaria tenuissima, Chaetomium atrobrunneum, Scopulariopsis fl ava, and a Stemphylium sp. are reported for the first time as patulin producers. Pure patulin was observed to inhibit the growth of D. oryza e and G. oryzae at minimum concentrations of 0.50 and at 0.25 mug/mL, respectively, for P. oryzae. The diameter of the zones of inhibition i ncreased with patulin concentration. There were low correlations betwe en the quantity of patulin in the extracts and the level of in vitro i nhibition of mycelial growth of each target phytopathogen.