A selective and indicative medium for groups ofPenicillium viridicatumproducing different mycotoxins in cereals

Abstract

A medium, pentachloronitrobenzene-rose bengal-yeast extract-sucrose agar (PRYES), for the isolation of molds occurring during storage of cereals was developed and compared with other selective media. The basal medium was yeast extract agar containing 15% sucrose (wt/vol). In addition to the sucrose content further selective measures included the addition of antibacterial antibiotics chloramphenicol and chlortetracycline (50 mg/l), the fungicides rose bengal (25 mg/l each), and pentachloronitrobenzene (1 g/l) and a low incubation temperature (20.degree. C). Members of the Mucorales were completely inhibited, and fast-growing species of other molds were slightly inhibited, allowing important storage molds to develop. The important ochratoxin A and citrinin-producing Penicillium viridicatum group 2 was indicated by a typical violet brown reverse on PRYES. Producers of xanthomegnin and viomellein (P. viridicatum group 1 and P. aurantiogriseum) were indicated on PRYES by their yellow reverse and obverse colors. The medium was used for screening 40 samples of barley, and molds with the characteristic colors were all identified as the species mentioned above.