Microfungi in grain and grain feeds and their potential toxicity.
A study was carried out to identify the microfungi in grain (spring and winter wheat) and grain feeds of domestic origin and determine their composition with special attention on toxigenic and allergenic species. The total number of fungi was estimated on wort agar or on the nutrient substratum of Czapek. The species and number of Fusarium were defined on the selective medium of Nash & Snyder. For a mycological survey of grain samples, the moist chamber method was used in 1992. The fungi were determined by microscopy, using corresponding nominators. The classification of Fusarium has been made according to Gerlach & Nirenberg (1982). The toxicity of isolated fungi was defined by means of a test organism, Bacillus stearothermophilus. Spring wheat of the years 1992-94 and winter wheat of the years 1992, 2002 and 2003, and spoilt grain feeds of the years 1997-2002 were investigated. Approximately half of the identified 63 fungi species were either potentially toxigenic or allergenic. In 1992-94, on average, Alternaria spp. occurred on 72% of spring wheat seeds and on 45% of winter wheat seeds, Cladosporium spp. on 20% and 8%, Aspergillus spp. on 6% and 9%, Verticillium spp. on 13% and 23%, Fusarium spp. on 23% and 64% of the seeds, respectively. Penicillium spp. was represented very differently: in 1992 and 1994 on 10%, in 1993 on 80-90% of the seeds. The species known as toxicants were also from the genera Chaetomium, Cochliobolus, Gliocladium, Mortierella, Mucor, Rhizopus, Stachybotrys and Trichothecium. In spoilt grain feeds, the potential toxicants were represented from the genera Acremonium, Alternaria, Aspergillus, Cladosporium, Fusarium, Penicillium, Rhizopus, and Trichothecium. Allergenic species were represented by the genera Epicoccum, Penicillium, Aspergillus, and Ulocladium. The toxicity of fungi isolated from grain, on the basis of the growth inhibition zone of B. stearothermophilus, was 0-7 mm, whereas on fungi isolated from spoilt feeds it was 0-18 mm. The most toxic fungi were Penicillium cyclopium [P. aurantiogriseum], Penicillium sp., Trichothecium roseum, Aspergillus terreus, Paecilomyces variotii, Rhizopus nigricans [R. stolonifer], and Acremonium sp.