Microfungi in grain and grain feeds and their potential toxicity
¹Estonian Research Institute of Agriculture, Teaduse 13, Saku, 75501, Harjumaa, Estonia;
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²Agricultural Research Centre, Teaduse 4/6, Saku, 75501, Harjumaa, Estonia;
The aim of the research work was to study 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 the year of 1992. The fungi were determined by microscopy, using corresponding nominators (Raper et al., 1949; Raper et al., 1965; Arx, 1970; Bilai et al., 1988). 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 (Watson & Lindsay, 1982). Spring wheat of the years 1992, 1993, 1994 and winter wheat of the years 1992, 2002 and 2003, and spoilt grain feeds of the years 1997–2002 were investigated.
About half of the identified 63 fungi species are either potentially toxigenic or allergenic. In 1992–1994; on average Alternaria spp. occurred on 72% of spring wheat seeds and on 45% of winter wheat seeds, Cladosporium spp. on 20% and 8% of the seeds, Aspergillus spp. on 6% and 9% of the seeds, Verticillium spp. on 13% and 23% of the seeds, 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, andTrichothecium. 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 werePenicillium cyclopium, Penicillium sp., Trichothecium roseum, Aspergillus terreus, Paecilomyces varioti, Rhizopus nigricans, and Acremonium sp.