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<table style="height: 460px;" border="0" cellspacing="0" cellpadding="0" width="498" align="left"><tbody><tr><td height="460" align="left" valign="top"><p>Our research focused on identify the <em>Alternaria</em> species from grapes (surface sterilized berries and non-surface sterilized berries) of Slovak origin and characterize their toxinogenic potential in <em>in vitro</em> conditions. We analyzed 47 samples of grapes, harvested in years 2011, 2012 and 2013 from various wine-growing regions. For the isolation of species, the method of direct plating berries and surface-sterilized berries (using 1 % freshly pre-pared chlorine) on DRBC (Dichloran Rose Bengal Chloramphenicol agar) was used. For each analysis was used 50 berries. Only undamaged berries have been used for analysis. The cultivation was carried at 25 &plusmn;1&deg;C, for 5 to 7 days in dark. After incubation, the colonies of <em>Alternaria</em> were transferred on PCA - potato-carrot agar and CYA - Czapek-yeast extract agar and cultured for 7 days at room temperature and natural light. A total 4 species-groups of the genus <em>Alternaria</em> were isolated from grapes berries: <em>Alternaria alternata </em>(1369 isolates),<em> Alternaria arborescens </em>(734 isolates),<em> Alternaria infectoria</em> (143 isolates),<em> </em>and <em>Alternaria tenuissima</em> (3579 isolates). According to European Union legislation mycotoxins produced by species genus <em>Alternaria</em><em> </em>are not monitored in foods and food commodities.<em> </em>Mycotoxins such as alternariol and alternariol monomethylether are mutagenic and genotoxic in various <em>in vitro</em> systems. Selected strains were tested for production of altenuene, alternariol monomethylether and alternariol. In neither case of <em>A. infectoria</em> species-group isolates was confirmed the production of tested mycotoxins in <em>in vitro</em> conditions by TLC method. The ability to produce altenuene, alternariol monomethylether and alternariol in <em>in vitro</em> conditions was detected in isolates of <em>Alternaria alternata</em>, <em>Alternaria arborescens</em> and <em>Alternaria tenuissima</em> species-groups. Isolates of <em>Alternaria alternata </em>species-group (44 tested isolates) were able to produce altenuene (24 isolates), alternariol monomethyleter (42 isolates) and alternariol (43 isolates). Only one isolate did not produce any mycotoxins. Isolates of <em>Alternaria arborescens</em> species-group (38 tested isolates) were able to produce altenuene (24 isolates), alternariol monomethyleter (33 isolates) and alternariol (36 isolates). Only two isolates did not produce any mycotoxins. Isolates of <em>Alternaria tenuissima</em> species-group (87 tested isolates) were able to produce altenuene (42 isolates), alternariol monomethyleter (41 isolates) and alternariol (73 isolates). Thirteen isolates did not produce any mycotoxins.</p></td></tr></tbody></table>