Abstract
The Southern Slovak wine growing region is warmest part of Slovakia and is suitable for cultivating the grapes for production of wines at high quality. From the eight vineyards were collected 8 samples of wine grapes (white 7, blue 1) during harvesting 2011, 2012 and 2013. The aim of this work was to gain more knowledge about mycobiota on grapes originating from Slovakia, to identify Aspergillus and Penicillium species according to their morphopogy and evaluate the presence of secondary metabolites (also including intracellular and extracellular mycotoxins) produced in in vitro conditions by thin layer chromatography method from fresh grape berries. Fifty wine grapes per bunch (approximately 7 - 8 berries per plate) that showed no symptoms were randomly selected on Dichloran Rose Bengal Chloramphenicol agar medium. The plates were then incubated aerobically at 25 ±1 °C for 5 to 7 days in the dark. Of these samples were identified 17 genera. One hundred percent of samples were colonies by the genus Penicillium and 75% by the genus Aspergillus. During the survey, 135 isolates belonging to 9 Penicillium species (P. aurantiogriseum, P. canescens, P. citrinum, P. crustosum, P. decumbens, P. expansum, P. funiculosum, P. chrysogenum and P. purpurogenum) and 26 isolates belonging to 3 Aspergillus species (A. clavatus, A. flavus and A. section Nigri) were isolated and identified from exogenous contamination. The main occurring penicillium species of the samples were P. expansum (37.5% Fr), followed P. citrinum, P. chrysogenum and P. crustosum (25% Fr). The main occurring aspergillus species of the samples were A. section Nigri (62.5%). Eight potentially toxigenic species were tested for their toxigenic ability. It was confirmed the production of various mycotoxins such as aflatoxin B1, citrinin, patulin, cyclopiazonic acid, penitrem A and roquefortin C. Out of 34 strains, 56% produced at least one mycotoxin.
Highlights
Fruits contain high levels of sugars and other nutrients, and they possess an ideal water activity for microbial growth, their low pH makes them susceptible to fungal spoilage
The aim of this work was to gain more knowledge about mycobiota on grapes originating from Slovakia, to identify Aspergillus and Penicillium species according to their morphopogy and evaluate the presence of secondary metabolites produced in in vitro conditions by thin layer chromatography method from fresh grape berries
135 isolates belonging to 9 Penicillium species (P. aurantiogriseum, P. canescens, P. citrinum, P. crustosum, P. decumbens, P. expansum, P. funiculosum, P. chrysogenum and P. purpurogenum) and 26 isolates belonging to 3 Aspergillus species (A. clavatus, A. flavus and A. section Nigri) were isolated and identified from exogenous contamination
Summary
Fruits contain high levels of sugars and other nutrients, and they possess an ideal water activity for microbial growth, their low pH makes them susceptible to fungal spoilage. The grape microbial ecosystem is composed of highly diverse microorganisms, including fungi (Rousseaux et al, 2014). Climate change (warmer weather, heat waves, higher levels of precipitation and drought) may affect the distribution of fungal population, including those present on grapes, thereby affecting the presence of mycotoxins or off-flavours in wine (Paterson and Lima, 2011). Many species of fungi can colonize grapes during the withering process, and the most important of these for enhancing wine quality is Botrytis cinerea (Lorenzini et al, 2012). Grape rotting and spoilage can be caused by a variety of fungal species, including Penicillium, Aspergillus, Alternaria, Cladosporium and Rhizopus. Aspergillus section Nigri are the most important mycotoxigenic (ochratoxigenic) fungi present on grapes (5 – 83% infected berries) (García-Cela et al, 2015).
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