Summary. The aim of this study was to determine the influence of different concentrations of T-2 toxin and zearalenone on physiological status of 4 brewing yeast strains during wort fermentation. T-2 toxin was used at concentration of 5, 10 i 15 μg∙ml^-1 and ZEA of 5 i 50 μg∙ml^-1. The viability, biomass growth and acidification power of yeasts were enhanced. It was stated that zearalenone at concentration of 50 μg∙mL^-1 influenced the yeast growth and their metabolic activity at first step of fermentation. T-2 toxin had stronger influence at all stages of fermentation causing decrease of viability and acidification power of yeasts. T-2 toxin at concentration of 15 μg∙mL^-1 inhibited biomass growth of S.ca. 13 i S.c. 46 strains.

ISSR amplification was evaluated for its applicability to onions identification. The procedure was tested on six onions including: Allium cepa L. (onion), Allium tuberosum Rottl. ex Spreng. (chinese chives), Allium ascalonicum L. (shallot), Allium cepa L. var. proliferum (top onion), Welsh onion (Allium fistulosum L.) and Welsh onion ‘Sprint’. Thirty primers homologous to microsatellite repeats based on various di-, tetra- and penta- SSR motifs with 3’ selective nucleotides for anchoring, were screened against the onion genome by 2% agarose gel electrophoresis. Out of the 30 primers 16 gave stable patterns amplifying a total of 187 loci of which 159 (85%) were polymorphic. Clearly detectable ISSR amplicons ranged from 139 to 2213 bp in size. The average number of loci gene-rated per primer was 12. Specific ISSR loci were detected for each onion species. The highest number (15) of species-specific loci were obtained for A. tuberosum, whereas the lowest number (3) was detected for A. ascalonicum. UPGMA cluster analysis was used to construct a dendrogram and to estimate the genetic distances between the Allium species. The tree revealed one separate group including A. fistulosum ‘Sprint‘, A. cepa var. proliferum, A. fistulosum and A. ascalonicum. In this group the smallest divergence is observed between A. fistulosum ‘Sprint‘ and A. cepa var. proliferum (77.9% similarity). The two other species: A. cepa and A. tuberosum are approximately equidistant from the group.

Specific growth rate of five Yarrowia lipolytica strains growing in acetate medium (0,6%) supplemented with glycerol, ethanol or glucose (concentration range between 0 to 1%) was estimated. The studied strains differ in acetate utilisation, citric acid secretion and colony morphology. The rate of yeast growth, as well as, the biomass level changed as a consequence of the presence of second carbon source in acetate culture. Addition of ethanol inhibited (completely or partly) the growth in acetate medium of all tested strains, while glycerol and glucose stimulates the wild strain growth (A101), induced acetate growth of acu^- mutants (A101.1.31 and A101.1.31.K1) and inhibited the growth of revertant strain (A101.1.22). The maximal specific growth rate was observed for glycerol growing yeast, and a periodic variation of μ was observed in the case of very small amount of available C source. The maximal specific growth rate of wild strains on glucose was higher than on acetate.