Drought is considered as one of the most important abiotic stress factor, which can cause a severe impact on agriculture. The development of new cultivars of barley is therefore more focused on improving of abiotic stress tolerance to drought, as well as on maintaining of good health status, appropriate yield levels and quality parameters. This work was aimed at evaluation of barley cv. Tadmor, which is specifically adapted to drought and can be potentially used as a source of drought tolerance in barley breeding programmes. F5 generation lines derived from reciprocal crosses between cv. Tadmor and cv. Jersey (advanced European spring malting barley) together with parent cultivars were cultivated at two sites (Brno, Žabčice). The assessment was aimed at traits associated with yield (thousand grain weight - TGW, percentage of sieving fraction over 2.0 mm, grain yield per plant) and quality (protein and starch content). The effect of water-limited conditions at Žabčice site was demonstrated particularly in the TGW and the percentage of sieving fraction over 2.0 mm, while the lines from Tadmor x Jersey cross sustained the stress significantly better than those from Jersey x Tadmor cross. The lines grown in Žabčice reached in average a higher level of protein content and a lower level of starch content. The significant effect of genotype was detected only in protein content and was non-significant for starch. The reaction of selected lines on osmotic stress was studied in and independent experiment under controlled conditions. The plant stress reaction was evaluated according to changes in osmotic potential in leaves and accumulation of proline. Lines with Tadmor as a female parent showed higher values of osmotic potential in comparison with those derived from the reciprocal cross. The increase in osmotic potential under stress was strongly associated with the content of proline. The last part was focused on evaluation of susceptibility to powdery mildew caused by Blumeria graminis. The symptoms of powdery mildew on experimental lines were assessed in field and the lines, which were classified as resistant/susceptible, were further analysed for the presence of mlo allele. According to the results all resistant lines carried mlo9. With regard to all evaluated parameters, positive reaction on physiological drought stress and genetically controlled resistance against powdery mildew two lines can be recommended for further work.

The thesis deals with the role of drought and the effects on growth, morphology and yield of barely. The evaluation of the physiological mechanisms at the level of the osmotic adjustment of plants was done at two locations differing in the soil water regime. These mechanisms were studied on a group of 20 recombinant inbred lines (RIL) derived from crosses between spring barley Jersey (spring malting cultivar) and Syrian landrace Tadmor, which was used as a donor of drought tolerance. The progeny derived from reciprocal crosses were evaluated for yield parameters (thousand grain weight, grain yield per plant, the proportion of grains over 2 mm) and qualitative parameters (starch content and nitrogen content). The physiological status of the plants was evaluated using relative water content, osmotic potential (OP) and proline content as an osmotically active substance. The effect of location on all above mentioned parameters was estimated on parental varieties as well as on RIL lines. According to the results several lines were selected which exhibit relatively high stability of yield and qualitative parameters at both locations. The relationship between the yield parameters and values associated with the mechanism of osmotic adjustment (RWC, OP and proline content) was not clearly demonstrated. Decrease of OP and increase of proline content in plants cultivated under dry conditions at location Žabčice mostly corresponded to increased level of plant wilting, therefore it is possible that only passive mechanism for OP was involved. This mechanism did not affect the drought tolerance.

Salinity induced by various sodium salts (NaCl and Na2SO4) led to changes in growth parameters that differs depending on used cultivar and pH of applied salt solution. Cultivar Radegast showed the highest sensitivity to salinity that was reflected in a reduction of shoot and root growth, a decrease of tissue water content, an excessive sodium accumulation in shoots and a radical formation of ROS in the root tips. Subsequent experiment using various types of humic acids revealed that technical humic acid (HA; 6.0 mg . l-1), unlike Lignohumát Max, stimulates NaCl-treated plant growth and simultaneously reduces accumulation of sodium in their tissues.HA applied into culture solution is able to induce an enhancement of certain metabolites(syringic acid and lactic acid in shoots, quinic acid and malic acid in roots, andascorbic acid, reduced glutathione, phytochelatin 2 and free amino acids in shoots). However, NaCl caused a decrease of majority free amino acids (except for proline and histidine), phenolic acids and antioxidants in leaves. On the other hand, an increase of lactic acid and quinic acid was observed in roots. Salinity significantly induced oxidative stress; it is evident from the increased activity of antioxidant enzymes (APX, CAT, GR and SOD). HA was able to mitigate NaCl-induced oxidative stress, as also evidenced by fluorescence microscopy. Simultaneously, HA was also able to reduce NaCl-induced excessive accumulation of sodium content in cultivar Radegast.

This work summarises the results of experiments with common wheat lines (T. aestivum L. emed. Fiori et Paol.) during the growing season 2013/2014. Field experiments were carried out in two locations -- Žabčice and Branišovice. Two winter wheat varieties (Etela and Meritto) commonly cultivated in the Czech Republic and 45 Syrian lines with potentially high drought tolerance were evaluated in this work as well as Syrian variety CHAM 6. Spikes analyses were performed and the evaluated characters included awn length, spike length, spike weight, spikelet number, rachis length, rachis segments number, grains per spike number, and grains per spike weight. We focused also on grain yield per plant and the weight of thousand grains. The effect of location was highly significant for both characters -- yield per plant was higher in Žabčice, thousand grain weight in Branišovice. Two quality indicators were assessed -- the content of proteins and starch. As to protein content, all lines and control varieties exceeded the standard given in ČSN 461100-2. The amount of starch was between 66 and 68 %. The response to day length was characterised according to the photoperiod loci Ppd-D1. Photoperiod insensitive allele Ppd-D1a was more common in lines of Syrian origin than sensitive allele Ppd-D1b. To evaluate the tolerance to drought the osmotic potential was determinated and the greatest ability of osmotic adjustment was found in line 27/1.

Current agriculture is facing a serious challenge of decreasing precipitation and irregular occurrence of drought periods including their unfavorable distribution during the vegetation season. This leads to growing interest in planting highly drought-resistant crops like sorghum. In comparison with other crops, sorghum excels in low water demand, though exhibits high susceptibility to low temperatures, which hampers its spread to new regions. Surprisingly, there is not enough information about the nature of sorghum's reaction to cold exposure. The aim of this diploma thesis was to describe reactions of young sorghum plants exposed to cold stress, low water availability and their combination and to verify the possibility of plant hardening through previous low-stress load. The special focus was paid to changes in carbohydrate metabolism, which plays generally very important role in plant defense reactions. The other analyzed physiological traits were leaf tissue osmotic potential, proline content and basic morphometric characteristics. Experimental design consisted of pot experiments conducted in growth chambers and the experiments performed under controlled conditions in vitro, using two sorghum genotypes "Ruzrok" and "01Z1800012". Both genotypes exhibited similar response to stress treatment....

Natural strains of the Saccharomyces cerevisiae growing on solid médium form structured, biofilm -like colonies. This ability is depended on the surface adhesin Flo11p. The expression of the FLO11 gene is upregulated by the RNA-binding protein Whi3p, which is likely to have a negative effect on the level of the transcription factor Yap6p. The aim of this study was to determine whether Yap6p affects colony morphology and FLO11 expression. Analysis of FLO11 expression using the fluorescent proteins pFlo11-GFP and Flo11p-DsRed in WHI3-deletion strains demonstrated a negative effect of Yap6p on FLO11 expression and confirmed changes in the effect of Yap6p on FLO11 expression in the presence of NaCl. In the strain overexpressing YAP6, the fluorescence values of pFlo11-GFP and Flo11p-DsRed were lower than in the strain with deletion of the YAP6 and in the presence of NaCl there was observed the largest increase in fluorescence. Although Yap6 protein is thought to have a negative effect on FLO11 expression under standard culture conditions, it seems to be responsible for a significant increase in FLO11 expression in the presence of mild osmotic stress. In WHI3-deletion strains, there was observed a significant increase in structuredness of colonies growing in the presence of NaCl. Analysis of structured...

Section Restricti is one of the last sections of the genus Aspergillus that hasn't been revised in the modern taxonomic era. All species are osmophilic, have simple morphology and they are mainly important because of the food, feed and seed spoilage, some of them also have negative influence to the indoor air. The section consists of seven species according to the last taxonomic revision from 2008 based only on molecular data. It currently consists of six asexual and one homothalic species. 126 isolates from the section coming from four continents were studied in this thesis, including ex-type strains. Revision of the section was carried out combining molecular phylogenetic analysis and conventional taxonomic methods. Modern methods of species delimitation based on multispecies coalescent model were used for the phylogenetic reconstruction. From the conventional methods analysis of morphology (macro- and micromorphology including scanning electron microscopy) and physiology (ability of growing in osmotic gradient and several different temperatures) was performed. Apart from the seven known species, eight new undescribed species were discovered. Majority of the new species belongs to the Aspergillus penicillioides species complex. Key words: Aspergillus restrictus, osmophilic fungi, species...

ROLE OF THE YXKO GENE OF BACILLUS SUBTILIS IN RESPONCE TO ENVIRONMENTAL STRESS Abstract Mutation of the yxkO gene, which encodes a putative ribokinase and belongs to the σB general stress response regulon, leads to reduced salt tolerance under potassium limitation in Bacillus subtilis. The biological function of the yxkO gene has not been determined yet, but it may be involved in the high affinity potassium uptake system, which has been described in Escherichia coli in contrast to Bacillus subtilis. Our goal was to describe another features of a mutant in the yxkO gene and to try to propose the role of this gene. Using the integration vector pMutin4, we prepared a Bacillus subtilis strain MP2 with a yxkO gene inactivation. The MP2 strain displays limited growth in a rich medium and it is a sensitive strain to tetracycline. Furthermore, this strain is unable to form endospores and the cells are longer, which indicates a septum formation defect. We accomplished a 2-D protein gel analysis to compare expression profiles of the MP2 strain and the 1A680 standard strain after salt and ethanol stress. The MP2 strain shows changes in productions of some energy metabolism enzymes and flagellin protein. We conclude that yxkO is a regulatory gene, whose product has a pleiotropic effect on many of cell functions.

This thesis deals with the characterization of bacterial cells capable of polyhydroxyalkanoates (PHA) accumulation. The dissertation thesis is written in the form of a discussed published publications which are attached to the thesis as appendixes. The work develops a study of the current topic of the protective functions of PHA and clarifies protective mechanisms against selected stressors. Firstly, we focused on the protective effects of PHA granules against UV radiation and osmotic stress, specifically hypotonic conditions. In the case of UV exposition, the cells protected themselves by scattering UV radiation on the intracellular granules protecting especially nucleoid. When exposed to osmotic stress, the amorphous state of PHA granules is very important since it is capable of stabilization of cell membranes under hypertonic stress, afterwards, bacterial cells can maintain their integrity during the subsequent hypotonic challenge. In general, the amorphous state of PHA granules is key to ensure the proper biological functions of PHA whether as storage or protective polymer. Therefore, in the next part of this work, we focused on the core of the stabilization mechanism that protects native PHA granules from crystallization and thus the intracellular polymer maintains in a thermodynamically unfavorable amorphous phase state. Based on experimental work, we applied selected stresses because we proposed a new model of stabilization of the amorphous state of PHA granules in vivo. It consists of two mechanisms, where small volumes of PHA granules reduce the rates of crystallization and at the same time the water present in the granules plays the role of a low molecular plasticizer. Due to the metabolic apparatus of bacterial cells, PHA are simultaneously synthesized and degraded which leads to an increment of intracellular concentration of monomers that also figure in the protective effect of PHA. In this context, we aimed at the description of the mechanism of cryoprotective effects of 3-hydroxybutyrate, the monomer of the most common of PHA, poly(3-hydroxybutyrate). Hence, we constructed an equilibrium and non-equilibrium phase diagram of the 3HB-water system to prove that 3HB is a very effective cryoprotectant. This fundamental understanding of the protective properties of PHA monomers could be also used in the food industry or cryopreservation of biological samples.