Variation in chromosome numbers and nuclear DNA contents in genetic resources of Lactuca L. species (Asteraceae)

Fifty accessions of 25 Lactuca species,L. serriola ×L. sativa and Mycelismuralis were analyzed for chromosome number and relative DNA amountvariation. In the majority of Lactuca species studiedchromosome counts, as earlier reported (n = 8, 9, 17), were verified; however,for L. dregeana andL. homblei (probablyL. schweinfurthii orL. longespicata) the chromosome number(n = 9) was determined for the first time. Relative nuclear DNA content,estimated by using flow cytometry (DAPI staining), showed that 2C DNA contentranged from 2.02 pg in L.capensis to 17.96 pg inL. canadensis. Statistical and clusteranalysis of data based on relative nuclear DNA contents correspond fairly wellwith recently accepted taxonomic classification of the genusLactuca. However, the position of certain species as wellas clarification of taxonomic determinations of someLactuca accessions needs further examination.     

Proximate and fatty acid composition of 13 important freshwater fish species in central Europe

We aimed to investigate proximate and fatty acid composition of important freshwater fish species in the Czech Republic. Sampled fish include seven species from intensive farming: African catfish, rainbow trout, Wels catfish, Nile tilapia, brook trout, northern whitefish, and pikeperch; eight species from semi-intensive culture systems: common carp, northern pike, pikeperch, grass carp, European perch, tench, silver carp, and catfish; and three species from extensive culture systems: rainbow trout, tench, and common carp. The fat content and fatty acid composition were highly influenced by the culture systems. Simultaneously, we observed a significant dependence of fatty acid composition on the fat content. The content of saturated fatty acids was below 34% in all analyzed fish. Northern pike, pikeperch, and European perch contained with over 50% the highest proportion of polyunsaturated fatty acids. Intensively cultured fish reached the highest content of eicosapentaenoic and docosahexaenoic fatty acid. Nutritional quality was determined by atherogenic and thrombogenic indexes which ranged from 0.27 to 0.63 and 0.20 to 0.61 and by ratios n-3/n-6 (0.54–3.45) and polyunsaturated/saturated fatty acids (0.67–2.01). Results demonstrated that the flesh of all studied species are of high nutritional quality.     

Antimicrobial Activity of the Marine Alkaloids,Clathrodin and Oroidin,and Their Synthetic Analogues

Marine organisms produce secondary metabolites that may be valuable for the development of novel drug leads as such and can also provide structural scaffolds for the design and synthesis of novel bioactive compounds. The marine alkaloids, clathrodin and oroidin, which were originally isolated from sponges of the genus, Agelas, were prepared and evaluated for their antimicrobial activity against three bacterial strains (Enterococcus faecalis, Staphylococcus aureus and Escherichia coli) and one fungal strain (Candida albicans), and oroidin was found to possess promising Gram-positive antibacterial activity. Using oroidin as a scaffold, 34 new analogues were designed, prepared and screened for their antimicrobial properties. Of these compounds, 12 exhibited >80% inhibition of the growth of at least one microorganism at a concentration of 50 µM. The most active derivative was found to be 4-phenyl-2-aminoimidazole 6h, which exhibited MIC₉₀ (minimum inhibitory concentration) values of 12.5 µM against the Gram-positive bacteria and 50 µM against E. coli. The selectivity index between S. aureus and mammalian cells, which is important to consider in the evaluation of a compound’s potential as an antimicrobial lead, was found to be 2.9 for compound 6h.     

Structure and variation in the wild-plant pathosystem: <Emphasis Type="Italic">Lactuca serriola–Bremia lactucae</Emphasis>

Over the past decade, extensive research on the wild-plant pathosystem, Lactuca serriola (prickly lettuce)–Bremia lactucae (lettuce downy mildew), has been conducted in the Czech Republic. Studies focused on pathogen occurrence and distribution, host range, variation in symptom expression and disease severity, interactions of B. lactucae with another fungal species (Golovinomyces cichoracearum) on L. serriola, variation in resistance within natural populations of L. serriola, the structure and dynamics of virulence within populations of B. lactucae, sexual reproduction of B. lactucae, and a comparison of virulence structure and changes in B. lactucae populations occurring in wild (L. serriola) and crop (L. sativa) pathosystems. The incidence of B. lactucae on naturally growing L. serriola and other Asteraceae was recorded. Lactuca serriola was the most commonly occurring host species, followed by Sonchus oleraceus. Over the duration of these studies, the incidence of B. lactucae in L. serriola populations varied between 45–87%. Disease incidence and disease prevalence were partly related to the size, density and different habitats of L. serriola populations. In addition to B. lactucae infection, infection by the lettuce powdery mildew fungus (Golovinomyces cichoracearum) was quite common, including co-infection. Variation in resistance to B. lactucae was studied by using ten isolates (NL and BL races with known virulence patterns) at a metapopulation level, i.e. 250 L. serriola samples representing 16 populations from the Czech Republic (CZ). Our comparisons revealed broad variation in host resistance among host populations and also intrapopulation variability. In the CZ populations, 45 resistance phenotypes were recorded, the most frequent were race-specific reaction patterns. Structural and temporal changes in virulence variation of B. lactucae populations on L. serriola were studied during 1998–2005. Altogether, 313 isolates of B. lactucae originating from the Czech Republic were examined for the presence of 32 virulence factors (v-factors), and 93 different virulence phenotypes (v-phenotypes) were recorded. A study of v-factor frequency showed that common v-factors in B. lactucae populations match some of the race-specific resistance genes/factors (Dm genes or R-factors) originating from L. serriola. The highest frequency was recorded by v-factors v7, v11, v15–17, and v24–30. In contrast, v-factors (e.g. v1–4, 6, and 10) matching Dm genes originating from L. sativa were very rare. This demonstrates the close adaptation of B. lactucae virulence to the host (L. serriola) genetic background. Temporal changes in virulence frequencies over the period were recorded. In many v-factors (v11, v14, v16, and v25–28), fluctuations were observed, some (v14 and v17) shifting to higher frequencies, and others (v5/8 and v23) decreasing. The occurrence of mating types was studied (1997–1999) in a set of 59 B. lactucae isolates. Both compatibility types (B1 and B2) were recorded; however the majority of the isolates (96%) were type B2. A comparative study of B. lactucae virulence variation between the wild (L. serriola) and crop (L. sativa) pathosystems showed major differences. Migration and gene flow between both pathosystems and the potential danger of wild B. lactucae populations for cultivated lettuce are discussed. This paper summarizes comprehensive and unique research on an oomycete pathogen (B. lactucae) that is shared between a crop (lettuce, L. sativa) and its close wild relative (prickly lettuce, L. serriola). The data demonstrate clear evidence about race-specific interactions, variation and changes in virulence, and coevolutionary relationships in the wild pathosystem L. serriola–B. lactucae. Conclusions contribute to the broadening and better understanding of gene-for-gene systems in natural host–pathogen populations and their relationships to crop pathosystems.     

Characterisation of the curing of liquefied wood by rheometry, DEA and DSC

Liquefied wood is a naturally based product which has the potential to be used as an adhesive. The bonding of wood with liquefied wood requires a high enough temperature to cure the liquid polymers and achieve bond strength. Dielectric analysis, rheometry and differential scanning calorimetry were used to analyse the curing process of low solvent liquefied wood. For the liquefaction, ethylene glycol was used as a solvent and sulphuric acid was used as a catalyst. The dielectric analysis was used for in situ measurements of the curing of liquefied wood during the bonding of wood. It was found that curing started after a temperature of 100 °C had been reached in the bond. This is correlated with the water evaporation and the diffusion of water and ethylene glycol from the liquefied wood into the wood substrate. Rheological measurements proved the influence of the substrate on the curing of the liquefied wood during bonding. Differential scanning calorimetry showed that the curing of liquefied wood occurs in two parts: first, the initial elimination of water and ethylene glycol from the liquefied wood, and then the chemical reaction of the liquefied wood at higher temperatures.     

Influence of nitric oxide and reactive oxygen species on development of lettuce downy mildew in <Emphasis Type="Italic">Lactuca</Emphasis> spp.

The role of nitric oxide and reactive oxygen species, molecules indispensable for plant-pathogen signalling, was studied in the Lactuca spp.-Bremia lactucae pathosystem. Using a leaf disc model the translaminar effect of various compounds affecting their metabolism was studied by light microscopy. Time course studies revealed a slowdown in the development of B. lactucae (race BL16) infection structures by rutin (scavenger of reactive nitrogen and oxygen species) and SNP (NO donor) within 48 h post inoculation, followed by a retardation of sporulation. Application of the specific NO scavenger, PTIO, accelerated penetration of B. lactucae but had no further effects on the plant-pathogen interaction. Inhibitors of NO synthase (L-NAME) and nitrate reductase (sodium tungstate) did not influence pathogen development. Our results suggest that drastic change in the NO: hydrogen peroxide ratio seems to determine the pathogen’s fate. NO synthase-like activity significantly increased early after B. lactucae challenge in resistant L. virosa. Confocal laser scanning microscopy revealed the accumulation of nitric oxide in the penetrated cells, pointing to a role in the initiation of the hypersensitive reaction. The tips of germ tubes and appressoria of B. lactucae also accumulated NO, suggesting an essential role for this molecule in penetration of the biotrophic pathogen. Additionally, temporal changes in endogenous levels of rutin and quercetin in extracts from Lactuca spp. leaves will be discussed in connection to their role as part of the antioxidative machinery that influences the plants’ susceptibility/resistance to lettuce downy mildew.     

Automatic assessing and monitoring of weaving density

Image restoration using the spectral approach is applied to the problem of automatic assessing of weaving density. A restored image of one set of yarns is obtained with the aid of two dimensional discrete Fourier transform. From the line profile of restored images Fisher’s test of periodicity find out the significant periodical components of specific frequency and defines model of time series. On the basis of frequency of model, the weaving density can be computed automatically. This method is then used for detection of defects associated with the change of weaving density, i.e. the weft direction defects. The detection is based on monitoring of weaving density in direction of length of fabric. Change of weaving density value against expected value indicates failure of regular structure. Control charts were used as a tool for judge the existence of failure or defects of regular structure.     

Virulence variation of cucurbit powdery mildews in the Czech Republic – population approach

Kosman diversity models were applied to analyses of virulence (disease reaction patterns) variation of 115 isolates of two cucurbit powdery mildew (CPM) species, Golovinomyces orontii (Go) and Podosphaera xanthii (Px), collected in the Czech Republic from 2010 through 2012. Diversity within and distances between Go and Px populations and each other in a spatio-temporal context and with regard to original host plant species were analyzed based on virulence patterns of individual isolates on a set of 21 melon (Cucumis melo L.) race differential genotypes. Significant differentiation among the Go and Px pathogen populations was revealed, and the results clearly demonstrate and confirm that the set of differential C. melo genotypes is well composed because of high differentiation capacity. Differentiation of pathogens among years was significant for both species. No significant difference between Go isolates from different host plant species was established due to high variability among Go isolates, but there was significant host-specific differentiation among Px isolates. Differentiation of pathogens among regions was not detected. These results revealed high virulence variation in isolates of Go and Px, and their spatio-temporal fluctuations. High diversity in virulence of Go isolates supports the treatment of Go as a complex of different (sub)species with distinct virulence factors. Similar relationships of selected Go isolates in a UPGMA dendrogram in a previously reported multigene phylogenetic tree support the logic and suitability of the Kosman assignment based approach to population studies of organisms with asexual or mixed modes of reproduction. The approach applied in this study provides a complex view of virulence structures of powdery mildew populations, and when combined with race determination and denomination on melon, it may serve as a base to understandvirulence variation of these CPM species from a spatio-temporal viewpoint.     

Czech traditional agroforestry: historic accounts and current status

Agroforestry in the Czech Republic has vanished both from the landscape and public conscience. That raises questions about its history and fate; there are examples of this land use type from all neighbouring countries. The article looks at the record of such systems in a historical land tax survey, the Franciscan cadastre made in the Czech Republic in the mid nineteenth century. With this source, patterns of preindustrial-era subsistence systems were analysed in a considerable part of what is now the Czech Republic. Any correlation among occurrences of various land uses (including agroforestry cultures) and influences of chosen natural and cultural factors was statistically tested and further visualised by multivariate analysis. The main existing agroforestry types and their historical distribution were investigated. The results have shown that cropland with fruit trees, and meadows, and pastures with either fruit trees or wood use, were a common part of Czech countryside in the mid-nineteenth century. Some agroforestry plots were found in the 1689 total studied cadastral areas. The types of agroforestry and the overall subsistence patterns were attuned to elevation, soil fertility, population density, and the dominant language group of the inhabitants. Cropland and pastures with fruit trees were associated with more fertile inland lowlands with sound infrastructure and prevalently Czech inhabitants (so-called ‘old settlement’ areas), wood meadows and pastures with cadastral units located in border regions at higher elevations characterised by lower soil fertility, a greater ratio of coniferous forests and predominantly inhabited by Czech Germans. Traditional agroforestry, as is discussed, however, did not survive the industrialisation of agriculture.