Genetic variation of <Emphasis Type="Italic">Phoma sorghina</Emphasis> isolates from Southern Africa and Texas

Genetic variability of Phoma sorghina, a ubiquitous facultative phytopathogen, was investigated on 41 isolates cultivated from surface-sterilized sorghum grains originating from South Africa and Texas; pearl millet isolates from Namibia were also included. Most of the isolates from Texas produced intense red pigments, especially on Czapek-Dox agar plates. Many African isolates formed conspicuous dark radial substrate hyphae with intercalated chlamydospores on oatmeal plates. Conidial dimensions and shape were very variable (mean lengths 4.5–5.7 μm). Haplotypes were defined based on 53 markers from banding patterns obtained with rep-PCR (primers: M13core, ERIC IR). The shared geographic origin was partially reflected in the clades of the haplotype phylogram. The values of G _ST were intermediate; 16–37 % of the variation was found between the populations. Nm values of gene flow were 0.84–1.15. Average gene diversity H _E was moderate (0.256). Sequences of ITS-rDNA were obtained from 21 isolates. Allele 1 was found in 9 isolates scattered throughout the clades, allele 2 occurred in 6 isolates (5 of them from the same clade), alleles 3 and 4 were shared by two isolates each and two isolates were unique. Alleles 1 and 2 were also found among highly related sequences from GenBank. All shared an 8-bp deletion near the 5′ end of ITS2 that was not found in any other Phoma/Didymella species and which may be a typical marker for P. sorghina. Among related species, members of legume-associated Ascochyta/Didymella complex, Epicoccum spp., D. applanata and P. glomerata were found.     

The influence of 2,4-dichlorophenoxyacetic acid on cell cycle Kinetics and Sister-Chromatid Exchange Frequency in Garlic (Allium sativum L.) Meristem Cells

The effect of 2,4-dichlorophenoxyacetic acid (2,4-D) at low concentrations on cell cycle duration and sister-chromatid exchange (SCE) frequency was studied using meristem root-tip cells ofAllium sativum L. 2,4-D induced a marked prolongation of the cell cycle. At the same time, small but statistically significant increases in SCE frequencies were observed at 5 μM and 15 μM 2,4-D concentrations. The significance of these findings in the evaluation of mutagenic activity of 2,4-D is discussed.     

Ecological factors of flowering and pollen quality in three willow species

During 1977 to 1980 the course of flowering and pollen quality were investigated inSalix cinerea, S. fragilis, andS. pentandra, the dominant woody species in a wetland area called “Mokré louky” near T?eboň, South Bohemia, Czechoslovakia. Results were compared with basíc climatological data, and decisive factors of flowering were estimated. BothS. cinerea andS. pentandra produced morphologically well developed pollen with a high degree of viability. Comparison in twelve habitats showed that the pollen ofS. fragilis was very sensitive to climatic factors, and that the marsh habitat “Mokré Louky” was hostile to the generative reproduction of this species. Optimal conditions for pollen germination in vitro were defined for all the three willows.     

Reconstructing dry and wet summers in SE Slovenia from oak tree-ring series

We present a reconstruction of the June weather conditions in SE Slovenia from 1497 to 2003 based on the De Martonne aridity index (AI). The AI were derived from oak (Quercus spp.) tree-ring series of living trees and historic wood, which exhibited a clear response to June precipitation (positive) and temperature (negative). In the reconstructed AI time series we classified negative and positive deviations from the mean as strong (+/-1.28 SD) or extreme (+/-1.645 SD), and thus identified 50 years with a likely dry and hot June, as well as 40 years with a likely wet and cool June. Historical sources and chronicles were used to validate the AI reconstruction in the pre-instrumental period before 1896. The years 1501, 1540, 1546, 1616, 1718, 1788, 1822, 1834, 1839 and 1841, with extreme or strong negative AI deviations, are mentioned in Slovenian chronicles because of crop failures, droughts or extremely hot summers. The years 1691, 1705, 1798, 1799 and 1847, with extreme or strong positive AI deviations, are mentioned as years with a cool and rainy summer. We discuss the relevance of June weather conditions for the growth of plants in the region between the Alps, the Mediterranean and the continental Pannonian lowland, and the possible changes due to the current climate change scenario.     

Selenium enhances the antimutagenic activity of probiotic bacterium Enterococcus faecium M-74

The antibacterial activity of the probiotic bacterium Enterococcus faecium M-74 was assessed on De Man–Rogosa–Sharpe (MRS), Todd–Hewitt (T–H), M17 (M-17) and brain heart infusion (BHI) media with sodium selenite pentahydrate (+Se) and without sodium selenite pentahydrate (–Se) under aerobic or anaerobic conditions against nine bacterial pathogens. The highest antibacterial activity was found to be in the MRS medium under anaerobic conditions. There were no differences in the antibacterial activity between MRS(+Se) and MRS(–Se) media. The antimutagenic activity of MRS(+Se) and MRS(–Se) extracts after culture with E. faecium M-74 as well as of live and killed cells of E. faecium M-74 grown in the presence or absence of Se against the genotoxicity of ofloxacin (OFL) and acridine orange (AO) was determined in the Euglena gracilis assay. The MRS(+Se) extracts showed a significantly higher activity in reducing the genotoxicity of OFL and AO than MRS(–Se) extracts. The live cells of the probiotic strain M-74 exhibited higher antimutagenic activity than the killed bacterial cells, but differed depending on the mutagen used. However, the live bacterial cells grown in the presence of Se showed significantly higher antimutagenic activity. These results suggest a potential benefit for the future development of new Se-enriched probiotics exhibiting higher antimutagenic properties.     

Expression of nestin,desmin and vimentin in intact and regenerating muscle spindles of rat hind limb skeletal muscles

We describe the expression and distribution patterns of nestin, desmin and vimentin in intact and regenerating muscle spindles of the rat hind limb skeletal muscles. Regeneration was induced by intramuscular isotransplantation of extensor digitorum longus (EDL) or soleus muscles from 15-day-old rats into the EDL muscle of adult female inbred Lewis rats. The host muscles with grafts were excised after 7-, 16-, 21- and 29-day survival and immunohistochemically stained. Nestin expression in intact spindles in host muscles was restricted to Schwann cells of sensory and motor nerves. In transplanted muscles, however, nestin expression was also found in regenerating “spindle fibers”, 7 and 16 days after grafting. From the 21st day onwards, the regenerated spindle fibers were devoid of nestin immunoreactivity. Desmin was detected in spindle fibers at all developmental stages in regenerating as well as in intact spindles. Vimentin was expressed in cells of the outer and inner capsules of all muscle spindles and in newly formed myoblasts and myotubes of regenerating spindles 7 days after grafting. Our results show that the expression pattern of these intermediate filaments in regenerating spindle fibers corresponds to that found in regenerating extrafusal fibers, which supports our earlier suggestion that they resemble small-diameter extrafusal fibers.     

New approach in studies of microalgal cell lysis

A new approach to the studies of the microalgal cell lysis by utilizing a combination of two complementary methods is presented. Delayed fluorescence (DF) is a measure of the living algal biomass, detecting only cells with active photosynthesis. Thermal lens spectrometry (TLS) detects the total pigment amount released from lysed cells. Both methods select for photosynthetic organisms, reducing possible background from other sources (e.g. heterotrophic bacteria, zooplankton, and abiotic substances). The DF/TLS method was tested with a laboratory Skeletonema costatum culture exposed to a geometric dilution series of the lysing factor poly- APS. The exposure resulted in similar EC₅0 values for DF intensity, TLS and dissolved esterase activity of 0.8±0.2, 1.77±0.35, and 1.25±0.1 mg poly-APS l⁻¹, respectively. The combined DF/TLS method enabled a rapid evaluation of the living vs. dead cells without any sample pretreatment or manipulation.     

Do young on‐grown eels,Anguilla anguilla (Linnaeus, 1758), outperform glass eels after transition to a natural prey diet?

Survival rates among European eels, Anguilla anguilla (Linnaeus, 1758), on‐grown using a formulated diet in a commercial aquaculture facility, were compared with glass eels from the same cohort following their transition to a natural prey diet in the laboratory. Treatments included zero, 42‐day, and 196‐day periods of grow‐out prior to 30‐day experimental periods when eels were fed Chironomus spp. larvae (10 tanks, each containing 240‐L water and 40 glass or 10 on‐growing eels; 12:12 hr photoperiod; water temperature 18°C). All glass eels survived, compared to 87% (42‐day) and 99% (196‐day) for on‐grown eels. Although the eels on‐grown for 196 days had a high survival rate, they did lose weight. Farm‐reared eels may have accumulated sufficient resources over the 196‐days to survive the first 30 days after weaning from a formulated diet, but not for an additional 30 days (84% survival). Lack of superior survival rates among on‐grown eels challenges the presumed benefits of releasing on‐grown eels for population restoration.     

Abortive embryogenesis in hybrid swarm populations of <Emphasis Type="Italic">Pinus sylvestris</Emphasis> L. and <Emphasis Type="Italic">Pinus muga</Emphasis> Turra

Comparative study on fertilization process in Pinus sylvestris, Pinus mugo and in their putative hybrid swarm individuals was done involving pre-zygotic and post-zygotic stages. The amount of surviving ovules from open pollination reflecting the mode of interaction between pollen grains and nucellar tissue of an ovule averaged at 8.1 of sound ovules per conelet in Pinus sylvestris, 7.3 ovules in the hybrid swarm population and at 4.9 ovules in Pinus mugo. A strong correlation was observed between the number of surviving ovules and the proportion of germinating seeds in the compared species and hybrids. Normal course of embryogenesis in Pinus sylvestris and Pinus mugo contrasted with increased frequency of disturbances observed in the hybrid swarm individuals. The differential survival rates of the ovules and deviations from typical pattern of embryogenesis are discussed from the standpoint of cross-ability relationship between Pinus sylvestris and Pinus mugo.