AFLP fingerprinting of sesame (<Emphasis Type="Italic">Sesamum indicum</Emphasis> L.) cultivars: identification,genetic relationship and comparison of AFLP informativeness parameters

Amplified fragments length polymorphism (AFLP) was used to distinguish 20 cultivars of sesame (Sesamum indicum L.) and to elucidate the genetic relationship among these genotypes. The data were also used to estimate the usefulness of parameters currently used to assess the informativeness of molecular markers. A total of 339 markers were obtained using 8 primer combinations. Of the bands, 91% were polymorphic. Five primer combinations were able to distinguish all 20 cultivars used. None of the remaining three primer combinations could distinguish all accessions if used alone, but using all three combinations reduced the probability of a random match to 5 × 10⁻⁵. Polymorphic information content (PIC), resolving power (Rp) and marker index (MI) of each primer combination failed to correlate significantly with the number of genotypes resolved. Jaccard’s similarity coefficients ranged from 0.31 to 0.78. Fifteen cultivars were grouped by four UPGMA-clusters supported by bootstrapping values larger than 0.70. The grouping pattern was similar to the grouping generated by principal coordinate analysis. The results demonstrated that AFLP-based fingerprints can be used to identify unequivocally sesame genotypes, which is needed for cultivar identification and for the assessment of the genetic variability of breeding stocks. We recommend to use the number of cultivars identified by a primer combination instead of PIC, Rp and MI; and to calculate the maximal, instead of average probability of identical match by chance in the assessment of the informativeness of a marker for cultivar identification.     

The content of total mercury and methylmercury in common carp from selected Czech ponds

The aim of the present study was to investigate concentrations of total mercury (THg) and methylmercury (MeHG) in the common carp from Czech ponds of Rožmberk, Spolsky, Nezmar, and Velky Bědny. Seven common carps (Cyprinus caprio) from each of the ponds were caught. Muscle tissue, the liver, and the soft and hard roe were used for the tests. Total mercury and methylmercury were found in all the muscle tissue samples examined. Detection limits for total mercury and methylmercury determination methods were 0.001 mg kg^–1 and 0.013 mg kg⁻¹ respectively. Methylmercury levels in the liver and gonads were below the method’s limits of detection. THg and MeHg concentrations in muscle tissues were 0.018–0.063 mg kg^–1 w.w. and 0.019–0.063 mg kg^–1 w.w. respectively. MeHg made up 90–100% of THg in muscle tissues. Total mercury and methylmercury concentrations were significantly (P < 0.05) higher in fish from the Spolsky pond than from the Nezmar pond. MeHg/THg ratios were significantly (P < 0.05) higher in fish from the Rožmberk, Spolsky and Nezmar ponds compared with fish from the Velky Bědny pond.     

Stenotrophomonas maltophilia as a part of normal oral bacterial flora in captive snakes and its susceptibility to antibiotics

Only little is known about normal oral bacterial flora in captive snakes containing Stenotrophomonas maltophilia. This microbe has been reported as a causative agent of numerous infections in reptiles. Therefore, the goal of the study was to detect its presence in the mouths of a significant number of healthy captive snakes and determining its susceptibility to antibiotics at 30 and 37 degrees C. The isolates were obtained in 1999-2005 from mouth swabs of 115 snakes of 12 genera and 22 species-most often Elaphe guttata (24 individuals; 20.9%). Susceptibility to 24 antibiotics was tested by the microdilution method. The microbe was demonstrated in 34 (29.6%) individuals. Overall, 47 strains of S. maltophilia were acquired. Evaluation using PFGE profiles and antibiograms resulted in confirmation of one strain of S. maltophilia in 23 (20.0%) individuals, two strains in nine (7.8%) and three in two (1.8%) snakes. All tested antibiotics were more effective at 37 degrees C, with the partial exception of cotrimoxazole and cefoperazone/sulbactam. At a temperature of 37 degrees C, the lowest frequency of resistance to levofloxacin (no resistant strains), cotrimoxazole and ofloxacin (97.9% of susceptible strains) was recorded. At 30 degrees C, the most active agents were cotrimoxazole (97.9% of susceptible strains), levofloxacin (91.5%) and ofloxacin (85.1%). In conclusion, S. maltophilia is present in the mouths of about one third of healthy captive snakes, showing good susceptibility to cotrimoxazole, some fluoroquinolones and aminoglycosides. The antibiotics (particularly aminoglycosides) are more effective at 37 degrees C.     

Sand fly saliva: effects on host immune response and Leishmania transmission

The feeding success of sand flies (Diptera: Phlebotominae) is linked to the vast array of pharmacological substances in their saliva, which interferes with the host haemostasis and immune response. Modification of feeding site plays also an important role in Leishmania transmission. In naive hosts, co-inoculation of saliva and Leishmania parasites increases the chance of successful transmission. Disease exacerbation seems to be associated with enhanced production of type 2 cytokines and selective inhibition of some macrophage functions including the production of NO and H202. On the other hand, hosts repeatedly exposed to sand fly bites develop anti-saliva immune response that results in a protection against Leishmania infection. This led to a new interesting approach to anti-Leishmania vaccine--using salivary components to block parasite transmission. The review is therefore focused on the interactions that run between immunomodulatory molecules in sand fly saliva and host immune response, with the impact on Leishmania infection development. Recent studies revealed that saliva-based vaccine for leishmaniasis might be effective and feasible, however, several questions still require to be solved. The knowledge based on experimental mouse model cannot be fully extrapolated to dogs or humans and due to differences in salivary antigens between sand fly species the protective effect is species-specific. On the other hand, the specificity of salivary antigens enables the use of anti-saliva antibodies for monitoring the exposure of hosts to sand fly bites and might be used as a marker of risks for Leishmania transmission in endemic areas.     

Fenoxycarb,an insect growth regulator with juvenile hormone activity: A candidate for Heliothis virescens (F.) control on cotton

Tobacco budworm eggs, deposited on cotton plants (Gossypium hirsutum L.) treated with fenoxycarb, do not produce viable larvae. The insects die either at the end of embryonic development or during 1st-2nd larval instars, even when the larvae hatching on the treated leaves are transferred to untreated plants. This ovo-larvicidal activity and indications of good foliar persistence make fenoxycarb a promising candidate for the control of tobacco budworm on cotton. This type of application could open new aspects for the control of lepidopterous pests with this novel compound.     

Wheat genetic resources enhancement by the International Maize and Wheat Improvement Center (CIMMYT)

The International Maize and Wheat Improvement Center (CIMMYT) acts as a catalyst and leader in a global maize and wheat innovation network that serves the poor in the developing world. Drawing on strong science and effective partnerships, CIMMYT researchers create, share, and use knowledge and technology to increase food security, improve the productivity and profitability of farming systems and sustain natural resources. This people-centered mission does not ignore the fact that CIMMYT’s unique niche is as a genetic resources enhancement center for the developing world, as shown by this review article focusing on wheat. CIMMYT’s value proposition resides therefore in its use of crop genetic diversity: conserving it, studying it, adding value to it, and sharing it in enhanced form with clients worldwide. The main undertakings include: long-term safe conservation of world heritage of both crop resources for future generations, in line with formal agreements under the 2004 International Treaty on Plant Genetic Resources for Food and Agriculture, understanding the rich genetic diversity of two of the most important staples worldwide, exploiting the untapped value of crop genetic resources through discovery of specific, strategically-important traits required for current and future generations of target beneficiaries, and development of strategic germplasm through innovative genetic enhancement. Finally, the Center needs to ensure that its main products reach end-users and improve their livelihoods. In this regard, CIMMYT is the main international, public source of wheat seed-embedded technology to reduce vulnerability and alleviate poverty, helping farmers move from subsistence to income-generating production systems. Beyond a focus on higher grain yields and value-added germplasm, CIMMYT plays an “integrative” role in crop and natural resource management research, promoting the efficient use of water and other inputs, lower production costs, better management of biotic stresses, and enhanced system diversity and resilience.     

Enzyme activities and microbial biomass in topsoil layer during spontaneous succession in spoil heaps after brown coal mining

Changes in the activity of extracellular enzymes (cellobiohydrolase, β-glucosidase, β-xylosidase, chitinase, arylsulfatase and phosphatases) and the changes in microbial community and abiotic properties in the topsoil layer, as well as soil abiotic properties during primary succession were investigated in a brown coal mine deposit area near Sokolov, Czech Republic. The study considered the chronosequence of 4 post-mining plots, 4-, 12-, 21- and 45-year old. The 4-year old site had no vegetation cover. Herbs and grasses (mainly Calamagrostis epigeios) were present on the 12-year old plot, shrubs (Salix caprea) occurred on the 21-year old plot and tree cover (Betula spp. and Populus tremuloides) developed on the 45-year old plot. Soil pH gradually decreased with site age, while the content of P, K, C and N peaked in the 21-year old site, being significantly lower in the 45-year old site and much lower in the 4- and 12-year old sites. Phosphatase activities were strongly affected by seasonality while the activities of all the other enzymes measured were more influenced by the effects of succession age and soil layer than by seasonality. Succession age was also the most important factor affecting the total and bacterial PLFA contents, followed by the effects of soil layer and season while for the fungal biomass content-related properties (ergosterol, fungal PLFA and the fungal/bacterial PLFA ratio), season was the most important. Activities of individual enzymes in the topsoil (0–5 cm depth) were significantly affected by both site age and season. Cellobiohydrolase and β-xylosidase were more affected by site age while chitinase and phosphatases were more affected by season. Enzyme activity increased with succession age. Comparison of the effect of site and season on enzyme activity showed that season played a principal role in the enzyme activity of the entire 0–5 cm component of topsoil, as well the soil layers when evaluated separately.     

Effect of drought on yield variability of key crops in Czech Republic

The relationship between seasonal agricultural drought and detrended yields (within a period from 1961 to 2000) of selected crops was assessed in the conditions of the Czech Republic, which are to some extent representative of a wider area of Central Europe. Impact of water stress was analyzed using time series of yields for 8 crops (spring barley, winter wheat, grain maize, potato, winter rape, oats, winter rye and hay from permanent meadows) for 77 districts in the Czech Republic (average district area is 1025 km²). Relative version of Palmer’s Z-index (rZ-index or rZ-i) was used as a tool for quantification of agricultural drought. The monthly values of the rZ-index for each individual district were calculated as the spatial average (only for the grids of arable land). The study showed that severe droughts (e.g., in 1981 and 2000) are linked with significant reduction in yields of the main cereals and majority of other crops through the most drought prone regions. We found a statistically significant correlation (p ≤ 0.05) between the sum of the rZ-index for the main growing period of each crop and the yield departures of spring barley within 81% (winter wheat in 57%, maize in 48%, potato in 89%, oats in 79%, winter rye in 52%, rape in 39%, hay in 79%) of the analyzed districts. This study also defined the crop-specific thresholds under which a soil moisture deficit (expressed in terms of rZ-index) leads to severe impact at the district level. This can be expressed as the sum of the monthly rZ-index during the period of high crop sensitivity to drought; for spring barley it is ?5, winter wheat ?5, maize ?9, rape ?12, winter rye ?10, oat ?4, potato ?6 and for hay ?3. The length of the sensitive period is also crop-specific and includes the months that are important for the yield formation. The results show that yields of spring barley (and spring crops in general) are significantly more affected by seasonal water stress than yields of winter crops and hay from permanent meadows. The study proved that a severe drought spell during the sensitive period of vegetative season does have a quantifiable negative effect, even within more humid regions. These results demonstrate that, at least in some areas of the CR (and probably most of Central Europe), drought is one of the key causes of interannual yield variability.