HPLC determination of fenoxaprop and fenoxaprop-ethyl in different soils

This paper describes a method for the determination of fenoxaprop ethyl and fenoxaprop residues in four soil types using two extraction procedures: extraction with 0.1 M hydrochloric acid/methanol, partitioning with dichloromethane and extraction with ethyl acetate. The extracts were purified on florisil or alumina cartridge. The analyses were performed by reverse phase HPLC with UV detection at 280 nm. The best results in terms of recovery, clean-up efficiency and independence of soil characteristics were obtained with the combination ethyl acetate extraction alumina clean-up. Under these conditions, the recoveries were higher than 70 % and the detection limit was 0.02 mg kg^?1 soil.     

重庆市农村居民点整理潜力评价探讨

以重庆市各区、县为农村居民点整理潜力评价单元,选用农村人均超标用地面积、新增耕地系数和农村居民点闲置等评价指标,采用特尔菲法确定评价指标的权重,最后以三个评价指标的综合总分值为依据,对重庆市农村居民点整理潜力进行等级划分,为全市确定农村居民点整理的重点区域、重点项目以及时序安排提供依据.     

Classical swine fever: the global situation

A historical and current perspective is given of classical swine fever and its impact on pig production in different regions of the world. Data were obtained from a variety of sources including returns to the Office International des Epizooties, official government reports, other published material and local information through personal contacts. The disease has been recognized for about 170 years and efforts to control it by official intervention began in the nineteenth century. Despite this it remains a lingering problem in many parts of the world where it has both, an economic impact on swine production and a constraining effect on trade due to the measures necessary to prevent spread.     

Effects of oral administration of metronidazole on small intestinal bacteria and nutrients of cats

OBJECTIVE: To determine effects of oral administration of metronidazole on the number and species of duodenal bacteria and selective nutrients of cats. ANIMALS: 6 healthy domestic shorthair cats. PROCEDURE: Undiluted duodenal fluid was obtained for quantitative and qualitative bacterial culture to determine species and number of bacteria in healthy cats. Blood samples were assayed for taurine, total protein, albumin, cobalamin, and folate concentrations. Cats then were given metronidazole (20 mg/kg of body weight, PO, q 12 h) for 1 month, after which bacterial cultures and serum assays of nutrients were repeated. Nine months after cessation of antibiotic treatment, duodenal bacteria were re-evaluated and serum was assayed for total protein, albumin, cobalamin, and folate concentrations. RESULTS: Oral administration of metronidazole caused a significant decrease in aerobic and anaerobic bacterial counts in the duodenum of healthy cats, accompanied by emergence of Streptococcus spp and Corynebacterium spp. Serum concentrations of cobalamin and albumin increased when duodenal bacterial counts were decreased, although changes in folate or taurine concentrations were not detected. Measured variables did not differ, when comparing results obtained before and 9 months after cessation of metronidazole. CONCLUSIONS AND CLINICAL RELEVANCE: Oral administration of metronidazole decreased the number of aerobic bacteria and altered indigenous flora in the small bowel of cats. Normal duodenal flora appeared to be stable, because species of bacteria were re-established by 9 months after cessation of metronidazole. Bacterial flora appeared to have an impact on nutrients, because albumin and cobalamin increased during antibiotic administration and returned to preadministration concentrations after cessation of the antimicrobial.     

<Emphasis Type="Italic">Verticillium</Emphasis> disease of <Emphasis Type="Italic">Agaricus bisporus</Emphasis>: variations in host contribution to total fungal DNA in relation to symptom heterogeneity

The pathogenic fungus Verticillium fungicola, responsible for dry bubble disease of the common mushroom Agaricus bisporus, causes various symptoms on its host, bubbles (undifferentiated spherical masses), bent and/or split stipes (blowout) and spotty caps. Host DNA quantification by real-time PCR was used to observed relationships between the type of symptom and the relative amount of A. bisporus and V. fungicola in diseased mushrooms. Verticillium fungicola is involved in bubble formation but does not appear to regulate its growth. Quantifications in bubbles and stipe-bubbles (morphology between bubble and sporophore with stipe blowout) showed that the pathogen has no effect on the growth of undifferentiated host hyphae but prevents morphological differentiation if not initiated and stops it when initiated hyphae are affected. Mushrooms with stipe blowout exhibiting both mature and abortive lamellae reveal that V. fungicola has a restricted area of action in host tissues. Despite their visual aspect, healthy looking parts of mushrooms showing spots or stipe blowout were actually contaminated. Discolouration and symptom development are two distinct events. The colour of the tissues was correlated to the percentage of A. bisporus DNA, suggesting that discolouration is not an efficient defensive mechanism, and occurs at the time V. fungicola developed enough to induce tissues necrosis.     

Contamination of bean seeds by <Emphasis Type="Italic">Xanthomonas axonopodis</Emphasis> pv. <Emphasis Type="Italic">phaseoli</Emphasis> associated with low bacterial densities in the phyllosphere under field and greenhouse conditions

Xanthomonas axonopodis pv. phaseoli and its variant fuscans are the causal agents of common bacterial blight of bean. Production of seeds is recommended in arid climates with the use of pathogen-free seeds. However, contamination of seeds still occurs in these seed production areas. To verify if low contamination levels of sown seeds could explain these field contaminations, we used seeds that were naturally contaminated with CFBP4834-R, a rifamycin-resistant X. axonopodis pv. phaseoli fuscous strain, to contaminate field plots at different rates. We also inoculated seeds to verify some parameters of plant colonization and seed transmission. In growth chambers, seedling contamination was always successful from seeds contaminated with CFBP4834-R having population sizes greater than 1 × 10³ CFU seed⁻¹ and were not successful below 1 × 10² CFU seed⁻¹. In the greenhouse, the efficiency of contamination of seeds was not significantly different between contaminated plants that had a low or a high CFBP4834-R population size and reached between 40% and 52% whatever the origin of the inoculum (aerial or seed-borne). In field experiments, under low relative humidity, plots with 0.1–0.003% contamination rates or plots sown with seeds that were inoculated with low CFBP4834-R population sizes (1 × 10² and 1 × 10⁴ CFU seed⁻¹) led to an asymptomatic colonization of bean during the entire growing season with low CFBP4834-R population sizes. Seeds were contaminated both in primary and secondary foci. The contamination of seeds without symptom expression during the growing season represents a risk for eventual disease outbreaks.     

Resistance of Pinus contorta to the European race of Gremmeniella abietina

Pinus contorta seedlings, together with Pinus resinosa and Pinus banksiana seedlings, were planted adjacent to 25‐year‐old red pine trees infected by the European (EU) race of Gremmeniella abietina. Resistance to this race was assessed over 5 years. All P. resinosa seedlings were dead after that period while 65% of P. contorta and 86% of P. banksiana seedlings appeared resistant to the disease. The tip blight that occurred on P. contorta was slightly longer than that observed on P. banksiana. In microscopy, one, two, or even more suberized boundaries were seen to be initiated near the surface of the shoot at the base of healthy needles where they extended downward in the direction of the vascular cambium. Suberized boundaries occasionally crossed the xylem and joined together in the pith region to form continuous barriers around necrotic tissues. However, in most cases, these suberized barriers were not continuous across the shoot and compartmentalization was then completed by other barriers mainly constituted of parenchyma cells and xylem tracheids that accumulated phenolic compounds. Meristematic‐like cells were observed adjacent to the necrophylactic periderm. Tissue regeneration, restoration of cambial activities and formation of traumatic resin canals also seemed to be associated with the defence system of P. contorta against the EU race of G. abietina.     

Regeneration strategies in a temperate hardwood floodplain forest of the Upper Rhine: sexual versus vegetative reproduction of woody species

The regeneration mechanisms of woody species in the hardwood floodplain forest of the Upper Rhine are not well known, although they are of primary importance for future forest development. To gain a better understanding of the balance between sexual and asexual regeneration strategies and to assess the role of the seed bank in regeneration, the similarities in species composition and abundance of four fundamental compartments involved in regeneration (the seed rain, the seed bank, the recruits and the canopy) were compared in three hardwood forest stands with different flooding conditions. The results show that the floristic composition of the recruits is very similar to that of the canopy, whereas the composition of the seed bank is very dissimilar to the latter and comprises very few hardwood species. However, some species such as Fraxinus excelsior, Carpinus betulus and Acer pseudoplatanus which are very rare in the seed bank release a high number of diaspores, and seedlings of these species germinate abundantly in the field in the year following seed release. Moreover, the germinating seeds originate from the litter layer and not from the soil itself. This shows that most woody species regenerating by seed in the hardwood Rhine forest build transient seed banks and that the role of persistent seed banks for regeneration is very limited. Furthermore, it appears that many woody species have developed strategies favouring vegetative propagation for their regeneration, particularly understorey species, such as Cornus sanguinea and Prunus padus. As vegetatively grown individuals better withstand prolonged inundation in their early life stages than seedlings, species relying on vegetative regeneration strategies might be advantaged by regular and prolonged flooding of the Rhine forest over species regenerating only by seeds.