Production of DAPG and HCN by Pseudomonas sp. LBUM300 contributes to the biological control of bacterial canker of tomato

Bacterial canker caused by Clavibacter michiganensis subsp. michiganensis is known to cause significant economic losses to tomato production worldwide. Biological control has been proposed as an alternative to current chemical containment methods, which are often inefficient and may leave adverse effects on the environment. However, only little headway has so far been made in developing biocontrol strategies against C. michiganensis subsp. michiganensis. To address this knowledge gap, we investigated the antagonistic capacity of PCA, produced by Pseudomonas sp. LBUM223, and DAPG and HCN, both produced by Pseudomonas sp. LBUM300, on C. michiganensis subsp. michiganensis under in vitro and in planta conditions. Nonsynthesizing isogenic mutants of the producer strains were also developed to further dissect the role of each individual metabolite on C. michiganensis subsp. michiganensis biological control. Novel specific quantitative polymerase chain reaction TaqMan assays allowed quantification of C. michiganensis subsp. michiganensis in tomato plants and rhizospheric soil. Pseudomonas spp. LBUM223 and LBUM300 significantly repressed C. michiganensis subsp. michiganensis growth in vitro, while their respective nonproducing mutants showed less or no significant antagonistic activity. In planta, only Pseudomonas sp. LBUM300 was capable of significantly reducing disease development and C. michiganensis subsp. michiganensis rhizospheric population, suggesting that the production of both DAPG and HCN was involved. In summary, simultaneous DAPG/HCN production by Pseudomonas sp. LBUM300 shows great potential for controlling bacterial canker of tomato.     

Woody species composition,diversity and structure of riparian forests of four watercourses types in Burkina Faso

Riparian forests are classified as endangered ecosystems in general,particularly in sahelian countries like Burkina Faso because of human-induced alterations and civil engineering works.The modification of this important habitat is continuing,with little attention being paid to the ecological or human consequences of these changes.The objective of this study is to describe the variation of woody species diversity and dynamic in riparian forests on different type of watercourse banks along phytogeographical gradient in Burkina Faso.All woody species were systematically measured in 90 sample plots with sides of 50 m × 20 m.Density,dominance,frequency and species and family importance values were computed to characterize the species composition.Different diver-sity indices were calculated to examine the heterogeneity of riparian forests.A total of 196 species representing 139 genera and 51 families were recorded in the overall riparian forests.The species richness of individuals with dbh ≥ 5cm increased significantly from the North to the South along the phytogeographical gradient and varied significantly between the different types of riparian forests.Similarity in tree species composition between riparian forests was low,which indicates high beta diversity and reflects differences in habitat conditions and topography.The structural characteristics varied significantly along the phyto-geographical gradient and between the different types of riparian forests.The diameter class distribution of trees in all riparian forests showed a reverse "J" shaped curve except riparian forest of stream indicating vegetation dominated by juvenile individuals.Considering the ecological importance of riparian forest,there is a need to delineate and classify them along watercourses throughout the country.     

Learning performances of honeybees (Apis mellifera L) are differentially affected by imidacloprid according to the season

To establish the sublethal concentrations domain, acute and chronic oral tests were conducted on caged honeybee workers (Apis mellifera L) using imidacloprid and a metabolite, 5-OH-imidacloprid, under laboratory conditions. The latter showed a 48-h oral LD50 value (153 ng per bee) five times higher than that of imidacloprid (30 ng per bee). Chronic feeding tests indicated that the lowest observed effect concentrations (LOEC) of imidacloprid and of 5-OH-imidacloprid on mortality of winter bees were 24 and 120 microg kg(-1) respectively. Behavioural effects of imidacloprid and 5-OH-imidacloprid were studied using the olfactory conditioning of proboscis extension response at two periods of the year. Winter bees surviving chronic treatment with imidacloprid and 5-OH-imidacloprid had reduced learning performances. The LOEC of imidacloprid was lower in summer bees (12 microg kg(-1)) than in winter bees (48 microg kg(-1)), which points to a greater sensitivity of honeybees behaviour in summer bees, compared to winter bees.     

Use of space by bank voles (Clethrionomys glareolus) in a polish farm landscape

Movements of bank voles (Clethrionomys glareolus) were studied in a farmland mosaic in Poland. Distances crossed by animals in short-time periods are significantly longer in heterogenous than in homogenous habitats. In long-time and large-spatial scales, a significant portion of the animals in a population travel among habitat elements of the mosaic, reducing the degree of isolation of patch populations and decreasing the probability of local extinction.     

Cinosulfuron: chemical and biological degradability, adsorption and dissipation in flooded paddy field sediment

Cinosulfuron is a sulfonylurea herbicide largely used in the extensive cultures of flooded rice in North Italy. The degradation of cinosulfuron has been investigated in sterile aqueous solutions at 30 degrees C at different pH values. It was rapidly degraded at acidic pH (half-lives 3, 9 and 43 days at pH 4, 5 and 6, respectively) while the half-life was > 1 year at pH 7 and 9. Two degradation products formed by cleavage of the sulfonylurea bridge were identified by LC-MS. Degradation by selected mixed microbial cultures tested in aerobic and anaerobic conditions was very slow and attributable to chemical hydrolysis due to the acidic pH of the cultural broths. Degradation took place in freshly collected rice field water treated for two years with cinosulfuron but, in this case also, chemical hydrolysis prevailed over microbial degradation. In contrast, in flooded sediment simulating the paddy field environment, the dissipation rate of cinosulfuron was higher than expected from chemical hydrolysis according to the pH of the system, indicating the involvement of soil microflora. Although the herbicide exhibited a reduced affinity for the sediment surfaces demonstrated by the low value of the K(f) Freundlich coefficient (0.87 on a micromolar basis), the rapid dissipation observed in the simulated paddy field should prevent its leaching to ground water.     

Evaluation of Natural Chemical Compounds Against Root-lesion and Root-knot Nematodes and Side-effects on the Infectivity of Arbuscular Mycorrhizal Fungi

The survival of two species of plant parasitic nematodes: the root-lesion nematode Pratylenchus brachyurus, and the root-knot nematode Meloidogyne javanica, was evaluated in saturated atmospheres of 12 natural chemical compounds. The infectivity of two isolates of arbuscular mycorrhizal fungi: Glomus mosseae and Glomus intraradices, under identical experimental conditions, was also determined. All the compounds tested exerted a highly significant control against M. javanica and among them, benzaldehyde, salicilaldehyde, borneol, p-anisaldehyde and cinnamaldehyde caused a mortality rate above 50% over P. brachyurus. The infectivity of G. intraradices was inhibited by cinnamaldehyde, salicilaldehyde, thymol, carvacrol, p-anisaldehyde, and benzaldehyde, while only cinnamaldehyde and thymol significantly inhibited mycorrhizal colonization by G. mosseae.     

The canine veterinary medicine in the Middle Ages according to the Livre de chasse by Gaston Phoebus

Gaston Phoebus (1331-1391) of Foix-Béarn was a mighty vassal of the king of France as well as of the king of England. His book, the Livre de Chasse was the first technical treaty of this scope. It was fundamental for the regulation of hunting in Europe, as it was copied and plagiarized later on by a number of authors. Chapter 16 is about diseases of the dog and their treatment. In this article Phoebus views about pathology, etiology and therapy are discussed. The absence of superstition, magic and preconceived notions is remarkable. His writings are based on personal observations which are detailed. His therapy is generally rational and probably often effective, never harmful. His love of hounds is evident. It is regrettable that this highly rational approach didn't have a longer lasting effect on the development of canine medicine.     

Effects of nutrient supply and dietary bulk on O2 uptake and nutrient net fluxes across rumen,mesenteric- and portal-drained viscera in ewes

We assessed the effects of nutrient supply and dietary bulk, both increasing with hay intake, on O2 uptake and nutrient net fluxes across the portal-(PDV) and mesenteric- (MDV) drained viscera, and the rumen in adult ewes. Four ewes, fitted with a ruminal cannula, with catheters in the mesenteric artery, the portal, mesenteric and right ruminal veins, and with a blood flow probe around the right ruminal artery, were used in a 4 x 4 Latin square design. Treatments consisted of 500 g DM/d hay (LL, low bulk and low nutrient supply), 500 g DM/d hay + infused nutrients (LH, low bulk and high nutrient supply), 750 g DM/d hay + infused nutrients (MH, medium bulk and high nutrient supply), and 1,000 g DM/d hay (HH, high bulk and high nutrient supply). Infused nutrients consisted of volatile fatty acids (VFA) and casein dissolved in salts and infused continuously in the rumen to provide the same amount of metabolizable energy (7.6 MJ/d) and digestible protein (63 g/d) for LH, MH, and HH. Both increases in bulk and nutrient supply increased O2 uptake in the MDV and PDV. Dietary bulk stimulated mainly blood flow, whereas nutrient supply stimulated mainly O2 extraction rate. The O2 uptake by the rumen was not significantly affected by hay intake, although blood flow increased due to nutrient supply. Increase in hay intake had no effects on portal net release of lactate and net uptake of glucose but increased VFA, 3-D-hydroxybutyrate, ammonia, and amino acids (AA) net release and urea net uptake across PDV. The increase in portal nutrient net fluxes with hay intake was entirely related to the increase of nutrient supply for VFA, 3-D-hydroxybutyrate, ammonia, and urea, irrespective of the amount of casein infused for AA. Dietary bulk had no effect on total energy net release in the portal vein. We conclude that despite the increase in portal O2 uptake, increasing dietary bulk had no significant impact on portal recovery of energy. In ruminal tissues, which were the main site of energy absorption, O2 uptake appeared low and was not sensitive to dietary manipulation. In contrast, in mesenteric tissues, which contribute poorly to energy absorption with forage diets, O2 uptake appeared high and very sensitive to dietary manipulation.