Colonization and infestation ability of Bolboschoenus maritimus Palla in rice paddies of the Camargue,France

Bolboschoenus maritimus is one of the major weed constraints for irrigated rice‐cropping systems in the Camargue, France. This perennial plant propagates mainly through the production of numerous tubers. Observations in both controlled conditions and on‐field studies were used to enhance the level of knowledge of the biology, functioning and infestation dynamics of B. maritimus, with a view to rationalize weed control practices. It was found that B. maritimus displayed a great potential to produce a large number of shoots, rhizomes and tubers. Its propagation in the field plots depended on the initial weed density and its spatial colonization did not show any preferred direction (isotropic). Further observations that were made in the paddy fields showed an interaction between the different cultural practices that were tested and the infestation dynamics of B. maritimus. Efficient control of B. maritimus infestation in the field should make use of the data reported here, based on three levels: (i) prevention of weed stem proliferation during the cropping season with specific herbicides; (ii) elimination of the tubers after the rice crop; and (iii) reduction of the tuber‐germinating ability.     

Urban plant species patterns are highly driven by density and function of built-up areas

This paper aims to assess the relative importance of the type of built-up area in structuring plant species composition and richness in urbanised environments. The study was carried out in the city of Brussels where all vascular plant species were recorded in 189 grid cells of 1 km² each. The effect of urban land use type on species composition was investigated using first Canonical Correspondence Analysis. Densely built-up area was the most powerful predictor for species composition, followed by industrial built-up areas, half open or open built-up areas with plantations, and open built-up areas with much natural vegetation in the surroundings. Indicator species were found for each type of built-up area and a response curve to the amount of built land was produced using Generalised Additive Modelling. Various types of built-up areas had different effects on environmental conditions as inferred by Ellenberg’s indicator values, as well as on the species richness, species rarity, number of exotic species and proportion of extinction-prone species. It is concluded that future ecological studies should not treat urban areas as homogeneous areas by combining all anthropogenic factors into one aggregated variable. Instead, the urban matrix should be categorised in subsystems as it is multidimensional and highly variable across space.     

Extracts enriched in different polyphenolic families normalize increased cardiac NADPH oxidase expression while having differential effects on insulin resistance, hypertension, and cardiac hypertrophy in high-fructose-fed rats

Insulin resistance and oxidative stress act synergistically in the development of cardiovascular complications. The present study compared the efficacy of three polyphenolic extracts in their capacity to prevent hypertension, cardiac hypertrophy, increased production of reactive oxygen species (ROS) by the aorta or the heart, and increased expression of cardiac NAD(P)H oxidase in a model of insulin resistance. Rats were fed a 60%-enriched fructose food and were treated once a day (gavage) for 6 weeks with 10 mL/kg of water only (F group) or the same amount of solution containing a red grape skin polyphenolic extract enriched in anthocyanins (ANT), a grape seed extract enriched in procyanidins and rich in galloylated procyanidins (PRO), or the commercial preparation Vitaflavan (VIT), rich in catechin oligomers. All treatments were administered at the same dose of 21 mg/kg of polyphenols. Our data indicate that (a) the ANT treatment prevented hypertension, cardiac hypertrophy, and production of ROS, (b) the PRO treatment prevented insulin resistance, hypertriglyceridemia, and overproduction of ROS but had only minor effects on hypertension or hypertrophy, while (c) Vitaflavan prevented hypertension, cardiac hypertrophy, and overproduction of ROS. All polyphenolic treatments prevented the increased expression of the p91phox NADPH oxidase subunit. In summary, our study suggest that (a) the pathogeny of cardiac hypertrophy in the fructose-fed rat disease involves both hypertension and hyperproduction of ROS, (b) polyphenolic extracts enriched in different types of polyphenols possess differential effects on insulin resistance, hypertension, and cardiac hypertrophy, and (c) polyphenols modulate the expression of NAD(P)H oxidase.     

External Phosphorus Load Estimates and P-Budget for the Hydroelectric Reservoir of Bort-les-Orgues,France

This paper presents two methods used to estimate the externalphosphorus load for the hydroelectric reservoir ofBort-Les-Orgues (in France's `Massif Central' region). The Pload calculated from export coefficients (150 t yr^-1) agreedwith field measurements taken during a one-year survey carriedout from March 1996 to February 1997 (121 t yr^-1). Exportcoefficients represent a good option for estimating phosphorusloads of other reservoirs in the region of Bort-Les-Orgues,provided that they display similar characteristics. Theseexternal load estimates are greater than the maximum permissibleload for a mesotrophic lake calculated from the OECD equations(40 t yr^-1); thus, a yearly reduction of about 60 t shouldideally be achieved. This target, however, is probably tooambitious, and measures to reduce both point and non-pointsources must be implemented for the reservoir to tbe mesotrophic.Moreover, Bort-Les-Orgues is a tourist area. As such, thepresence of algal blooms (a regular occurrence on the lake) dueto an excess of P in the lake's water inflow could actuallyexert a negative impact on regional economy.     

Topography and crop management are key factors for the development of american leaf spot epidemics on coffee in costa rica

ABSTRACT We monitored the development of American leaf spot of coffee, a disease caused by the gemmiferous fungus Mycena citricolor, in 57 plots in Costa Rica for 1 or 2 years in order to gain a clearer understanding of conditions conducive to the disease and improve its control. During the investigation, characteristics of the coffee trees, crop management, and the environment were recorded. For the analyses, we used partial least-squares regression via the spline functions (PLSS), which is a nonlinear extension to partial least-squares regression (PLS). The fungus developed well in areas located between approximately 1,100 and 1,550 m above sea level. Slopes were conducive to its development, but eastern-facing slopes were less affected than the others, probably because they were more exposed to sunlight, especially in the rainy season. The distance between planting rows, the shade percentage, coffee tree height, the type of shade, and the pruning system explained disease intensity due to their effects on coffee tree shading and, possibly, on the humidity conditions in the plot. Forest trees and fruit trees intercropped with coffee provided particularly propitious conditions. Apparently, fertilization was unfavorable for the disease, probably due to dilution phenomena associated with faster coffee tree growth. Finally, series of wet spells interspersed with dry spells, which were frequent in the middle of the rainy season, were critical for the disease, probably because they affected the production and release of gemmae and their viability. These results could be used to draw up a map of epidemic risks taking topographical factors into account. To reduce those risks and improve chemical control, our results suggested that farmers should space planting rows further apart, maintain light shading in the plantation, and prune their coffee trees.     

Clove-transmissibility of <Emphasis Type="Italic">Pseudomonas salomonii</Emphasis>, the causal agent of ‘Café au lait’ disease of garlic

Bacterial blight of garlic, caused by Pseudomonas salomonii, results in leaf and sheath necrosis and sometimes leads to soft rot and plant death. The epidemiology of this bacterial disease, known as ‘Café au lait’ disease, is poorly understood and no resistant cultivars are currently available. To develop control strategies for this disease, we investigated principal sources of inoculum. The pathogen was isolated from bulbs from plants with typical vegetative symptoms of bacterial blight. Subsequent development of typical foliar symptoms on plantlets originating from symptomatic bulbs demonstrated transmission of the pathogen in the planting material. In one of three field experiments the contamination rate of planting stock influenced the disease incidence in field-grown garlic. The importance of planting stock as a source of inoculum was demonstrated here and should be evaluated relative to other potential sources such as crop debris, soil or alternate hosts in order to develop successful control strategies.     

Expression of defence genes in stolbur phytoplasma infected tomatoes,and effect of defence stimulators on disease development

In tomato, the stolbur disease caused by ‘Candidatus Phytoplasma solani’ alters developmental processes resulting in malformations of both vegetative and reproductive organs, two stolbur phytoplasma strains PO and C induce mutually distinct symptoms. The aim of the present study was to determine the effect of stolbur phytoplasma-infection on the Salicylic (SA) and Jasmonic (JA) acids hormone signalling pathways and to assess whether pre-activation of these defence pathways could protect tomato against the stolbur disease development. Expression of SA- and JA-dependent marker genes was studied in tomato by qRT-PCR. Results indicated that the SA-mediated defence response was activated by the stolbur phytoplasma strains PO and C in contrast to the JA-dependent defence pathway which was repressed by strain PO but activated by strain C. The two stolbur strains, PO and C, generated different responses, suggesting that the two strains might have distinct virulence factors, in agreement with the fact that they induce distinctive symptoms. In stolbur PO-infected tomato, pre-activation of the JA-dependent defence pathway by methyl jasmonate (MeJA) before infection had no effect on the disease development whereas pre-activation of the SA-dependent defence pathway by treatment with benzothiadiazole (BTH) prior to graft-inoculation of the phytoplasma resulted in a minor delay in phytoplasma multiplication and symptom production. As grafting implicates a high inoculum as compared to insect inoculation, it would be of interest to test BTH treatment in natural conditions.     

Analytical discrimination of poisonous and nonpoisonous chemotypes of giant fennel (Ferula communis L.) through their biologically active and volatile fractions

Giant fennel (Ferula communis L.) from Sardinia is characterized by two chemotypes with different biological activities. One chemotype is poisonous, due to prenylcoumarins, and responsible for ferulosis, which mainly affects sheep and goats, cattle, and horses; the other chemotype is nonpoisonous and contains daucane esters. The two chemotypes cannot be distinguished botanically. High-performance liquid chromatography-diode array-ultraviolet detection-mass spectrometry (HPLC-DAD-UV-MS) analysis of the composition of the fractions containing the biologically active metabolites and of the volatile fractions, by gas chromatography-mass spectrometry (GC-MS), of both essential oil and headspace sampled by headspace solid-phase microextraction (HS-SPME) are here shown to be effective in discriminating the poisonous and nonpoisonous chemotypes. HS-SPME with CAR/PDMS/DVB in combination with GC-MS has also been found to be a successful, fully automated one-step method for rapid and unequivocal discrimination of the two chemotypes, using aristolene and allohedycaryol as markers of the poisonous and nonpoisonous chemotypes, respectively.