Fungal biodegradation of a phenylurea herbicide,diuron : structure and toxicity of metabolites

Microbial degradation, organic synthesis and ecotoxicology were used to investigate the fate of diuron after spreading on soils. Quantitative biodegradation assays were performed with fungal strains, showing that diuron was degraded but not entirely mineralized. The modifications observed consisted in demethylation of the terminal nitrogen atom. The identified metabolites were synthesized in sufficient amounts to confirm their structures and determine their non‐target toxicity using four biotests. The two metabolites exhibited higher effects than parent diuron. This limited biodegradability and potential aquatic toxicity suggest that diuron is of higher environmental concern than previously recognized. © 2000 Society of Chemical Industry     

Is acetyl/butyrylcholine specificity a marker for insecticide‐resistance mutations in insect acetylcholinesterase?

Substrate specificity has been widely studied in vertebrate cholinesterases and it has been shown that two phenylalanines in the acyl pocket of acetylcholinesterase govern the acceptance of the acetyl/butyryl moiety of the choline esters. As an insecticide‐resistance mutation has been evidenced in the acyl pocket of Drosophila melanogaster and Musca domestica acetylcholinesterase we investigated the possibility of linking changes in acetyl/butyrylthiocholine specificity with mutations in insect acetylcholinesterase. We thus analyzed the effect of 28 mutations in Drosophila enzyme on acetyl/butyrylthiocholine, N‐methyl/N‐propyl‐carbamates and ethyl/methyl‐paraoxon preference. It appeared that the highest changes on acetyl/butyrylthiocholine and N‐propyl/N‐methyl‐carbamates preference were due to mutations in the acyl pocket. Nevertheless, other insecticide‐resistance mutations, not located in the acyl pocket, also modified these substrate preferences. Moreover, the effect of mutations in the acyl pocket was hidden when some other insecticide‐resistance mutations were combined in the enzyme. Consequently, acetyl/butyrylthiocholine preference alteration cannot be used as a marker to localize a mutation in the insect AChE. © 2000 Society of Chemical Industry     

Yield response of sugar beets to water stress under Western European conditions

The average yield of sugar beet has almost doubled within the last 30 years. With the raise in average yields and the increase in sensitivity to water stress of sugar beets, the yield response factor (Ky) derived by Doorenbos and Kassam (1979) needs an update. In this article, the soil water balance model BUDGET (Raes et al., 2006) was calibrated and validated to obtain correct estimations of the evapotranspiration deficit (1 − ETa/ETc, where ETa = actual crop evapotranspiration and ETc = maximum crop evapotranspiration under standard conditions) of sugar beets in two locations in France. Datasets of observed soil water contents of several years and different irrigation treatments were used. The simulated evapotranspiration deficits and observed yields were used to derive a seasonal Ky. The obtained linear and polynomial yield response relation between observed yield decline and evapotranspiration deficit showed a high goodness-of-fit. The coefficient of determination (R²) = 0.83, the Nash-Sutcliffe efficiency (EF) = 0.79, the relative root mean squared error (RRMSE) = 0.26 for linear; the coefficient of determination (R²) = 0.85, the Nash-Sutcliffe efficiency (EF) = 0.79, the relative root mean squared error (RRMSE) = 0.25 for polynomial). The results suggested a more pronounced response of sugar beet to water stress in Europe as compared to the values previously reported by Doorenbos and Kassam (1979). The comparison between the observed and simulated yields (with the updated Ky) for another site in France confirmed the findings.     

Macromolecular Features of Amaranth Starch

High-performance size-exclusion chromatography (HPSEC), static light scattering (SLS) and dynamic light scattering (DLS) techniques were used for the structural characterization of amaranth starch, solubilized in water by microwave heating in a high-pressure vessel. Apparent average molar mass (M _w) gyration radius (R _G), and hydrodynamic radius (R _H) values were obtained from Berry and Zimm treatment of light-scattering data. When heating time increased from 35 to 90 sec, the M _w, R _G, and R _H decreased, demonstrating a possible polymer degradation due to temperature. Apparent M _r values from HPSEC at 35 sec (27 ± 2 × 10⁷ g/mol) and 50 sec (20 ± 2 × 10⁷ g/mol) were lower than those determined by SLS (35 sec = 69 × 10⁷ g/mol, 50 sec = 56 × 10⁷ g/mol). However, at 70 and 90 sec, the inverse pattern was obtained. The fractal dimensions (d′_f) from HPSEC study for samples dissolved for 35 (3.26), 50 (3.24), and 70 sec (3.14) are characteristic of a particle that has the internal structure of hard sphere, and for samples dissolved for 90 sec (2.19), are characteristic of a fully swollen, randomly branched macromolecule. From SLS, d′_f decreased with increasing treatment time (d′_f = 2.44, 2.18, 1.50, and 1.03 for 35, 50, 70, and 90 sec, respectively). The particle-scattering factors and Kratky plots, well-suited for studying the internal structure of a macromolecule, showed a sample degradation when treatment time increased. Results from DLS showed bimodal distributions with differences in the peak locations when treatment time increased. The ratio of R _G to R _H (ρ) for samples analyzed were between 0.88 and 1.3; these values are characteristic of a sphere or globular structure.     

An unexpected host for the endangered giant freshwater pearl mussel Margaritifera auricularia (Spengler, 1793) as a conservation tool

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Synthesis and insecticidal evaluation of imidacloprid analogs

Imidacloprid analogues containing a nitroalkylidene instead of a nitroguanidine unit have been prepared and evaluated for investigation as potential insecticides. No nitroalkylidene analogue showed significant activity against the test insects. © 1998 Society of Chemical Industry     

Genetic variability of growth and wood chemical properties in a clonal population of Eucalyptus urophylla × Eucalyptus grandis in the Congo

Thirty-four Eucalyptus urophylla × Eucalyptus grandis hybrids were evaluated with a view to selecting for improved growth and wood-quality traits for plantations in the Congo. Height, circumference at breast height and volume were measured at 12, 27, 37, 49 and 60 months. Lignin content, the syringyl/guaiacyl ratio and total extractives content were predicted by near-infrared spectroscopy using wood powder samples collected from trees at breast height. While wood chemical properties were stable and under strong genetic control, growth traits were not. The genetic correlation between lignin content and growth was weak and negative, whereas the environmental correlation was also weak but positive. The genetic improvement of E. urophylla × E. grandis clones, based on growth features, leads to a limited decrease in lignin content and syringyl content and to a limited increase in extractives content.     

Special issue “Deepen knowledge in plant pathology for innovative agroecology”

This study aimed to determine the genetic variability of isolates of rotting of pineapple fruitlet core in Brazil on the states of Paraiba, Pernambuco and Rio Grande do Norte, based on phylogenetic analysis of the RPB2 gene, morphocultural markers and aggressiveness of the isolates. The phylogenetic reconstruction of maximum parsimony and bayesian inference of the isolates were performed. Twenty-seven phylogenetic lineages were characterized with morphocultural markers on potato dextrose agar and synthetic nutrient-poor agar. The aggressiveness of these lineages were characterized in leaves and fruits of pineapple ‘Pérola’ cultivar. The Phylogenetic reconstruction showed close relationship between isolates of this study and phylogenetic lineages of F. guttiforme, F. ananatum and F. oxysporum by analysis of RPB2 gene. Phylogenetic lineages of this study shared significant morphocultural markers similar to those described for this species. Overall, the lineages related with Fusarium oxysporum Species Complex were more aggressive to the fruits of the Fusarium lineages related with Fusarium fujikuroi Species Complex. It is possible that F. ananatum and F. guttiforme or other lineages closely related to these species or F. oxysporum are present in the fields causing pineapple rotting fruitlet core in fruits of pineapple ‘Pérola’ in Brazil. The used markers determined high genetic variability in isolates analyzed in leaves and pineapple fruit ‘Pérola’ in the states of Paraíba, Pernambuco and Rio Grande do Norte of Brazil and the pathogenic lineages analyzed were better adapted to the fruits than to the detached leaves in pineapple ‘Pérola’ analyzed.     

Assessment of household risk management strategies for coastal aquaculture: the case of clam farming in Thaibinh Province,Vietnam

Clam farmers have experienced different types of risks that have been further exacerbated by the rapid expansion of clam farming areas, increased growing densities, and increased market difficulties in recent years in the Thaibinh Province of Vietnam. Most farmers have been seriously affected by production risk, market risk, and financial risk, while a number of others have met with success in almost all of their clam-raising cycles. This study applied a differentiating comparative analysis method and multiple discriminant analysis method to discuss the differences in risk management strategies between and among clam farming households and the impacts of those differences on their success/failure rates. In general, the tactics are related to increase in farm size, the application of technical innovations, diversifying livelihood activities, and accessing secure financial sources all provided better conditions for clam growth, diminished losses, and led to speedier recovery from shocks. To support farmers in managing risks, several government interventions are needed: (1) better re-zoning of clam farming areas in parallel with an increase in the farm size of each household, (2) promoting sustainable linkages between the farmers and the formal financial market and output market, and (3) investing more funding into research and extension related to sustainable clam farming practices and to the improvement of farmers’ skills in cooperative works and management.