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Naphtho-gamma-pyrones produced by Aspergillus tubingensis G131: new source of natural nontoxic antioxidants
No full textSeven naphtho-gamma-pyrones (N gamma Ps), including asperpyrone E, aurasperone A, dianhydroaurasperone C, fonsecin, fonsecinone A, fonsecin B, and ustilaginoidin A, were isolated from Aspergillus tubingensis G131, a non-toxigenic strain. The radical scavenging activity of these N gamma Ps was evaluated using ABTS assay. The Trolox equivalent antioxidant capacity on the seven isolated N gamma Ps ranged from 2.4 to 14.6 mu mol L-1. The toxicity and ability of the N gamma Ps to prevent H2O2-mediated cell death were evaluated using normal/not cancerous cells (CHO cells). This cell-based assay showed that N gamma Ps: (1) Are not toxic or weakly toxic towards cells and (2) are able to protect cells from oxidant injuries with an IC50 on H2O2-mediated cell death ranging from 2.25 to 1800 mu mol mL(-1). Our data show that A. tubingensis G131 strain is able to produce various N gamma Ps possessing strong antioxidant activities and low toxicities, making this strain a good candidate for antioxidant applications in food and cosmetic industries
On the necessity of combining ethnobotany and genetics to assess agrobiodiversity and its evolution in crops : a case study on date palms (Phoenix dactylifera L.) in Siwa Oasis, Egypt
No full textCrop diversity is shaped by biological and social processes interacting at different spatiotemporal scales. Here, we combined population genetics and ethnobotany to investigate date palm (Phoenix dactylifera L.) diversity in Siwa Oasis, Egypt. Based on interviews with farmers and observation of practices in the field, we collected 149 date palms from Siwa Oasis and 27 uncultivated date palms from abandoned oases in the surrounding desert. Using genotyping data from 18 nuclear and plastid microsatellite loci, we confirmed that some named types each constitute a clonal line, that is, a true-to-type cultivar. We also found that others are collections of clonal lines, that is, ethnovarieties, or even unrelated samples, that is, local categories. This alters current assessments of agrobiodiversity, which are visibly underestimated, and uncovers the impact of low-intensity, but highly effective, farming practices on biodiversity. These hardly observable practices, hypothesized by ethnographic survey and confirmed by genetic analysis, are enabled by the way Isiwans conceive and classify living beings in their oasis, which do not quite match the way biologists do: a classic disparity of etic versus. emic categorizations. In addition, we established that Siwa date palms represent a unique and highly diverse genetic cluster, rather than a subset of North African and Middle Eastern palm diversity. As previously shown, North African date palms display evidence of introgression by the wild relative Phoenix theophrasti, and we found that the uncultivated date palms from the abandoned oases share even more alleles with this species than cultivated palms in this region. The study of Siwa date palms could hence be a key to the understanding of date palm diversification in North Africa. Integration of ethnography and population genetics promoted the understanding of the interplay between diversity management in the oasis (short-time scale), and the origins and dynamic of diversity through domestication and diversification (long-time scale)
Modelling the control of Aedes albopictus mosquitoes based on sterile males release techniques in a tropical environment
No full textThe Sterile Insect Technique (SIT), used to control insect populations, consists of releasing males sterilized by ionizing radiations. Wild females that mate with these males can no longer produce viable offspring, which may drives the population decline. Although this method has proved its efficiency, its effect may be more limited for fast-reproducing large-population species, such Aedes albopictus. A novel approach, named "boosted SIT" has been designed to strengthen the SIT technique: It consists of coating sterile males with a biocide that will be transferred to the mated females, which will then contaminate the oviposition sites. This study is aimed at exploring demographic effects of both techniques (SIT and boosted SIT) through their inclusion in a weather-driven abundance model of the Aedes albopictus population dynamics in the geographical context of La Reunion Island. Sensitivity analysis showed that the date to start the release, as well as the quantity of sterile males released and their competitiveness, are of key importance for both control methods. According to our results, boosted SIT allows 1) Increasing the effectiveness of the SIT when the sterile males released are of medium quality in terms of competitiveness, and 2) extending the optimal window to start the control period
Moroccan groundwater resources and evolution with global climate changes
No full textIn semi-arid areas, many ecosystems and activities depend essentially on water availability. In Morocco, the increase of water demands combined to climate change induced decrease of precipitation put a lot of pressure on groundwater. This paper reports the results of updating and evaluation of groundwater datasets with regards to climate scenarios and institutional choices. The continuous imbalance between groundwater extraction and recharge caused a dramatic decline in groundwater levels (20 to 65 m in the past 30 years). Additionally, Morocco suffers from the degradation in groundwater quality due to seawater intrusion, nitrate pollution and natural salinity changes. Climate data analysis and scenarios predict that temperatures will increase by 2 to 4 degrees C and precipitation will decrease by 53% in all catchments over this century. Consequently, surface water availability will drastically decrease, which will lead to more extensive use of groundwater. Without appropriate measures, this situation will jeopardize water security in Morocco. In this paper, we zoom on the case the Souss-Massa basin, where management plans (artificial recharge, seawater desalination, and wastewater reuse) have been adopted to restore groundwater imbalance or, at least, mitigate the recorded deficits. These plans may save water for future generations and sustain crop production
A decision support system for determining sugarcane pest reservoir
No full textAnticipating the establishment of pest reservoirs, and therefore pest infestation in sugarcane agrosystems, is a challenge for the implementation of integrated pest management (IPM) programs. The objective of this work was to develop a decision support system that suggests host plant species and pest natural enemies located in a production area. A knowledge base system (KBBI) was developed and coupled to DECIPESTS, a decision support system for PEST management in sugarcane. According to an observed damage, KBBI suggests the wild and cultivated plants that host the potential pests previously identified by DECIPESTS. The comparison with a local floristic inventory enables to determine pest reservoirs. Applied to a case study in Senegal, the system showed, for instance, that Eldana saccharina can be hosted by nine wild plant species located in the irrigation canals and two neighboring cultivated crops of socioeconomic importance in the area. This latter result indicates that the management of Eldana saccharina has to be tackled jointly by local farmers to be successful. While DECIPESTS uses a tactical approach to identify possible causes of pest infestation, its combination with KBBI makes it a strategic tool to enhance IPM strategy at a local scale
Source and deposition age of the Diale-Dalema metasedimentary series (Kedougou-Kenieba Inlier, Senegal) constrained by U-Pb geochronology on detrital zircon grains
No full textThe Diale-Dalema metasedimentary series is exposed in the Kedougou-Kenieba Inlier that corresponds to the northwestern branch of the Eburnean orogenic belt in the southern West African Craton. Here we conducted a U-Pb geochronological study on metapelites, metagraywackes and metavolcanic breccia of the Diale-Dalema metasedimentary series in order to identify the sedimentary sources and establish the lithostratigraphic sequence of the Kedougou-Kenieba Inlier. This new U-Pb geochronological dataset from five samples representing different stratigraphic levels yields a dominant population of Paleoproterozoic detrital zircon grains with ages ranging from c. 2200 to 2100 Ma. The youngest weighted mean ages at c. 2120 Ma are identical for all five samples within error and provide a maximum deposition age for the sediments of the Diale-Dalema series. The dominant ages are similar to those obtained on metamorphosed plutonic and volcanic rocks of the Mako belt and thus suggest a dominant proximal source for the clastic sediments of the Diale-Dalema series and a distal or geographically isolated position relative to the Archean Leo-Man or Reguibat craton nuclei. Deposition ages are only a few Myr older than available ages for metamorphism and intrusion of plutons forming the Saraya batholith. This is consistent with deposition along an active convergence zone marked by the succession, within a few tens of Myr, of (1) magmatic accretion of the Mako plutonic and volcanic rocks in the context of volcanic arc, associated with local uplift, exhumation and erosion at c. 2200-2160 Ma, (2) deposition of clastic sediments forming the Diale-Dalema series at c. 2120-2110 Ma followed by (3) their burial and exhumation at c. 2090-2060 partially contemporaneous with (4) the intrusion of the Saraya batholith at c. 2080-2070 Ma
Avec la hausse des températures, l'aquaculture bientôt un point chaud de l'antibiorésistance ?
No full textUne étude récente souligne les effets du réchauffement climatique sur l'antibiorésistance dans les fermes aquacoles. Une situation qui constitue une menace pour la sécurité alimentaire mondiale
Co-acquired nanovirus and geminivirus exhibit a contrasted localization within their common aphid vector
No full textSingle-stranded DNA (ssDNA) plant viruses belong to the families Geminiviridae and Nanoviridae. They are transmitted by Hemipteran insects in a circulative, mostly non-propagative, manner. While geminiviruses are transmitted by leafhoppers, treehoppers, whiteflies and aphids, nanoviruses are transmitted exclusively by aphids. Circulative transmission involves complex virus-vector interactions in which epithelial cells have to be crossed and defense mechanisms counteracted. Vector taxa are considered a relevant taxonomic criterion for virus classification, indicating that viruses can evolve specific interactions with their vectors. Thus, we predicted that, although nanoviruses and geminiviruses represent related viral families, they have evolved distinct interactions with their vector. This prediction is also supported by the non-structural Nuclear Shuttle Protein (NSP) that is involved in vector transmission in nanoviruses but has no similar function in geminiviruses. Thanks to the recent discovery of aphid-transmitted geminiviruses, this prediction could be tested for the geminivirus alfalfa leaf curl virus (ALCV) and the nanovirus faba bean necrotic stunt virus (FBNSV) in their common vector, Aphis craccivora. Estimations of viral load in midgut and head of aphids, precise localization of viral DNA in cells of insect vectors and host plants, and virus transmission tests revealed that the pathway of the two viruses across the body of their common vector differs both quantitatively and qualitatively