The Essential Oil of Ocimum americanum from Senegal and Gambia as a Source of Methyleugenol for the Control of Bactrocera dorsalis, Fruit Fly

The fruit fly, Bactrocera dorsalis (Diptera: Tephritidae) is one of the most important pests in all mango-producing areas, particularly in West Africa. In Senegal, O. americanum leaves have been used for several years to control this fly. However, to our knowledge, no chemical studies have been carried out. Thus, the aim of this study is to determine the chemical composition of the essential oil of O. americanum leaves collected in Senegal and Gambia. The essential oil obtained by hydrodistillation of these leaves is analyzed by GC/FID and GC/MS. Yields of essential oils from O. americanum leaves are 3.84% and 2.13%, respectively. Analysis of these essential oils by GC/FID and GC/MS allowed the identification of 23 compounds representing almost 100% of the total compositions. These essential oils are mainly dominated by methyleugenol (72.0% and 75.8%, respectively). Other components in significant percent are trans-β-caryophyllene (13.9% and 13.0%, respectively), germacrene D (4.1% and 3.7%, respectively), β-elemene (3.3% and 0.9%, respectively). Due to the high methyleugenol content, this study explains the attractive potential of O. americanum towards B. dorsalis. In perspective, we plan to evaluate the attractive effect of the essential oil and leaf powder of O. americanum against B. dorsalis, a real pest of mango orchards in Senegal.

<i>In Vitro</i>Germination and Early Vegetative Growth of Five Tomato (<i>Solanum lycopersicum</i>L.) Varieties under Salt Stress Conditions

In Senegal, tomato (Solanum lycopersicum L.) cultivation is affected by salinity in many agro-ecological zones. The selection of salt tolerant varieties would be an alternative solution to enhance the production. Thus, germination and growth are studied under axenic conditions for five varieties of tomato subjected to increasing concentrations of NaCl [0, 35, 70 and 105 mM], and supplemented in an MS/2 medium for 30 days. The results reveal that salt negatively affects the evaluated parameters. The Rodeo and Lady Nema varieties have the lowest final germination rates (50%) unlike the Mongal variety (55%). These last two varieties have a decrease of 71.78% and 81.28% in the height of the stem, respectively, in the presence of NaCl at [105 mM] while that of the Rodeo variety is 70%. The Xewel variety has the greatest average number of leaves in the presence of [NaCl 35 mM] (4.95 leaves) and [NaCl 70 mM] (4.77 leaves). The Lady Nema variety records the longest taproot length (2.99 cm) unlike the Rodeo variety (2.25 cm) at [NaCl 105 mM]. The Ganila variety reveals the highest number of secondary roots at the concentrations of [0, 35 and 105 mM] of NaCl with, respectively, 44.12, 29.25, and 4.25 roots. The Lady Nema variety records the highest fresh weight of aerial (0.055 g) and root parts (0.014 g) and the lowest root dry weights (0.0023 g). These results allow to conclude that the Lady Nema and Mongal varieties seem more tolerant, Ganila and Xewel are moderately tolerant and Rodeo is more sensitive to the presence of salt.

Trend Analysis in Rainfall, Reference Evapotranspiration and Aridity Index in Southern Senegal: Adaptation to the Vulnerability of Rainfed Rice Cultivation to Climate Change

Rainfall and evapotranspiration are two vital elements for food production under rainfed agriculture. This study aims at investigating the combined changes in these variables in the form of aridly index in the southern Senegal. The temporal trends in annual and monthly (from May to October) aridity index, rainfall and evapotranspiration are examined and adaptation strategies to the vulnerability of rainfed rice cultivation to the changes are developed. The results show a significant decreasing trend in annual rainfall at all study locations for the period 1922-2015. When analyzing the trends in sub-periods, there are two clear patterns in the annual rainfall series: a decreasing trend for the period 1922-1979 and a reversal increasing trend for the period 1980-2015. An increasing trend is also observed in annual reference evapotranspiration. The results reveal that the region will be drier with a significant increase in aridity at the annual and most monthly series. Appropriate adaptation strategies should be implemented to diminish the adverse influence of the increasing aridity on rice productivity for a sustainable agriculture.

Larvicidal activity of Neem oil and three plant essential oils from Senegal against Chrysodeixis chalcites(Esper, 1789)

Objective: To evaluate the insecticide, larvicidal and repellent activity of the essential oils from Callistemon viminalis, Melaleuca leucadendron, and Hyptis suaveolens against Chrysodeixis chalcites and to compare it with neem oil(Azadirachta indica). Methods: The essential oils of the leaves of these aromatiques plants were extracted by steam distillation and contacts tests were carried out. Results: Essential oils in ethanol from Callistemon viminalis showed a higher biological activity than the neem with 100% larval mortality at the concentration of 2 μg/m L for 6 h, 100% and 90% in ethanol from Melaleuca leucadendron and Hyptis suaveolens, respectively at the concentration of 4 μg/m L for 24 h. By inhalation, the essential oils from Melaleuca leucadendron and of Hyptis suaveolens were more effective with mortality rates of larvae 100% and 50% respectively at 2 μg/L air applied after 24 h. Nevertheless, the neem has shown to be a repulsive plant and anti-nutritional plant. A significant difference in the percentages of consumption between leaves treated with neem oil and the control samples was observed(Newman-Keuls test) except for Melaleuca leucadendron. Conclusions: The results of the study highlight remarkable biocide, properties of tested extracts, which provides important opportunities for the development of biopesticides.

Effects of protein and mineral supplementation on the performance of lactating dairy cows gobra and crossbreed guzerat during the dry season in senegal

The purpose of this study carried out in the township of Dahra was to access the effect of dry season protein and mineral supplementation of Gobra and Crossbreed Guzerat cows on milk production. The experimental design is a completely randomized block. The treatments were: supplement of molasse-urea blocks with supplement of hay;supplement of molasse-urea blocks without any hay;no supplement of molasse-urea blocks and supplement of hay;no supplement of molasse-urea block without any hay. For each breed, the treatments were replicated three times on a lot of cows with the similar zootechnic parameters. A total of twelve lactating cows per breed were then used. The supplement of block + hay has significantly (p < 5%) allowed obtaining the largest average daily quantity of milk: 1.9 ± 0.7L/day/cow and 2.4 ± 0.8 L/day/cow respectively in Gobra and Crossbreed Gobra*Guzerat. The increases in production compared to the control treatment (without supplement) are 52.63% and 100% respectively in the breed Gobra and Gobra*Guzerat. The supplement of hay comes in the second place and contributes to an additional production of 66.66% in both breeds of cow. Then, the supplement of block follows and it allows increasing the production of 44.44% and 50% respectively in Gobra and Crossbreed. In both races, the supplement of block + hay has allowed obtaining the highest profits of $1.6/L/day/cow for Gobra and $ 2.8/L/day/cow for the Crossbreed, that equals to an increase by $ 0.3 and $ 0.9 compared to the control treatment. The supplement of hay and the block supplement have respectively given a profit of 0.4 and $ 0.3/L/day/cow in Gobra and 0.6 and $ 0.4/L/day/cow in the Crossbreed. The adoption of supplementation molasse-urea block + hay by producers appears an alternative to boost milk production in dry season.

Response to Inoculation with Arbuscular Mycorrhizal Fungi of Two Tomato (Solanum lycopersicum L.) Varieties Subjected to Salt Stress under Semi-Controlled Conditions

Salinity is a major problem that seriously impacts agricultural production, particularly that of tomato (Solanum lycopersicum L.). However, the plant has the ability to associate with Arbuscular Mycorrhizal Fungi to better tolerate salt stress. Thus, thanks to the extension of the AMF hyphae, the hydromineral nutrition and the tolerance to excess toxic ions (Na+ and Cl-) of the plant are optimized. In this context, the contribution of AMF to the salt stress tolerance of two tomato varieties under semi-controlled conditions was studied. To do this, the frequency and intensity of mycorrhization, the relative mycorrhizal dependency, the survival rates, the aerial and root dry weights, the mineral (P, K+, Na+) and proline contents of the plants subjected to four levels of salinity [0, 70, 140 and 210 mM of NaCl] were evaluated. All the parameters assessed appeared to be dependent on the variety, the fungal strain and the NaCl concentration. With the Lady Nema variety, inoculation with the Claroideoglomus etunicatum strain at [NaCl 140 mM] resulted in the highest frequencies (54%), intensities (40.47%), and relative mycorrhizal dependencies (19.65%). This same symbiotic couple recorded high survival rates (55%) and aerial (2.03 g) and root (0.50 g) dry weights. Significant contents of K+ (Leaves: 7.5 mg⋅g-1;Roots: 4.4 mg⋅g-1 of dry matter), P (Leaves: 15.15 mg⋅g-1 of dry matter) and proline (975 nmoles⋅g-1 of fresh matter) were also recorded by this pair, with the lowest Na+ contents (Leaves: 1.93 mg⋅g-1;Roots: 0.96 mg⋅g-1 of dry matter). For the Mongal variety, at [NaCl 140 mM], the highest frequencies (50.36%), intensities (35.14%) and relative mycorrhizal dependencies (43.95%) were obtained thanks to inoculation with Rhizophagus fasciculatus. The highest survival rates (59%) and aerial (2.58 g) and root (0.79 g) dry weights were also obtained with this symbiotic couple. The contents of K+ (Leaves: 6.1 mg⋅g-1;Roots: 3.09 mg⋅g-1 of dry matter), P (Leaves: 12.49 mg⋅g-1 of dry matter) and proline (942 nmoles⋅g-1 of fresh matter) the most important and those in Na+ the lowest (Leaves: 2.03 mg⋅g-1;Roots: 1.53 mg⋅g-1 of dry matter) were also recorded for this same pair. Thus, the best fungal partner for the Lady Nema variety is C. etunicatum, followed by F. mosseae and R. fasciculatus, while for the Mongal variety it is R. fasciculatus, followed by C. etunicatum and F. mosseae.

RETRACTED:Effect of Long-Term Inorganic Fertilization on Diversity and Abundance of Bacterial and Archaeal Communities at Tillage in Irrigated Rice Field

Short Retraction Notice The paper does not meet the standards of "Advances in Bioscience and Biotechnology". This article has been retracted to straighten the academic record. In making this decision the Editorial Board follows COPE's Retraction Guidelines. The aim is to promote the circulation of scientific research by offering an ideal research publication platform with due consideration of internationally accepted standards on publication ethics. The Editorial Board would like to extend its sincere apologies for any inconvenience this retraction may have caused. Editor guiding this retraction: Prof. Abass Alavi (EiC of ABB). Please see the article page for more details. The full retraction notice in PDF is preceding the original paper which is marked "RETRACTED".

Response to Inoculation with Arbuscular Mycorrhizal Fungi of Two Tomato (Solanum lycopersicum L.) Varieties Subjected to Water Stress under Semi-Controlled Conditions

In arid and semi-arid regions, the growth and development of cultivated plants, especially tomato (Solanum lycopersicum L.), are severely limited by water deficit. Thus, to cope with this constraint, the plant establishes symbiotic relationships with arbuscular mycorrhizal fungi (AMF) in the soil whose extension of the hyphae allows a better and deeper exploration;this notably improves the hydromineral nutrition of the plant. Therefore, the choice of fungal partner becomes crucial for the establishment of a crop in water-deficient soil. In this context, the contribution of AMF to the water stress tolerance of two varieties of tomato plants was assessed under semi-controlled conditions. Parameters, such as the mycorrhizal frequency, intensity of mycorrhization, relative mycorrhizal dependency, growth, and biochemical parameters (carbon, nitrogen, phosphorus, and proline contents) of plants subjected to three levels of water stress (T100, T70, and T30), were evaluated. The highest frequencies and intensities of mycorrhization and relative mycorrhizal dependencies were obtained with plants of the Xewel variety inoculated with Rhizophagus fasciculatus (F: 95.24%, 88.35%, and 13.64%;M: 40.52%, 37.52%, and 11.22%;D: 23.7%, 54.4%, and 78.82%) and in those of the Lady Nema variety inoculated with Claroideoglomus etunicatum (F: 95.12%, 87.01%, and 15.25%;M: 40.66%, 37.99%, and 11.42%;D: 19.27%, 57.01%, and 70.98%), respectively at water regimes of T100, T70 and T30. These same symbiotic couples recorded, at T30, the best survival rates (+ 40%) and the higher aerial (77% and 74%) and root dry weights (80% and 59%). Plants of the Xewel variety inoculated with R. fasciculatus recorded the highest contents of carbon (T70: 30.59% and T30: 21.55%) and phosphorus (T70: 0.18% and T30: 0.17%). Plants of the Lady Nema variety recorded the highest nitrogen contents with 3.51% and 3.20%, respectively at T70 and T30. Plants of the Lady Nema variety, inoculated with C. etunicatum, also recorded the highest proline contents (572.25, 739.44, and 1165 nmoles•g−1 of fresh material), followed by those of the Xewel variety inoculated with R. fasciculatus (580.36, 763.65, and 1112.11 nmoles•g−1 of fresh matter), respectively at T100, T70, and T30. For the Lady Nema variety, the best fungal partner is C. etunicatum, followed by R. fasciculatus and, finally, Funneliformis mosseae. However, for the plants of the Xewel variety, R. fasciculatus is the most efficient, followed by F. mosseae and C. etunicatum. This suggests that, in tomatoes, the efficiency of mycorrhizal symbiosis under water stress conditions is not only dependent on the host plant but on both associated symbiotic partners. Hence, it is a need for screening to identify the best symbiotic couples in a stressful environment.

Effect of the Continuum Removal in Predicting Soil Organic Carbon with Near Infrared Spectroscopy (NIRS) in the Senegal Sahelian Soils

Spectroscopy plays a major role in the access of the analytical parameters of the soil. It tends to substitute the conventional laboratory analysis because hyperspectral data were least expensive and easier to obtain. The objective of this study was to evaluate the effect of the continuum removal (CR) in the validation of the accurate prediction model of the soil properties with Vis-NIR spectroscopy data. Few studies using Vis-NIR reflectance spectroscopy have well focused the calculation of the CR method;its effect in the calibration of the accurate models was also not well emphasized. In this study, we used the remote sensing software ENVI 4.7 to compute the CR function where the value of the continuum for each sample and for each spectral wavelength was obtained by dividing the reflectance values of the full spectrum (FS) with those of the continuum curve (CC). The partial least square regression (PLSR) model was applied in the spectral data from the soil of the Senegal Sahelian region. It was calibrated with both data from the full spectrum (FS) and those obtained after the application of the continuum removal. With the application of the CR, ultraviolet wavelengths (350 - 429 nm) and those of near infrared (2491 - 2500 nm) were removed from the explanatory variables of PLSR model. With the FS, all wavelengths between 350 and 2500 nm were taken into account in predicting soil properties. Our findings show a positive effect of the application of CR in the estimation of soil organic carbon. In calibration, the R2 increased up to 10% with the continuum removal in the model of 12 components (CP). In terms of validation, it’s the 15-component model which is the most accurate with the same range in calibration between the FS and the CR. The lowest RMSE ranged from 0.04 with the FS to 0.03 with the application of the CR in calibration and validation. These results show that the interest of this study as soil organic carbon is recognized as a key indicator of fertility of the soil in Sahelian-African regions. For future studies, it’s important to apply the model of neural networks to better evaluate the effect of continuum removal in predicting soil properties from the spectral data and other methods of preprocessing like the multiplicative scatter correction (msc).

Functional groups of Sahelian trees in a semiarid agroforestry system of Senegal

Aims Addressing plant responses to water stress is critical to understand the structure of plant communities in water-limited environments and to forecast their resilience to future changes in climate.In a semiarid agroforestry system in the Sahelian savannah of Leona(Senegal),we selected nine common tree species and explored their stress-resistance mechanisms.These species represent a variety of life forms and are of high regional socio-economic importance.We hypothesized that different species would show different suites of traits to cope with water stress and expected to identify functional groups differing in strategies to withstand water shortage.Methods Along a dry and a wet season,we monitored four traits reflecting above-and below-ground strategies of resource acquisition such as predawn leaf water potential(ψpd),specific leaf area(SLA),leaf thickness and leaf area index(LAI).We also measured two mor-phological traits:trunk diameter and tree height.LAI andψpd were measured six times during the dry and rainy seasons,and the other traits were measured once.Important Findings We identified two functional classes subdivided into two func-tional groups of each class.The first class included deciduous and semi-deciduous species that generally had large SLA,low leaf thickness and small-to-intermediate inter-seasonal varia-tions inψpd.The second class included evergreen species of two functional groups that differ in SLA,leaf thickness and the mag-nitude of inter-seasonal variations ofψpd throughout the year.The four functional groups identified in this study represent plant strategies differing in their response to changing environmental conditions.

Grazing effects on vegetation dynamics in the savannah ecosystems of the Sahel

Background The savannah ecosystems of Sahel have experienced continuous and heavy grazing of livestock for centuries but still,their vegetation response to grazing pressure remains poorly understood.In this study,we analysed the herbaceous plant dynamics,measured by species diversity,composition,cover,and biomass in response to grazing pressure in the savannah ecosystems of Sahel.In Senegal,we selected four savannah sites represented with high,moderate,light and no grazing intensity levels.Transect survey methods were used for sampling the vegetation data within each of the sites.Species richness and composition were analysed using species accumulation curve and multivariate analyses.Furthermore,we used General Linear Models and a piecewise Structural Equation Model(pSEM)to examine the relationships between grazing intensity,vegetation cover,diversity and biomass.Results The herbaceous species diversity and composition varied significantly among the different grazing intensity levels(p<0.001).The plant species composition shifted from the dominance of grass cover to the dominance of forb cover with increasing grazing pressure.Moreover,the attributes of species diversity,herbaceous biomass,and ground cover were higher on sites with low grazing than sites with high and moderate grazing intensity.Across all sites,species diversity was positively related to total biomass.The pSEM explained 37%of the variance in total biomass and revealed that grazing intensity negatively influenced total biomass both directly and indirectly through its negative influence on species diversity.Conclusions Managing grazing intensity may lead to higher plant production and higher mixed forage establishment in the dryland savannah ecosystems.This information can be used to support land management strategies and promote sustainable grazing practices that balance the needs of livestock with the conservation of ecosystem health and biodiversity.