Responses of potatoes plants inoculated with arbuscular mycorrhizal fungi and litter in greenhouse

A pot experiment was set to examine the impact of the foliar litter (Hardwickia binata and Azadirachta indica) and an arbuscular mycorrhizal (AM) fungus on the development of two varieties of potato plants (Aida, Atlas). Three litter doses (0, 25 and 50 g) were applied to the pots after bedding plantlets. The plants were inoculated with AM, Glomus aggregatum. Mycorrhizal colonization, shoot dry weight, size and number of minitubers were evaluated after 12 weeks on the potato growth. Results show that shoot dry weight of plants was improved by litter of the H. binata at 25 and 50 g. Thus, A. indica litter increased size of plants Aida at 50 g and the minitubers numbers Atlas at 25 g. On the other hand, root colonization decreased with increase in the dose of litter with both varieties of potato.Key words: Arbuscular mycorrhizal fungi, potato, litter, micropropagation

Effect of rotation of cowpea (Vigna unguiculata) with fonio (Digitaria exilis) and millet (Pennisetum glaucum) on Macrophomina phaseolina densities and cowpea yield

Macrophomina phaseolina, the causal agent of charcoal rot, causes great damage to cowpea in the Sahel. One of the few options to manage the disease is by cropping nonhosts that may reduce the soil inoculum below a damage threshold level. To test this, fonio (Digitaria exilis) and millet (Pennisetum glaucum) were cropped continuously for 3 years in plots with a natural infestation of 24-53 microsclerotia g(-1) soil at the onset of the experiment. Next, a susceptible cowpea variety was grown to quantify disease incidence and severity on these soils. Fonio and millet both reduced microsclerotial densities in soils from the first year onwards. Reductions under fonio (81% after the 2(nd) year; 86% after the 3(rd) year) were significantly stronger than under millet (56 and 66% for the 2(nd) and 3(rd) year respectively). Fonio was not infected by M. phaseolina, while the root systems of millet had low densities of microsclerotia. Cowpea yielded significantly more hay and pods after 3 years of fonio than of millet. Cowpea yields and disease incidence (dead plants) could be explained well by pre-planting microsclerotial densities. We conclude that rotation of cowpea with a gramineous crop may lead to a relatively fast decline of inoculum density. In the case of a high inoculum density, fonio can be grown for three years to reduce M. phaseolina densities in soi

Evaluation de la contamination métallique des moules Mytilus gallo provincialis et des sédiments marins au niveau des côtes de la région de Dakar (Sénégal)

Les rejets industriels et domestiques au Sénégal sont versés directement dans le milieu aquatique sans aucun traitement préalable. Dans le présent travail, nous avons étudié le degré de contamination du littoral dakarois par un suivi spatio-temporel des teneurs de certains éléments métalliques (cadmium, chrome et plomb) au niveau des moules et des sédiments. Pour cela, six stations de prélèvement ont été choisis en fonction des activités qui s’y déroulent: la zone de Mbao, les plages de débarquement des produits halieutiques de Hann et Soumbédioune, les alentours du port de Dakar, Cap Manuel et l’île de Sarpent. En plus, cette étude vise à évaluer la variation intersaison de cette contamination. Les métaux lourds étudiés dans ce travail sont dosés par un spectromètre d’émission atomique à arc électrique. Les résultats obtenus montrent une contamination importante dans tout l’étendu du littoral, surtout pendant la saison des pluies (Août) dans les moules et en saison sèche (Mai) au niveau des sédiments. Les teneurs en plomb, chrome et cadmium les plus élevées, accumulées par les moules ont été détectées au port avec des valeurs respectives de 380, 298 et 18,5 μg/g de poids sec et à Hann avec respectivement 307, 268 et 3 μg/g de poids sec. Les résultats de mesure ont montré également, dans les deux sites, des teneurs en plomb, chrome, et cadmium très élevées au niveau des sédiments avec des valeurs respectives de 707, 1150 et 24 μg/g de poids sec au port. Pour Hann, les concentrations mesurées sont respectivement de 654, 752 et 5 μg/g de poids sec. Les limites de détection des électrolytes varient entre 0,01 et 0,1 mg/L. Les valeurs trouvées sont largement supérieures à la norme établie par la Communauté Economique Européenne (CEE). En effet, la norme autorisée pour le plomb, le cadmium et le chrome au niveau des moules est de 1,5 μg/g du poids sec.Mots clés: Métaux lourds, moule, sédiment, toxicité, émission atomique

Sufficient conditions for the existence of a center in polynomial systems of arbitrary degree

In this paper, we consider polynomial systems of the form $\dot x=y+P (x,y)$, $\dot y=-x+Q(x,y)$, where $P$ and $Q$ are polynomials of degree $n$ wihout linear part. For the case $n=3$, we have found new sufficient conditions for a center at the origin, by proposing a first integral linear in certain coefficient of the system. The resulting first integral is in the general case of Darboux type. By induction, we have been able to generalize these results for polynomial systems of arbitrary degree

New sufficient conditions for a center and global phase portraits for polynomial systems

In this paper we consider cubic polynomial systems of the form: $\dot x=y+P(x,y)$, $\dot y=-x+Q(x,y)$, where $P$ and $Q$ are polynomials of degree 3 without linear part. If $M(x,y)$ is an integrating factor of the system, we propose its reciprocal $V(x,y)=\frac{1}{M(x,y)}$ as a linear function of certain coefficients of the system. We find in this way several new sets of sufficient conditions for a center. The resulting integrating factors are of Darboux type and the first integrals are in the Liouville form. By induction, we have generalized these results for polynomials systems of arbitrary degree. Moreover, for the cubic case, we have constructed all the phase portraits for each new family with a center

Cetacean research in Senegal 1995-97, an overview. Scientific Committee document SC/49/SM10, International Whaling Commission, Bournemouth, UK

Historically Senegal is the West-African nation with the best kept faunistical records for cetaceans. We found verifiable evidence for at least 18 species, but limited life history data. Quantified information on interactions with soaring coastal fisheries is wanting. Here we present preliminary results of recent field work in central and central-south Senegal, which aim was to help design a long-term research plan with Senegalese scientists, offer training and reinitiate data collecting.With limited monitoring we encountered evidence of dolphin by-catches but no wide-spread directed dolphin fishery. However the presence of tell-tale conditions including spreading acceptance for consumption of dolphin meat and indications of overexploitation of some fish stocks are known warning signs. Future efforts should cover larger areas and generally be more intensive. Three carcasses of Atlantic hump-backed dolphin Sousa teuszii found on Sangomar island had rope tied around the tailstock. Fishermen at Djifer and Joal-Fadiouth confirmed regular incidental takes and landings. In the Siné-Saloum delta, inshore S. teuszii and T. truncatus are probably the most affected species. Senegal’s EEZ waters support large industrial fisheries which may constitute an additional source of by-caught small cetaceans. We here document 21 new specimen records and a series of sightings. Dolphins occurring in the Casamance river and upstream in the salt-water canals of the Saloum delta are identified as T. truncatus