Effect of Ethephon Stimulation on Downward Tapping in Latex Production Metabolism on Upward Tapping in PB 217 Clone of Hevea Brasiliensis

In Hevea brasiliensis, Ethephon is used as an exogenous stimulant of latex production. In downward tapping, it has been shown that its misuse has negative consequences on the metabolism of the latex cells of the tree. However, little is known about the impact of this downward tapping practice on latex-producing metabolism in upward tapping. The aim of this study was to determine the effect of stimulation in downward tapping on the latex-producing metabolism in clones PB 217, when the trees are subsequently tapped up. Study was carried out by monitoring the evolution of biochemical parameters of latex and rubber production. From this study, it was found during the last two years of downward tapping that in PB 217 clone, the optimal metabolism of latex production was obtained with 13 Ethephon stimulations per year. When subsequent tapping is done upward, the stimulation frequencies of the trees greater than 4 times per year in downward tapping have a negative impact on the latex-producing metabolism in PB 217 clone of Hevea brasiliensis. However, in cumulative production over the 10 years of downward tapping added to the 2 years of upward tapping, it is the frequency of 13 stimulations per year in downward tapping which is the highest

Optimisation de la biométhanisation des effluents de manioc issus de la filière de fabrication de l’attiéké (semoule de manioc)

Cette étude s’est penchée sur les conditions optimales de biodigestion des effluents de manioc de la filière attiéké (semoule de manioc). Ces effluents proviennent de la fabrique d’attiéké d’Azito (village Ebrié de la commune de Yopougon dans le district d’Abidjan). Les six digesteurs expérimentaux utilisés, ont été alimentés comme suit : 1) effluent de manioc; 2) effluent + bouse de vache; 3) effluent + urine ; 4-5 et 6) effluent + urine + différentes quantités de bouse de vache. Aux résultats, les digesteurs ont fonctionné de façon mésophile avec des températures comprises entre 24,0 et 35,6 °C. Les digesteurs sans urine ont un pH variant entre 3 et 4 durant l’expérimentation. Pour ceux contenant de l’urine humaine, le pH a oscillé entre 6,46 et 10,29. Concernant le volume de gaz produit, il est significativement plus important dans les digesteurs contenant de l’urine que dans les digesteurs sans ajout d’urine. Le test d’inflammabilité du gaz produit est positif sauf pour le premier digesteur. Dans l’ensemble, les résultats de l’étude montrent que l’ajustement du pH avec l’urine humaine avant le démarrage du traitement des effluents de manioc issus de la filière de fabrication de l’attiéké par digestion anaérobie, est nécessaire pour l’optimisation du processus de biométhanisation.Mots clés: Digestion anaérobie, effluents de manioc, bioga

Caractérisation des sables et morphologie du fond du lac du barrage hydroélectrique de Taabo (Côte d\'Ivoire)

Une analyse sédimentologique et minéralogique réalisée sur un cycle hydrologique entre octobre 2004 et août 2005 a permis d\'évaluer les charges solides en suspension et de caractériser les sédiments du lac du barrage de Taabo. La concentration moyenne en matières en suspension (12 mg.L-1) et la turbidité moyenne (20 NTU) montrent que les eaux du lac sont relativement peu chargées. Ces charges en suspension sont composées d\'une fraction inorganique et d\'une fraction organique. Les sables qui composent les sédiments de ce lac sont majoritairement moyens à grossiers et médiocrement classés avec une moyenne granulométrique de 451,48 μm et un indice de classement moyen de 1,13. Les vases et les sables fins occupent les zones profondes du lac et les zones envahies par les végétaux aquatiques. Les sables moyens sont localisés aux voisinages des berges tandis que les sables grossiers sont situés aux voisinages des îles et de la digue. Le cortège minéralogique des sédiments est caractérisé de minéraux lourds (l\'amphibole, la tourmaline, le diopside et l\'épidote) et de minéraux légers (le quartz et les feldspaths). Par ailleurs, cette étude a permis de réaliser la première carte bathymétrique du lac de Taabo 26 ans après sa mise en eau.A sedimentological and mineralogical study carried out on a hydrological cycle from October 2004 to August 2005 has permitted to assess the solid suspended matters and to characterize the sediments of the Taabo dam lake. The average of suspended matters concentration (12 mg.L -1) and the average of turbidity (20 NTU) reveal that the lake is relatively little loaded with suspended matters. These suspended matters are compound of an inorganic fraction and an organic fraction. Sands size in the sediments of this lake are from middle to coarse and badly classified. The grain size average is 451,48 μm; the standard deviation average is 1,13. Muds and fine sands are found in the deeper zones of the lake and also in the zones invaded by the aquatic plants. Middle sands are located near banks while coarse sands are located aside the islands and the dam. The minerals found in the sediments are characterized by heavy minerals (the amphibole, tourmaline, diopside and epidote) and light minerals (quartz and feldspars). Elsewhere, this study has permitted to carry out the first bathymetric Map of this lake 26 years after its setting in water. Keywords: keywordBarrage, lac, granulométrie, minéralogie, bathymétrie, Taabo./Dam, lake, grain size, mineralogy, bathymetry, Taabo.Sciences & Nature Vol. 4 (1) 2007: pp. 93-10

Entomological investigations carried out from 2002 to 2010 into the involvement of water bugs (Heteroptera - Hemiptera) in transmission of Mycobacterium ulcerans to humans in Côte d’Ivoire (West Africa)

Ulcer is a disease caused by a mycobacterium present in the environment: Mycobacterium ulcerans.This communicable disease occurs essentially in wet tropical regions, and in particular in west Africa where it is endemic. It is the third most common mycobacterial disease affecting humans after leprosy and tuberculosis, although it is more prevalent than either leprosy or tuberculosis in some rural areas of several countries (Benin, Côte d’Ivoire and Ghana). This has led WHO to act, and in 1998 to declare Buruli ulcer an « emerging disease » and to recognize it as a neglected tropical disease. Its development is a source of concern in Côte d’Ivoire, the country most affected in the world, with an aggregate number of 30 000 cases and more than 2000 cases detected each year. It particularly affects children living in isolated rural areas around bodies of stagnant or slowly flowing water.  In order to control the disease, it is essential fully to understand its epidemiology. In this connection, there are several hypotheses on the mode of transmission of M. ulcerans to humans. Since 1999, the involvement of water bugs belonging to the order of the hemiptera has been invoked by Portaels. In 2002, this hypothesis was confirmed by Marsollier et al. for water bugs of the genus Naucoris taken from the region of Daloa in Côte d’Ivoire, where the disease is endemic. In 2008, Portaels also found M. ulcerans in samples taken from the environment (Gerridae) in Ghana. In 2007, studies began in Côte d’Ivoire into the specific diversity, biology, ecology, ethology and role of aquatic heteroptera in the transmission of M. ulcerans to humans. Samples of aquatic heteroptera were collected each month from different aquatic environments in endemic areas of Côte d’Ivoire. The insects were identified by family, genus and occasionally species. Their distribution, population dynamics and ecological distribution in the water points investigated were correlated with human activities. Monospecific batches of water bugs were regularly composed in order to identify the molecular signatures of M. ulcerans using PCR at the bacteriology laboratory of the Institut Pasteur in Côte d’Ivoire and at the bacteriology laboratory of the Groupe d’Etudes des Interactions Hôtes-Pathogènes (Host-Pathogen Study Group) at the University Teaching hospital in Angers, France. Eighteen (18) species belonging to 8 families were identified. After the aquatic insects collected had been identified, 283 monospecific batches were composed and sent to the Institut Pasteur in Côte d’Ivoire (IPCI) for PCR. Twenty four (24) of the 283 batches i.e. 8,5% containing the following, 14 Diplonychus sp, 2 Naucoris sp, 3 Micronecta sp, 2 Ranatra fusca, 2 Anisops sp and 1 Laccotrephes ater, respectively belonging to the families Belostomatidae, Naucoridae, Corixidae, Ranatridae and Nepidae tested positive under PCR. Thirty five (35) samples of saliva were collected from specimens of the genus Diplonychus. Six of the samples (i.e. 17%) tested positive under PCR. Out of 109 other monospecific batches sent to the laboratory in Angers, France, 33 (i.e. 30%) tested positive under PCR. They comprised 11 batches of Diplonychus sp (Belostomatidae), 8 batches of Micronecta sp (Corixidae), 2 batches of Laccocoris sp (Naucoridae), 4 batches of Ranatra fusca (Ranatridae), 3 batches of Anisops sp, 1 lot de Anisops sardea et 1 lot de Enithares sp (Notonectidae), 2 batches of Plea pullula (Pleidae) and 1 batch of de Laccotrephes sp (Nepidae). Clearly, not only is Diplonychus sp the genus most commonly found, it is also that most affected by M. ulcerans. This justifies the decision to breed this genus in the laboratory since 2008, in order to improve our understanding of its biology and ethology and to standardize physical and chemical parameters so as to determine the best conditions for breeding the insect which would provide an animal model for experimental infections. We have now bred six successive generations in the laboratory. To conclude, although some aquatic heteroptera that host M. ulcerans are strictly phytophagous, (e.g. the Corixidae), the great majority of water bugs are carnivorous predators that are hosts and vectors of M. ulcerans. The absence of a reliable key for determining the family, genus and species in central and west Africa has led us to draw up an iconographic catalogue to determine the taxonomy of these insects

Agronomic Performance of Hevea brasiliensis Muell. Arg. Clone IRCA 331 Grown in Southwestern Côte d'Ivoire

In order to test the agronomic performance of the newly developed clones, a Large-Scale Clone Trial (LSCT) comprising Hevea brasiliensis clones GT 1, IRCA 202, IRCA 331, IRCA 707, PB 280 and PB 310 was established in southwestern Côte d'Ivoire. They were planted in completely randomized blocks with six clone treatments and four replications of 112 trees per clone. The measured parameters included isodiametric growth of the trunk, rubber yield, trees stand, latex physiological parameters and sensitivity to tapping panel dryness (TPD). Collected data was analyzed using Statistica 7.0 statistical software. After ten years of downward tapping and four years of upward tapping, clone IRCA 331 showed significantly higher rubber productivity than all other clones. Its productivity gain, relative to the reference control GT 1, was 63% in downward tapping and 80% in upward tapping. Despite its high level of productivity, the annual rate of isodiametric growth of clone IRCA 331 tree trunks (2.56 cm/year) remained statistically equivalent to that of clone GT 1 (2.62 cm/year) at latex harvesting stage. In addition, the physiological profile of clone IRCA 331 was good and similar to that of the control. Clones IRCA 331, GT1 and PB 280 got the lowest sensitivity to TPD. However, only clones GT1 and IRCA 331 maintained a good stand of tappable trees throughout the experimental period. This experiment highlighted the agronomic performance of the clone IRCA331 and allowed to put it in class 1. Clone IRCA 331 can therefore be used as a clone of first choice to improve national productivity