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Cocoa (Theobroma cacao L.) is sensitive to water deficit stress which is the main factor limiting its productivity. Morpho-physiological responses of cocoa hybrids to differential water deficits at young age showed significant differences under controlled condition. Physiological parameters, viz., water status, gas exchange, photosynthesis and photochemical activities, despite having good correlation among them, may not contribute as selection criteria separately. However, simultaneously they distinguished the hybrids under induced water stress. Three different behavioral groups were categorized, the first group showed small reduction in photosynthesis, followed by maintenance of water use efficiency with low conductance and low transpiration rate in the hybrids VTLCP-22, VTLCP-24 and VTLCH-4. The second group included hybrids VTLCP-27, VTLCP-25 and VTLCP-26, which had adequate functioning of PSII, net photosynthetic activity, reduced transpiration rate, high stomatal resistance and vegetative vigor. Third group comprising of hybrids VTLCH-3, VTLCP-11, VTLCP-28 and VTLCP-29 has high transpiration rate, reduction of PSII photochemical activity and low CO2. Cocoa exhibited significant genotypic variation with physiological parameters at young age and breeding for these traits may improve the performance and sustainability under specific growing conditions.

Rice yellow mottle virus, of the genus Sobemovirus, causes a major disease in Africa especially in the lowland and irrigated rice ecologies. Yield losses due to the virus were estimated between 5-100% and depend on genotype. This study, conducted in a screen house, aimed at assessing the impact of eight RYMV isolates from a restrictive environment Gagnoa (Côte d’Ivoire) on 10 differential rice varieties. The plants were inoculated manually by rubbing the leaves from the leaf base to the tip with fingers moistened with inoculum. Virus content and percentage yield reduction of different rice cultivars have been assessed. Result showed that an important variability was observed in the reaction of different rice genotypes infected by different isolates of RYMV. In susceptible cultivars Bouaké 189, PNA647F4-56 and H232-44-1-1 virus content and yield reduction varied respectively from 0.08 to 0.264 and 20 to 95%. In resistant cultivars, Gigante, Lac 23, Morobérékan and Faro 11, virus content and yield reduction varied respectively from 0.03 to 0.188 and 5 to 17%. The lowest virus content and yield reduction was observed with the isolate 7 from upland rice. The significant difference in the interaction observed between the different genotypes of rice and isolates of RYMV suggested the existence of different strains of RYMV within a restrictive environment.© 2015 International Formulae Group. All rights reserved.Keywords: AfricaRice, Sobemovirus, aggressive, virus content, yield reduction, virulence

Transgenic plants with their huge potential as the high yields, resistance to diseases, insects and water stress seem to be a solution for Africa and could contribute to poverty reduction and the increase of agricultural production in this area of the world often face starvation. However GMOs dragging a trail of controversy and risk maligned with a series of impacts that concern the human health, environmental, social and economic. Is the dangerousness of transgenic plants a concern people of Ivory Coast? Investigations were carried out on 400 farmers and 1000 educated people in through a series of questions.

Dans le but d'évaluer les dégâts et déterminer l'influence du swollen shoot du cacaoyer sur la production de cacao en Côte d'Ivoire, des essais épidémiologiques ont été instalés en zones infectées. Chaque es a été mis en place dans un foyer dans une cacaoyère atteinte par la maladie. Des cacaoyers ont été marqués de proche en proche en s'éloignant du centre du foyer tandis que des témoins ne présentant aucun signe de Ja maladie ont été repérés dans la partie saine de la cacaoyère. Ainsi, Les superficies détruites ont été estimées et la vitesse de progression de la maladie évaluée. Dans chaque essai, une description des symptômes, des comptages et des mesures de poids et la tailles des cabosses ont été effectués périodiquement sur les arbres repérés. Les résultats des observations épidémiologiques montrent que les manifestations de la maladie différent d'une localité à l'autre. Les dégâts et les pertes enregistrés sont considérables. Elles sont plus fortes sur le matériel végétal traditionnel par rapport aux cacaoyers sélectionnés. Par ailleurs, une forte réduction du nombre de cabosses, du volume des cabosses et du poids des fèves a été mise en évidence sur les cacaoyers les plus proches du centre du foyer par rapport aux témoins. Cette étude a montré que le swollen shoot du cacaoyer constitue un sérieux facteur de dégradation des cacaoyères en Côte d'Ivoire et nécessite sans délai des mesures de lutte assez rigoureuses étant donné que les foyers de la maladie deviennent difficiles à maîtriser lorsque leur taille augmente. Face à la situation actuelle de la maladie, la méthode de l'arrachage des cacaoyers ateints suivie de la replantation avec du matériel sélectionné constitue une première approche transitoire de lutte en attendant la selection d'hybrides de cacaoyers résistants aux principaux isolats viraux identifiés en Côte d'Ivoire.

Objectives: An experiment in southeast of Cote d'Ivoire on the combined effect of tapping systems and height of opening on clone PB 235 agronomic parameters and susceptibility to tapping panel dryness was led in order to determine the best exploitation system. Methodology and results: The clone was planted at the density of 510 trees per hectare (7 m x 2.80 m) comparing two tapping systems S/2 d3 6d/7 ET2.5% Ba2(2) 2/y(m) (high tapping intensity) and S/2 d4 6d/7 ET2.5% Pa1(1) 8/y(m) (low tapping intensity) and two opening heights (1.20 m and 0.75 m above ground level) using a split-plot lay out. Measurements included yield, growth, and rate of tapping panel dryness (TPD), dry rubber and sucrose contents. Results shown that the opening of clone PB 235 at 0.75 m doesn't affect significantly growth but gives lower yields and higher rates of TPD mainly with high tapping intensity. Intensive tapping results in a decrease of sucrose content and significant increase in the rate of TPD. Conclusions and potential application of findings: The opening height has significant effect on clone PB 235 yield but not on it's growth. Tapping intensity could be the main factor of the appearance of clone PB 235 TPD. Opening trees at 0.75 m above the ground cannot be practical in the exploitation system of this clone. The lower tapping frequency (S/2 d4 6d/7) combined with high intensity of stimulation (8/y(m)) allows a better carbohydrates supply and enhances the maintaining of a better sucrose availability. The low tapping intensity S/2 d4 6d/7 8/y(m) at 1.20 m above ground level is the best one that need to be applied on clone PB 235.

Oil palm defence reaction to the vascular wilt disease was characterized by the production of phenolic compounds in the roots and pseudobulbs infected at the prenursery stage. The study was aimed at discriminating between tolerant and sensitive ones by the phenolic reaction of the roots and pseudobulbs after their infection with the Fusarium oxysporum f.sp.elaeidis, the pathogenic agent of vascular wilt disease of oil palm. Principal Component Analysis (PCA) and Discriminant Analysis (DA) show that although the phenolic metabolism was different in both organs; all the phenols belonged to the flavonoids and can be used to distinguish the tolerant clones and sensitive ones.

L'incidence de plusieurs circonférences ou délais de mise en saignée sur les paramètres du profil physiologique et de la sensibilité à l'encoche sèche d'Hevea brasiliensis a été étudiée pendant une dizaine d'années dans le sud-est hévéicole de la Côte d'Ivoire. L'étude a été réalisée à partir de saignées dites précoces (mise en saignée à 40, 45 cm de circonférence) et/ou tardives (ouverture à 55, 60 et 65 cm de circonférence) appliquées aux clones GT 1, PB 217 et PB 235. Cette étude montre que la mise en saignée du clone GT 1 à 40 cm de circonférence et des clones PB 217 et PB 235 à 50 cm constituent les meilleurs traitements du point de vue des paramètres physiologiques et de l'encoche. Ces circonférences à l'ouverture ont été obtenues à environ 6 ans après la plantation, quel que soit le clone. Les résultats satisfaisants enregistrés montrent la prépondérance de la notion "âge d'ouverture" sur celle de circonférence de mise en saignée. Ainsi, l'âge de 6 ans après plantation semble être le meilleur délai de mise en saignée des hévéas, parce qu'il constitue un bon repère de maturité physiologique chez Hevea brasiliensis.