Caractérisation physico-chimique des sols en vue de l’amélioration de la productivité du manioc (Manihot esculenta Crantz) dans la région de Damara au centre-sud de Centrafrique

La présente étude vise à améliorer la productivité du manioc (Manihot esculenta), aliment de base des centrafricains. Plus spécifiquement, il s’agit de (i) caractériser les propriétés physico-chimiques du sol et (ii) déterminer les indicateurs de fertilité des sols étudiés. La collecte des données a consisté à prélever le sol de la couche 0-20 cm, sur les champs de manioc du site expérimental de LaSBAD. Les sols ont été prélevés suivant un dispositif de randomisation, en vue de constituer un échantillon composite de 1 kg par champs. Ils sont séchés, tamisés et analysés au laboratoire de sol du CIRAD-Montpellier-France. Les résultats analytiques de sol ont été comparés à des valeurs de références. Les sols étudiés présentent une texture loameuse et un pH optimal de 5,5, favorable à la culture du manioc, et sont très pourvus en matière organique. Le bilan des éléments nutritifs révèle des carences en calcium et en échangeable. L’analyse en composantes principales a montré une corrélation entre les indicateurs de la fertilité des sols. L’utilisation des légumineuses et la fertilisation organo-minérale à une dose adéquate sont des solutions envisageables pour améliorer la productivité du manioc en Centrafrique.Mots clés: indicateur de fertilité, productivité, manioc, propriété physico-chimique, CentrafriqueEnglish Title: Characterization physicochemical soils to improve productivity of cassava (Manihot esculenta Crantz) in the region of Damara in south-central of Central African RepublicEnglish AbstractThe present study is a contribution to the improvement of cassava (Manihot esculenta) tubers’ productivity in the Republic of Central Africa. Especially it aims to characterize the physicochemical properties of soil and (ii) assess fertility indicators of soil. Data collection was consisted to sample the soil from horizon 0-20 cm in cassava fields of producers and the agricultural site of the LaSBAD. Soils were sampled randomly to form a composite sample of 1 kg per field. Soil samples were dried, sieved, and analysed within the laboratory of soil of CIRAD in Montpellier-France. The analytical results of soils were compared to reference values. The studied soils are in their surface organic loamy texture and optimal of 5.5 pH suitable for the cultivation of cassava. They are well supplied with organic matter. The nutrient balance showed that the most significant deficiencies include calcium and magnesium exchangeable. The principal component analysis showed a best correlation relationship between indicators of soil fertility. The use of legumes, and fertilization organicmineral at one dose adequate were possible conceivable solutions to improve cassava in Central African Republic.Keywords: Diagnosis of deficiency, soils’ fertility, cassava, savannah, Central African Republi

Evaluation de la teneur en protéines et en chlorophylle dans les feuilles de cinq variétés locales de manioc infectées par la mosaïque en République Centrafricaine

Assessment of Protein and Chlorophyll contents in Leaves of Five Local Varieties of Cassava Infected by African Mosaic Virus in Central African Republic. In Central African Republic, cassava has become a staple and a source of income for almost all the rural population. Cassava Mosaic Virus is a major threat to cassava production and food security for the population. The loss of production due to this disease in the country is estimated at 50%. This decrease is linked from the physiological point of view to reduction of the leaf surface, but also to a drop of the chlorophyll level. In the Central African Republic, a part of the population prefers infected cassava leaves because they would be tastier. The objective of this study was to compare the levels of protein and chlorophyll in infected and healthy leaves to verify the hypothesis that high protein content in the leaves could be associated to their contamination by the virus. The results obtained showed that the protein content is higher in the infected leaves than in the healthy ones. The rate rises on average from 12.77±0.86% of the dry weight of the leaves in healthy plants to 22.88±2.93% in diseased plants. Chlorophyll content is low in plants severely affected by the mosaic virus, and higher in healthy plants with a respective content of 13.19±1.09 mg/l and 21.81±2,17 mg/l

Surveillance de l'endometre sous traitement hormonal de substitution par echo-Doppler

Objectives: To determine endometrial thickness, uterine and endometrial blood flow in postmenopausal women receiving hormone replacement therapy (HRT). Study design: forty hundred forty eight women were divided into six groups based on HRT. The endometrial thickness of all of them were examinated with Aloka 2000 and pulsatility and resistance index of uterine and endometrial arteries (if visible) were calculated. P < 0.05 was considered as significative. Result: The endometrial thickness was 2.8 mm ± 2.6 in group without HRT (n = 168), this endometrial thickness was significatively (p < 0.0001) lower than group with oestrogen alone: 8.7 mm ± 6, HRT sequential: 6.7 mm ± 3, HRT continous: 4 mm ± 3.1 (p<0.01), Progestagen alone: 8 mm ± 5.8 and Tibolone 6.7 mm ± 4. The mean RIs and PIs of uterine arteries are significantly lower in women receiving HRT (group 2-6) than women without HRT (0.72 ± 0.12 versus 0.92 ± 0.01) p < 0.01 and 2.16 ± 0.8 versus 2.46 ± 0.8 p < 0.01. The endometrial PI of 1.17 ± 0.4 in the HRT group was not significantly different from that in the no HRT group (1.85 ± 0.4) p = 0.06. Conclusion: The endometrial thickness was considerably lower with continous hormone replacement therapy around 4 mm. Moderate endometrial blood flow were present in all groups. The color doppler ultrasound reflects the hormonal status and change in the uterine and endometrial perfusion depending on hormonal therapy.SCOPUS: re.jinfo:eu-repo/semantics/publishe

Doppler couleur energie au cours du cycle menstruel

Doppler ultrasonography has been used over the last few years to investigate uteroovarian hemodynamics during the menstrual cycle in women and in nonhuman primates. In the present study, pulsed and energy Doppler imaging was used to determine the PI and RI values of the arcuate, radial, and endometrial uterine arteries and ovarian stroma on days 9, 12, 15, 23, and 26 of the menstrual cycle in ten young volunteers. Cycles were classified as ovulatory (n = 7) or nonovulatory (n = 3) based on the temperature curve and on whether a corpus luteum was visible upon ultrasonography. PI and RI values of the arcuate and radial uterine arteries on the dominant side were significantly lower during the luteal phase than during the follicular phase (P < 0.05). Only during ovulatory cycles were the endometrial arteries visualized during the luteal phase. Thickness of the endometrium was positively correlated with endometrial PI and RI values (r = 0.47; P < 0.01). Perifollicular flows were visualized on day 9 during both ovulatory and nonovulatory cycles. No significant differences were found in perifollicular PI and RI values between the dominant side and the nondominant side; neither were significant differences found in anovulatory cycle PI and RI values between the right side and the left side. PI values for ovarian stroma arteries on the side of ovulation decreased throughout the cycle, from 1.36 ± 0.28 on D9 to 1.25 ± 0.82 on D23 and 1 ± 0.21 on D26; the decrease was less marked on the opposite side. Pulsed and energy Doppler imaging demonstrates endometrial vascularization and increased blood flows in the ovarian stroma and corpus luteum indicating better perfusion during ovulatory cycles.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Occurrence and Distribution of Banana bunchy top virus Related Agro-Ecosystem in South Western, Democratic Republic of Congo

Banana bunchy top virus (BBTV) is one of the most severe and widespread virus limiting produc- tion and distribution of planting material of banana (Musa spp.) crops in the world. In Democratic Republic of Congo (DRC), these crops play a major role in daily life of almost 70% of citizen. Many factors influence banana production negatively such as Banana bunchy top disease. Epidemiol- ogical survey was conducted in experimental stations and farmers’ fields for two consecutive sea- sons covering 72 sites in five provinces of south western of RDC. The objective of this study was to evaluate the presence and distribution of the Banana bunchy top virus in five provinces of South Western of DRC, with emphasis on the agro-ecological factors. A total of 174 Musa spp. leaves samples were collected and analyzed by PCR. The results revealed the presence of BBTV in all provinces investigated. The frequency of BBTV was 6.3% in Bandundu, 12.1% in Kasaï Oriental, 17.8% Bas Congo, 1.1% in Katanga and 7.5% Kinshasa Urban and Peri-urban. Results also re- vealed that BBTV occurred in experimental station and farmers’ fields, both having all cooking and dessert bananas. The high prevalence of BBTV seemed to be linked to multiple introductions of planting materials in the Bas Congo province during 1990 and 2002. However, the province of Katanga had not experienced the introduction of planting material. This factor would explain the lowest prevalence of Banana bunchy top virus in this province. The results indicated that there was a real need to facilitate access to genetically improved and healthy certified planting material in these provinces

Epidemiological assessment of cassava mosaic disease in Central African Republic reveals the importance of mixed viral infection and poor health of plant cuttings

Cassava is a vital crop in Africa and represents the main food crop in Central African Republic (CAR). CAR has recently faced large reductions in cassava yields that have led to a surge in market prices. To better understand the causes of the reduction in yield, we identified biotic constraints to cassava production by means of a large-scale plant epidemiological survey conducted in 2007 and 2008. Standard protocols were used for the assessment of the major cassava pests and diseases. Cassava mosaic disease (CMD) was shown to be the most serious constraint to cassava in CAR, with symptoms observed at all localities surveyed. CMD is distributed throughout the country, with an average incidence of 85%. Importantly, 94% of diseased plants had cutting-derived CMD infection suggesting that farmers mostly use virus-infected cuttings for planting. PCR amplification and direct sequencing of partial fragments of the Rep ORF revealed that the causal agents of CMD in CAR are African cassava mosaic virus (ACMV) and the Uganda strain of East African cassava mosaic virus (EACMV-UG). We also demonstrated that 58% of CMD samples present mixed infections (ACMV and EACMV-UG) and that these samples had significantly higher symptom severities. Our results suggest that mixed infection and synergism between CMGs, could be an important feature in the yield reduction of cassava plants in CAR, similar to the other severe CMD epidemics reported in East Africa

Diversite génétique du manioc (Manihot esculenta crants, euphorbiaceae) a l’echelle du village Boukoko en centrafrique

Le manioc (Manihot esculenta Crantz) est une plante à multiplication végétative, introduite dans les années 1850 par le Nord-Est de la République Centrafricaine (Tisserant, 1953). Des accessions sont mises en collection dans la station du Centre de Recherche Polyvalent Régional du village Boukoko (CRPR-Boukoko). A l’issu des enquêtes auprès des techniciens du centre de recherche et des agriculteurs, 61 accessions ont été signalées (dont 19 accessions introduites et 42 locales) pour 183 prélèvements à raison de trois échantillons par accession. 11 marqueurs microsatellites : NS189, NS376, SSRY100, SSRY101, SSRY103,  SSRY161, SSRY179, SSRY182, SSRY19, SSRY20, SSRY51, ont permis d’évaluer la diversité génétique. Le nombre d’allèles obtenus sur l’ensemble des locus est compris entre 4 et 6 avec une moyenne de 5,63. Le locus SSRY20 est le plus polymorphe avec 10 allèles. Sur les 183 échantillons collectés, 80 présentent des génotypes multilocus distincts. Ces résultats montrent une grande diversité génétique des accessions retrouvées dans ce village.Mots clés : Diversité génétique, Manihot esculenta Crantz, village Boukoko (RCA).Cassava (Manihot esculenta Crantz) is a vegetatively propagated plant, introduced in the 1850s by the North-Eastern Central African Republic (Tisserant, 1953). Accessions are set in the collection station Versatile Regional Research Centre of the village Boukoko. At the end of the survey research center technicians and farmers, 61 accessions have been reported (including 19 accessions introduced and 42 local) for 183 samples with three samples per accession. 11 microsatellite markers: NS189, NS376, SSRY100, SSRY101, SSRY103, SSRY161, SSRY179, SSRY182, SSRY19, SSRY20, SSRY51, were used to assess genetic diversity. The number of alleles obtained throughout loci is between 4 and 6 with an average of 5.63. SSRY20 locus is more polymorphic with 10 alleles. Of the 183 samples  collected, 80 have distinct multilocus genotypes. These results show a high genetic diversity of accessions found in this village.Keywords: Genetic diversity, Manihot esculenta Crantz, village Boukoko (RCA)