Assessing the severity and the incidence of Cassava Root Necrosis Disease (CRND) in western Democratic Republic of Congo

Open Access ArticleCassava is the staple food in the Democratic Republic of Congo (DRC) where both the roots and leaves are consumed. This crop is susceptible to several viral diseases, including Cassava Mosaic Disease(CMD) and Cassava Brown Streak Disease(CBSD) in eastern DRC. Following earlier studies that show root necrosis occurring in western DR Care not due to CBSD but to Cassava Root Necrosis Disease (CRND), an exploratory survey was conducted in western DRC from 2016 to 2017 in order to determine the distribution, the severity and the incidence of this disease (previously known as CBSD-like disease). NGS ( Next Generation Sequencing) results confirmed all the previous negative results obtained using PCR and CBSV primers. This suggests that microorganisms such as bacteria or fungi could be responsible for cassava root necrosis in western DRC and is not CBSD as predicted. Five provinces (Bas-Congo, Kinshasa, Bandundu, Equateur and Kasai-Oriental) were surveyed and data were collected according to the harmonized protocols adopted by countries within the West African Virus Epidemiology (WAVE) project. Statistical tests (ANOVA) performed on our data showed that CRND severity did not vary significantly among the provinces of Kinshasa, Bandundu and Bas-Congo which are the areas most affected by the disease. Bas-Congo and Kinshasa provinces presented the highest maximum disease severity (score 3 and 5 respectively), while Equateur province had the lowest disease severity score. Equateur province also had the highest percentage of healthy plants and few plants presented mild symptoms. The overall average of cassava root necrosis severity in western DRC ranged around 1.88 ± 0.08, an approximate score of 2. The overall mean incidence of CRND in western DRC was 22.24 ± 2.4% but reached 100% in localities considered as hotspots (Lukuakua in Bas-Congo and Nguma in Plateau des Batékés). The behaviour of cassava varieties against CRND is similar with CBSD in East Africa, most of improved varieties and landraces are susceptible to both diseases. Correlation analyses showed a positive correlation (r = 0.6940) between severity and incidence of CRND. Therefore, Bas-Congo province is the most affected province, while the province of Equateur is the least affected province in western DRC. Further investigations, including genomic surveillance, should also be conducted in the eastern DRC where CBSD is confirmed to know if CRND is found in conjunction with CBSD and to report possible instances of mixed infections. For medium-term disease control, our study suggests that the development and deployment of control measures including cultivars with resistance to CRND and CBSD should be a priority

Utilisations des produits forestiers autres que le bois (PFAB) au Cameroun. Cas du projet forestier du Mont Koupé

Utilization of Non Wood Forest Products in Cameroon. The Case of the Forest Project of the Koupe Mont. A survey using some elements of the RAA method described by Gueye and Schoonmaker (4) led to the identification of 26 plant species belonging to 15 botanical families in the Koupe Mountain forest project (Cameroon). This study deals with the utilization of non wood forest products. The small number of species reported by the study can be explained by the fact that the survey took into account only the species really used by the local population and not all those present in the forest. Study established that : harvesting and utilization of these resources generate incomes, create jobs and allow local population satisfying their needs of food, fodder, medicine, resins, dyes, fiber, handicrafts, flavorings, building materials... Unfortunately, due to organizational problems and absence of structures, the commercialization of these products does not contribute to the welfare of the local population and to the development of the production area which remained dominated by agriculture. In order to ensure the perennial characteristic of the highly demanded species, measures permitting their conservation and their sustainable utilization such as : regulation of the type and the rate of harvesting, use of non destructive harvesting techniques, their domestication through agroforestry techniques, their introduction in home-gardens... should be taken. The management of these resources requires the involvement and effective participation of the rural community. This can be achieved through mass sensitization, training and use of the media

Dégâts des bruches sur le pouvoir germinatif des graines de quatre variétés de Niébé infesté pendant 60 jours à Ngandajika

Objectif: L’objectif de cette étude est de déterminer l’impact des dégâts des bruches sur le pouvoir germinatif des graines de niébé et d’identifier des variétés résistantes ou tolérantes aux attaques de bruches pendant le stockage. Le bruche (Callosobruchus maculatus) est un petit coléoptère doté de taches sombres sur les élytres. C’est un parasite qui s’attaque aux graines pendant l’emmagasinage.Méthodologie et résultats: Au cours de ce travail, nous avons étudié le comportement de quatre (4) variétés améliorées de niébé (Yamashi, Mujilanga, IT82D-889 et Diamant) sélectionnées par l’Institut National d’Études pour la Recherche Agronomiques centre de Ngandajika sur le développement de Callosobruchus maculatus infesté dans les graines de ces variétés. Cette étude était menée in vitro au laboratoire du centre de Recherche de l’INERA Ngandajika. Les résultats révèlent que le taux d’accroissement des bruches infestés pendant 60 jours varie de 50.41% à 91.99%. Et la variété Diamant à présenté un pouvoir germinatif beaucoup plus faible 0.75% que les trois autres variétés (Mujilanga 7.75%, Yamashi 8.25% et IT82D-889 12.75%.Conclusion et application des résultats: Cette étude a permis de conclure que la variété Diamant a perdu le pouvoir germinatif après une durée de conservation de 60 jours. Ces résultats suggéreraient que pour une période de conservation après récolte, les graines de niébé de la variété Diamant ne peuvent plus être considérées comme semences. Il est par conséquent important de demander aux producteurs de semences de cette variété de ne pas utiliser la semence de cette variété après 60 jours de conservation sans traitement phytosanitaire et d’utiliser ainsi la semence fraichement récoltée.Mots clés: pouvoir germinatif, résistance variétaleEnglish AbstractObjective: The objective of this study is to determine the impact of damage from weevils on the germination of the seeds of cowpea and identify varieties resistant or tolerant to attack by weevils during storage. Callosobruchus maculatus. The weevil (Callosobruchus maculatus) is a small beetle with dark spots on the wing covers. This parasite attacks the seeds during storage. Methodology and results: During this work, we studied the behaviour of four (4) improved varieties of cowpea (Yamashi, Mujilanga, IT82D-889 and Diamond) selected by the National Research Institute for Agronomic Research centre on the development Ngandajika of Callosobruchus maculatus infested in the seeds of these varieties. This study was conducted in vitro laboratory research centre INERA Ngandajika. The results reveal that the rate of increase of weevils infested for 60 days ranged from 50.41% to 91.99%. Diamond and variety germination presented a much lower 0.75% than the other three varieties (Mujilanga 7.75%, 8.25% and IT82D Yamashi-889 12.75%.Conclusion and application of results: This survey permitted to conclude that the variety Diamant lost the germinating power after a length of conservation of 60 days. These results would suggest that for one period of conservation after harvest, the seeds of cowpea of the variety Diamant could not be considered more like seeds. It is therefore important to ask the producers of seeds of this variety to not to use the seed of this variety after 60 days of conservation without phytosanitary treatment and to use the freshly harvested seed.Keywords: germinating power, variety resistanc