Unsuccessful Cassava Brown Streak Disease (CBSD) evaluation attempts in western Democratic Republic of Congo and implications with cassava root necrosis disease (CRND) etiology

Open Access ArticleCassava brown streak disease (CBSD) is the second most important virus disease after Cassava mosaic disease (CMD), infecting cassava (ManihotesculetaCrantz) in Africa. The disease is caused by two distinct viruses, Cassava brown streak virus [2, 3] and Ugandan Cassava brown streak virus (family, Potyviridae: genus, Ipomovirus). Transmission of CBSV from one plant to another is reported to occur through grafting CBSV-free with infected cuttings and subsequent dissemination by infected cuttings. The basic approach to control of CBSD is selecting planting material from symptomless mother plants. Graft inoculation is the most efficient and effective of the techniques for CBSD virus transmission and consequently cuttings are the most effective way of the disease spreading. In early 2000s, cassava root necrosis similar to those of CBSD were reported in western provinces of Democratic Republic of Congo (RDC) (Kinshasa and Kongo Central) and up to date PCR diagnoses did not detect any causal agent related to the observed symptoms and the disease which was still referred as ‘CBSD-like disease’. Due to lack of molecular data and the similarity of root symptoms with CBSD, the existence of a virus has always been suspected to be the cause of CBSD-like propagation. Thus, 2 field experiments were proposed in order to verify the existence of a systematic transmission of a possible CBSD related virus, knowing that CBSD viruses are transmitted efficiently by cuttings. The first trial focused on the field evaluation of CBSD – like infected and apparently uninfected planting materials, while the second trial involved the importation of tanzanian CBSD resistant genotypes for evaluation in INERA Mvuazi research center under CBSD-like infection conditions. Results of the first trial did not show a systemic transmission of any CBSD-like pathogen while CBSD-resistant parents involved in the second trial all succumbed to CBSD-like disease

First report and preliminary evaluation of cassava root necrosis in Angola

Open Access ArticleCassava is a main staple food for 800 million people world-wide. Production is limited by pest and pathogens. The most devastating cassava viruses are Cassava Brown Streak Virus and Uganda Cassava Brown Streak Virusboth causing severe root necrosis called Cassava Brown Streak Disease. In the last 10 years, the Cassava Brown Streak Disease (CBSD)has spread across Africa from the east coast of Africa to central Africa. Similar root necrosis to cassava brown streak disease has also been identified in the Democratic Republic of Congo where the first symptoms were identified in 2002 in Kinshasa and Kongo central province. In 2012, the presence of CBSD was confirmed in eastern Democratic Republic of Congo. All attempts since 2002 in western Democratic Republic of Congo to identify the cause of these root necrosis have failed. In 2017, a team of scientists surveying the Songololo Territory in the Kongo central province at the northern Angola, identified the same root necrosis similar to CBSD in several localities bordering Angola. These unexpected results will foreshadow the presence of cassava root necrosis in Angola. This preliminary investigation in northern Angola was conducted specifically in the Zaire province and the territory of Mbanza Kongo at approximatively 62 kms from the Democratic Republic of Congo border in order to verify, whether or not, these root necrosis are present in Angola. Results obtained from this exploratory survey in several fields of the Zaire province and territory of Mbanza Kongo confirmed, for the first time, the presence of cassava root necrosis in Angola, similar to CBSD, as identified in western DRC

Impacts des rejets accidentels sur la qualité environnementale des sédiments de la rade portuaire d’Abidjan (lagune Ebrié ; Côte d’Ivoire)

La densité du trafic maritime s’est intensifié depuis la création du port d’Abidjan situé dans l’estuaire de la lagune Ebrié en Côte d’Ivoire. En outre sa rade portuaire est le lieu de rejets industriels et urbains. Les sédiments de la rade portuaire d’Abidjan, ont été analysés par spectrométrie d’adsorption en vue de déterminer les teneurs en éléments traces métalliques (ETM), afin d’évaluer le facteur d’enrichissement et la qualité du sédiment. Les sédiments de ce fond lagunaire ne sont pas pollués en Cd, et sont de bonne qualité environnementale. Leur teneur en Pb ne constitue pas de danger pour le biota. La pollution en Cr, Ni et Cu est modéré et les sédiments sont de mauvaises qualité. Concernant l’arsenic et le zinc, les échantillons dont le facteur d’enrichissement est inférieur à 1,3 ne constituent pas de danger pour l’environnement. Pour le reste des échantillons, l’arsenic (As) fortement enrichis, présente un danger pour les sédiments. Il en est de même pour Pb.Mots clés : ETM; Facteur d’enrichissement, qualité environnementale, rade portuaire, Abidjan, Côte d’Ivoir

Attempts to identify Cassava Brown Streak Virus in western Democratic Republic of Congo

Open Access ArticleRoot necrosis similar to those of the cassava brown streak disease (CBSD) were observed on cassava in western provinces of the Democratic Republic of Congo (DR.Congo) in the early 2000’s. However molecular laboratory diagnosis were not able to detect any causative agent responsible for the attacks, hence, the disease related to these symptoms was named CBSD-like disease. In order to assess the distribution and the incidence of the CBSD-like disease, surveys were carried out in four western provinces, comprising, Kwango and Kwilu, Sud Ubangi, Kinshasa and Kongo Central. CBSD-like disease was observed in all surveyed provinces on the basis of root symptoms because foliar symptoms were different to those of the documented cases of CBSD in other parts of east Africa. CBSD-like disease incidence was high in Kongo Central and Sud Ubangi, exceeding an average of 50 %, but low in Kwango and Kwilu (32.8%) and in Kinshasa (19.1%). During the surveys, cassava leaf samples were collected for lab identification of the causal agent. PCR diagnosis was done on these samples using primers specific for the two known CBSVs. All samples tested negative with no amplification of DNA fragments of the correct size. Thus, further analysis on the causative organism is needed using Next Generation Sequencing (NGS) approaches. NGS approaches will help also to identify the causative organism in other Central Africa countries (Angola, Congo-Brazzaville and Gabon) where such cassava root necrosis have been reported or are suspected

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

Effet antibiose de quatre cultivars de bananier et bananiers plantains sur Cosmopolites sordidus Germar (Coleoptera: Curculionidae) à Kisangani, RD Congo

Black weevil (Cosmopolites sordidus Germar) development on bananas and plantains (Musa sp.) was assessed on four cultivars named: Libanga likale (AAB), Litete (AAB), Lokusu (AAB) and Yangambi Km5 (AAA). Rearing black weevil with Litete cultivar has shown better insect growth larvae expressed from most of parameters such as larvae number (31), adults emergency frequency (26.6), larvae's mortality rate (14.1%) and post-larvae development cycle (30 to 34 days) compared to Yangambi (9.3 larvae). Therefore, black weevil showed good response on plantains cultivars. Sex ratio (male: female) was either for among plantains cultivars but highly influenced from Yangambi Km5 with 1.8:1. Yangambi Km5 antibiosis showed high larvae mortality rate of 63.67%, weak emergency rate (28) and long post-larvae development of 50 days. This shows that the cultivar 'Litete' was the most susceptible to weevils. Keys words: banana, Musa cultivars, weevils, emergency, development cycleLe développement du charançon noir (Cosmopolites sordidus Germar) des bananiers et bananiers plantains (Musa sp.) a été évalué sur quatre cultivars: Libanga likale (Musa AAB), Litete (Musa AAB), Lokusu (Musa AAB) et Yangambi Km5 (Musa AAA). Le charançon noir élevé sur le cultivar Litete a montré une meilleure croissance exprimée dans la plupart des paramètres comme le nombre de larves (31), la fréquence d’émergence des adultes (26.6), le taux de mortalité larvaire (14,1%) ainsi que la longueur du cycle de développement post-larvaire (30 à 34 jours). Le charançon noir s’y développe plus vite et plus nombreux. Le ratio sexuel est similaire chez les cultivars de bananiers plantains mais fortement influencé chez Yangambi Km5 où il est de 1,8 :1. L’antibiose de Yangambi Km5 se manifeste par un taux de mortalité larvaire élevé de 62.8%, faible taux d’émergence des adultes (9.3) et un cycle de développement post-larvaire plus long (50 jours) et un ratio sexuel déséquilibré. Ceci montre que le cultivar Litete est le plus sensible aux charançons par rapport aux cultivars étudiés. MOTS-CLEFS: bananier, Musa, cultivars, charançons, émergence, cycle de développemen

Determination of optimal sowing periods for short and medium cycle rice varieties in Yangambi

Open Access Article; Open Access ArticleRice is the staple food for more than 2.5 billion people in developing countries with very high annual consumption exceeding in some countries 100 kg per capita. The African continent has become one of the main import poles for rice with about one quarter (1/4) of world imports because of its low production, which barely reaches 1.5% of world production. Following the agricultural calendar and in accordance with studies conducted at INERA - Yangambi on the probable periods of sowing rice in Yangambi, it appears that rice can be sown from March 15 to October 15 during the year and mainly in the wetlands of the tropics. A variety of rice, so that it can express its genetic potential, must benefit from the maximum of water and light so that one can hope for optimal yields. It is in this context that this study was conducted and with the objective of contributing to the search for the appropriate sowing dates for short and medium cycle rice varieties that would help farmers maximize their income. Depending on each sowing date, observations were made on the number of panicles per m², the number of grains per panicle, the length of the panicle, the weight of a thousand grains and the yield. The results showed that optimal planting times for rainfed rice are good when short-cycle and when rice is planted from 16 May and from 15 June for medium-cycle rice varieties. Some short and / or medium cycle varieties are favorable for sowing dates around June 29th. The benefit from this relatively late sowing of June is alluding to bird damage and so the varieties that adapt to these dates have been identified. Le riz représente la base de l'alimentation de plus de 2,5 milliards de personnes dans les pays en voie de développement avec des consommations annuelles très importantes dépassant dans certains pays les 100 kg/habitant. Le continent africain est devenu l'un des principaux pôles d'importation de riz avec environ le quart (1/4) des importations mondiales à cause de sa faible production qui atteint à peine 1,5% de la production mondiale. Suivant le calendrier agricole et conformément aux études entreprises à l’INERA – Yangambi sur les périodes probables de semis du riz à Yangambi, il ressort que le riz peut être semé du 15 Mars au 15 Octobre au courant de l’année et principalement dans les régions humides des tropiques. Une variété de riz, pour qu’elle puisse exprimer son potentiel génétique, doit bénéficier du maximum de l’eau et de la lumière pour qu’on puisse espérer des rendements optima. C’est dans ce cadre que cette étude a été menée et avec pour objectif de contribuer à la recherche des dates de semis convenables des variétés de riz, à cycles court et moyen, qui aideraient les agriculteurs à maximiser leur revenu. En fonction de chaque date de semis, les observations ont porté sur le nombre de panicules par m², le nombre de grains par panicule, la longueur de la panicule, le poids de mille grains et le rendement. Les résultats obtenus ont montré que les périodes optimales de semis du riz pluvial sont bonnes lorsque le riz à cycle court est semé à partir du 16 mai et à partir du 15 juin pour les variétés de riz à cycle moyen. Certaines variétés à cycle court et/ou moyen sont favorables aux dates de semis oscillant autour du 29 juin. L’avantage qui découle de ce semis relativement tardif du mois de juin fait allusion aux dégâts des oiseaux et ainsi, les variétés qui s’adaptent à ces dates ont été identifiées

Comparison of indoor contact time data in Zambia and Western Cape, South Africa suggests targeting of interventions to reduce Mycobacterium tuberculosis transmission should be informed by local data.

BACKGROUND: In high incidence settings, the majority of Mycobacterium tuberculosis (M.tb) transmission occurs outside the household. Little is known about where people's indoor contacts occur outside the household, and how this differs between different settings. We estimate the number of contact hours that occur between adults and adult/youths and children in different building types in urban areas in Western Cape, South Africa, and Zambia. METHODS: Data were collected from 3206 adults using a cross-sectional survey, on buildings visited in a 24-h period, including building function, visit duration, and number of adults/youths and children (5-12 years) present. The mean numbers of contact hours per day by building function were calculated. RESULTS: Adults in Western Cape were more likely to visit workplaces, and less likely to visit shops and churches than adults in Zambia. Adults in Western Cape spent longer per visit in other homes and workplaces than adults in Zambia. More adults/youths were present at visits to shops and churches in Western Cape than in Zambia, and fewer at homes and hairdressers. More children were present at visits to shops in Western Cape than in Zambia, and fewer at schools and hairdressers. Overall numbers of adult/youth indoor contact hours were the same at both sites (35.4 and 37.6 h in Western Cape and Zambia respectively, p = 0.4). Child contact hours were higher in Zambia (16.0 vs 13.7 h, p = 0.03). Adult/youth and child contact hours were highest in workplaces in Western Cape and churches in Zambia. Compared to Zambia, adult contact hours in Western Cape were higher in workplaces (15.2 vs 8.0 h, p = 0.004), and lower in churches (3.7 vs 8.6 h, p = 0.002). Child contact hours were higher in other peoples' homes (2.8 vs 1.6 h, p = 0.03) and workplaces (4.9 vs 2.1 h, p = 0.003), and lower in churches (2.5 vs 6.2, p = 0.004) and schools (0.4 vs 1.5, p = 0.01). CONCLUSIONS: Patterns of indoor contact between adults and adults/youths and children differ between different sites in high M.tb incidence areas. Targeting public buildings with interventions to reduce M.tb transmission (e.g. increasing ventilation or UV irradiation) should be informed by local data