Diagnostic de l’incidence des Pathogènes Fongiques du Riz au Sud Bénin et Identification Morphologique de Cercospora oryzae

Rice (Oryza sativa L.) is one of the most widely grown cereals in Benin. Even though the country is agricultural, food self-sufficiency has never been reached, and rice import is always important every year. For rice, diseases are the factor causing poor quality and the reduction of harvests. This is the reason that leads us to monitor the rice disease present in Benin. The incidence of the disease was assessed by visual observation of the symptoms in the field and the identity of the pathogens was confirmed by the laboratory tests. For this, a sampling was carried out in 6 departments (Mono, Couffo, Ouemé, Plateau, Atlantic, Zou), 9 municipalities (Zè, Abomey-Calavi, Comé, Grand-Popo, Adjohoun, Pobè, Adja Ouéré, Dogbo, Ouinhi) and 12 sites (Awokpa, Docomey, Gative, Matekpo, Kodé-Ague, Gouti, Odja-Igbagi, Houeli-Gaba, Kpodji, Aizè, Zaloko, Zoungo) in southern Benin. A survey was conducted during the sampling to gather information that can help us identify the pathogen. Isolation was carried out using standard mushroom media (PDA, Rice Flour, Agar-Agar). The isolates were then identified by observation of petri dish colonies by microscopic observations of spores and mycelia. The symptoms found are very varied and the incidence of some symptoms is low except cercosporiosis and rice blast on rice leaves. In the sites of Gative, Docomey, Kpodji, Matekpo, the found symptoms of cercosporiosis do not vary and the incidence is close to 100%. The isolation of the microorganisms from samples of each of these regions confirms the results obtained: Cercospora oryzae was the dominant pathogenic species in the site of Gative, Docomey and Kpodji, Curvularia oryzae wasthe dominant pathogenic species in the Aizè site, Houeli Gaba, Zoungo, Magnaporthe grisaea corresponded to the dominant pathogenic species in the Zaloko site, Aizè, Docomey while Helminthosporium oryzae corresponded to the dominant pathogenic species in the site of Odja Igbagi, Awokpa, Kodé Ague. These differences are likely to be due to climate conditions and the different mode of cultivation between sites also in the use of seeds.Le riz (Oryza sativa L.), est l’une des céréales la plus cultivée au Bénin. Même si le pays est à vocation agricole, l’autosuffisance alimentaire n’a jamais été atteinte, et l’importation du riz est toujours importante chaque année. Pour le riz, les maladies constituent le facteur entraînant la mauvaise qualité et la réduction des récoltes. C’est la raison qui nous amène à réaliser le suivi de la maladie de riz présent au Bénin. L’incidence de la maladie a été évalué par l’observation visuelle des symptômes au champ et l’identité des pathogènes a été confirmée par les tests au laboratoire. Pour cela un échantillonnage a été réalisé dans 6 départements (Mono, Couffo, Ouemé, Plateau, Atlantique, Zou), 9 communes (Zè, Abomey-Calavi, Comé, GrandPopo, Adjohoun, Pobè, Adja Ouéré, Dogbo, Ouinhi) et 12 sites (Awokpa, Docomey, Gative, Matekpo, Kodé-Ague, Gouti, Odja-Igbagi, Houeli-Gaba, Kpodji, Aizè, Zaloko, Zoungo) au Sud du Bénin. Une enquête a été réalisée durant l’échantillonnage pour récolter les informations qui peuvent nous aider à l’identification de l’agent pathogène. L’isolement a été réalisé en utilisant les milieux standards pour champignons (PDA, Farine de riz, Agar-Agar). Les isolats ont été ensuite identifiés par l’observation des colonies sur boite de Pétri, par des observations microscopique des spores et mycéliums. Les symptômes trouvés sont très variés et l’incidence de certains d’entre eux est faible sauf la Cercosporiose et la Pyriculariose sur feuilles. Dans les sites de Gative, Docomey, Kpodji, Matekpo, les symptômes trouvés de la Cercosporiose ne varient pas et l’incidence est proche de 100 %. L’isolement des microorganismes à partir d’échantillons de chacune de ces régions confirme les résultats obtenus dont Cercospora oryzae correspondait à l’espèce pathogène dominante dans le site de Gative, Docomey et Kpodji, Curvularia oryzae correspondait à l’espèce pathogène dominante dans le site de Aizè, Houeli Gaba, Zoungo, Magnaporthe grizaea correspondait à l’espèce pathogène dominante dans le site de Zaloko, Aizè, Docomey tandis que Helminthosporium oryzae correspondait à l’espèce pathogène dominante dans le site de Odja Igbagi, Awokpa, Kodé Ague. Ces différences trouvent probablement leur origine dans les conditions climatiques et le mode de culture différente entre les sites ainsi que dans l’utilisation des semences

Spatial parameters associated with the risk of banana bunchy top disease in smallholder systems

The Banana Bunchy Top Disease (BBTD), caused by the Banana Bunchy Top Virus (BBTV) is the most important and devastating in many tropical countries. BBTD epidemiology has been little studied, mixed landscape smallholder systems. The relative risks associated with this disease vary between geographical areas and landscapes. This work analyzed the management and vegetation conditions in smallholder gardens to assess the factors linked to landscape-level BBTV transmission and management. Mapping was done in this study area which is in a BBTD-endemic region, involving farmers actively managing the disease, but with household-level decision making. A spatial scanning statistic was used to detect and identify spatial groups at the 5% significance threshold, and a Poisson regression model was used to explore propagation vectors and the effect of surrounding vegetation and crop diversity. Spatial groups with high relative risk were identified in three communities, Dangbo, Houéyogbé, and Adjarra. Significant associations emerged between the BBTD prevalence and some crop diversity, seed systems, and BBTD management linked factors. The identified factors form important candidate management options for the detailed assessment of landscape-scale BBTD management in smallholder communities

Farmers’perceptions on the pineapple mealybug [Dysmicoccus brevipes (Cockerell) (Homoptera: Pseudococcidae)] and control methods in Benin

Objectives: This study aimed at evaluating the perceptions of farmers on the pineapple mealybug, the different control methods adopted against the pest and the socio-cultural factors that influence these perceptions.Methodology and Results: A survey was conducted among 180 pineapple producers using a semistructured questionnaire in five main pineapple production areas in Benin. Binomial regression and Factorial  Correspondence Analysis (FCA) were performed to determine the  sociocultural factors that influence farmers’ knowledge on the pineapple mealybug. Fifty eight percent of farmers perceived mealybug as pineapple insect pest while 22.22% reported the insect as the MWP disease vector. Experience in Pineapple production and participation in training determined the knowledge of farmers on the mealybug as important pineapple insect pest and as MWP disease vectors. Only trained farmers used to apply control methods.Conclusions and application of findings: This study shows that it is the trained producers who have a better knowledge of the mealybug and adopt some control methods. It is therefore an emergency that training seminars be organized for a large number of producers followed by supervision in sight of making them qualified to better control the proliferation of mealybug and limit the spread of wilt disease.Key words: Farmers ‘perceptions, pineapple mealybug, control methods, Beni

Survey of farmers’ knowledge of cassava mosaic disease and their preferences for cassava cultivars in three agro-ecological zones in Benin

Abstract Background Cassava is an important crop in Africa that is widely cultivated for its starchy tuberous root, which constitutes a major source of dietary carbohydrates. Cassava mosaic disease (CMD) is the most devastating disease affecting cassava in Africa and causes enormous losses in yield. In Benin, specifically, cultivars resistant to CMD are not commonly planted, and even when CMD is observed in fields, farmers do not implement control measures, presumably because they lack proper knowledge and training. Our study aimed to evaluate farmers’ knowledge of CMD to determine whether there is consistency between farmers’ criteria for selecting cassava cultivars and the currently CMD-recommended cassava varieties. Methods We conducted structured interviews with 369 farmers in 20% of townships in each of three agro-ecological zones in Benin between November 2015 and February 2016. Farmers were selected randomly in each household, and their fields were assessed for CMD incidence and severity. Results All farmers surveyed, representing a broad demographic pool with regard to education level, age group, and years of experience in cassava production, successfully recognized CMD symptoms in photos, but most (98.60%) said they did not know the causes and vectors of the disease. Most farmers (93.51%) reported that they obtain planting material from neighboring fields or their own fields. In total, 52 unique cultivars were identified, of which 3 (5.76%) were preferred based on their yield and precocity and 3 (5.76%) were preferred based on taste or ability for transformation. The assessment of disease incidence and severity showed that the areas most affected by CMD were Comè Township (37.77% of fields affected) and agro-ecological zone VIII (26.33%). Conclusion Farmers already know how to recognize the symptoms of CMD and could implement control measures against it if they are trained by researchers. Across all surveyed areas, we identified six preferred cultivars based on the four most commonly stated preference criteria (precocity, yield, gari, and taste. Our results suggest that farmers will be more likely to use CMD-resistant cultivars and clean plant material if the plants meet their existing preference criteria. We suggest that CMD-resistant cultivars will be embraced only if the recommended cultivars are strategically aligned with the characteristics desirable to the cassava farmers in each region

Response of cassava cultivars to African cassava mosaic virus infection across a range of inoculum doses and plant ages.

Cassava production in Africa is constrained by cassava mosaic disease (CMD) that is caused by the Cassava mosaic virus (CMV). The aim of this study was to evaluate the responses of a range of commonly cultivated West African cassava cultivars to varying inoculum doses of African cassava mosaic virus (ACMV). We grafted 10 cultivars of cassava plants with different inoculum doses of CMV (namely two, four, or six CMD-infected buds) when the experimental plants were 8, 10, or 12 weeks old, using non-inoculated plants as controls. Three cultivars showed disease symptoms when grafted with two buds, and four cultivars showed disease symptoms when grafted with four or six buds. Most cultivars became symptomatic six weeks after inoculation, but one ('TMS92/0326') was symptomatic two weeks after inoculation, and two ('Ntollo' and 'Excel') were symptomatic after four weeks. Root weight tended to be lower in the six-bud than in the two-bud dose, and disease severity varied with plant age at inoculation. These results indicate that the level of CMD resistance in cassava cultivars varies with inoculum dose and timing of infection. This will allow appropriate cultivars to be deployed in each production zone of Africa in accordance with the prevalence of CMD