Genetic diversity among yam mosaic virus (YMV) isolates infecting yam of the complex Dioscorea cayenensis rotundata in Togo

Phylogenetic analyses were carried out using partial CP-encoding nucleotide sequences and 3´-UTR of 31 YMV isolates originated from the five major yam-growing areas of Togo (Maritime, Plateaux, Central, Kara and Savannas Regions). The aim of this study is to know the genetic structure of YMV populations in Togo in order to develop yam resistant genotypes against the virus. Three major clusters of YMV isolates were observed. Clustering of the 31 isolates did not correlate with the geographical origin but, isolates from Maritime, Plateaux and Central Regions, were genetically more variable than isolates from Kara and Savannas Regions. Comparison of the 31 isolates of Togo with 15 nucleotide sequences from Genbank and originated from other parts of Africa and Caribbean, showed that few isolates from Togo were close to the isolates belonging to phylogenetic groups I and III of Africa but the majority were rather, genetically different. These results revealed that YMV isolates infecting yams in Togo, are genetically variable and they are different a little from isolates of other African countries, suggesting a high pathogenic potential of YMV populations in the various yam–growing areas of Togo and consequently problems of improved yam varieties introduction in the country.Keywords: Yam mosaic virus, Dioscorea cayenensis rotundata, molecular variability, genetic group, phylogenetic analysis, yam-growing are

Importance du virus de la marbrure de niébé et du virus de la mosaïque jaune du niébé au Togo

Deux virus du niébé (Vigna unguiculata), le virus de la marbrure du niébé et le virus de la mosaïque jaune du niébé, ont été étudiés. Les deux virus ont été identifiés et caractérisés à l'aide de la gamme de plantes indicatrices et de méthodes sérologiques. Les deux virus sont très répandus dans les principales régions productrices du niébé. Le virus de la mosaïque jaune du niébé a été retrouvé dans 65 % des échantillons virosés et le virus de la marbrure du niébé dans 35 % des échantillons. Des infections mixtes ont été souvent observées impliquant ces deux virus et d'autres virus du niébé. Le virus de la mosaïque du niébé transmis par le puceron, le virus de la marbrure peu sévère du niébé et le virus de la mosaïque du sud du haricot ont aussi été identifiés. L'étude des symptômes induits par ces deux virus sur une série de plantes indicatrices révèle que les Chenopodium amaranticolor, Phaseolus vulgaris cv. Saint-Fiacre, Vigna unguiculata cv. Locale Blanche et Glycine max cv. Jupiter pourraient être utilisés pour la séparation des deux virus lorsqu'ils sont en mélange. Les Crotalariajuncea, Phaseolus vulgaris cv. Saxa et Sesbania rostrata n'ont pas été infectés par ces deux virus. Vingt-trois cultivars du niébé ont été évalués en utilisant un isolat de chacun des deux virus et plusieurs sont résistants à l'un des deux virus, mais pas aux deux conjointement. Le cultivar du niébé TVxl850-01E ne démontre aucun symptôme face aux deux virus.Two cowpea (Vigna unguiculata) viruses, cowpea mottle virus and cowpea yellow mosaic virus were studied. The two viruses were identified and characterized by host range and serology. Both viruses were widespread in major cowpea producing areas. Cowpea yellow mosaic virus was found in 65 % and cowpea mottle virus in 35 % of infected samples. Mixed infections were often observed including both viruses and other cowpea viruses. Cowpea aphid-borne mosaic virus, cowpea mild mottle virus and southern bean mosaic virus were also identified. Host range studies showed that Chenopodium amaranticolor, Phaseolus vulgaris cv. Saint-Fiacre, Vigna unguiculata cv. Locale Blanche, and Glycine max cv. Jupiter could be used to separate both viruses from mixed infections. Crotalaria juncea, Phaseolus vulgaris cv. Saxa, and Sesbania rostrata were not host plants for both viruses. Twenty-three cowpea cultivars were screened using an isolate of each virus. Several cowpea cultivars were resistant to only one of the viruses but not to both. Cowpea cultivar TVxl850-01E was found to produce no symptoms with both viruses

Regulation status of quarantine pests of rice seeds in the Economic Community of West African States (ECOWAS)

Open Access JournalThe ever growing international trade has limited efforts towards the prevention of introduction, spread and establishment of invasive organisms. Non-native pests can cause severe loss of production and lead to restriction in exchange of genetic materials and seed marketing across regions. Regulating pests’ movement through quarantine measures and establishment of regional boards has been identified as a way to deal with introduction and expansion of invasive organisms. This review analyzes the different pest regulations in the West African sub-region with a specific focus on the implementation of quarantine measures in rice as a case study. The various regulations related to seed production, certification and marketing, and quarantine regulations in West Africa were analyzed and their enforcement and performance were assessed through comparison to international standards, especially the International Plant Protection Convention (IPPC). Although a regional regulation on seeds and phytosanitary measures has been elaborated, ECOWAS countries are still enforcing their national phytosanitary legislations, which are nearly the same in all West African countries - they all aim at ensuring plant health by applying preventive and curative measures to prevent the introduction and spread of pests in their territory by controlling the import and export of plant materials and disseminating appropriate pest management techniques to boost agricultural production. Most ECOWAS countries are yet to submit their phytosanitary legislation to IPPC to comply with Article VII.2i of the endorsed convention. In addition, the entry points are not well defined and provided to the IPPC according to the Article VII.2d of the convention. When the quarantine list is available, the organisms regulated for each crop species are not stated, posing a real problem not only for rice genetic resource exchanges for research purposes but also for rice seed trade. Efforts and resources should be devoted by each country to research on pests and regulatory mechanisms in order to define, among others, pest status in the region, and to update regularly the quarantine pests list in the West African region

Global Overview of Flora and Plant Diversity in Togo (West Africa)

The flora constitutes an important reference tool very used in biology. Its constant update is fundamental in order to promote new directions in conservation. The current study was developed as a synthesis of the analytical flora in Togo. It aims to produce an inventory of this flora by emphasizing its distribution along ecological zones. Its purpose is to make an assessment of the greatest entities of the flora including those of introduced, threatened to disappearance plant species. This synthesis was possible thanks to the use of data retrieved from the existing analytical flora associated with some reports on this flora. Information was organized according to the junctions, of introducing and threatened to disappearances species. They were analyzed on the basis of the phytogeographical types and life forms, and then classified according to ecological zone. From this synthesis it appeared that the flora of Togo would lay out 3468 species distributed among the algae (201especes), Bryophytes (13 species), Pteridophyts (129 species), Gymnosperms (13 species), and Angiosperms (2992 species). The phanerophytes, therophytes, the lianas, and hemicryptophytes dominate the biological spectrum, whereas the guineo-congolian (GC), Sudano-Zambezian (SZ), and transition zone species (GC-SZ) represents phytogeographical types. Face to the new challenges, especially economic, and environmental which fit all in a sustainable context of resources management, an update of all the flora will be a strategic element in the framework of management and conservation of biodiversity

Inventaire Des Nématodes Parasites et Mycorhization Naturelle de l’Igname (Dioscorea spp.) Dans La Région Centrale Du Togo

L'igname, Dioscorea spp. est une culture très importante au Togo avec plusieurs espèces cultivées. Toutefois, le complexe D. cayennensis- rotundata est le plus répandu dans les exploitations. Malheureusement, les nématodes sont des parasites majeurs qui entravent sa production. A cet effet, cette étude a été conduite dans trois préfectures de la région centrale du Togo dans le but d’identifier les nématodes parasites qui font intrusion dans les champs d’igname et d’évaluer la mycorhization naturelle de la plante. Des prélèvements de sol et de racines ainsi que l’inspection des tubercules d’igname pour les dégâts de fissuration et de galles dues aux nématodes ont été effectués à différents endroits de différents champs d’igname dans chaque préfecture. Des échantillons de sol et de racines ramenés au laboratoire, ont été extraits des nématodes et identifiés sur la base de critères morphologiques en utilisant les clés d’identification. Le taux de mycorhization a été évalué par la coloration des racines. Les résultats ont révélé la présence des genres Scutellonema, Meloïdogyne, Aphelenchoides et Xiphinema dans les champs avec Scutellonema spp. et Meloidogyne spp. comme nématodes majeurs sur les ignames. L’évaluation des dégâts visuels des nématodes sur les tubercules a montré que les taux de fissures causées par Scutellonema spp. vont de 80 à 100% alors que les taux de galles causées par Meloidogyne spp. sont de 60 à 70%. Le taux de mycorhization naturelle des plantes d’ignames va de 10 à 86,66% en milieu naturel de culture en fonction des sites et des cultivars. Cette étude est la première réalisée en milieu paysan au Togo pour inventorier la diversité des nématodes de l’igname. Les résultats de cette étude servent de base à l’élaboration des stratégies de gestion des nématodes pour une production durable de l’igname. Yam, Dioscorea spp. is an important crop in Togo with several cultivated species. However, D. cayennensis- rotundata complex is the most widespread in the exploitations. Unfortunately, the nematodes are major pests that hindered its production. Therefore, this study was conducted in three different counties in central region of Togo. The objectives were to identify the parasitic nematodes associated with yam crop, to evaluate the damage of these parasitic and the natural mycorhization of the yam. Soil and root were sampled and inspection of yam tubers for nematode cracking and gall damage were done at different locations of different yam fields in each county. From soil and root samples taken into the laboratory were extracted the nematodes and identified based on morphological criteria using the identification keys. The rate of mycorrhization was assessed by staining of the roots. The results revealed the presence of the genus Scutellonema, Meloïdogyne, Aphelenchoides and Xiphinema in the fields and showed that Scutellonema spp. and Meloidogyne spp. are the major parasitic nematodes of yam in the areas of the study. The assessment of the visual damages of the nematodes on the tubers showed that the crack rates due to Scutellonema spp. were between 80 and 100% while the gall rates due to Meloidogyne spp. varied between 60 and 70%. The frequency of natural mycorhization of yams ranging from 10 to 86, 66% and is related to the site and the variety. This study could be the first carried out in Togo to inventory the nematodes diversity of the yam. These results will contribute to nematodes management strategies elaboration for durable production of yam

Global Overview of Flora and Plant Diversity in Togo (West Africa)

The flora constitutes an important reference tool very used in biology. Its constant update is fundamental in order to promote new directions in conservation. The current study was developed as a synthesis of the analytical flora in Togo. It aims to produce an inventory of this flora by emphasizing its distribution along ecological zones. Its purpose is to make an assessment of the greatest entities of the flora including those of introduced, threatened to disappearance plant species. This synthesis was possible thanks to the use of data retrieved from the existing analytical flora associated with some reports on this flora. Information was organized according to the junctions, of introducing and threatened to disappearances species. They were analyzed on the basis of the phytogeographical types and life forms, and then classified according to ecological zone. From this synthesis it appeared that the flora of Togo would lay out 3468 species distributed among the algae (201especes), Bryophytes (13 species), Pteridophyts (129 species), Gymnosperms (13 species), and Angiosperms (2992 species). The phanerophytes, therophytes, the lianas, and hemicryptophytes dominate the biological spectrum, whereas the guineo-congolian (GC), Sudano-Zambezian (SZ), and transition zone species (GC-SZ) represents phytogeographical types. Face to the new challenges, especially economic, and environmental which fit all in a sustainable context of resources management, an update of all the flora will be a strategic element in the framework of management and conservation of biodiversity

Criblage de clones d’ignames du complexe Dioscorea cayenensis-rotundata pour la résistance au virus de la mosaïque de l’igname (YMV) au Togo

Le virus de la mosaïque de l’igname (YMV), genre Potyvirus, entrave gravement la culture d’ignames au Togo. Pour contrôler le virus, la recherche des sources locales résistantes d’ignames a été entreprise. Une collection de 36 clones sains d’ignames sélectionnés lors d’essais de résistance aux viroses de 120 accessions du complexe D. cayenensis- rotundata, a été criblée au champ avec des bandes infectantes de YMV et en serre par inoculation avec l’isolat 12-8/05 de YMV. Des feuilles prélevées sur les plants d’igname ont été analysées par la RT-PCR pour la détection du YMV utilisant des amorces spécifiques. Les résultats ont montré que 15 clones au champ et 12 clones en serre ont été sains. Les analyses RT-PCR ont révélé 10 clones résistants et 2 clones tolérants au YMV. Un des 10 clones résistants a été, cependant, infecté au champ par d’autres virus auxquels les 9 autres clones, TgKe2, TgKe8, TgKra7, TgKra8, TgKra12, TgKou6, TgKou4, TgKou9, et TgDrElé ont également résisté probablement une résistance de type horizontal. Ces résultats suggèrent la nécessité d’étendre le criblage à d’autres espèces d’ignames en vue de répertorier les sources de résistance disponibles dans chaque espèce exploitables dans le programme d’amélioration variétale.Mots clés : Dioscorea cayenensis-rotundata, virus de la mosaïque de l’igname, criblage, RT-PCR

Caractérisation d'isolats du virus de la mosaïque de la tomate (ToMV) isolés au Québec

ThèseThèse, 1982Thèse (Maître ès Sciences), Université Laval, 198