Peu de travaux ont été conduits dans la partie Sud du Parc National de Taï. La diversité des ligneux de diamètre supérieur ou égal à 10 cm a été mesurée et les espèces prépondérantes analysées. Des 156 espèces appartenant à 47 familles, 21 sont endémiques à la Haute Guinée, dont 3 ivoiriennes. Douze sont inscrites sur la liste rouge de l'UICN. La distribution des diamètres des espèces et ,particulièrement celle des prépondérantes, montre que la partie Sud du Sud du Parc National de Taï est semblable aux autres forêts tropicales.
Sugarcane streak mosaic virus (SCSMV; Poaceavirus; Potiviridae) is the causal agent of streak mosaic disease of sugarcane (Saccharum interspecific hybrids), a major industrial crop that is widely cultivated in tropical and subtropical regions for sugar and ethanol production. was first reported by Hall et al. (1998) from quarantined germplasm material exhibiting mosaic symptoms imported from Pakistan into the USA. Subsequently, the virus was also reported to occur in most of the Asian countries like Bangladesh, India, Indonesia, Iran, Sri Lanka, Thailand, Vietnam and China (Chatenet et al. 2005; Hema et al. 2008, Kasemsin et al. 2016, Putra et al. 2014, Xu et al. 2010, Moradi et al. 2015; Moradi et al. 2018, Zhang et al. 2018). Until now, there is no report of SCSMV outside the Asian continent. From February to October 2018, sugarcane plants exhibiting symptoms such as irregular yellow and green mosaic, interveinal chlorotic specks, and streaks were observed in Bafing (Borotou-Koro), Marahoué (Zuénoula) and Tchologo (Ferkéssédougou) regions of Côte d’Ivoire (Fig. 1a). Varieties under large-scale commercial cultivation such as R570, R579, SP711406, Co997, Co449, M1176/77, M2593/92, M2580/95, and M1400/86 were all symptomatic. A total of 94 sugarcane leaf samples were collected from these regions and, among those, 82 showed disease symptoms and 12 were symptomless. Samples were first tested for the presence of sugarcane mosaic virus (SCMV), which causes mosaic a disease that is already present in Africa. Serological tests with infected sap using a Double Antibody Sandwich (DAS)- Enzyme Linked Immuno Sorbent Assay (ELISA) kit (DSMZ, RT-0166, Braunschweig, Germany) were negative for SCMV and no amplification product was obtained by RT-PCR using primers specific to the coat protein (CP) gene of SCMV (Putra et al. 2003). The 82 symptomatic leaves tested positive by DAS-ELISA with SCSMV antiserum (polyclonal antibodies were graciously provided by Prof. Hema M. of the Sri Venkateswara University, Tirupati, AP, India), whereas the 12 symptomless samples tested negative. To confirm these results, virus free greenhouse-grown sugarcane varieties Co997 and M1176/77, were mechanically inoculated with 10 sap extracts from 10 SCSMV-infected sugarcane leaf samples. Sap was also extracted from DAS-ELISA negative sugarcane leaves and used as negative control. For sap preparation, leaves were homogenized with a mortar in 2 mL of phosphate buffer 0.01 M pH 7.2 (ratio 1:10). Fifteen 4-week-old plants per variety were inoculated separately with each sap. All inoculated plants exhibited streak mosaic symptoms 13 days post-inoculation (fig. 1b), and the presence of SCSMV in the inoculated plants was confirmed by DAS-ELISA. Total RNA was extracted from four symptomatic leaf samples, one symptomless and one DAS-ELISA positive sample using TRIzol reagent (Invitrogen, Carlsbad, CA, USA). cDNA was synthesized using M-MLV Reverse Transcriptase (Promega, Cat.No.M1705, Madison, WI, USA) following the manufacturer’s instructions. A 690-nucleotide fragment of the CP gene was amplified by reverse transcription-polymerase chain reaction (RT-PCR) with primers SCSMV-F690 and SCSMV-R690 (Viswanathan et al. 2008). All primers were synthesized by Eurogentec (Seraing, Belgium). Aliquots of RT-PCR products (5 μl) were analyzed by electrophoresis on 1.2 % (w/v) agarose gel, stained with ethidium bromide and visualized on a UV transilluminator (Fig. 2). An amplification product of the expected size was obtained for all five symptomatic or DAS ELISA positive but not for the symptomless sample. Two RT-PCR products were sequenced and deposited in GenBank under accession Nos. LR594547 and LR594582. These partial CP gene sequences shared highest nucleotide identity with two isolates of SCSMV from India in GenBank: 91% with JN315855 and 90% with EF655859, thus confirming that SCSMV was occurring in sugarcane in Côte d’Ivoire. To our knowledge, this is the first report of natural infection of sugarcane by SCSMV in Africa. Streak mosaic is a serious threat to the entire sugar industry in West Africa and needs further investigations as it may affect sugarcane yields and impact local economies. Our findings further illustrate the need to develop virus-free germplasm for local, national, and international distribution of sugarcane.
RÉSUMÉObjectif : Cette étude vise à caractériser la végétation du Parc National du Mont Péko en termes de composition floristique et de présence d'espèces à statut particulier ainsi que la valeur du parc pour la conservation. Méthodologie et résultats : Un échantillonnage de la végétation a été conduit dans trois zones du Parc National du Mont Péko (PNMP), en Côte d'Ivoire. Quinze placettes de 400 m 2 ont été mises en place. La flore est riche de 384 espèces appartenant à 88 familles. Les familles les plus riches en espèces sont celles des Fabaceae, des Rubiaceae, des Malvaceae et des Moraceae. Parmi les espèces recensées, 74 sont endémiques, rares et menacées d'extinction au plan national, régional ou international. L'étude a montré que quatre des principales valeurs pour la conservation de la biodiversité sont atteintes par la forêt du parc. Conclusion et application : Cette étude met en évidence l'importance de la sauvegarde du Parc National du Mont Péko, une aire protégée montagneuse, fragile et menacée de disparition. Aussi, la présence de nombreuses espèces à statut particulier justifie l'inclusion du parc dans le « Guinean Forests of West Africa Hotspot» d'importance mondiale pour leur biodiversité. Les différentes caractéristiques du parc révélées par cette étude sont des connaissances nécessaires aux plans de gestion. Mots clés : Biodiversité, valeur de conservation, Mont Péko, Côte d'Ivoire Abstract Objective: This study aims to assess the plant species diversity and the conservation value for biodiversity of the Mont Péko National Park. Methodology and results: A botanical sampling was conducted in three areas of the Mont Péko National Park (PNMP), Côte d'Ivoire. Fifteen plots of 400 m 2 were established. Three hundred eighty-four (384) plant species belonging to 88 families have been recorded. The richest botanical families are the Fabaceae, Rubiaceae, Malvaceae, and Moraceae. Among the recorded species, 74 are endemics, rare and threatened at national, regional or international level. The study shows that four of the main conservation values for biodiversity are realized.
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