Caractéristiques Agronomiques et Identification des Facteurs Déterminant la Faible Productivité des Agroforêts à Cacaoyers (Theobroma Cacao L.) au Togo

Les agroforêts à cacaoyers du Togo sont caractérisées par leur faible productivité. L’objectif de cette étude est d’identifier les caractéristiques agronomiques et les facteurs déterminant la faible productivité des cacaoyers. Une enquête a été menée auprès de 385 cacaoculteurs suivie d’une prospection réalisée dans 88 vergers de cacaoyers répartis en quatre tranches d’âge : les jeunes plantations entrant en production (5 à 10 ans), les cacaoyers adultes en pleine production (10 à 20 ans), les cacaoyers vieillissants dont la production est en déclin (21 à 30 ans) et les vieilles plantations (>30 ans). Les résultats ont montré que la tranche d’âge moyenne des vergers est comprise entre 10 et 20 ans. Ces vergers sont essentiellement installés sur les anciens champs de cacaoyers (42,6%) et sur précédent forestier (40,3%) avec du matériel végétal constitué en grande partie d’hybrides sélectionnés (82,9%). Les fréquences de désherbages, des traitements phytosanitaires (insecticides et fongicides) et d’applications de fumure (organique et minérale) sont inférieures aux normes recommandées par la recherche. Les rendements moyens sont faibles et sont compris entre 218,64 kg/ha dans les vieilles plantations (> 30 ans) et 450,77 kg/ha dans les plantations adultes en pleine production (10 à 20 ans). En ce qui concerne les différentes sous zones agroécologiques, les résultats ne révèlent aucune différence significative pour les rendements. Ces rendements varient de 305,76 kg/ha dans la sous zone de plateaux à 376,59 kg/ha dans la sous zone de Kloto-Litimé. Cette faible productivité est liée au faible niveau de gestion et d’entretien des vergers, aux caractéristiques des peuplements cacaoyers et des peuplements associés. Cocoa agroforests in Togo are characterized by their low productivity. The objective of this study is to identify the agronomic characteristics and factors determining the low productivity of cocoa trees. A survey was conducted among 385 cocoa farmers followed by a survey carried out in 88 cocoa orchards and four age groups were considered: young plantations entering production (5 to 10 years), adult cocoa trees in production (10 to 20 years), aging cocoa trees in production (21 to 30 years) and old plantations (>30 years). The results showed that the mean age group of orchards is 10 to 20 years old. These orchards are mainly installed on old cocoa fields (42.6%) and on previous forest (40,3%) with plant material consisting largely of selected hybrids (82,9%). The frequencies of weeding, phytosanitary treatments (insecticides and fungicides) and manure applications (organic and mineral) are below the standards recommended by research. Average yields are low and range between 218,64 kg/ha in old plantations (> 30 years) and 450,77 kg/ha in adult plantations in production (10 to 20 years). With regard to the different agro-ecological sub-zones, the results show that yields vary from 305,76 kg/ha in the plateau sub-zone to 376,59 kg/ha in the Kloto-Litimé sub-zone. This low productivity is linked to the low level of management and maintenance of orchards, to the characteristics of cocoa stands and associated stands. &nbsp

Arbuscular mycorrhizal fungal communities in sub-Saharan Savannas of Benin, West Africa, as affected by agricultural land use intensity and ecological zone

The rapid decline of soil fertility of cultivated lands in the sub-Saharan savannas of West Africa is considered to be the main cause of the increasingly severe constraints of food production. The soils in this tropical area are highly fragile, and crop yields are limited by characteristically low levels of available phosphorus. Under such preconditions, the multiple benefits of the arbuscular mycorrhizal (AM) symbiosis are likely to play a pivotal role for maintaining natural soil fertility by enhancing plant nutrient use efficiency, plant health, and stabilization of a favorable soil structure. Thus, it is important to explore the impact of the commonly applied farming practices on the native AM fungal community. In the present study, we determined the AM fungal species composition in three ecological zones differing by an increasingly prolonged dry season from South to North, from the Southern Guinea Savanna (SG), to the Northern Guinea Savanna (NG), to the Sudan Savanna (SU). In each zone, four "natural” and four "cultivated” sites were selected. "Natural” sites were three natural forest savannas (at least 25-30years old) and a long-term fallow (6-7years old). "Cultivated” sites comprised a field with yam (Dioscorea spp.) established during the first year after forest clearance, a field under mixed cropping with maize (Zea mays) and peanut (Arachis hypogaea), a field under peanut, and a field under cotton (Gossypium hirsutum) which was the most intensively managed crop. Soil samples were collected towards the end of the wet season in each zone. AM fungal spores were extracted and morphologically identified. Soil subsamples were used to inoculate AM fungal trap cultures using Stylosanthes guianensis and Brachiaria humidicola as host plants to monitor AM root colonization and spore formation over 10 and 24months, respectively. A total of 60 AM fungal species were detected, with only seven species sporulating in the trap cultures. Spore density and species richness were generally higher in the natural savannas and under yam than at the other cultivated sites and lowest under the intensively managed cotton. In the fallows, species richness was intermediate, indicating that the high richness of the natural savannas was not restored. Surprisingly, higher species richness was observed in the SU than in the SG and NG, mainly due to a high proportion of species in the Gigasporaceae, Acaulosporaceae, and Glomeraceae. We conclude that the West African savannas contain a high natural AM fungal species richness, but that this natural richness is significantly affected by the common agricultural land use practices and appears not to be quickly restored by fallo

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

Efficacité des pièges à paraphéromone dans la protection des vergers de manguiers greffés contre les mouches des fruits au Togo

Les mouches de fruits en infestant les mangues greffées causent des pertes considérables et un manque à gagner aux différents  acteurs en passant par les producteurs jusqu’aux consommateurs. Pour venir à bout de ces insectes nuisibles, la pulvérisation des insecticides chimiques de synthèse est généralement la solution la plus commune et de premier recours dans toutes les régions du Togo. Mais cette méthode reste dangereuse pour la santé humaine et environnementale et peu rentable économiquement. Cette étude a pour objective de tester l’efficacité du piège Biofeed, une solution alternative, respectueuse de l’environnement et de la santé de l’Homme. Trois vergers d’environ 1 ha pour les trois traitements (piège Biofeed, piège M3 et le control) ont été choisis dans chacune des cinq régions du Togo. Les pièges ont été installés à la prématuration des fruits à une densité de 25 pièges/ha et sont suivis toutes les deux semaines jusqu’à la récolte finale en procédant aux échantillonnages des mangues pour l’évaluation du taux infestation et identification des espèces de mouche de fruits. Après la pose et le suivi des infestations, les pièges Biofeed se sont révélés efficaces en réduisant sur le plan national les dégâts des mouches de fruits de 73,60% tandis que les pièges M3 n’ont entrainé qu’une réductionde 39,94%. Les vergers ayant bénéficiés de ces pièges ont connu des taux d’infestations faibles promettant une bonne récolte. L’incubation des mangues récoltées dans les vergers ont permis de recenser 4 genres de mouches de fruits (Bactrocera, Ceratitis, Dacus, Zeugodacus) et Bactrocera dorsalis est l’espèce la plus abondante retrouvée sur ce fruit d’importance économique. Mots clés : Mouches de fruit, mangue greffée, piège Biofeed, piège M3.   English  title: Efficacy of parapheromone traps in the protection of grafted mango orchards against fruit flies in TogoFruit flies by infesting grafted mangoes cause considerable losses and loss of profit to the various actors range from producers to consumers. To control these pests, synthetic chemical insecticides use is generally the most common and first resort solution in all regions of Togo. But this method remains dangerous for human and environmental health. The objective of this study was to test the effecacy of Biofeed trap, an alternative solution that is environmentally friendly in comparison with a trap already used in the field (M3 traps based on food bait). Three orchards of about 1 ha for the 3 treatments (Biofeed trap, M3 trap and control) were chosen in each of the five regions of Togo. The traps were installed at the premature fruit maturity at a density of 25 traps / ha and were monitored every two weeks until the final harvest by sampling the mangoes for the assessment of the infestation rate and identification of fruits fly species. After setting traps and monitoring the infestations, Biofeed traps proved effective by reducing fruit fly damage by 73.60% nationally, while M3 traps by 39.94%. The orchards that benefited from these traps had low infestation rates that promissing a good harvest. Incubation of the mangoes harvested in the orchards have allowed to identify 4 genera of fruit flies (Bactrocera, Ceratitis,Dacus, Zeugodacus) and Bactrocera dorsalis is the most abundant species found on this economically important fruit.Keywords: Fruit flies, grafted mango, Biofeed and M3 traps

Effets De La Fertilisation Sur Les Nématodes Parasites Et Le Rendement En Rhizomes Frais Du Gingembre, Zingiber officinale Rosc

Ginger, Zingiber officinale is one of the most cultivated spices in the world. Therefore its production is often subject to high pest and disease pressures, particularly that of plant parasitic nematodes. For the sustainable management of parasitic nematodes of ginger, a trial was conducted at Agronomic Research Station of the Graduate School of Agronomy at the University of Lomé to assess the efficacy of some organo-mineral fertilizers on parasitic nematodes. An organic manure based on house waste valorization in three doses (0tha -1 ; 15tha-1 and 25tha-1 ) and five mineral fertilizer formulations from simple mineral fertilizers (Urea 46%, the chloride of potassium and the triple superphosphate): N0P0K0; N45P15K60; N70P50K50; N90P30K100 and N125P90K100) were used according to a split plot design. The inventory of the nematodes permitted to count five genders of nematodes: Meloidogyne; Xiphinema; Longidorus; Helicotylenchus and Pratylenchus. The results indicated that an input of 25 tons of organic manure associated with mineral fertilizer of N70P50K50 and N125P90K100 reduce nematode density by up to 58.62% in roots and 95.88% in soil compared to the treatment without manure and mineral fertilizer. The yield of fresh rhizomes vary from 2.9 to 7.7 t/ha with little statistically effects of the manures. This study reveals that nematodes constitute a serious phytosanitary problem for ginger and that the contribution of organo-mineral fertilization makes it possible to reduce the density of nematodes under ginger

Evaluation Au Champ Du Potentiel De Croissance Et De La Production Du Riz (Oryza Sativa L.) Variété IR841 Inoculé En Pépinière Par Quatre Souches De Champignons Mycorhiziens À Arbuscules

The growth and production of rice (Oryza sativa L.) variety IR841 were evaluated in response to arbusular mycorrhizal fungus (AMF) inoculation. Four strains of AMF (Acaulospora spinosa, BEN 10, Glomus mosseae and G. hoi) were tested at 1.96 x 105 ; 3.91 x 105 and 7.82 x 10 5 spores/ha during two growing seasons 2016 and 2017, in a complete random block design. Uninoculated plants and plants fertilized with chemical fertilizer were used as control. The experiments conducted for 19 weeks including 5 weeks in nursery and 14 weeks in field tests showed better development and production of rice in inoculated plants compared to uninoculated controls. The tested rice variety was highly dependent on arbuscular mycorhization. For each strain the rate of mycorhization was dose dependent. The different growth parameters such as the height of the plant, the development of the root system, the total biomass, the number of tillers, the number of fertile panicles per plant, the number of paddy grains per panicle and the paddy grain yield, were positively correlated with the rate of root mycorhization. This study showed that biofertilizers based on mycorrhizal fungi provide important benefits to the plant, and can be used to improve the growth and yield of rice in Togo. The results are discussed in terms of usingAMF as alternative to chemical fertilizer in rice production system

Arbuscular mycorrhizal fungi in the Sub-Saharan Savannas of Benin an their association with yam (Dioscorea spp.) : potential of yam growth promotion and reduction of nematode infestation

The arbuscular mycorrhiza is the most widely occurring and important microbial symbiosis for agricultural crops and well known to facilitate plant mineral nutrient uptake, particularly under conditions of P-limitation - as it is common in tropical soils due to leaching or/and severe immobilization - and, moreover, it is understood to improve plant water relations and provide resistance against pests and pathogens. Yam (Dioscorea spp.) is the most important tuber crop in terms of coverage area in West Africa, particularly in Benin and Togo. Alarmingly, the annual yam production per hectare has recently decreased considerably due to a loss of soil fertility and pest and disease (especially nematode) damage. Under field conditions, yam and arbuscular mycorrhizal fungi (AMF) are naturally associated with each other. Currently, however, data on the ecology of AMF in West Africa are lacking with very limited information on the mycorrhizal status of yam. There may be potential to improve growth and to protect plants against nematodes by AMF but this is possibly dependent on specific AMF-nematode-host combinations. The present project aimed at studying AMF indigenous to West Africa, with respect to yam growth promotion and yam nematode suppression. The specific objectives focused on assessing the (1) diversity of AMF, including their distribution, abundance and relation to agronomic practices and ecological conditions; (2) the mycorrhizal status of yam; and (3) the specific associations between (a) yam-AMF, and (b) yam-AMF -nematode in vivo under greenhouse conditions. In the first part of our study, we determined the influence of three ecological zones (from wettest to driest) and of land use intensity on the diversity of AMF in the yam growing area of Benin, West Africa. In each zone, four ‘natural’ and four ‘cultivated’ sites were selected. ‘Natural’ sites included three natural forest savannas (at least 25-30 years old) and a long-term fallow (6-7 years old). ‘Cultivated’ sites comprised yam fields established immediately following forest clearance, mixed cropping maize (Zea mays) and peanut (Arachis hypogaea) fields, peanut fields, and fields under cotton (Gossypium hirsutum), which was the most intensively managed crop. Soil samples were collected towards the end of the wet season in each zone. AMF spores were extracted and identified morphologically. A total of 60 AMF species was detected, with only seven species sporulating in AMF trap cultures that were set up with various AMF host plants. Higher species richness was observed in the northern most, driest ecological zone Sudan Savanna (SU) than in the adjacent zones to the south with increasing humidity, namely the Northern Guinea Savanna (NG) and the Southern Guinea Savanna (SG), mainly due to a high proportion of species in the Gigasporaceae, Acaulosporaceae and Glomeraceae. Within each ecological zone, spore density and species richness were generally higher in the natural savannas and in association with yam than in the other cultivated sites. These parameters were lowest under the intensively managed cotton, and intermediate in the fallows, indicating that the high richness of the natural savannas is not necessarily restored during fallowing. Assuming that yam is an arbuscular mycorrhizal crop, we addressed the question of which AMF species are associated with yam. Our aim was to propagate the AMF communities from three natural forests and three adjacent yam fields of the SG in Benin in trap cultures and to assess the AMF richness, identifying those associated with yam. Soil samples were collected in the dry season (February 2005) and used to identify AMF spores directly and also to establish AMF trap cultures on yam (tissue culture plantlets of D. rotundata and D. cayenensis) and, for comparison, on Sorghum bicolor. In the trap cultures, AMF root colonization was particularly high in yam (70-95%), compared with S. bicolor (11-20%). Based on spore morphotyping, 37 AMF species were detected in the ‘trap’ rhizosphere of S. bicolor, while 28 and 29 species were identified as fungal symbionts of D. cayenensis and D. rotundata, respectively. Following eight months cultivation in trap cultures, yam tuber dry weight was generally higher in mycorrhizal than in non-mycorrhizal control pots. We also hypothesized that indigenous AMF species and strains isolated from yam plantlets in trap cultures may be more beneficial for yam plant growth compared to non-indigenous isolates. We screened indigenous AMF species and strains that have been isolated from the trap cultures and compared their effects on micro-propagated white yam plantlets (D. rotundata) (cv. TDr89- 02461) against exotic AMF isolates in pot experiments over seven months. First, we tested several indigenous and non-indigenous (South America and Asia) G. etunicatum strains with regard to their effect on yam growth promotion and mineral accumulation in the tissues. Secondly, three isolates each of nine indigenous AMF species and three additional non-tropical AMF species were screened on the same yam cultivars. We found that most tropical AMF isolates of G. etunicatum increased yam tuber dry weight, while the non-tropical AMF isolates had a lower or no effect, but instead increased tuber P concentrations, when compared to nonmycorrhizal controls. Glomus mosseae, G. hoi, G. etunicatum, Acaulospora scrobiculata and A. spinosa generally had a positive effect on tuber growth, while isolates of G. sinuosum and Kuklospora kentinensis generally did not. Finally, we assessed the interaction between yam and AMF in the presence or absence of plant parasitic nematodes. Yam vplants cultivated in vitro were used, which were inoculated with commercial inocula of G. mosseae and G. dussii (Biorize, Dijon France). In the presence of nematodes (Scutellonema bradys and Meloidogyne spp.), inoculation of G. mosseae generally increased growth of micropropagated yam plantlets and yam tuber weight production, especially cultivars from D. alata. Tubers were, in general, less infected with S. bradys, but not necessarily with Meloidogyne spp. However, application of G. mosseae and G. dussii to micropropagated plantlets resulted in improved quality of yam tubers, when challenged with nematodes, compared to nematode inoculation without AMF, indicating a positive effect of AMF on yam productivity. Our results indicate that the AMF richness is high in the ‘yam belt’ of Benin, but that it is strongly influenced by the ecological zone and by the intensity of land cultivation after forest clearance. Our results also indicate that in controlled pot studies, AMF can suppress nematode damage and additionally lead to improved quality and weight of yam tubers. The present results remain preliminary, however, while results from ongoing studies currently in the field will help to determine further their potential in the longer term. These results provide exciting prospects for African crop production, in addition to illuminating the wide and diverse species richness of West African AMF and their potential benefits

Bioferlizing and Nematodes Control Potentials of Four Native Isolates of Arbuscular Mycorrhizal Fungi on Sweet Pepper (Capsicum annuum) in Togo

Aims: The aim of the study was to investigate the effectiveness of four isolates of the native Arbuscular Mycorrhizal Fungus (AMF) in improving pepper plant yield as well as to assess their potential for the control of nematodes. Study Design: The experimental set up consisted of a Completely Randomized Block Design with 5 treatments corresponding to the four isolates of AMF– BEN10, GM142, 472, and WA330 – tested in comparison with the untreated plants as a control treatment. Place and Duration of Study: The study was conducted in 2020 from June to September « at the Research Station of the Faculty of Agronomy, University of Lomé, Togo». Methodology: The seeds of pepper were inoculated with the four AMF isolates in the nursery. Six weeks after, the seedlings were transplanted on 3mx6m beds. Several growth parameters such as the number of leaves and branches, plant height, number of flower buds and fruit weight were recorded each three weeks after transplantation. Nematode density was assessed four times (before transplanting, at the flowering, during fruiting, and after the last harvest of pepper fruits). Results: The AMF increased significantly the marketable pepper fruit weight by 39%, and reduced significantly the root nematode density by 20-34%. A positive correlation (P<0.0001; r = 0.816) was observed between the mycorrhization frequency and mycorrhization intensity, the former was varied from 70% to 91% and the latter from 60% to 85%. The plant height, the number of leaves, the branches and the number of flower buds were not affected by AMF inoculation. Conclusion: The present study showed the potential of AMF to be considered alternative candidate to chemical fertilizers and pesticides for sustainable production of sweet pepper in Togo

Effet de quatre souches de champignons mychoriziens arbusculaires sur Meloidogyne spp., principal nématode parasitaire du soja (Glycine max, L.) au Togo.

Objectif : L’objectif de cette étude est d’évaluer l’effet de quatre souches de champignon mycorhizien arbusculaire d’origine locale sur la production du soja et le contrôle des nématodes parasitaires, Meloidogyne sp. au champ.Méthodologie et résultats : L’essai a été conduit à la Station d’Expérimentation Agronomique de Lomé au Togo, de Juillet à Octobre 2016 suivant un dispositif de Fisher à quatre répétitions. Glomus mosseae, Glomus hoï, Acaulospora spinoza et BEN 10 ont été testées en comparaison au témoin. L’inoculation a été faite lors du semis du soja. Il ressort de cette étude que les plants de soja inoculés sont fortement mycorhizés. Sur les quatre souches dans cette étude, Glomus mosseae a induit la meilleure réduction de la densité des nématodes dans les racines, entrainant une amélioration du rendement en graines du soja.Conclusion et applications des résultats : Cette étude a montré que l’inoculation directe des CMA pendant le semis entraine une réduction de la densité des nématodes parasites et améliore le rendement du soja. Elle peut donc être un des moyens écologiquement durable de production du soja au Togo.Mots clés : Inoculation mycorhizienne, nématodes, rendement, soja