HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific re... more HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.
Les champignons ectomycorhiziens des arbres forestiers en Afrique de l’Ouest
Figure 2(A) Sporophores (flèche) de Pisolithus stobus au voisinage d'Eucalyptus camaldulensin... more Figure 2(A) Sporophores (flèche) de Pisolithus stobus au voisinage d'Eucalyptus camaldulensins ;(B) sporophores matures et primordiums de Pisolithus strobus Figure 3Ectomycorhizes jaune ocre de Pisolithus sp. et d'Eucalyptus camaldulensis Figure 10Exacavation pour prélever des ectomycorhizes sur une racine suivie depuis le tronc. On note la proximité d'un sporophore (flèche) de Pisolithus strobus. Figure 23Synthèse ectomycorhizienne en minirhizotron ;(A) carton recouvert de mycélium ;(B) p..
Les champignons ectomycorhiziens des arbres forestiers en Afrique de l’Ouest
INTRODUCTION Les micro-organismes du sol sont extrêmement diversifiés et comprennent des groupes ... more INTRODUCTION Les micro-organismes du sol sont extrêmement diversifiés et comprennent des groupes très différents dont les plus importants sont les bactéries, les champignons et les protozoaires. Parmi les micro-organismes telluriques figurent certains champignons qui induisent, au niveau des racines de plantes, des organes nouveaux appelés mycorhizes, les symbioses végétales les plus répandues dans les écosystèmes terrestres (Fortin et al., 2008 ; Smith et Read, 2008). Les mycorhizes jouent ..
Les champignons ectomycorhiziens des arbres forestiers en Afrique de l’Ouest
INTRODUCTION Dans les régions tempérées, les champignons ectomycorhiziens améliorent de façon rem... more INTRODUCTION Dans les régions tempérées, les champignons ectomycorhiziens améliorent de façon remarquable la croissance et la nutrition minérale des arbres (Smith et Read, 2008). Ils permettent aussi aux arbres de mieux résister à certaines maladies racinaires et d’exploiter au mieux les ressources en eau. En revanche, dans les régions tropicales naturelles où la diversité des essences forestières est plus grande, il existe très peu de données équivalentes sur le rôle des champignons ectomyco..
INTRODUCTION De nombreuses espèces de champignons ectomycorhiziens sont des comestibles de valeur... more INTRODUCTION De nombreuses espèces de champignons ectomycorhiziens sont des comestibles de valeur. Parmi celles-ci, la truffe noire du Périgord, le matsutake, les chanterelles et les bolets sont, mondialement, les plus connus des champignons forestiers. Cependant, la plupart de nos informations proviennent des pays tempérés. Très peu de connaissances sont actuellement disponibles sur la comestibilité des champignons tropicaux. Cela est particulièrement vrai en Afrique de l’Ouest, même si une ..
Global trade increases plant introductions, but joint introduction of associated microbes is over... more Global trade increases plant introductions, but joint introduction of associated microbes is overlooked. We analyzed the ectomycorrhizal fungi of a Caribbean beach tree, seagrape (Coccoloba uvifera, Polygonacaeae), introduced pantropically to stabilize coastal soils and produce edible fruits. Seagrape displays a limited symbiont diversity in the Caribbean. In five regions of introduction (Brazil, Japan, Malaysia, Réunion and Senegal), molecular barcoding showed that seagrape mostly or exclusively associates with Scleroderma species (Basidiomycota) that were hitherto only known from Caribbean seagrape stands. An unknown Scleroderma species dominates in Brazil, Japan and Malaysia, while Scleroderma bermudense exclusively occurs in Réunion and Senegal. Population genetics analysis of S. bermudense did not detect any demographic bottleneck associated with a possible founder effect, but fungal populations from regions where seagrape is introduced are little differentiated from the Caribb...
Pterocarpus officinalis (Jacq.) is a leguminous forestry tree species endemic to Caribbean swamp ... more Pterocarpus officinalis (Jacq.) is a leguminous forestry tree species endemic to Caribbean swamp forests. In Guadeloupe, smallholder farmers traditionally cultivate flooded taro (Colocasia esculenta) cultures under the canopy of P. officinalis stands. The role of arbuscular mycorrhizal (AM) fungi in the sustainability of this traditional agroforestry system has been suggested but the composition and distribution of AM fungi colonizing the leguminous tree and/or taro are poorly characterized. An in-depth characterization of root-associated AM fungal communities from P. officinalis adult trees and seedlings and taro cultures, sampled in two localities of Guadeloupe, was performed by pyrosequencing (GS FLX+) of partial 18S rRNA gene. The AM fungal community was composed of 215 operational taxonomic units (OTUs), belonging to eight fungal families dominated by Glomeraceae, Acaulosporaceae, and Gigasporaceae. Results revealed a low AM fungal community membership between P. officinalis and C. esculenta. However, certain AM fungal community taxa (10% of total community) overlapped between P. officinalis and C. esculenta, notably predominant Funneliformis OTUs. These findings provide new perspectives in deciphering the significance of Funneliformis in nutrient exchange between P. officinalis and C. esculenta by forming a potential mycorrhizal network.
Ectomycorrhizal networks may facilitate the establishment and survival of seedlings regenerating ... more Ectomycorrhizal networks may facilitate the establishment and survival of seedlings regenerating under the canopies of tropical forests and are often invoked as a potential contributor to monodominance. We identified ectomycorrhizal fungi in a monodominant Gilbertiodendron dewevrei (Fabaceae) rain forest in Cameroon, using sporocarps and ectomycorrhizae of three age categories (seedlings, intermediate trees, and large trees) and tentatively revealed nutrient transfer through ectomycorrhizal networks by measuring spontaneous isotopic (13 C and 15 N) abundances in seedlings. Sporocarp surveys revealed fewer ectomycorrhizal fungal taxa (59 species from 1030 sporocarps) than molecular barcoding of ectomycorrhizal roots (75 operational taxonomic units from 828 ectomycorrhizae). Our observations suggest that ectomycorrhizal fungal diversity is similar to that in other mixed tropical forests and provide the first report of the Tuber-Helvella lineage in a tropical forest. Despite some differences, all age categories of G. dewevrei had overlapping ectomycorrhizal fungal communities, with families belonging to Thelephoraceae, Russulaceae, Sebacinaceae, Boletaceae, and Clavulinaceae. Of the 49 operational taxonomic units shared by the three age categories (65.3% of the ectomycorrhizal fungal community), 19 were the most abundant on root tips of all categories (38.7% of the shared taxa), supporting the likelihood of ectomycorrhizal networks. However, we obtained no evidence for nutrient transfer from trees to seedlings. We discuss the composition of the ectomycorrhizal fungal community among the G. dewevrei age categories and the possible role of common ectomycorrhizal networks in this rain forest.
We studied belowground and aboveground diversity and distribution of ectomycorrhizal (EM) fungal ... more We studied belowground and aboveground diversity and distribution of ectomycorrhizal (EM) fungal species colonizing Coccoloba uvifera (L.) L. (seagrape) mature trees and seedlings naturally regenerating in four littoral forests of the Guadeloupe island (Lesser Antilles). We collected 546 sporocarps, 49 sclerotia, and morphotyped 26,722 root tips from mature trees and seedlings. Seven EM fungal species only were recovered among sporocarps (Cantharellus cinnabarinus, Amanita arenicola, Russula cremeolilacina, Inocybe littoralis, Inocybe xerophytica, Melanogaster sp., and Scleroderma bermudense) and one EM fungal species from sclerotia (Cenococcum geophilum). After internal transcribed spacer (ITS) sequencing, the EM root tips fell into 15 EM fungal taxa including 14 basidiomycetes and 1 ascomycete identified. Sporocarp survey only weakly reflected belowground assessment of the EM fungal community, although 5 fruiting species were found on roots. Seagrape seedlings and mature trees had...
• The influence of two fluorescent pseudomonads strains (HR13 and HR26) on the ectomycorrhizal sy... more • The influence of two fluorescent pseudomonads strains (HR13 and HR26) on the ectomycorrhizal symbiosis between Pisolithus alba and Acacia holosericea is reported here. • We measured ectomycorrhizal establishment, fungal growth in the soil (by HPLC) and soil microbial biomass (using the fumigation-extraction method) in treatments with or without pseudomonads. • Bacteria inoculated with the fungal symbiont stimulated ectomycorrhizal formation and shoot or root biomass. Only HR13 significantly increased fungal biomass in the soil. The bacteria stimulated fungal growth and production of phenolic compounds. Sequence analysis of the two fluorescent Pseudomonas revealed 99% homologuey between HR13 and P. monteilii , and 98% between HR26 and P. resinovorans. • It is clear that some bacteria (Mycorrhiza Helper Bacteria) can stimulate the establishment of the ectomycorrhizal symbiosis in tropical conditions.
Although mycorrhizal symbiosis are well known on European, North American, South American, Southe... more Although mycorrhizal symbiosis are well known on European, North American, South American, Southeast Asian, and Australian plant species from natural or anthropogenic ecosystems, data from Africa are still scarce and neglected. The international workshop on "Mycorrhiza: a biological tool for sustainable development in Africa" held in Dakar, Senegal, February 21-23, 2011, was therefore particularly timely. Eighty-seven participants from 23 countries attended the workshop, which included oral presentations, poster sessions, excursion and many free-ranging discussions. Abstracts of all the talks and posters, and details of the participants can be found on the website http://www.ird.sn/web-mycorhizes2011/. The aim of the workshop was to present state of the knowledge and perspectives in mycorrhizal research on tropical and Mediterranean plant species in Africa. The contents addressed diversity and function of mycorrhiza associated with forest and agricultural plants, in Mediterranean and tropical, wet and seasonally dry ecosystems. Impacts of mycorrhiza on plant diversity and composition, regeneration and dynamics of ecosystems, and biomass production in forestry and agriculture, were topics for oral presentations
The ectomycorrhization of two Australian Acacia species (A. mangium and A. holosericea) with two ... more The ectomycorrhization of two Australian Acacia species (A. mangium and A. holosericea) with two basidiomycetes (Pisolithus and Scleroderma) was studied in sterilized and unsterilized soils. The three fungal isolates, two exotic strains (Pisolithus COI 007 and COI 024) and one indigenous (Sclerodermal) enhanced the development of the Acacia species. In the unsterilized soil, the number of nodules per plant of indigenous rhizobia was increased when the plants had associated mycorrhizae. The plant parasitic nematode community was reduced by the fungal strains, especially for H. pararobustus with A. holosericea. The ectomycorrhizal associations of the Australian Acacias, mostly unknown in West Africa, appears to be very promising for use of these trees in afforestation programs.
Controlled mycorrhizal infection and phosphate fertilizer use: applications to the domestication ... more Controlled mycorrhizal infection and phosphate fertilizer use: applications to the domestication of the jujube tree. Abstract-Introduction. The jujube tree, Zizyphus mauritiana Lam., is a forest fruit tree required for its fruit by the populations of the Sahel. The species domestication was approached starting from silvicultural techniques like controlled mycorrhizal infection and fertilization with rock phosphates (RP). This document presents a summary of the results acquired on these subjects. Materials and methods. The mycorrhizal dependence of the jujube tree and of twelve other forest fruit tree species was studied regarding two arbuscular mycorrhizal fungi, Glomus aggregatum and G. intraradices. In addition, the capacity of the tree for mobilizing phosphorus from West Africa RP was evaluated in sandy soil, low in assimilable phosphorus and to a slightly acid pH. Jujube trees inoculated with G. aggregatum were then put in the field to follow growth parameters. Results and discussion. Among the thirteen forest fruit tree species studied, the jujube tree proved to be most dependent on mycorrhizal symbiosis with G. aggregatum which acts on its growth and its supply with assimilable phosphorus. The mycorrhized jujube trees mobilize more effectively the phosphorus of the Tilemsi (Mali) RP that those of the Taïba (Senegal) and Kodjari (Burkina Faso) RP. In tree nurseries, controlled mycorrhizal infection has beneficial effects on the growth of jujube trees of various origins. In plantation, this beneficial effect of the inoculation was also observed on some 20 month old trees. Conclusion. The techniques of controlled mycorrhizal infection and fertilization with RP are ready to improve the growth and the phosphatic nutrition of the jujube trees in tree nurseries and the field. However, they will have to be tested in other forest sites to evaluate their effects on the fodder and fruit-bearing production of the jujube trees. West africa / Zizyphus mauritiana / domestication /mycorrhizal infection / arbuscular mycorrhizae / fertilizer application / rock phosphate / phosphorus Mycorhization contrôlée et fertilisation phosphatée : applications à la domestication du jujubier. Résumé-Introduction. Le jujubier, Zizyphus mauritiana Lam., est un arbre fruitier forestier très recherché pour ses fruits par les populations du Sahel. La domestication de cette espèce a été abordée à partir de techniques sylvicoles comme la mycorhization contrôlée et la fertilisation phosphatée avec des phosphates naturels (PN). Le document présente une synthèse des résultats acquis sur ces sujets. Matériel et méthodes. La dépendance mycorhizienne du jujubier et de douze autres espèces d'arbres fruitiers forestiers vis-à-vis de deux champignons mycorhiziens à arbuscules Glomus aggregatum et G. intraradices a été étudiée. Par ailleurs, la capacité de l'arbre à mobiliser du phosphore à partir de PN d'Afrique de l'Ouest a été évaluée dans un sol sableux, pauvre en phosphore assimilable et à pH faiblement acide. Des jujubiers inoculés avec G. aggregatum ont été ensuite mis au champ afin de suivre des paramètres de croissance. Résultats et discussion. Parmi les treize espèces d'arbres fruitiers forestiers étudiés, le jujubier s'est révélé être le plus dépendant de la symbiose mycorhizienne avec G. aggregatum qui agit sur sa croissance et son alimentation en phosphore assimilable. Les jujubiers mycorhizés mobilisent plus efficacement le phosphore des PN de Tilemsi (Mali) que celui des PN de Taïba (Sénégal) et de Kodjari (Burkina Faso). En pépinières, la mycorhization contrôlée a des effets bénéfiques sur la croissance de jujubiers de différentes provenances. Cet effet bénéfique de l'inoculation a aussi été observé en plantation sur des arbres de 20 mois. Conclusion. Les techniques de mycorhization contrôlée et de fertilisation avec des PN sont aptes à améliorer la croissance et la nutrition phosphatée des jujubiers en pépinières et au champ. Cependant, elles devront être testées dans d'autres sites forestiers afin d'évaluer leurs effets sur la production fourragère et fruitière des jujubiers. Afrique occidentale / Zizyphus mauritiana / domestication / mycorhization / mycorhize à arbuscule / fertilisation / phosphate naturel / phosphore Fertilisation phosphatée du jujubier
Tropical legumes from fallowed areas in Senegal were inoculated with a tropical strain of Glomus ... more Tropical legumes from fallowed areas in Senegal were inoculated with a tropical strain of Glomus aggregatum to test their relative mycorrhizal dependency in a greenhouse experiment. Twelve species among the seventeen tested showed a significant growth increase when mycorrhizal. Their mycorrhizal dependency varied from 92.7% for Indigofera stenophylla to 26.2% for Prosopis julifora. A significant positive correlation was found between mycorrhizal dependency and root hair length. The results confirm the high mycorrhizal dependency of legumes which are economically very important in the restoration of soil fertility of fallowed areas in the Sahelian and Soudano-Sahelian zones.
Several strains of Bradyrhizobium, Mesorhizobium and Sinorhizobium strains were tested for their ... more Several strains of Bradyrhizobium, Mesorhizobium and Sinorhizobium strains were tested for their compatibility with an Australian acacia: Acacia holosericea. All bacterial strains induced some nodule formation on roots. However, the rhizobia which greatly increased the development of seedlings belonged to the Bradyrhizobictm genus. The root-knot nematode MeEoitIogyne javanica, strongly inhibited the symbiosis with most of the rhizobial strains. The rhizobia had no effect on nematode multiplication except for bacterial strain ORS 1020 where the final nematode population was higher than in the control treatment. The hypothesis concerning the interactions between nematodes and the nitrogen fixative process are discussed. Moreover, this investigation underlines the decreasing effect of nematodes on the potential benefits that may result from growing A. holosericea inoculated with selected rhizobial strains. 0 2000 Editions scientifiques et medicales Elsevier SAS Forest tree I rhizobia / nematode I Meloidogyne javanica I Acacia holosericea I Bradyrhizobium sp. I Mesorhizobium plurifarium I Sinorhizobium terangae R&urn6-Influence du nkmatode & galles Meloidogyne javanica sur la symbiose fixatrice d'azote entre plusieurs souches de Rhizobia et Acacia holosericea (A Cunn. ex G. Don). Plusieurs souches de Bradyrhizobium, Mesorhizobium et Sinorhizobium ont et6 testees pour leur compatibilite avec un acacia australien : Acacia holosericea. Dans tous les traitements bacteriens, des nodules ont Ctt observes sur les racines. Les effets positifs les plus marques sur le developpement de la plante ont Cd obtenus avec les rhizobia appartenant au genre Bradyrhizobium. Le nematode phytoparasite Meloidogyne javanica a significativement inhibe la symbiose dans la plupart des traitements bacteriens. Les rhizobia n'ont eu aucun effet sur le developpement du nematode except6 pour le traitement bacterien ORS 1020 ou le nombre final de nematodes Ctait superieur a celui du traitement temoin. Les hypotheses concernant les interactions entre les nematodes et la symbiose fixatrice d'azote sont discutees. Ces travaux montrent l'importance des nematodes phytoparasites dans les pratiques d'inoculation contr6lCe destintes a ameliorer le dtveloppement d'arbres a croissance rapide comme A. holosericea. 0 2000 editions scientifiques et medicales Elsevier SAS Arbres de for@t 1 rhizobia I nkmatode I Meloidogyne javanica 1 Acacia holosericea I Bradyrhizobium sp. I Mesorhizobium plurifarium I Sinorhizobium terangae
The diversity of ectomycorrhizal (ECM) fungi on adult trees and seedlings of five species, Anthon... more The diversity of ectomycorrhizal (ECM) fungi on adult trees and seedlings of five species, Anthonotha fragrans, Anthonotha macrophylla, Cryptosepalum tetraphyllum, Paramacrolobium coeruleum and Uapaca esculenta, was determined in a tropical rain forest of Guinea. Ectomycorrhizae were sampled within a surface area of 1600 m 2 , and fungal taxa were identified by sequencing the rDNA Internal Transcribed Spacer region. Thirty-nine ECM fungal taxa were determined, of which 19 multi-hosts, 9 single-hosts and 11 singletons. The multi-host fungi represented 92% (89% when including the singletons in the analysis) of the total abundance. Except for A. fragrans, the adults of the host species displayed significant differentiation for their fungal communities, but their seedlings harboured a similar fungal community. These findings suggest that there was a potential for the formation of common mycorrhizal networks in close vicinity. However, no significant difference was detected for the d 13 C and d 15 N values between seedlings and adults of each ECM plant, and no ECM species exhibited signatures of mixotrophy. Our results revealed (i) variation in ECM fungal diversity according to the seedling versus adult development stage of trees and (ii) low host specificity of ECM fungi, and indicated that multi-host fungi are more abundant than single-host fungi in this forest stand.
HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific re... more HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.
Les champignons ectomycorhiziens des arbres forestiers en Afrique de l’Ouest
Figure 2(A) Sporophores (flèche) de Pisolithus stobus au voisinage d'Eucalyptus camaldulensin... more Figure 2(A) Sporophores (flèche) de Pisolithus stobus au voisinage d'Eucalyptus camaldulensins ;(B) sporophores matures et primordiums de Pisolithus strobus Figure 3Ectomycorhizes jaune ocre de Pisolithus sp. et d'Eucalyptus camaldulensis Figure 10Exacavation pour prélever des ectomycorhizes sur une racine suivie depuis le tronc. On note la proximité d'un sporophore (flèche) de Pisolithus strobus. Figure 23Synthèse ectomycorhizienne en minirhizotron ;(A) carton recouvert de mycélium ;(B) p..
Les champignons ectomycorhiziens des arbres forestiers en Afrique de l’Ouest
INTRODUCTION Les micro-organismes du sol sont extrêmement diversifiés et comprennent des groupes ... more INTRODUCTION Les micro-organismes du sol sont extrêmement diversifiés et comprennent des groupes très différents dont les plus importants sont les bactéries, les champignons et les protozoaires. Parmi les micro-organismes telluriques figurent certains champignons qui induisent, au niveau des racines de plantes, des organes nouveaux appelés mycorhizes, les symbioses végétales les plus répandues dans les écosystèmes terrestres (Fortin et al., 2008 ; Smith et Read, 2008). Les mycorhizes jouent ..
Les champignons ectomycorhiziens des arbres forestiers en Afrique de l’Ouest
INTRODUCTION Dans les régions tempérées, les champignons ectomycorhiziens améliorent de façon rem... more INTRODUCTION Dans les régions tempérées, les champignons ectomycorhiziens améliorent de façon remarquable la croissance et la nutrition minérale des arbres (Smith et Read, 2008). Ils permettent aussi aux arbres de mieux résister à certaines maladies racinaires et d’exploiter au mieux les ressources en eau. En revanche, dans les régions tropicales naturelles où la diversité des essences forestières est plus grande, il existe très peu de données équivalentes sur le rôle des champignons ectomyco..
INTRODUCTION De nombreuses espèces de champignons ectomycorhiziens sont des comestibles de valeur... more INTRODUCTION De nombreuses espèces de champignons ectomycorhiziens sont des comestibles de valeur. Parmi celles-ci, la truffe noire du Périgord, le matsutake, les chanterelles et les bolets sont, mondialement, les plus connus des champignons forestiers. Cependant, la plupart de nos informations proviennent des pays tempérés. Très peu de connaissances sont actuellement disponibles sur la comestibilité des champignons tropicaux. Cela est particulièrement vrai en Afrique de l’Ouest, même si une ..
Global trade increases plant introductions, but joint introduction of associated microbes is over... more Global trade increases plant introductions, but joint introduction of associated microbes is overlooked. We analyzed the ectomycorrhizal fungi of a Caribbean beach tree, seagrape (Coccoloba uvifera, Polygonacaeae), introduced pantropically to stabilize coastal soils and produce edible fruits. Seagrape displays a limited symbiont diversity in the Caribbean. In five regions of introduction (Brazil, Japan, Malaysia, Réunion and Senegal), molecular barcoding showed that seagrape mostly or exclusively associates with Scleroderma species (Basidiomycota) that were hitherto only known from Caribbean seagrape stands. An unknown Scleroderma species dominates in Brazil, Japan and Malaysia, while Scleroderma bermudense exclusively occurs in Réunion and Senegal. Population genetics analysis of S. bermudense did not detect any demographic bottleneck associated with a possible founder effect, but fungal populations from regions where seagrape is introduced are little differentiated from the Caribb...
Pterocarpus officinalis (Jacq.) is a leguminous forestry tree species endemic to Caribbean swamp ... more Pterocarpus officinalis (Jacq.) is a leguminous forestry tree species endemic to Caribbean swamp forests. In Guadeloupe, smallholder farmers traditionally cultivate flooded taro (Colocasia esculenta) cultures under the canopy of P. officinalis stands. The role of arbuscular mycorrhizal (AM) fungi in the sustainability of this traditional agroforestry system has been suggested but the composition and distribution of AM fungi colonizing the leguminous tree and/or taro are poorly characterized. An in-depth characterization of root-associated AM fungal communities from P. officinalis adult trees and seedlings and taro cultures, sampled in two localities of Guadeloupe, was performed by pyrosequencing (GS FLX+) of partial 18S rRNA gene. The AM fungal community was composed of 215 operational taxonomic units (OTUs), belonging to eight fungal families dominated by Glomeraceae, Acaulosporaceae, and Gigasporaceae. Results revealed a low AM fungal community membership between P. officinalis and C. esculenta. However, certain AM fungal community taxa (10% of total community) overlapped between P. officinalis and C. esculenta, notably predominant Funneliformis OTUs. These findings provide new perspectives in deciphering the significance of Funneliformis in nutrient exchange between P. officinalis and C. esculenta by forming a potential mycorrhizal network.
Ectomycorrhizal networks may facilitate the establishment and survival of seedlings regenerating ... more Ectomycorrhizal networks may facilitate the establishment and survival of seedlings regenerating under the canopies of tropical forests and are often invoked as a potential contributor to monodominance. We identified ectomycorrhizal fungi in a monodominant Gilbertiodendron dewevrei (Fabaceae) rain forest in Cameroon, using sporocarps and ectomycorrhizae of three age categories (seedlings, intermediate trees, and large trees) and tentatively revealed nutrient transfer through ectomycorrhizal networks by measuring spontaneous isotopic (13 C and 15 N) abundances in seedlings. Sporocarp surveys revealed fewer ectomycorrhizal fungal taxa (59 species from 1030 sporocarps) than molecular barcoding of ectomycorrhizal roots (75 operational taxonomic units from 828 ectomycorrhizae). Our observations suggest that ectomycorrhizal fungal diversity is similar to that in other mixed tropical forests and provide the first report of the Tuber-Helvella lineage in a tropical forest. Despite some differences, all age categories of G. dewevrei had overlapping ectomycorrhizal fungal communities, with families belonging to Thelephoraceae, Russulaceae, Sebacinaceae, Boletaceae, and Clavulinaceae. Of the 49 operational taxonomic units shared by the three age categories (65.3% of the ectomycorrhizal fungal community), 19 were the most abundant on root tips of all categories (38.7% of the shared taxa), supporting the likelihood of ectomycorrhizal networks. However, we obtained no evidence for nutrient transfer from trees to seedlings. We discuss the composition of the ectomycorrhizal fungal community among the G. dewevrei age categories and the possible role of common ectomycorrhizal networks in this rain forest.
We studied belowground and aboveground diversity and distribution of ectomycorrhizal (EM) fungal ... more We studied belowground and aboveground diversity and distribution of ectomycorrhizal (EM) fungal species colonizing Coccoloba uvifera (L.) L. (seagrape) mature trees and seedlings naturally regenerating in four littoral forests of the Guadeloupe island (Lesser Antilles). We collected 546 sporocarps, 49 sclerotia, and morphotyped 26,722 root tips from mature trees and seedlings. Seven EM fungal species only were recovered among sporocarps (Cantharellus cinnabarinus, Amanita arenicola, Russula cremeolilacina, Inocybe littoralis, Inocybe xerophytica, Melanogaster sp., and Scleroderma bermudense) and one EM fungal species from sclerotia (Cenococcum geophilum). After internal transcribed spacer (ITS) sequencing, the EM root tips fell into 15 EM fungal taxa including 14 basidiomycetes and 1 ascomycete identified. Sporocarp survey only weakly reflected belowground assessment of the EM fungal community, although 5 fruiting species were found on roots. Seagrape seedlings and mature trees had...
• The influence of two fluorescent pseudomonads strains (HR13 and HR26) on the ectomycorrhizal sy... more • The influence of two fluorescent pseudomonads strains (HR13 and HR26) on the ectomycorrhizal symbiosis between Pisolithus alba and Acacia holosericea is reported here. • We measured ectomycorrhizal establishment, fungal growth in the soil (by HPLC) and soil microbial biomass (using the fumigation-extraction method) in treatments with or without pseudomonads. • Bacteria inoculated with the fungal symbiont stimulated ectomycorrhizal formation and shoot or root biomass. Only HR13 significantly increased fungal biomass in the soil. The bacteria stimulated fungal growth and production of phenolic compounds. Sequence analysis of the two fluorescent Pseudomonas revealed 99% homologuey between HR13 and P. monteilii , and 98% between HR26 and P. resinovorans. • It is clear that some bacteria (Mycorrhiza Helper Bacteria) can stimulate the establishment of the ectomycorrhizal symbiosis in tropical conditions.
Although mycorrhizal symbiosis are well known on European, North American, South American, Southe... more Although mycorrhizal symbiosis are well known on European, North American, South American, Southeast Asian, and Australian plant species from natural or anthropogenic ecosystems, data from Africa are still scarce and neglected. The international workshop on "Mycorrhiza: a biological tool for sustainable development in Africa" held in Dakar, Senegal, February 21-23, 2011, was therefore particularly timely. Eighty-seven participants from 23 countries attended the workshop, which included oral presentations, poster sessions, excursion and many free-ranging discussions. Abstracts of all the talks and posters, and details of the participants can be found on the website http://www.ird.sn/web-mycorhizes2011/. The aim of the workshop was to present state of the knowledge and perspectives in mycorrhizal research on tropical and Mediterranean plant species in Africa. The contents addressed diversity and function of mycorrhiza associated with forest and agricultural plants, in Mediterranean and tropical, wet and seasonally dry ecosystems. Impacts of mycorrhiza on plant diversity and composition, regeneration and dynamics of ecosystems, and biomass production in forestry and agriculture, were topics for oral presentations
The ectomycorrhization of two Australian Acacia species (A. mangium and A. holosericea) with two ... more The ectomycorrhization of two Australian Acacia species (A. mangium and A. holosericea) with two basidiomycetes (Pisolithus and Scleroderma) was studied in sterilized and unsterilized soils. The three fungal isolates, two exotic strains (Pisolithus COI 007 and COI 024) and one indigenous (Sclerodermal) enhanced the development of the Acacia species. In the unsterilized soil, the number of nodules per plant of indigenous rhizobia was increased when the plants had associated mycorrhizae. The plant parasitic nematode community was reduced by the fungal strains, especially for H. pararobustus with A. holosericea. The ectomycorrhizal associations of the Australian Acacias, mostly unknown in West Africa, appears to be very promising for use of these trees in afforestation programs.
Controlled mycorrhizal infection and phosphate fertilizer use: applications to the domestication ... more Controlled mycorrhizal infection and phosphate fertilizer use: applications to the domestication of the jujube tree. Abstract-Introduction. The jujube tree, Zizyphus mauritiana Lam., is a forest fruit tree required for its fruit by the populations of the Sahel. The species domestication was approached starting from silvicultural techniques like controlled mycorrhizal infection and fertilization with rock phosphates (RP). This document presents a summary of the results acquired on these subjects. Materials and methods. The mycorrhizal dependence of the jujube tree and of twelve other forest fruit tree species was studied regarding two arbuscular mycorrhizal fungi, Glomus aggregatum and G. intraradices. In addition, the capacity of the tree for mobilizing phosphorus from West Africa RP was evaluated in sandy soil, low in assimilable phosphorus and to a slightly acid pH. Jujube trees inoculated with G. aggregatum were then put in the field to follow growth parameters. Results and discussion. Among the thirteen forest fruit tree species studied, the jujube tree proved to be most dependent on mycorrhizal symbiosis with G. aggregatum which acts on its growth and its supply with assimilable phosphorus. The mycorrhized jujube trees mobilize more effectively the phosphorus of the Tilemsi (Mali) RP that those of the Taïba (Senegal) and Kodjari (Burkina Faso) RP. In tree nurseries, controlled mycorrhizal infection has beneficial effects on the growth of jujube trees of various origins. In plantation, this beneficial effect of the inoculation was also observed on some 20 month old trees. Conclusion. The techniques of controlled mycorrhizal infection and fertilization with RP are ready to improve the growth and the phosphatic nutrition of the jujube trees in tree nurseries and the field. However, they will have to be tested in other forest sites to evaluate their effects on the fodder and fruit-bearing production of the jujube trees. West africa / Zizyphus mauritiana / domestication /mycorrhizal infection / arbuscular mycorrhizae / fertilizer application / rock phosphate / phosphorus Mycorhization contrôlée et fertilisation phosphatée : applications à la domestication du jujubier. Résumé-Introduction. Le jujubier, Zizyphus mauritiana Lam., est un arbre fruitier forestier très recherché pour ses fruits par les populations du Sahel. La domestication de cette espèce a été abordée à partir de techniques sylvicoles comme la mycorhization contrôlée et la fertilisation phosphatée avec des phosphates naturels (PN). Le document présente une synthèse des résultats acquis sur ces sujets. Matériel et méthodes. La dépendance mycorhizienne du jujubier et de douze autres espèces d'arbres fruitiers forestiers vis-à-vis de deux champignons mycorhiziens à arbuscules Glomus aggregatum et G. intraradices a été étudiée. Par ailleurs, la capacité de l'arbre à mobiliser du phosphore à partir de PN d'Afrique de l'Ouest a été évaluée dans un sol sableux, pauvre en phosphore assimilable et à pH faiblement acide. Des jujubiers inoculés avec G. aggregatum ont été ensuite mis au champ afin de suivre des paramètres de croissance. Résultats et discussion. Parmi les treize espèces d'arbres fruitiers forestiers étudiés, le jujubier s'est révélé être le plus dépendant de la symbiose mycorhizienne avec G. aggregatum qui agit sur sa croissance et son alimentation en phosphore assimilable. Les jujubiers mycorhizés mobilisent plus efficacement le phosphore des PN de Tilemsi (Mali) que celui des PN de Taïba (Sénégal) et de Kodjari (Burkina Faso). En pépinières, la mycorhization contrôlée a des effets bénéfiques sur la croissance de jujubiers de différentes provenances. Cet effet bénéfique de l'inoculation a aussi été observé en plantation sur des arbres de 20 mois. Conclusion. Les techniques de mycorhization contrôlée et de fertilisation avec des PN sont aptes à améliorer la croissance et la nutrition phosphatée des jujubiers en pépinières et au champ. Cependant, elles devront être testées dans d'autres sites forestiers afin d'évaluer leurs effets sur la production fourragère et fruitière des jujubiers. Afrique occidentale / Zizyphus mauritiana / domestication / mycorhization / mycorhize à arbuscule / fertilisation / phosphate naturel / phosphore Fertilisation phosphatée du jujubier
Tropical legumes from fallowed areas in Senegal were inoculated with a tropical strain of Glomus ... more Tropical legumes from fallowed areas in Senegal were inoculated with a tropical strain of Glomus aggregatum to test their relative mycorrhizal dependency in a greenhouse experiment. Twelve species among the seventeen tested showed a significant growth increase when mycorrhizal. Their mycorrhizal dependency varied from 92.7% for Indigofera stenophylla to 26.2% for Prosopis julifora. A significant positive correlation was found between mycorrhizal dependency and root hair length. The results confirm the high mycorrhizal dependency of legumes which are economically very important in the restoration of soil fertility of fallowed areas in the Sahelian and Soudano-Sahelian zones.
Several strains of Bradyrhizobium, Mesorhizobium and Sinorhizobium strains were tested for their ... more Several strains of Bradyrhizobium, Mesorhizobium and Sinorhizobium strains were tested for their compatibility with an Australian acacia: Acacia holosericea. All bacterial strains induced some nodule formation on roots. However, the rhizobia which greatly increased the development of seedlings belonged to the Bradyrhizobictm genus. The root-knot nematode MeEoitIogyne javanica, strongly inhibited the symbiosis with most of the rhizobial strains. The rhizobia had no effect on nematode multiplication except for bacterial strain ORS 1020 where the final nematode population was higher than in the control treatment. The hypothesis concerning the interactions between nematodes and the nitrogen fixative process are discussed. Moreover, this investigation underlines the decreasing effect of nematodes on the potential benefits that may result from growing A. holosericea inoculated with selected rhizobial strains. 0 2000 Editions scientifiques et medicales Elsevier SAS Forest tree I rhizobia / nematode I Meloidogyne javanica I Acacia holosericea I Bradyrhizobium sp. I Mesorhizobium plurifarium I Sinorhizobium terangae R&urn6-Influence du nkmatode & galles Meloidogyne javanica sur la symbiose fixatrice d'azote entre plusieurs souches de Rhizobia et Acacia holosericea (A Cunn. ex G. Don). Plusieurs souches de Bradyrhizobium, Mesorhizobium et Sinorhizobium ont et6 testees pour leur compatibilite avec un acacia australien : Acacia holosericea. Dans tous les traitements bacteriens, des nodules ont Ctt observes sur les racines. Les effets positifs les plus marques sur le developpement de la plante ont Cd obtenus avec les rhizobia appartenant au genre Bradyrhizobium. Le nematode phytoparasite Meloidogyne javanica a significativement inhibe la symbiose dans la plupart des traitements bacteriens. Les rhizobia n'ont eu aucun effet sur le developpement du nematode except6 pour le traitement bacterien ORS 1020 ou le nombre final de nematodes Ctait superieur a celui du traitement temoin. Les hypotheses concernant les interactions entre les nematodes et la symbiose fixatrice d'azote sont discutees. Ces travaux montrent l'importance des nematodes phytoparasites dans les pratiques d'inoculation contr6lCe destintes a ameliorer le dtveloppement d'arbres a croissance rapide comme A. holosericea. 0 2000 editions scientifiques et medicales Elsevier SAS Arbres de for@t 1 rhizobia I nkmatode I Meloidogyne javanica 1 Acacia holosericea I Bradyrhizobium sp. I Mesorhizobium plurifarium I Sinorhizobium terangae
The diversity of ectomycorrhizal (ECM) fungi on adult trees and seedlings of five species, Anthon... more The diversity of ectomycorrhizal (ECM) fungi on adult trees and seedlings of five species, Anthonotha fragrans, Anthonotha macrophylla, Cryptosepalum tetraphyllum, Paramacrolobium coeruleum and Uapaca esculenta, was determined in a tropical rain forest of Guinea. Ectomycorrhizae were sampled within a surface area of 1600 m 2 , and fungal taxa were identified by sequencing the rDNA Internal Transcribed Spacer region. Thirty-nine ECM fungal taxa were determined, of which 19 multi-hosts, 9 single-hosts and 11 singletons. The multi-host fungi represented 92% (89% when including the singletons in the analysis) of the total abundance. Except for A. fragrans, the adults of the host species displayed significant differentiation for their fungal communities, but their seedlings harboured a similar fungal community. These findings suggest that there was a potential for the formation of common mycorrhizal networks in close vicinity. However, no significant difference was detected for the d 13 C and d 15 N values between seedlings and adults of each ECM plant, and no ECM species exhibited signatures of mixotrophy. Our results revealed (i) variation in ECM fungal diversity according to the seedling versus adult development stage of trees and (ii) low host specificity of ECM fungi, and indicated that multi-host fungi are more abundant than single-host fungi in this forest stand.
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