Authors : Nathalie Diagne *1, 2, 3 , Diegane Diouf 1, 2 , Sergio Svistoonoff 3 , Aboubacry Kane 1, 2 , Kandioura Noba 1 , Laurent Laplaze 2,3 , Claudine Franche 3 , Didier Bogusz 3 and Robin Duponnois 4 Département de Biologie Végétale, Université Cheikh Anta Diop (UCAD), BP 5005, Dakar, Sénégal1 Laboratoire Commun de Microbiologie IRD/ISRA/UCAD, Centre de Recherche de Bel Air, BP 1386, Dakar, Sénégal2 Equipe Rhizogenèse, Unité mixte de Recherche Diversité et Adaptation et Développement des Plantes (DIADE), Institut de Recherche pour le Développement (IRD), 911 avenue Agropolis, BP 5045, 34394 Montpellier, Cedex 5, France3 Laboratoire des Symbioses Tropicales et Méditerranéennes (LSTM), TA10/J, IRD, UMR 113 CIRAD/INRA/IRD/SUP- AGRO/UM2 34398 Campus International de Baillarguet, Montpellier, Cedex, France4 ABSTRACT The reduction of vegetation cover has considerably increased. A lot of efforts are being undertaken to repair degraded lands. In African countries, exotic plants were established in this purpose to rehabilitate affected ecosystems. These exotic plantations play a key role in improving soils fertility partly because they are able to establish a symbiotic relationship with mycorrhizal fungi which promote plant development and allow better resistance of plant to stresses. Some of these reforestation programs were not successful in certain zones but this situation is overcome when these exotic trees are transferred together with appropriated mycorrhizal fungi from their zone of origin. Nevertheless, furthers studies carried out with exotic trees also showed that inoculation with local or more specific mycorrhizal fungi strains can strongly stimulate plant development. Therefore, it is important to find mycorrhizal fungi strains that are more beneficial for the establishment of exotic trees in foreign areas. In this chapter, we will expose i) the major reforestation programs carried out in arid and semi-arid African zones with exotic trees, discuss ii) the role of mycorrhizal symbiosis in their establishment and iii) in the mitigation of negative influence of these exotic trees in soil microbiota. Keywords: Reforestation, Exotic trees, Arbuscular mycorrhizal fungi, Ectomycorrhizal fungi * Corresponding author: nathalie.diagne@ird.fr; Nathalie.diagne@gmail.com CHAPTER 11 (PP. 215-234) ARBUSCULAR AND ECTOMYCORRHIZA FUNGI: USEFUL BIOLOGICAL TOOL TO PROMOTE ESTABLISHMENT OF EXOTIC TREES IN ARID AND SEMI-ARID AFRICAN AREAS FUNGI: TYPES, ENVIRONMENTAL IMPACT AND ROLE IN DISEASE BOOK DESCRIPTION Fungi are very interesting organisms actively involved in a great number of environmental processes. Both animals and humans can also be affected by fungi, some of them especially important among immuno compromised individuals. This book provides research on the different types, impact and role in disease of fungi. Some of the topics discussed include gut fungi; carbohydrate uptake and catabolism in fungi; candida species as causative agents in infections; effect of polyene antibiotics on the potential pathogenicity factors in saprophytic micromycetes; and ectomycorrhizal fungi and their role in symbiosis.