Role of native and exotic mycorrhizal symbiosis to develop morphological, physiological and biochemical responses coping with water drought of date palm, Phoenix dactylifera

KEY MESSAGE : Arbuscular mycorrhizal (AM) symbiosis can improve date palm growth and alleviate drought-related impacts than non-mycorrhizal plants due to the ability of AMF for modifying plant metabolism and physiology. Date palm (Phoenix dactylifera L.) is an important agricultural and commercial crop in the North of Africa and Middle Eastern countries. During the last decade, date palm plantations were subjected to degradation due to an extensive exploitation and to drastic environmental conditions such as drought. Currently, there is a growing interest in the valorization of water due to environmental problems and economic aspects. The use of arbuscular mycorrhizal fungi (AMF) can offer a possibility to overcome these problems. The objective of this study was to study the influence of different Glomus species—Glomus intraradices, G. mosseae and Complex Aoufous (native AMF)—on the development of date palm grown under two water regimes (optimal irrigation, 75 % of field capacity or water deficit, 25 % of field capacity). Our results revealed that the beneficial effect of mycorrhizal symbiosis on plant growth depended on the fungal species and the water regime applied to the palm date seedling. While the native Complex Aoufous was the most effective in increasing the shoot height and biomass under well-watered conditions, G. intraradices was the most beneficial fungus for improving growth of plants that undergo restricted water supply. This positive effect of G. intraradices under drought conditions was not related to an enhancement of the antioxidant enzymatic activities in leaves; the association of palm date with G. intradices caused an increase in the elasticity of cell walls in leaves and allowed maintaining high water content in leaves without lowering leaf water potential under stressful conditions. The adequate selection of the AMF species is crucial for improving growth of palm date seedlings, and it must be in accordance with the water regime that will be applied to plants.