Abstract

Acidic conditions limit crop production on 40 % of the world's soils. These soils are characterized by a pH between 4.5 and 5.5, low phosphorus (P) availability, high contents of aluminum (Al) and manganese (Mn), and low soil basic cations. Edaphic conditions of acidic soils limit plant growth, mainly due to Al3+ phytotoxicity, which reduces water and nutrient acquisition from soils and severely limits root growth of sensitive species. However, the association of symbiotic arbuscular mycorrhizal (AM) fungi with plant roots often modifies plant response to acid soil factors through enhanced P acquisition and reduced Al exposure. Several management practices are implemented to mitigate the negative effects of acidic soils on plant growth, among which are lime application, P fertilization, and the use of Al-tolerant plants. In this regard, the inoculation with AM fungi appears as another management alternative, because of the well-documented AM contribution to plants growing in acidic soils. Several reports have demonstrated that AM fungal structures and glomalin-related soil protein (GRSP) protect plants against stress produced by high levels of Al. However, there is broad functional diversity among AM fungal genera or species in their capacity to confer Al-resistance to host plants in acidic soils. Therefore, the aim of this review is to summarize AM fungal diversity present in acidic soils as well as relate their presence with the potential to alleviate Al phytotoxicity.