Mycorrhizal Inoculation Effect on Water Deficit Tolerance of Cashew Seedlings (Anacardium occidentale L.) and Soil Nutrients Availability

This research aims to evaluate the effect of Arbuscular Mycorrhizal Fungi (AMF) in improving the resilience of cashew seedlings to water deficit and soil nutritional status. The split-plot experimental design was used. The treatments consist of two factors, the two-level water regime (30% useful water reserve and 70% useful water reserve) in main plots and the three-level inoculation (no inoculation, Glomus mosseae and Glomus aggregatum) in subplots. Each treatment is replicated nine times. The study was conducted at Agronomic Experimentation Station of the University of Lomé between June to November 2020. Induction of deficit hydric started three months after the setting up of the trial and lasted two months. At the end of the water shortage cycle, growth parameters were measured and leaf and soil samples were taken for laboratory analysis. Parameters assessed include mycorrhization rate, relative water content, leaf proline content, malondialdehyde content, mycorrhizal dependency, plant biomass and mineral content of the soil. The results show good mycorrhization rate, 70.86% for Glomus aggregatum and 54.92% for Glomus mosseae with mycorrhiza dependency of 12.87% and 11.74% respectively. Mycorrhizal inoculation reduced water stress symptoms in addition to the plant's intrinsic protective mechanisms. This was reflected in lower leaf proline and malondialdehyde content and improved relative water content of stressed but inoculated plants compared to uninoculated plants. The AMF also improved the availability of mineral nutrients in the soil, which resulted in better growth of inoculated plants under both water stress and normal watering conditions. The overall assessment of the research suggested that AMF can be used to improve cashew seedlings resistance against drought and to improve their growth through improvement of soil nutrient availability.