The Beneficial Effects of Arbuscular Mycorrhizal Fungi and Compost on Plant Tolerance to Drought and Salinity Stresses: A Study on Date Palm and Alfalfa

Abstract

Phoenix dactylifera L. and Medicago sativa L. are two important crops, which play economic, social, and ecological roles in oasis ecosystems. However, the ecosystems where these plants grow are subjected to drought and salinity, which are the main limiting factors for their productivity. The present study was carried out to evaluate the date palm and alfalfa response to drought and salinity stresses and to study the effect of arbuscular mycorrhizal fungi (AMF) and compost in enhancing the drought and salt tolerance. Date palm seedlings were grown under well-watered (75% field capacity: FC) and drought stress (25% FC) conditions with and without AMF inoculation on the one hand. On the other hand, date palm and alfalfa seedlings were grown under non-saline and saline conditions (0 and 240 mM NaCl; 0 and 120 mM NaCl respectively) with and without AMF inoculation and compost addition. Growth, mineral, physiological, as well as biochemical traits were evaluated in this study. Plant growth traits especially shoot and root dry weight were negatively affected by drought and salt stress. Nevertheless, mycorrhizal and composted plants showed higher growth parameters under drought and salt stress conditions compared to the untreated plants. AMF and compost mitigated the decline of P, K+, and Ca2+ concentrations induced by drought and salinity. Besides, AMF inoculation improved physiological traits through elevating photosynthetic efficiency, stomatal conductance, and leaf water potential under the two abiotic stresses. Furthermore, drought and salt stresses caused an increment in the antioxidant enzymes activities (superoxide dismutase, catalase and peroxidase, as well as ascorbate peroxidase). However, AMF inoculation induced further increase of these activities. In conclusion, colonization with AMF and compost addition could protect date palm and alfalfa plants against the negative drought and salt stress effects by mitigating their oxidative damage and improving their nutrient acquisition.KeywordsArbuscular mycorrhizal fungiCompostDrought stressSalt stressGrowthOxidative stressToleranceDate palmAlfalfa