The Application of Organic Fertilizer and Arbuscular Mycorrhiza Fungi Modifies the Physiological and Biochemical Responses of Stevia Plants under Salt Stress

The utilization of saline water for irrigating plants in arid and semi-arid regions has become imperative because of the scarcity of water resources. Nevertheless, under salt stress conditions, plants undergo a multitude of variation, which result in delayed growth and adversely affect the plant metabolism. Adopting appropriate and sustainable strategies such as using bio-organic fertilizers from animal and plant waste or integrating microorganisms (symbiotic fungi), can improve plant resilience against salt stress. The purpose of this study was to elucidate the impact of arbuscular mycorrhizal fungus (AMF) Rhizophagus irregularis alone and/or combined with compost on growth, nutrient uptake, antioxidant activities, and photosynthesis-related performance of Stevia rebaudiana Bertoni under salt stress conditions. Salt stress negatively affected all studied parameters. However, the application of R. irregulare strain in a substrate amended with 5% compost is more effective in enhancing salt stress tolerance in stevia plants compared to the compost and AMF strain applied separately. The synergistic effect of the co-application of these two biofertilizers under salt stress resulted in increased stomatal conductance (276%), chlorophyll fluorescence (38%), antioxidant enzyme activities, and the uptake of K⁺ (78%), Ca²⁺ (117%), and P (149%). In conclusion, the application of compost combined with AMF may be a promising sustainable strategy for improving salt stress resistance in stevia.