Priority impacts of plant growth promoting fungi and proline under NaCl stress: boosting chickpea plants tolerance and performance

Soil salinity threatens global agriculture by impairing plant growth, crop productivity, and soil health. This study was conducted to assess the impact of salinity on chickpea performance at the vegetative stage and the possible ameliorating role of arbuscular mycorrhizal fungi (AMF) and proline applications. A greenhouse experiment with 30 pots (5 replicates × 6 treatments) subjected half the treatments to 200 mM NaCl, AMF was applied at sowing, and proline was sprayed two weeks post-planting. Total pigments dramatically decreased [49.18%] in salt-stressed chickpea. Biomass, protein and carbohydrate metabolism were also affected. For instance, plant height and total fresh weight (TFW) showed inhibitions of 37.83% and 72.19% as compared to control. Conversely, chickpea under salt stress had an increased accumulation of H₂O₂ (13.12 mg/g DW) and higher electrolyte leakage (54.72%), however, proline or AMF supplementation decreased their levels. Also, the total protein content and antioxidant enzymes were higher in salt-stressed treatments. Under stress, the total carbohydrate contents in chickpea leaves were significantly enhanced by AMF inoculation (23.44%) and proline application (19.43%), when compared to the control. Moreover, salinity led to distortion of chickpea leaf anatomy including a decrease in upper and lower epidermis thickness, vessel numbers, as well as degradation of palisade and spongy parenchyma. Salinity also disrupted ion balance, increasing Na⁺ and decreasing K⁺ (lower K⁺/Na⁺ ratio), which elevated H₂O₂ levels and membrane leakage. These results revealed that AMF as a symbiotic microorganism and proline as a well-known osmoprotectant perform several tasks to alleviate NaCl stress by decreasing Na⁺ uptake, H₂O₂ content and membrane leakage. Subsequently, an enhancement in growth criteria, pigment fraction and carbohydrates was achieved with their applications under NaCl stress. Most obviously their applications maintained the chickpea leaf anatomy. As an innovative approach, we propose that AMF inoculation or proline application can reverse salinity-induced damage, offering a pathway to enhance crop tolerance in salt-affected regions.