Mechanistic Insight into the Physiological and Biochemical Traits Improvement by Mycorrhiza Biofertilization in Soybean Under Phosphorus-Starved Conditions

Phosphorus (P) deficiency in agricultural soils poses a critical challenge for plant growth and yield. Arbuscular mycorrhizal fungi (AMF) form symbiotic associations with plants and promote nutrient delivery, particularly inorganic P. This study aimed to investigate the impact of varying P levels on the growth and P-use of two soybean (Glycine max) cultivars, BU2 and Williams 82 (W82). Additionally, we assessed the influence of AMF on growth, root traits, P-uptake and efficiency, gas exchange, photosynthetic pigments, and antioxidant defense in BU2 and W82 under low-P (LP) conditions. Our experimental results revealed that applying AMF in LP conditions (LP + AMF) substantially improved phenotypic appearance and growth, associated with enhanced root traits and increased P contents in roots and shoots compared to LP conditions without AMF (LP − AMF). Plants with LP + AMF exhibited improved gas exchange and chlorophyll pigments, suggesting enhanced photosynthetic capacity. Notably, AMF symbiosis reduced hydrogen peroxide and malondialdehyde levels while strengthening antioxidant enzymes (catalase, ascorbate peroxidase, and glutathione S-transferase) activities, indicating enhanced antioxidant defense aid in reducing oxidative stress in both cultivars under LP. Overall, our findings provide insight into improving P-use efficiency by the application of AMF-based fertilization, particularly in the W82 cultivar, in enhancing root traits, P acquisition, photosynthesis, and antioxidant defenses under LP conditions.