Enhancing Peanut Crop Quality Under Arsenic Stress Through Agronomic Amendments

Arsenic (As) contamination poses a major challenge to sustainable crop production, particularly in legumes such as peanut (Arachis hypogaea L.), where it disrupts growth, nodulation, and redox homeostasis. This study evaluated the potential of circular-economy-based amendments derived from spent mushroom substrate (SMS) of Pleurotus djamor and plant growth-promoting bacteria (PGPB) to mitigate As stress in peanut plants. Six growth conditions were tested under 20 µM arsenate, including single and combined inoculations with P. djamor and Pseudomonas fluorescens, as well as a residue-only benchmark (E). Results showed that the unamended control (AP) exhibited the highest As accumulation, oxidative stress (H2O2, TBARs), and biomass loss, whereas SMS-based amendments attenuated these effects. Treatments HB (SMS + P. djamor + PGPB) and B (SMS + PGPB) combined low As translocation with enhanced antioxidant performance (SOD, CAT), maintaining growth and pigment stability. Amendment H (SMS + P. djamor) preferentially activated phytochelatin-related genes (PCS2, CAD1), while E minimized As uptake but lacked circular applicability. Overall, SMS-PGPB interactions promoted As retention in roots and strengthened ROS-scavenging defenses. These findings highlight SMS-based amendments as viable, sustainable strategies to enhance peanut quality and resilience under As stress, supporting their integration into circular agronomic systems.