Exogenous myo-inositol alleviates abiotic stress in rapeseed by modulating ion homeostasis and antioxidant defense

Soil salinization is a major abiotic stress that severely constrains global agricultural productivity. The application of exogenous bioactive substances represents a promising strategy to enhance crop salt tolerance. In this study, we investigated the protective role of exogenous myo -inositol in rapeseed under salinity stress. Here, we demonstrated that exogenous application of 20 μM myo -inositol significantly alleviates salt stress in rapeseed seedlings. Myo -inositol effectively mitigated growth inhibition, maintained chlorophyll levels and photosynthetic activity, and stabilized membrane integrity under salt stress. Physiological and molecular evidence indicated that myo -inositol activates the antioxidant system by enhancing the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), thereby reducing reactive oxygen species accumulation. Notably, myo -inositol triggered a species-specific ion homeostasis strategy by increasing Na + accumulation, associated with the upregulation of BnHKT1 and downregulation of vacuolar BnNHX homologs. Concurrently, myo -inositol stimulated proline biosynthesis for osmotic adjustment. Furthermore, qRT-PCR analysis showed that myo -inositol fine-tunes the expression of key genes involved in antioxidant defense, osmotic adjustment, and stress signaling. These findings demonstrate that myo -inositol enhances rapeseed salt tolerance through an integrated mechanism involving antioxidant activation, transcriptional reprogramming, and a species-specific ion homeostasis strategy, establishing its potential as an effective biostimulant for saline agriculture. • Exogenous myo -inositol (20 μM) significantly enhances salt tolerance in rapeseed by promoting growth and photosynthetic performance. • Myo -inositol activates antioxidant enzymes (SOD, POD, CAT) and reduces ROS accumulation under salt stress. • A novel ion regulation strategy is induced: myo -inositol increases Na + uptake while modulating ion transporter gene expression ( BnHKT1 and BnNHXs ). • Transcriptomic reprogramming reveals myo -inositol fine-tunes osmotic, ionic, and stress signaling pathways to coordinate salt stress responses.