Boosting salinity resilience and silymarin production in Silybum marianum: a sustainable strategy using mango-residue biochar and foliar α-tocopherol

Abstract

Abstract Background Soil salinity (ECe=8.55 dS m-1), a predominant abiotic stress factor, significantly impairs the growth, yield and pharmaceutical quality of the medicinal plant Silybum marianum (milk thistle). Objective This study evaluated the potential of mango-residue biochar and foliar α-tocopherol (α-Toco) on the physiological stability, agronomic performance, and pharmaceutical quality of milk thistle under saline conditions. Methods A two-season field trial was performed using a split-plot arrangement of biochar amendments (0–15 t ha⁻¹) and α-Toco applications (0–150 ppm). Results The integrated application of two treatments effectively mitigated salinity stress, leading to significant increases in growth and productivity. The optimal treatment (10 t ha⁻¹ of biochar and 150 ppm α-Toco) markedly enhanced both above- and below-ground biomass compared to the control. This synergistic effect was attributed to improved nutrient uptake (such as N, P, K ⁺ , Mg 2⁺ , Zn 2⁺ ), and reduced Na + accumulation. Furthermore, the highest treatment combination (15 t ha⁻¹ biochar × 150 ppm α-Toco), dramatically enhanced the antioxidant system by increasing endogenous α-tocopherol and ascorbate peroxidase activity. This treatment effectively alleviated oxidative damage, as evidenced by significant reductions in proline, H ₂ O ₂ levels, and IC₅₀ values. Most importantly, these physiological improvements resulted in the highest seed yield (1.95 t ha⁻¹) and a significant increase in silymarin content (up to 3.172%). Conclusions The synergy between biochar and α-Toco provides a sustainable strategy for enhancing milk thistle resilience and pharmaceutical quality in saline environments, offering a promising approach for the productive utilization of marginal lands under climate change conditions. Graphical Abstract