Cadmium-tolerant root microbes reduce cadmium accumulation in Ligusticum chuanxiong Hort

Ligusticum chuanxiong Hort. is an important medicinal plant whose dried rhizomes are used in traditional Chinese medicine for preventing and treating cardiovascular and cerebrovascular diseases. However, this plant tends to accumulate cadmium (Cd), and the Cd content in its rhizomes often exceeds the limit of 1 mg/kg stipulated by the Chinese Pharmacopoeia (2025 edition). This not only adversely affects the synthesis and accumulation of active compounds, but also leads to rejection of exported products, causing significant economic losses. Given three Cd-tolerant strains (Trichoderma afroharzianum F38, Mucor ctenidius F24, and Bacillus proteolyticus B90) isolated from L. chuanxiong roots with a maximum Cd tolerance of 3 mmol/L, this study performed a co-cultivation experiment under 20 mg/L Cd stress in hydroponics. The results demonstrated that Cd stress significantly inhibited plant growth and induced oxidative damage, manifested as increased malondialdehyde content and activation of the antioxidant enzyme system. Inoculation with any of the three Cd-tolerant strains alleviated growth inhibition and oxidative stress. All three strains significantly reduced Cd content in both aerial parts and underground parts, but with distinct characteristics: F38 reduced underground parts Cd content by 54.72% and promoted Cd translocation to aerial parts; F24 decreased aerial parts Cd content by 40.27%; while B90 exhibited a more prominent effect in enhancing overall plant Cd tolerance. Overall, the efficacy of the strains in mitigating Cd toxicity and promoting growth followed the order: F38 > F24 > B90. In conclusion, the Cd-tolerant strains isolated from the roots system of L. chuanxiong effectively reduced Cd accumulation and alleviated Cd stress, providing feasible microbial resources and micro-ecological regulation strategies to address Cd contamination in medicinal plants and ensure the safety of herbal materials.