Enhancement of growth and salt tolerance in Clematis chinensis by the plant growth- promoting fungus Trichoderma compactum SZ01

Abstract Background Salt-tolerant rhizosphere microorganisms with multiple plant growth–promoting (PGP) traits represent cost-effective biological inoculants for enhancing plant tolerance to abiotic stress. Results In this study, a salt-tolerant fungal strain, SZ01, was isolated from the rhizosphere of Clematis chinensis using PDA medium supplemented with 1% NaCl and identified as Trichoderma compactum based on morphological and molecular analyses. SZ01 tolerated NaCl concentrations up to 9%. Functional characterization revealed that SZ01 exhibited potassium solubilization, nitrogen fixation potential, and siderophore production, although it lacked the ability to solubilize organic or inorganic phosphorus. Pot experiments demonstrated that under salt stress, inoculation with SZ01 spore suspension significantly increased the fresh and dry weights of underground tissues, reduced Malondialdehyde (MDA) accumulation, and enhanced soluble sugar and proline contents compared with non-inoculated controls, indicating effective mitigation of salt-induced physiological damage. Transcriptomic analysis of C. chinensis leaves further showed that SZ01 treatment triggered extensive transcriptional reprogramming, particularly through modulation of MAPK and metabolic pathways, thereby optimizing stress-responsive gene expression. Secondary metabolite profiling of SZ01 under salt stress revealed the accumulation of chlorine-containing molecules potentially contributing to plant growth promotion. Conclusion These findings highlight the potential of SZ01 as a microbial inoculant to promote plant growth and productivity in saline–alkaline environments, with implications for both medicinal and agricultural crop production.