Induction of root rot resistance in Paris polyphylla by exogenous thiamine and nano-silicon: Efficacy and mechanistic insights

In plants, certain small chemical molecules can elicit immune responses that enable them to enhance resistance against pathogen invasion. To develop a safe and efficient strategy for controlling Paris polyphylla root rot, this study systematically evaluated the resistance-inducing effects and underlying molecular mechanisms of exogenous thiamine and nano-silicon. In vitro assays showed that thiamine and nano-silicon markedly inhibited Fusarium oxysporum mycelial growth and spore germination, with maximum inhibition rates of 30.25 % and 14.03 %, respectively. Pot experiments revealed that 15 mmol·L⁻¹ thiamine and 150 mg·L⁻¹ nano-silicon achieved control efficacies of 92.66 % and 88.32 %, respectively, against root rot. Physiological analyses indicated that both elicitors enhanced phenylalanine ammonia-lyase (PAL) and catalase (CAT) activities, promoted the accumulation of total phenolics, and elevated salicylic acid (SA) and jasmonic acid (JA) levels, thereby activating systemic acquired resistance (SAR). Transcriptomic profiling revealed that thiamine treatment was associated with the upregulation of genes involved in SA- and JA-related defence responses, including pathogen perception, MAPK–WRKY signalling, and phenylpropanoid metabolism, whereas nano-silicon treatment showed transcriptional signatures related to ROS regulation, antioxidant enzymes, and multiple hormone-associated pathways. Notably, the combined application of thiamine and nano-silicon did not display synergistic effects. Collectively, both thiamine and nano-silicon induced multilayered defence signalling that conferred systemic resistance of P. polyphylla to Fusarium infection, of which nano-silicon exhibited superior disease control potential and practical applicability. These findings provide new theoretical and practical insights into the eco-friendly management of root rot in P. polyphylla . • Thiamine and nano-silicon effectively suppressed Fusarium root rot in P. polyphylla . • Both elicitors enhanced PAL and CAT activities and increased phenolic accumulation. • Thiamine activated SA/JA-dependent MAPK–WRKY defense signaling networks. • Nano-silicon co-activated ROS, antioxidant enzymes, and multiple hormone pathways. • Combined treatment showed no synergy, with nano-silicon showing higher efficacy.