Inhibition mechanism of pectin-modified nano-selenium on Phytophthora capsici and the improvement of the resistance in pepper.

The principal disease impacting pepper production is Phytophthora blight, which nano‑selenium (nano-Se) controls well but has high storage requirements and low heat resistance. Varying pectin amounts yielded pectin-modified nano-Se (nano-Se@PT) with 0.1 %, 0.5 %, 1 %, and 2 % concentration. As pectin content grew, nano-Se@PT particle size reduced, zeta potential value rose, and thermogravimetric temperature climbed. The incorporation of nano-Se@PT can improve its stability and thermal resistance at 40 °C and 70 °C. Nano-Se@PT outperformed nano-Se in fungicidal and Phytophthora capsici inhibition. In vitro antifungal experiments showed that nano-Se@PT could significantly inhibit mycelium growth with an EC50 of about 4 mg/L. The particles adsorbed on the surface of mycelium, inducing death by destroying cell membranes, mitochondria, and nuclei. Non-targeted metabolomics analysis showed that nano-Se@PT treatment disrupted the mycelium growth and metabolism and changed amino acids, nucleotides, and sugar levels. In vivo experiments, 2 % nano-Se@PT had the lowest disease index and the best preventive therapy. Rhizosphere soil microbial analysis showed that nano-Se@PT recruited beneficial microorganisms such as Bacteroides, Lactobacillus, and Bifidobacterium in pepper plants, improving their Phytophthora capsici resistance and growth. The findings suggest that nano-Se@PT might be a unique pepper disease control technique and shed light on plant fungal disease management.