Polygalacturonic acid-functionalized pH/enzyme dual-responsive zeolitic imidazolate framework-8 nanopesticide system for prevention and control of rapeseed sclerotinia stem rot.

Traditional control agents have long struggled with the cell wall-degrading enzymes and oxalic acid secreted by S. sclerotiorum, resulting in poor control efficacy of sclerotinia stem rot (SSR). To overcome these predicaments, we designed a high-efficiency fungicide capable of site-specifically target-controlled release of active ingredients. Specifically, amino-functionalized zeolitic imidazolate framework-8 (ZIF-8-NH2) with triazole as the bridging ligand in hexaconazole (Hex)-loaded ZIF-8 was obtained via post-synthetic modification, followed by modifying with polygalacturonic acid (PG) to construct a pH and enzyme-dual-responsive nano-pesticide controlled-release system (ZIF-8-NH2@Hex@PG), which possesses superior UV resistance, leaf adhesion properties, and rainwater wash-off resistance, and is stimuli-responsive to the microenvironment with acidity and polygalacturonases (PGs). Bioactivity tests indicate that, compared to 10% Hex formulations and 98% Hex technical grade, ZIF-8-NH2@Hex@PG exhibits better antifungal activity (EC50 = 0.086 μg/mL), as well as protective (89.42%) and curative (76.67%) efficacy at 200 μg/mL against S. sclerotiorum, and also demonstrates broad-spectrum activity against three other pathogenic fungi in vitro. The fungicidal mechanism of ZIF-8-NH2@Hex@PG involves the disruption of hyphal and cellular integrity. Moreover, ZIF-8-NH2@Hex@PG shows good biocompatibility, reducing zebrafish toxicity and promoting rapeseed plant growth. This dual-responsive nanopesticide system provides a novel strategy for rapeseed stem rot control and intelligent agrochemicals green development.