Enhanced fungicidal activity and mechanism of pyraclostrobin nanoparticle with reactive oxygen species responsiveness against Rhizoctonia solani

The frequent application of pesticides has caused adverse effects on humans and the environment. Stimuli-responsive nanoparticles can enhance the control efficacy of pesticides to pest insects or fungus and reduce impacts on non-target organisms. In the present work, 4-(hydroxymethyl) phenylboronic acid pinacol ester (PBAP) groups were conjugated onto β-cyclodextrin (β-CD) to form a H2O2-eliminating material (Ox-bCD), and then the nanoparticiles (PYR@OxbCD) loaded pyraclostrobin (PYR) were successfully fabricated by a nanoprecipitation. The prepared PYR@OxbCD had excellent reactive oxygen species (ROS) release dependency, and significantly enhanced fungicidal activity against Rhizoctonia solani in vitro. PYR@OxbCD could accurately release PYR at infected rice plants, providing a better control efficacy than PYR suspension concentrate (SC). The contact angle of PYR@OxbCD on leaves was reduced, and the spreading and antiphotolysis properties were increased, which may lead to an increase of deposition and a lower dissipation rate. Furthermore, the released PYR from PYR@OxbCD enhanced the activity of peroxidase (POD) and catalase (CAT), and up-regulated the expression of defense genes including PAL, PR10, CHI, CAT, GluPOD and AsPOD. PYR@OxbCD exhibited a much weaker effect on microbial abundance in rice cropping systems. The study provides an idea for smart delivery of fungicides to prevent plant pathogens and offers a more comprehensive view about the resistance of R. solani-infected rice triggered by PYR@OxbCD in levels of phenotype, enzymatic activity, gene expression, and microbiome.