Nanosheet-Facilitated Spray Delivery of dsRNAs Represents a Potential Tool to Control Rhizoctonia solani Infection

Abstract

<i>Rhizoctonia solani</i> is one of the important pathogenic fungi causing several serious crop diseases, such as maize and rice sheath blight. Current methods used to control the disease mainly depend on spraying fungicides because there is no immunity or high resistance available in crops. Spraying double-strand RNA (dsRNA) for induced-gene silencing (SIGS) is a new potentially sustainable and environmentally friendly tool to control plant diseases. Here, we found that fluorescein-labelled <i>EGFP</i>-dsRNA could be absorbed by <i>R. solani</i> in co-incubation. Furthermore, three dsRNAs, each targeting one of pathogenicity-related genes, <i>RsPG1</i>, <i>RsCATA,</i> and <i>RsCRZ1</i>, significantly downregulated the transcript levels of the target genes after co-incubation, leading to a significant reduction in the pathogenicity of the fungus. Only the spray of <i>RsCRZ1</i> dsRNA, but not <i>RsPG1</i> or <i>RsCATA</i> dsRNA, affected fungal sclerotium formation. dsRNA stability on leaf surfaces and its efficiency in entering leaf cells were significantly improved when dsRNAs were loaded on layered double hydroxide (LDH) nanosheets. Notably, the <i>RsCRZ1-dsRNA-LDH</i> approach showed stronger and more lasting effects than using <i>RsCRZ1-dsRNA</i> alone in controlling pathogen development. Together, this study provides a new potential method to control crop diseases caused by <i>R. solani</i>.