Preparation of pH-Responsive\nKas@ZnO Quantum Dots\nfor Synergistic Control of Rice Blast and Enhanced Disease Resistance\nin Rice

The construction of controlled-release formulations improves\nthe\nsustained-release performance and utilization efficiency of pesticides,\nwhich are important aspects in plant protection and environmental\nchemistry. The current study employs kasugamycin (Kas), which is widely\nused to control <i>Magnaporthe oryzae</i>, conjugated with\ncarboxyl-functionalized ZnO quantum dots via amide linkages to yield\na pH-responsive pesticide delivery system (Kas@ZnO). Physicochemical\ncharacterizations indicated the successful preparation of the Kas@ZnO\nnanoparticles. <i>In vitro</i> drug release assessments\nindicated that Kas@ZnO exhibited a loading capacity of 21.05% and\ncould effect the controlled release of Kas in an acidic environment,\nwhich is beneficial given the unique acidic microenvironment of <i>M. oryzae</i>. Bioactivity assays demonstrated that Kas@ZnO\ncould simultaneously inhibit mycelial growth and spore germination.\nAdditionally, bioactivity tests showed that the control efficacy of\nKas@ZnO against rice blast reached 67.43% after 14 days of <i>in vivo</i> spray inoculation, which was higher than that obtained\nwith Kas (55.50%), suggesting improved beneficial effects of Kas@ZnO\napplication over a prolonged duration. Moreover, Kas@ZnO enhanced\nthe activity of defense-related enzymes in rice and upregulated the\nexpression of defense-related genes, such as <i>OsPR2</i>, <i>OsPR3</i>, <i>OsPR5</i>, <i>OsWRKY45</i>, <i>OsLYP6</i>, and <i>OsNAC4</i>. Ultimately,\nthe biosafety assessments revealed that Kas@ZnO did not exert any\nharmful effects on rice and demonstrated slight toxicity toward zebrafish.\nThese findings indicate that Kas@ZnO can function as a pH-sensitive\npesticide delivery system, allowing for targeted release of the pesticide\nwithin plant tissues. This technology demonstrates significant potential\nfor eco-friendly plant disease management.