Chitosan nanoparticles loaded with jasmonic acid induce plants’ resistance against Botrytis cinerea

Today, there is a growing need for environmentally friendly and sustainable compounds to manage plant diseases. The application of plant defense inducers is a promising eco-friendly strategy to combat fungal pathogens. Chitosan nanoparticles are polymeric, bio-based carriers of active compounds that are widely used in plant protection. In this study, we demonstrate that chitosan nanoparticles loaded with jasmonic acid (JA-CNPs) effectively induce the jasmonic acid defense pathway and reduce the severity of infection caused by the necrotrophic fungus Botrytis cinerea (strain B05.10) on Αrabidopsis thaliana and tomato leaves by 51 % and 45 %, respectively. To assess defense responses, a β-glucuronidase staining (GUS-staining) experiment was conducted using the PDF1.2:GUS A. thaliana transgenic line, demonstrating that JA-CNPs effectively induce the jasmonic acid (JA) pathway at a low concentration of 5 ppm. This effect remained evident even after artificial inoculation with B. cinerea conidia. Confocal microscopy revealed reduction of hyphal development of the pathogen in Arabidopsis leaves treated with 5 ppm JA-CNPs, when compared to control conditions. In vitro bioassays revealed that JA-CNPs did not directly affect B. cinerea conidial germination, reinforcing their role in defense induction in A. thaliana. Furthermore, transcriptional analysis of COI, ASK1, AXR1, and JAH3 in A. thaliana, as well as AOX, PME1, CHS1, and BOA3 in B. cinerea, revealed that JA-CNPs application influences key components of the plant's JA pathway and challenges the virulence mechanisms of the fungus, respectively. Overall, these findings highlight the potential of JA-CNPs as a promising tool for the control of B. cinerea, contributing to minimization of chemical fungicides in crop protection.