Green synthesis of demethoxycurcumin-loaded chitosan nanoparticles for the management of potato late blight caused by Phytophthora infestans.

Late blight caused by Phytophthora infestans remains a major threat to global potato production and often results in significant yield losses without effective control measures. The emergence of fungicide-resistant strains and environmental concerns associated with synthetic chemicals have intensified the search for sustainable alternatives. Here, we report the development of chitosan nanoparticles loaded with demethoxycurcumin (DM-CSNPs) as a novel solution for late blight management. Demethoxycurcumin was encapsulated via ionic gelation, achieving a maximum encapsulation efficiency of 86 % at 50 μg mL-1. Physicochemical characterization confirmed a uniform particle size (48.8-86.5 nm), favourable zeta potential (22.47 ± 0.63 mV), and sustained release kinetics (R2 = 0.992) following a zero-order model. Molecular docking and dynamic simulations revealed strong binding affinities of demethoxycurcumin toward key effector proteins RXLR and CRN (-9.3 and - 9.1 kcal/mol, respectively), supported by covariance matrix and deformability plots. In vitro assays demonstrated 100 % mycelial inhibition at 50 μg mL-1, while greenhouse trials showed significant disease suppression, with DM-CSNPs at 60 mg/L yielding an AUDPC value of 30.62, comparable to that of dimethomorph (21.68). Notably, no phytotoxic effects were observed even at elevated concentrations (100-200 mg/L). These findings established DM-CSNPs as a promising eco-friendly alternative to conventional fungicides, offering targeted delivery, enhanced stability, and effective disease control. This multidisciplinary approach, integrating nanotechnology and plant pathology, provides a foundation for future field-scale validation and scalable deployment in sustainable agriculture.