Evaluation of Tricyclazole-Encapsulated Chitosan Nanoparticles Against Blast Disease and on Physiological Attributes of Rice

Abstract

Rice blast, caused by Magnaporthe oryzae, is a major biotic stress that severely limits rice productivity worldwide. Although tricyclazole is widely used to manage blast, its prolonged use poses environmental and pathogen resistance risks. To address these concerns, the present study assessed the efficacy and safety of tricyclazole-loaded chitosan nanoparticles (CNPT), synthesized via the ionic gelation method, as a sustainable foliar application for managing blast disease in paddy (Oryza sativa L. var. MTU-1001). Two foliar applications of CNPT (at 30 and 50 days after transplanting) at 750 ppm proved most effective, significantly improving agronomic traits and suppressing disease under field conditions. Phytotoxicity screening under greenhouse and field conditions confirmed CNPT's safety up to 1000 ppm, with no visible symptoms of chlorosis or necrosis. CNPT treatment notably enhanced plant height (120.38 cm), tiller number (15.50 tillers/hill), leaf surface area (303.49 cm²/hill), panicle length (29.88 cm), and 1000-grain weight (39.55 g), while reducing chaffiness to 2.84%. Disease assessments revealed a marked reduction in blast severity, with the Percent Disease Index (PDI) reduced from 23.67% in untreated plots to 7.44% in CNPT-treated ones. Moreover, the Area Under Disease Progress Curve (AUDPC), which represents the cumulative disease intensity over time, was significantly lowered from 1205.25 to 372.00. These findings demonstrate that CNPT provides controlled release, improved plant health, and effective blast suppression, offering a promising, eco-friendly alternative for integrated disease management in rice cultivation.