Morphological Characterization and in vitro Evaluation of Nanoparticles and Fungicides against Bipolaris oryzae Causing Brown Spot of Rice

Abstract

Background: Brown spot, caused by Bipolaris oryzae, is one of the major fungal diseases limiting rice production. Aim: The present study aimed to evaluate the in vitro antifungal efficacy of different nanoparticles and fungicides against the pathogen and to assess their potential use in Integrated Disease Management (IDM).         Study Design: Completely Randomised Design (CRD).           Place and Duration of Study: Department of Plant Pathology, Sardar Vallabhbhai Patel University of Agriculture and Technology, Meerut, Uttar Pradesh, India, during 2025–2026.          Methodology: Bipolaris oryzae was isolated from naturally infected rice leaves and identified through cultural, morphological, and pathogenic characteristics. The antifungal activities of ZnO, CuO, and Ag nanoparticles at different concentrations, along with eight fungicides, were assessed using the poisoned food technique under in vitro conditions. Radial mycelial growth and percentage growth inhibition were recorded after 24, 48, 72, and 96 h of incubation.       Results: All treatments significantly reduced the mycelial growth of B. oryzae compared with the untreated control. Among the nanoparticles tested, Ag nanoparticles at 200 ppm produced the greatest inhibition of fungal growth, while CuO and ZnO nanoparticles showed comparatively lower but significant antifungal activity. Of the fungicides evaluated, Tebuconazole 50% + Trifloxystrobin 25% WG at 200 ppm was the most effective, recording the lowest radial mycelial growth (1.30 cm) and the highest growth inhibition (85.56%) after 96 h of incubation. Carbendazim 12% + Mancozeb 63% WP and Hexaconazole 5% SC were the next most effective treatments. Conclusion: The results demonstrate that Ag nanoparticles possess considerable antifungal activity against B. oryzae. Although the combination fungicide provided the greatest suppression among the fungicides, the performance of the nanoparticles suggests that they could be integrated with existing disease management practices to reduce dependence on conventional fungicides and support more sustainable management of brown spot disease in rice.