Chitosan-silver nanoparticles and Bacillus tequilensis modulate antioxidant pathways and microbiome dynamics for sheath blight resistance in rice
Muhammad Afzal, Xiyu Tan, Fang Ma, Dong Zeng, Minqing Huang, Xiaoyuan Chen, Xiaoying Zhang, Zhiyuan Tan
Abstract
Rice ( Oryza sativa ) is a vital staple crop for over two-thirds of the global population, contributing to 21% of the world's caloric intake. However, its productivity is severely impacted by biotic and abiotic stresses, particularly rice sheath blight (ShB) caused by Rhizoctonia solani, which threatens rice cultivation, especially in Southeast Asia. The limited availability of resistant varieties and the heavy reliance on chemical fungicides call for alternative, sustainable management strategies. This work explored a nano-biohybrid approach that integrates Bacillus tequilensis and chitosan-based silver nanoparticles (Ag-NC) to manage ShB while preserving rhizosphere microbial health. The combined treatment (T2=Ag-NC + B. tequilensis ) achieved a 90% reduction in disease incidence, surpassing both pathogen-infected controls (T1) and biocontrol-only (T3) interventions. Biochemical analyses revealed that T2 enhanced antioxidant defense, secondary metabolite production, and chlorophyll content compared to T1 plants. Furthermore, significant shifts in the rhizosphere microbial community were observed, with T2 promoting beneficial microbes such as Trichoderma and Bacillus, while maintaining microbial diversity. The study also revealed that the combined treatment significantly modulated the expression of key defense-related genes, including Chitinase, OsPR1a , and OsWRKY6 , providing a molecular basis for the enhanced pathogen resistance in rice. These findings highlight the potential of Ag-NC and B. tequilensis as an effective, eco-friendly strategy for disease management and microbiome preservation. However, the study also underscores the importance of optimizing nanoparticle concentrations to balance efficacy and ecological impact, providing insights for the sustainable application of nano-biohybrids in crop protection and soil health management.