Exploiting the potential of microbial consortia against sheath blight in basmati rice caused by Rhizoctonia solani

Sheath blight, caused by the necrotrophic fungus Rhizoctonia solani, poses a significant threat to Basmati rice production, leading to substantial yield and quality losses. Efforts were made to evaluate a microbial consortium comprising Trichoderma harzianum, Trichoderma asperellum, and Pseudomonas fluorescens against this disease. The compatibility of these strains was confirmed through prior assays, and the consortium was field-tested during the Kharif season of 2023-2024.Seed treatment with the consortium significantly reduced sheath blight incidence (54.08%), intensity (69.99%), lesion length (53.36%), and number of infected tillers (47.30%) relative to untreated controls. These reductions were comparable to those achieved with the chemical fungicide carbendazim, though the fungicide remained the most effective treatment overall. The consortium also improved growth and yield parameters, including panicle length (11.11%), plant fresh weight (15.23%), test weight (20.44%), and yield (49.52%) relative to untreated controls. Additionally, the microbial treatment enhanced key defense-related enzyme activities, with substantial increases observed for phenylalanine ammonia-lyase, total phenolic content, peroxidase, and polyphenol oxidase. Correlation analysis revealed that sheath blight incidence was strongly positively correlated with lesion length (r = + 0.97), disease intensity (r = + 0.98), and number of infected tillers (r = + 0.95), while strongly negatively correlated with yield (r = -0.99), plant fresh weight (r = -0.97), and test weight (r = -0.88). Defense enzyme activities showed moderate negative correlations with disease incidence (PAL: r = -0.57; TPC: r = -0.58; PO: r = -0.56; PPO: r = -0.57), indicating that higher enzyme activity is associated with reduced disease. These findings highlight the potential of microbial consortia as effective, sustainable alternatives to chemical fungicides for managing sheath blight while promoting basmati rice production.