Biological Control of Sheath Blight in Rice Using Native Trichoderma Isolates

Abstract

Sheath blight, caused by the soil-borne fungus Rhizoctonia solani, is among the most persistent diseases of irrigated rice, and Trichoderma is one of the most frequently proposed biological answers to it. Native isolates, collected from the soils and rice roots of the region where they will be used, are often preferred on the argument that they are already adapted to local conditions. This narrative review examines what published work says about that argument, drawing on the biology of the pathogen, the mechanisms by which Trichoderma suppresses it, the logic of isolate selection, formulation and delivery, and the design of the experiments that report control. It presents no new data. The evidence for antagonism is strong at the bench, where mycoparasitism, antibiotic metabolites and competition are readily seen, and the plant-mediated effects of Trichoderma make a field benefit plausible. The complication is that performance in a dish, a pot and a paddy are different questions. Results depend on isolate, formulation, timing, water management, canopy density and the host cultivar, and reports often omit the details needed to judge transfer. Integration with partially resistant cultivars and carefully timed fungicide use is the realistic setting for biocontrol, not a replacement for either. The review closes with the evidence a decisive multi-site trial would need to supply.