Thymol rich essential oil from Assam ecotype of Ocimum gratissimum as a biocontrol agent for sheath blight disease of rice

Abstract

Preventing crop losses caused by harmful plant pathogens through eco-friendly ways is paramount for food security and environmental sustainability. Envisioning this, the current study evaluates the biocontrol potential of essential oil extracted from Ocimum gratissimum from an Assam ecotype and its primary component, thymol, against Rhizoctonia solani, the pathogen causing sheath blight disease in rice. GC-MS analysis identified thymol as the dominant compound in the essential oil, contributing significantly to its antifungal activity. Both O. gratissimum essential oil and thymol showed strong in-vitro inhibition of R. solani, with complete growth inhibition at 1000 ppm, while thymol exhibited superior efficacy. Both agents also effectively inactivated sclerotia, a key survival mechanism of the pathogen. In-planta assays demonstrated a significant reduction in lesion size with O. gratissimum essential oil and thymol treatments, outperforming the chemical fungicide propiconazole. Thymol was particularly effective in reducing disease severity, making it a promising eco-friendly alternative. The unique phytochemical profile of the Assam ecotype of O. gratissimum further underscores its potential for sustainable disease management. These results underscore the potential of O. gratissimum essential oil and thymol as eco-friendly alternatives to synthetic fungicides. By reducing reliance on chemical inputs, their application can mitigate risks associated with fungicide resistance and environmental contamination while promoting sustainable disease management strategies.