Incidence, Prevalence, and Molecular Identification of Sclerotium rolfsii Causing Southern Blight in Tomato Fields of Mysuru District, Karnataka, India

Abstract

Introduction: Tomato (Solanum lycopersicum), a vital crop worldwide, is under significant threat from Sclerotium rolfsii, the fungal pathogen responsible for southern blight. This soil-borne pathogen, known for its wide host range and destructive nature, thrives in humid environments, causing severe losses in tomato production. Aim: A field survey was conducted between June and September 2024 across 30 villages in six taluks of Mysuru district, Karnataka, India, to assess the incidence, prevalence, and severity of southern blight in tomato fields. Results: Disease incidence ranged from 10.73% to 69.64%, while prevalence varied between 20% and 83.33%. Mysuru taluk recorded the highest disease intensity, with a mean incidence of 30.79% and a prevalence of 45.53%. The pathogen was isolated from infected tomato plants, and morphological identification revealed the characteristic sclerotia of S. rolfsii. Pathogenicity tests confirmed the fungus as the causative agent by reproducing typical symptoms on healthy tomato seedlings. Further molecular characterization of the internal transcribed spacer (ITS) region of the fungus confirmed its identity with high sequence similarity to known S. rolfsii strains in GenBank. Conclusion: These findings underscore the urgent need for targeted disease management strategies to mitigate the spread of southern blight and protect tomato production in the Mysuru region, safeguarding both local and global food security.