Collar Rot Disease of Betelvine (Piper betle L.) under Coastal Saline Zone of West Bengal

Abstract

Collar rot is an important disease of betelvine (Piper betle L.) caused by the soil borne fungus Sclerotium rolfsii Sacc. The pathogen was isolated from the infected vines cultivated in the coastal saline agro-climatic zone of West Bengal and characterized for its growth and survival under different pH, temperature and soil moisture. The pathogen was found to prefer acidic pH (optimum at pH 5.0 to 5.5) for its mycelial growth, formation of sclerotia and their germination. The saprophytic colonization ability of the fungus was drastically reduced at pH 7.7 and above. Germination of sclerotia was least at a soil moisture level of 20% of field capacity (FC). The increase in soil moisture increased the rate of sclerotial germination, resulting in quick loss of its viability. The saprophytic colonization ability of S. rolfsii was maximum at 60% of FC, which reduced rapidly above 70% of FC. The optimum temperature for maximum mycelial growth, sclerotial formation and its germination was 30±1°C. Mycelial growth, sclerotial formation, germination and saprophytic colonization ability of the fungus ceased completely at 40±1°C. These specific soil temperature and moisture requirements of the fungus S. rolfsii make the pathogen highly selective for its seasonal incidence and proliferation.