Effect of variability and edaphological characteristics on growth of Sclerotium rolfsii (Sacc) causing collar rot disease of sunflower in coastal region of West Bengal, India

Sunflower is an important oilseed crop in India. One of the major diseases is collar rot caused by Sclerotium rolfsii (Sacc). This study was conducted during 2014-15 and 2015-16 under in-vitro condition. To see the effect of soil temperature and soil moisture, the S. rolfsii (Sacc). was grow at different temperature and at different moisture level. Results showed that among the different soil pH tested, pH5.7 was the best for colonization on wheat seeds 61.67% followed by 6.1(58.33%). In case of soil temperature most preferable temperature for mycelial grow of the pathogen was 30 degrees C. The pathogen grown best in 30% soil moisture content followed by 25%. Variations were observed in colony morphology, mycelial growth, sclerotial size, colour and number of sclerotia. The number of sclerotia in different isolates varied from 352 (WBSR4) to 411 (WBSR9). Twenty five combinations showed compatible reaction out of 36 pairings in mycelial compatibility studies.