It is perceived that sclerotia of the pathogen, in addition to chlamydospores, play an important role in the epidemiology of rice false smut disease. The propagule has been identified only in five rice growing countries of the world, and never recorded in Bangladesh. This study was undertaken to identify the sclerotia, quantify their concentration on smut balls and estimate the time of its formation. Intensive field-by-field monitoring was conducted during 2014, 2015 and 2016 at experimental farm of the Bangladesh Rice Research Institute, Gazipur. After rigorous search, sclerotia of rice false smut pathogen was identified on the 14th of December 2014. The was observed in the later part of crop maturity during the ‘T. Aman’ season (early-November to mid-December) on olivaceous greenish-black smut balls, but not on orange smut ball. During the three years study, on average, 30.61±9.79% (± is 95%confidence interval) olivaceous greenish-black smut balls borne sclerotia, the average number being 1.63±0.09 per sclerotia-bearing ball. The ‘threshold temperature’ for sclerotia formation was estimated as above 11°C difference in day-night temperature. Consistence presence and high concentration of sclerotia in smut balls signify its role in the epidemiology of the disease in the agroecology of Bangladesh.
Key words: Sclerotia, olivaceous greenish-black smut balls, rice false smut, Ustilaginoidea virens, Villosiclava virens
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