Some nutritional factors regulating formation of sclerotia of Sclerotium rolfsii
Growth requirements of Sclerotium rolfsii Sacc. were studied. Sclerotia developed on solid media and primordia started forming when the entire surface of the media in the culture plates was covered with mycelia. The optimal temperature for sclerotium formation varied between 20 and 37 °C. A wide range of carbon sources stimulated the formation of sclerotia, glucose clearly being the most effective. Sclerotia failed to form when a carbon source was absent from the medium. Sclerotia developed in the presence of all the nitrogen sources tested; the highest yield was obtained on (NH4)2SO4 and poorest on L-lysine. Experiments on the growth response to different vitamins showed that S. rolfsii produced sclerotia even on the medium lacking vitamins; the best harvest was obtained on the medium containing ascorbic acid. Media lacking potassium, magnesium, calcium, and sodium supported a good growth of mycelium, but sclerotia failed to form in the medium lacking potassium.