Growth and sporulation of Ustilago scitaminea, in vivo and in vitro

Two hyphal forms of Ustilago scitaminea were observed in vivo: dikaryotic vegetative hyphae in the sugarcane stems and monokaryotic sporogenous hyphae in the peripheral layers of the whip, a sorus-bearing structure on infected stalks. The fungus was easily isolated from sugarcane tissue and cultured on six different media. A brown cerebriform colony was usually the first form to grow from tissue. A white mycelial colony commonly arose from the brown colony after 1–2 wk and grew rapidly over its surface. On a medium containing extracts of sugarcane, the fungus developed into black colonies in which teliospores were formed. Teliospore production was enhanced and development of black colonies prolonged if covered by a thin film of liquid medium. Without a moist covering, black colonies were commonly overgrown by white mycelium.