Sclerotial Biogenesis in the Basidiomycete Sclerotium rolfsii. A Scanning Electron Microscope Study

Abstract

Sclerotial biogenesis in Sclerotium rolfsii was studied using scanning electron microscopy. Three stages in sclerotial development were documented: sclerotial initials, development and mature stages. Initials developed from primordia, small tufts of mycelial hyphae held together very loosely. Each tuft grew in size and increased in hyphal density. Distinct structural details justifying further subdivision of the sclerotial initials stage were not observed. Differences among initials were determined temporally only with respect to size and degree of hyphal density. Sclerotia of the development stage already had assumed their spherical shape. An early and late developmental stage could be distinguished. Sclerotia of the former were covered with an extensive layer of loose aerial hyphae which obscured the sclerotial surface. Those of the latter stage had shed most of the aerial hyphae and exuded profusely. Mature sclerotia were compact, spherical and had shed completely the outer layer of aerial hyphae. The skin surface was rough and scaly.