VIEW ARTICLE

Electron Microscopic Observations on the Spore Wall and “Operculum” Formation in Chlamydospores of Thielaviopsis basicola. Pamela W. Tsao, Research Associate, Department of Plant Pathology, University of California, Riverside 92502; Peter H. Tsao, Associate Professor, Department of Plant Pathology, University of California, Riverside 92502. Phytopathology 60:613-616. Accepted for publication 22 October 1969. DOI: 10.1094/Phyto-60-613.

Chlamydospores of Thielaviopsis basicola in a chain were enveloped by a wall consisting of two layers. Within the chain envelope, each spore had a thick wall also consisting of an electron-dense outer layer and an electron-transparent inner layer. In the areas where lateral and end walls joined, the inner layer extended, by wedging obliquely, into the thick, outer layer of the spore wall, thus creating a circular weak junction at the rims. The spore wall may dehisce at the rim during spore germination, resulting in a split between the lateral wall and the end wall and thereby forming the “operculum”.