VIEW ARTICLE

Ultrastructure of Microsclerotia of Verticillium albo-atrum. M. F. Brown, Assistant Professor, Department of Plant Pathology, University of Missouri, Columbia, 65201; T. D. Wyllie, Associate Professor, Department of Plant Pathology, University of Missouri, Columbia, 65201. Phytopathology 60:538-542. Accepted for publication 22 October 1969. DOI: 10.1094/Phyto-60-538.

The ontogeny of microsclerotia of Verticillium albo-atrum was examined by stereoscan and transmission electron microscopy. Microsclerotia originate from swollen hyphal cells of single or intermingled hyphae and increase in size by prolific budding from globose cells. The entire mass becomes enveloped in a pigmented mucilaginous matrix. Many peripheral cells degenerate early in the development of the microsclerotium, leaving nonfunctional hyaline cells embedded in the matrix among heavily pigmented functional cells. The pigmented cells are connected by means of septal pores and retain organized cytoplasmic contents, including a single nucleus, numerous mitochondria, lipid droplets, ribosomes, woronin bodies, and other inclusions. A possible mechanism of microsclerotial germination is proposed.