Studies on Cenococcum geophilum. II. Sclerotium morphology, germination, and formation in pure culture and growth pouches

Abstract

Cenococcum geophilum sclerotium morphology, germination, and formation in pure culture and growth pouches is described. On agar, germination of most field-collected sclerotia occurred within 30 days. In vitro attempts to initiate sclerotia succeeeded to varying degrees for 20 of the 22 isolates (collected in three main habitats in Oregon) in agar or peat – vermiculite but not in liquid culture. Sclerotium formation was initiated in 1-month-old cultures by branching, lateral growth, and subsequent septation of hyphae. Surface cells of compact hyphae of young sclerotia elongated, became irregularly arranged, and melanized. In growth pouches, sclerotium initials developed on the paper wick from a hyphal mat formed from convoluted hyphae. Mature sclerotia appeared as small spherical structures with linear hyphae radiating out from the surface. Sections revealed a well-differentiated rind and a medulla with pseudoparenchymatous organization. Numerous nuclei and vacuoles were distributed in both rind and medullary hyphae. Key words: Cenococcum, sclerotium, initiation, in vitro.