STUDIES ON CENOCOCCUM-GEOPHILUM .2. SCLEROTIUM MORPHOLOGY, GERMINATION, AND FORMATION IN PURE CULTURE AND GROWTH POUCHES

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 a ttempts to initiate sclerotia succeeded to varying degrees for 20 of 6 he 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 su bsequent septation of hyphae. Surface cells of compact hyphae of young sclerotia elongated, became irregularly arranged, and melanized. In g rowth 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 wi th pseudoparenchymatous organization. Numerous nuclei and vacuoles wer e distributed in both rind and medullary hyphae.