Dormant and Germinating Diplodia Maydis Spores: Ultrastructure and Elemental Composition

Abstract

Diptodia maydis is one of the fungal pathogens causing stalk rot of corn. Previously we investigated the gross morphology of D. maydis on synthetic and natural substrates by SEM and established preparation procedures for D. maydis. The purpose of the present study was to compare the ultrastructure of D. maydis spores in thin sections with SEM results and in addition examine the elemental composition and distribution in dormant and germinating spores of D. maydis.SEM: Germinating and non-germinating spore cultures were double fixed in glutaraldehyde followed by OsO4. Samples were dehydrated in a graded series of alcohols thru 100%, then thru Freon TF and critical point dried with Freon 13 in a Bomar 900EX CPD. Specimens were mounted on SEM stubs, coated with carbon and PdAu and examined in a Cambridge Mark IIA SEM operated at 20 KV.TEM: Samples were double fixed with glutaraldehyde followed by OsO4, then dehydrated and embedded in Epon 812. Sections were stained with dipotassium tetramethyl osmate and examined in an Hitachi HU11AB TEM.