Light, scanning and transmission electron microscopy studies on the conidiogenesis of Cercospora zeae-maydis on maize

Abstract

Light, scanning and transmission electron microscopy were used to study conidiophore formation and conidiogenesis by Cercospora zeae-maydis Tehon & Daniels, the causal organism of grey leaf spot on maize, Zea mays L. Hyphae aggregate in the substomatal cavity and give rise to fascicles of 1–2 septate conidiophore initials which emerge through the stoma. A single, aseptate conidium develops from the conidiogenous cell of the conidiophore initial. As the conidium matures, septa are laid down. Extension growth of the conidiogenous cell terminally, leads to the lateral displacement of the conidium on the conidiophore. Schizolytic secession results in the secession of the conidium from the conidiogenous cell. On secession, a slightly everted geniscar, with a granular wall deposit, is left laterally on the parent conidiogenous cell. After conidial secession, the conidiophore continues to grow, producing a second conidium from the conidiogenous cell at the apex of the extended conidiophore. The second conidium, in turn, is also displaced to a lateral position as the conidiogenous cell continues to grow from beneath, displacing the second conidium laterally. This sympodial and successive proliferation of the fertile conidiogenous cell results in the formation of a characteristic 1–3, occasionally 4, geniculate conidiophore, bearing a single conidium at each apex.