VIEW ARTICLE

Ecology and Epidemiology

Sporodochium Development and Conidium Production in Cephalosporium gramineum. M. V. Wiese, Department of Botany and Plant Pathology, Michigan State University, East Lansing, MI 48824; A. V. Ravenscroft, Department of Botany and Plant Pathology, Michigan State University, East Lansing, MI 48824. Phytopathology 68:395-401. Accepted for publication 24 August 1977. Copyright © 1978 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-68-395.

Cephalosporium gramineum was induced to grow in and on moist, naturally-infested wheat straw (Triticum aestivum L.) in the field and laboratory. Its colonization of straw, sporulation, and sporodochium development were monitored with light and electron microscopes. In immature wheat plants, the fungus was confined to xylem vessels. In straw it developed extravascular, asporogenic hyphae that ramified all subepidermal tissues. Stomata were principal sites of hyphal emergence onto the straw surface where hyphal branching intensified and sporulating phialides differentiated at branch tips. Sporulation was independent of the organization of phialides into simple clusters or into sporodochia. Sporodochia developed above stomata and at sites within effuse, superficial mycelium. They originated from groups of short, branching hyphae (some branched penicillately) that proliferated centrifugally into hymenia. Sporodochia were convex initially but flattened with age. Their expanse of tightly compressed phialides supported masses of phialospores atop a thin, superficial stroma. Mucus covered the fungus, much of the substrate surface, and suspended masses of phialospores. The fungus became completely superficial as mycelium within the straw eventually lysed. Sporodochia developed within 4-8 wk and were most abundant on straw, especially leaf sheath tissue, kept moist and cool (12 C in the laboratory and on straw either upon or within 5 cm of the soil surface in the field). They developed slowly or not at all on air-dry straw, on straw at 21 C, or at 10-cm depths in soil. Phialides in sporodochia were typically elongate (1-2 × 5-25 μm) whereas on mycelium in vitro they were shorter, some being reduced to sessile collars on hyphae or on individual conidiogenous cells. Blastogenous-like sporulation, which was prevalent within the xylem of immature plants and in vitro, was not apparent on straw.