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Cytology and Histology

Ultrastructure and Mechanics of the Conidium-Conidiophore Attachment of Helminthosporium maydis. James R. Aist, Assistant Professor, Department of Plant Pathology, Cornell University, Ithaca, NY 14853; Donald E. Aylor(2), and Jean-Yves Parlange(3). (2)(3)Scientists, Department of Ecology and Climatology, The Connecticut Agricultural Experiment Station, New Haven, CT 06504. Phytopathology 66:1050-1055. Accepted for publication 17 March 1976. Copyright © 1976 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-66-1050.

The structural and mechanical adaptations of Helminthosporium maydis for conidium dispersal were examined. The structure of the attachment of mature conidia to conidiophores was determined by thin-section electron microscopy of attached or partially detached conidia and their conidiophores. Serial section analysis showed that six of the eight mature conidia examined were attached solely by a narrow isthmus of wall material. The forces required for conidium removal were measured by centrifugation of leaf lesions collected in the field and induced to sporulate in the laboratory. Based on the observed structure of the isthmus and the measured forces, it was estimated that the material comprising the isthmus was about as strong as wood fiber. A less-frequent type of attachment, involving a finger of cytoplasm which extended from the conidiophore into the base of the conidium also was observed.

Additional keywords: corn leaf blight, cell walls, dispersal, epidemiology.