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The vegetative life-cycle of the clover pathogen Cymadothea trifolii as revealed by transmission electron microscopy

Published online by Cambridge University Press:  12 July 2005

Uwe K. SIMON
Affiliation:
Universität Tübingen, Lehrstuhl Spezielle Botanik und Mykologie, Auf der Morgenstelle 1, D-72076 Tübingen, Germany. E-mail: uwe.simon@uni-tuebingen.de
Robert BAUER
Affiliation:
Universität Tübingen, Lehrstuhl Spezielle Botanik und Mykologie, Auf der Morgenstelle 1, D-72076 Tübingen, Germany. E-mail: uwe.simon@uni-tuebingen.de
Danny RIOUX
Affiliation:
Natural Resources Canada, Canadian Forest Service – Quebec Region, 1055 du P.E.P.S., P.O. Box 3800, Sainte-Foy, Quebec G1V 4C7, Canada.
Marie SIMARD
Affiliation:
Natural Resources Canada, Canadian Forest Service – Quebec Region, 1055 du P.E.P.S., P.O. Box 3800, Sainte-Foy, Quebec G1V 4C7, Canada.
Franz OBERWINKLER
Affiliation:
Universität Tübingen, Lehrstuhl Spezielle Botanik und Mykologie, Auf der Morgenstelle 1, D-72076 Tübingen, Germany. E-mail: uwe.simon@uni-tuebingen.de
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Abstract

The vegetative life-cycle of Cymadothea trifolii (anamorph Polythrincium trifolii), causing sooty blotch of clover, is described using chemically as well as cryofixed and freeze-substituted samples. The pathogen enters the leaf through stomata and proliferates intercellularly. Nutrients are assumedly obtained via an interaction apparatus produced within the pathogen's hyphae, opposite to which the host cell is triggered to invaginate its plasmalemma. Rare attempts of ‘self-parasitism’ were also seen. Entering the conidial stage, stromata are laid down under the lower epidermis. The dying tissue above may explain the necrotic spots observed on infected leaflets. Foot cells in the conidial stromata produce thick-walled conidiophores, which grow sympodially. New conidiophores may grow into empty shells of old ones. Conidia are detached after pores between them and conidiophores have become plugged by organelles resembling Woronin bodies. Conidia are usually two-celled and their walls contain chitin and β-1,3-glucans as indicated by labelling with gold-conjugated wheat germ agglutinin and anti-β-1,3-glucan antibodies. Both conidiophores and conidia contain a structure which we regard as a new organelle with as yet unknown function.

Type
Research Article
Copyright
© The British Mycological Society 2005

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