The life cycle of the smut fungus Moesziomyces penicillariae is adapted to the short-cycle of the host, Pennisetum glaucum |
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Authors: | Gnagna Diagne-Leye Idy Carras Sare Yves Martinez Mame Arama Fall-Ndiaye Seyed Kazem Sabbagh Amadou Tidiane Ba Christophe Paul Roux |
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Institution: | 1. Laboratoire de Biotechnologies des champignons (LBC), Département de Biologie Végétale, Faculté des Sciences et Techniques, Université Cheikh Anta Diop (UCAD), Dakar, Sénégal;2. Département de Biologie Végétale, Faculté des Sciences et Techniques, Université Cheikh Anta Diop, Dakar, Sénégal;3. CNRS, FR3450, BP 42617, F-31326 Castanet-Tolosan CEDEX, France;4. Department of Plant Pathology and Institute of Plant Biotechnology, University of Zabol, Iran;5. Université de Toulouse, UPS, UMR5546, Laboratoire de recherche en Sciences Végétales, BP 42617, F-31326 Castanet-Tolosan CEDEX, France;6. CNRS, UMR5546, BP 42617, F-31326 Castanet-Tolosan CEDEX, France |
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Abstract: | Moesziomyces penicillariae (Brefield) Vànky is a basidiomycete fungus responsible for smut disease on pearl millet, an important staple food in the sub-Sahelian zone. We revisited the life cycle of this fungus. Unlike other Ustilaginales, mating of sporidia was never observed and monoclonal cultures of monokaryotic sporidia were infectious in the absence of mating with compatible partner. These data argued for an atypical monokaryotic diploid cell cycle of M. penicillariae, where teliospores only form solopathogenic sporidia. After inoculation of monoclonal solopathogenic strains on spikelets, the fungus infects the ovaries and induces the folding of the micropilar lips, as observed during early pollination steps. The infected embryo then becomes disorganized and the fungus invades peripheral ovary tissues before sporulating. We evaluated the systemic growth abilities of the fungus. After root inoculation, mycelium was observed around and inside the roots. As argued by transmission electron microscopy (TEM) observations and polymerase chain reaction (PCR) detection using specific primers for M. penicillariae, the fungus can grow from roots to the caulinar meristems. In spite of this systemic growth, no sori were formed on the varieties of pearl millet tested after root inoculation. All together, these data suggest that the reduced life cycle of M. penicillariae – i.e. dispersal of ‘ready to infect’ solopathogenic sporidia, floral infection – is an adaptation to the aetiology of this disease to short-cycle pearl millet varieties from the sub-Sahel. |
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Keywords: | Life cycle Moesziomyces penicillariae Solopathogenicity Systemic growth |
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