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Fusarium spp. associated with rice Bakanae: ecology, genetic diversity, pathogenicity and toxigenicity

Authors

  • Ednar G. Wulff,

    Corresponding author
    1. University of Copenhagen, Faculty of Life Sciences, Department of Plant Biology and Biotechnology, Danish Seed Health Centre, Thorvaldsensvej 40, DK-1871, Frederiksberg C, Denmark.
      *E-mail ewu@life.ku.dk; Tel. (+45) 35 33 38 55; Fax (+45) 35 33 37 01.
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  • Jens L. Sørensen,

    1. Technical University of Denmark, Department of Systems Biology, Center for Microbial Biotechnology, Søltofts Plads 221, Building 221, DK-2800 kgs. Lyngby, Denmark.
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  • Mette Lübeck,

    1. Aalborg University, Department of Biotechnology, Chemistry and Environmental Engineering, Section for Sustainable Biotechnology, Lautrupvang 15, DK-2750 Ballerup, Denmark.
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  • Kristian F. Nielsen,

    1. Technical University of Denmark, Department of Systems Biology, Center for Microbial Biotechnology, Søltofts Plads 221, Building 221, DK-2800 kgs. Lyngby, Denmark.
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  • Ulf Thrane,

    1. Technical University of Denmark, Department of Systems Biology, Center for Microbial Biotechnology, Søltofts Plads 221, Building 221, DK-2800 kgs. Lyngby, Denmark.
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  • Jan Torp

    1. University of Copenhagen, Faculty of Life Sciences, Department of Plant Biology and Biotechnology, Danish Seed Health Centre, Thorvaldsensvej 40, DK-1871, Frederiksberg C, Denmark.
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*E-mail ewu@life.ku.dk; Tel. (+45) 35 33 38 55; Fax (+45) 35 33 37 01.

Summary

African and Asian populations of Fusarium spp. (Gibberella fujikuroi species complex) associated with Bakanae of rice (Oryzae sativa L.) were isolated from seeds and characterized with respect to ecology, phylogenetics, pathogenicity and mycotoxin production. Independent of the origin, Fusarium spp. were detected in the different rice seed samples with infection rate ranges that varied from 0.25% to 9%. Four Fusaria (F. andiyazi, F. fujikuroi, F. proliferatum and Fverticillioides) were found associated with Bakanae of rice. While three of the Fusaria were found in both African and Asian seed samples, F. fujikuroi was only detected in seed samples from Asia. Phylogenetic studies showed a broad genetic variation among the strains that were distributed into four different genetic clades. Pathogenicity tests showed that all strains reduced seed germination and possessed varying ability to cause symptoms of Bakanae on rice, some species (i.e. F. fujikuroi) being more pathogenic than others. The ability to produce fumonisins (FB1 and FB2) and gibberellin A3 in vitro also differed according to the Fusarium species. While fumonisins were produced by most of the strains of F. verticillioides and F. proliferatum, gibberellin A3 was only produced by Ffujikuroi. Neither fumonisin nor gibberellin was synthesized by most of the strains of F. andiyazi. These findings provide new information on the variation within the G. fujikuroi species complex associated with rice seed and Bakanae disease.

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