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Molecular Characterization of the Fusarium graminearum Species Complex in Japan

First author: Life Science Research Center, Gifu University, 1-1 Yanagido, Gifu 501-1193 Japan; second and tenth authors: Faculty of Applied Biological Sciences, Gifu University, 1-1 Yanagido, Gifu 501-1193 Japan; third author: National Center for Agricultural Utilization Research, U.S. Department of Agriculture, Agricultural Research Service, 1815 N University St., Peoria, IL 61604; fourth author: Department of Plant Pathology, University of Minnesota, St. Paul, MN 55108; fifth and sixth authors: National Agricultural Research Center for Kyushu Okinawa Region, National Agriculture and Bio-oriented Research Organization, 2421 Suya, Kumamoto 861-1192 Japan; seventh author: National Agricultural Research Center, National Agriculture and Bio-oriented Research Organization, 3-1-1 Kannondai, Ibaraki 305-8666 Japan; eighth author: National Agricultural Research Center for Tohoku Region, National Agriculture and Bio-oriented Research Organization, Yotsuya, Daisen, Akita 014-0102 Japan; and ninth author: River Basin Research Center, Gifu University, 1-1 Yanagido, Gifu 501-1193 Japan.

Members of the Fusarium graminearum species complex are important cereal pathogens worldwide and belong to one of at least nine phylogenetically distinct species. We examined 298 strains of the F. graminearum species complex collected from wheat or barley in Japan to determine the species and trichothecene chemotype. Phylogenetic analyses and species-diagnostic polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLPs) revealed the presence and differential distribution of F. graminearum sensu stricto (s. str.) and F. asiaticum in Japan. F. graminearum s. str. is predominant in the north, especially in the Hokkaido area, while F. asiaticum is predominant in southern regions. In the Tohoku area, these species co-occurred. Trichothecene chemotyping of all strains by multiplex PCR revealed significantly different chemotype compositions of these species. All 50 strains of F. graminearum s. str. were of a 15- or 3-acetyl deoxynivalenol type, while 173 (70%) out of 246 strains of F. asiaticum were of a nivalenol type. The possibility of gene flow between the two species was investigated by use of 15 PCR-RFLP markers developed in this study. However, no obvious hybrids were detected from 98 strains examined, including strains collected from regions where both species co-occur.

Additional keywords:Fusarium head blight, scab.