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A novel Asian clade within the Fusarium graminearum species complex includes a newly discovered cereal head blight pathogen from the Russian Far East

     ¹ University of Turku, Turku, Finland
² All-Russian Institute of Plant Protection, St. Petersburg, Russia
³ National Center for Agricultural Utilization Research, Peoria, Illinois
⁴ National Inst Agrobio Sciences, Kannondai, Tsukuba, Ibaraki, 305-8602, Japan
⁵ USDA, St. Paul, Minnota
⁶ Microbial Genomics and Bioprocessing Research Unit, NCAUR USDA, Peoria, IL, 61604-3999, United States of America

We investigated Fusarium graminearum complex (Fg complex) species diversity and toxin potential in European and Asian regions of the Russian Federation, and adjoining regions to the Northwest in Finland and the South near Harbin, in the Heilongjiang Province of China to expand our knowledge of the host range and geographic distribution of these economically devastating cereal head blight pathogens. Results of a recently described multilocus genotyping (MLGT) assay revealed that F. graminearum was the sole Fg complex pathogen in Northern regions of Europe and the predominant one in Asia (90.5%). Even though isolates of F. graminearum were segregating for 3-acetyldeoxynivalenol (3ADON) and 15-acetyldeoxynivalenol (15ADON) chemotype in nearly equal frequencies in the regions sampled on both continents, significant differences in the geographic distribution of isolates producing these acetyl ester derivatives of deoxynivalenol (DON) were observed in Europe. While 93.5% of the isolates in southern Russia (N = 43 of 46) possessed the 15ADON chemotype, isolates of F. graminearum recovered in Finland and northwestern Russia (N = 40) were exclusively 3ADON-producers. Based on results of the MLGT assay, species identity of 10 genetically novel Fg complex isolates from the Far East of Russia was investigated further via molecular phylogenetic analyses of multilocus DNA sequence data. Results of these analyses resolved these isolates as a phylogenetically distinct, reciprocally monophyletic sister lineage of F. asiaticum, which together with F. vorosii, form a newly discovered Asian clade within the Fg complex. Because this novel lineage fulfills the highly conservative criterion of genealogical exclusivity under phylogenetic species recognition, it is formally described herein as F. ussurianum. In addition to characterizing isolates of F. ussurianum morphologically, experiments were conducted to assess pathogenicity to wheat and trichothecene toxin potential in planta.

Key words: deoxynivalenol, genotyping, mycotoxin, nivalenol, phylogenetics