Submitted to: Mycologia
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/8/2009
Publication Date: 11/9/2009
Citation: Yli-Mattila, T., Gagkaeva, T., Ward, T.J., Aoki, T., Kistler, H.C., O Donnell, K. 2009. A Novel Asian Clade Within the Fusarium graminearum Species Complex Includes a Newly Discovered Cereal Head Blight Pathogen from the Far East of Russia. Mycologia. 101(6):841-852. Interpretive Summary: The Fusarium head blight (FHB) of small grain cereals such as wheat, barley and oats emerged over the past two decades to become one of the most economically devastating plant diseases worldwide today. To protect United States agriculture from the inadvertent introduction of foreign FHB pathogens associated with the globalization of world trade, it is critical to identify the sources of novel pathogens and characterize their toxin potential. In this study we conducted a survey of FHB in European and Asian regions of the Russian Federation. The results of this survey identified a novel FHB species in the Far East of Russia. Mycotoxin analyses and pathogenicity experiments demonstrated that this novel species could produce trichothecene toxins in vivo and induce FHB of wheat in an environmentally controlled greenhouse. These results will benefit Animal and Plant Health Inspection Service (APHIS) quarantine officials’ charged with preventing the introduction of foreign pathogens into the United States and help plant breeders develop cereal cultivars with broad based resistance to FHB.
Technical Abstract: We investigated B-trichothecene toxin-producing Fusarium head blight (B-FHB) species and their 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 genetic diversity and geographic distribution of these economically devastating cereal pathogens. Results of a novel multilocus genotyping (MLGT) assay revealed that Fusarium graminearum was the primary B-FHB pathogen in Northern regions of Europe (77.4%) and Asia (85.8%). 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 western Russia (N = 40) were exclusively 3ADON-producers. Based on results of the MLGT assay, species identity of 10 putatively genetically novel B-FHB 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 F. graminearum species 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.