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

Abstract

We investigated Fusarium graminearum complex (Fg complex) species diversity and toxin potential in European and Asian regions of the Russian Federation and adjoining regions northwest to Finland and south near Harbin, Heilongjiang Province, 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 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 Russian Far East was investigated further via molecular phylogenetic analyses of multi-locus 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 morphologically characterizing isolates of F. ussurianum, experiments were conducted to assess pathogenicity to wheat and trichothecene toxin potential in planta.

• deoxynivalenol
• genotyping
• mycotoxin
• nivalenol
• phylogenetics
• trichothecene

The visit of Tapani Yli-Mattila to the USDA-ARS-NCAUR in Peoria, Illinois, and to the All-Russian Institute of Plant Protection Institute in St Petersburg, and the visits of Tatiana Gagkaeva to the University of Turku were supported by the Nordic network project New Emerging Mycotox-ins and Secondary Metabolites in Toxigenic Fungi of Northern Europe, which is financially supported by the Nordic Research Board and by the Academy of Finland. Special thanks are due Prof K. Walter Gams for assistance with the species description, Dr Ludmila Malinovskay for supplying strains, Thomas Usgaard and Stacy Sink for excellent technical support, Don Fraser for preparing thePUBLICation figures, and Jennifer Ness for collecting the DNA sequence data. The mention of company names or trade products does not imply that they are endorsed or recommended by the U.S. Department of Agriculture over other companies or similar products not mentioned.