Phenotypic and pathogenic traits of two species of the Fusarium graminearum complex possessing either 15-ADON or NIV genotype Piérri Spolti & Nicole C. Barros & Larissa B. Gomes & Juliano dos Santos & Emerson M. Del Ponte Accepted: 9 January 2012 / Published online: 28 January 2012 # KNPV 2012 Abstract Fusarium head blight (FHB) in Brazil is caused mainly by two members of the Fusarium gra- minearum species complex, each possessing either a DON/15-ADON chemotype (F. graminearum sensu stricto, Fgss) or a NIV chemotype (F. meridionale, Fmer). In this work, we aimed to characterize and compare isolates belonging to each species, obtained either from wheat or barley, in relation to phenotypic traits (mycelial growth, sporulation and germination) and pathogenicity (in vitro glume infection and in vivo central floret inoculation) to two Brazilian wheat cul- tivars, Guamirim (moderate susceptible) and BRS 194 (susceptible). Results showed significantly higher growth rates, greater spore production and quicker germination for the Fgss isolates compared to the Fmer isolates, which were also more sensitivity to tebuconazole than the Fgss isolates. All isolates were capable of infecting glume tissues of both varieties, with an overall higher infection frequency for Fgss than Fmer isolates when inoculated in cv. Guamirim than in cv. BRS194, which showed similar infection frequency between the species. Accordingly, in the central-floret inoculation assay, Fgss isolates were also more aggressive than Fmer isolates towards cv. Guamirim, but not towards BRS194, based on the mean area under disease progress curves. It is hypoth- esized that phenotypic traits and host resistance may play a role in the selection of more aggressive popu- lations under field conditions, thus partially explaining the dominance of Fgss populations associated with FHB of wheat in Brazil. Keywords Triticum aestivum . Gibberella zeae . trichothecene genotype . chemotypes . Fusarium meridionale Introduction Fusarium head blight (FHB) is an economically dev- astating fungal disease for wheat and barley world- wide, mainly due to its potential to reduce yield and contaminate grain with harmful mycotoxins (McMullen et al. 1997; Goswami and Kistler 2004). The major causal agents of FHB worldwide are mem- bers of the Fusarium graminearum clade or species complex (Fg complex) (teleomorph: Gibberella zeae) in which at least fifteen phylogenetic species have been resolved by multilocus genealogical concordance (O’Donnell et al. 2004; Starkey et al. 2007; Yli-Mattila et al. 2009; Sarver et al. 2011). In Brazil, FHB epidemics occur more frequently in the southern regions of the country, where a combina- tion of the humid subtropical climate and extensive non-tillage adoption favour disease epidemics almost Eur J Plant Pathol (2012) 133:621–629 DOI 10.1007/s10658-012-9940-5 P. Spolti : N. C. Barros : L. B. Gomes : J. dos Santos : E. M. Del Ponte (*) Departamento de Fitossanidade, Faculdade de Agronomia, Universidade Federal do Rio Grande do Sul, Av. Bento Gonçalves 7712, 91540000 Porto Alegre, RS, Brazil e-mail: emerson.delponte@ufrgs.br