Evidence for an expanded host range of Fusarium oxysporum f. sp. chrysanthemi

Fusarium oxysporum, associated with wilt symptoms, has been reported in commercial nurseries in Northern Italy in several hosts of the Asteraceae family, such as chrysanthemum, Paris daisy, African daisy, and gerbera. Forma specialis chrysanthemi was assigned as the causal agent of this wilt disease. Severe wilting has recently been observed on the new Asteraceae host, orange coneflower (Rudbeckia fulgida). Morphological observations and sequencing of the translation elongation factor 1α (EF-1α) gene have indicated the involvement of F. oxysporum in this disease. The objective of this study was to identify the forma specialis of F. oxysporum isolated from orange coneflower. This was achieved by means of pathogenicity tests and phylogenetic analyses on the EF-1α and intergenic spacer (IGS) regions performed on single-spore isolates. The results of this study have characterized Fusarium oxysporum on orange coneflower for the first time. F. oxysporum f. sp. chrysanthemi was identified as the causal agent of the wilt disease. This represents the first report of this forma specialis on orange coneflower in Italy, as well as in the world.