|Aoki, Takayuki - National Institute Of Agrobiological Sciences (NIAS)|
|Johnston, Peter - Landcare Research|
|Geiser, David - Pennsylvania State University|
Submitted to: Mycologia
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/19/2014
Publication Date: 12/30/2015
Publication URL: http://handle.nal.usda.gov/10113/62169
Citation: Aoki, T., Vaughan, M.M., McCormick, S.P., Busman, M., Ward, T.J., Kelly, A.C., O'Donnell, K., Johnston, P.R., Geiser, D.M. 2015. Fusarium dactylidis sp. nov., a novel nivalenol toxin-producing species sister to F. pseudograminearum isolated from orchard grass (Dactylis glomerata) in Oregon and New Zealand. Mycologia. 107(2):409-418.
Interpretive Summary: This study was conducted to characterize a novel Fusarium species that was isolated from orchard grass (Dactylis glomerata) in Oregon and New Zealand. Because this grass is one of the world’s most important forage grasses, and because the novel Fusarium species is closely related to B type trichothecene toxin-producing pathogens (hereafter B clade) of wheat and barley, we conducted experiments to assess whether it was pathogenic to wheat and produce toxins in vitro and in vivo. In addition, morphological features of the isolates from orchard grass were compared with those of closely related fusaria in the B clade of Fusarium. Genetic analyses were also conducted to infer evolutionary relationships of the novel Fusarium with other members of the B clade. Results of this study revealed that the novel B clade species could induce head blight symptoms on wheat and produce nivalenol trichothecenes in vitro and in vivo. In addition to nivalenol, the isolates were able to produce the estrogenic compound zearalenone, which is a reproductive toxin. The novel species, which was formally described as Fusarium dactylitis, could be distinguished from all other B clade species by the production of morphologically distinct asexual spores. Lastly, analysis of the whole genome sequence of F. dactylitis NRRL 29380 revealed that it possessed the necessary genes to produce nivalenol but that it lacked two novel virulence genes recently discovered in the closely related species, F. pseudograminearm. The results of this study should be of interest to plant pathologists, mycotoxicologists, orchard grass breeders, and quarantine officials.
Technical Abstract: The B trichothecene toxin-producing clade (B clade) of Fusarium includes the etiological agents of Fusarium head blight, crown rot of wheat and barley and stem and ear rot of maize. B clade isolates also have been recovered from several wild and cultivated grasses, including Dactylis glomerata (orchard grass or cock’s foot), one of the world’s most important forage grasses. Two isolates from the latter host are formally described here as F. dactylidis. Phenotypically F. dactylidis most closely resembles F. ussurianum from the Russian Far East. Both species produce symmetrical sporodochial conidia that are similar in size and curved toward both ends. However, conidia of F. ussurianum typically end in a narrow apical beak while the apical cell of F. dactylidis is acute. Fusarium dactylidis produced nivalenol mycotoxin in planta as well as low but detectable amounts of the estrogenic mycotoxin zearalenone in vitro. Results of a pathogenicity test revealed that F. dactylidis induced mild head blight on wheat.