|WALLACE, EMMA - Oak Ridge Institute For Science And Education (ORISE)|
|SALGADO-SALAZAR, CATALINA - Oak Ridge Institute For Science And Education (ORISE)|
|GREGORY, NANCY - University Of Delaware|
Submitted to: Mycological Progress
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/30/2018
Publication Date: 10/14/2018
Citation: Wallace, E., Salgado-Salazar, C., Gregory, N., Crouch, J. 2018. Basidiophora delawarensis, a new downy mildew species that infects cultivated goldenrod (Solidago sphacelata) in the United States. Mycological Progress. 17(12):1283-1291. https://doi.org/10.1007/s11557-018-1444-z.
Interpretive Summary: Deadly downy mildew plant diseases are increasingly problematic in agricultural crops and cultivated and natural landscapes. This research describes a new downy mildew disease affecting the cultivated goldenrod variety 'Golden Fleece'. 'Golden Fleece' is an award winning perennial plant valued worldwide for its brilliant yellow late-season flowers, short stature and as a food source for pollinators such as butterflies and bees. The fungus-like water-mold causing this new downy mildew disease is a species never seen before, with uniquely sized spores and a distinct DNA fingerprint. This new downy mildew species was given a name, and photographs and descriptions were provided that can be used to diagnose future outbreaks if they occur. Native plants such as goldenrod are becoming increasingly popular as homeowner and landscapers work to incorporate ecologically sound choices into gardens, and it is vital to understand the diseases that can affect them. Knowledge of this new disease and this new downy mildew species will be useful to pathologists working to cultivate healthy, disease-free plants, and provides information to gardeners, landscapers, and commercial growers to diagnose the disease should it occur.
Technical Abstract: Species in the genus Basidiophora (Oomycota, Peronosporales) are plant pathogens causing downy mildew on several closely related hosts in the family Asteraceae, including the genera Conyza, Erigeron, Solidago and Symphyotrichum. Despite their widespread nature, little is known about the diversity, biology and economic impact of downy mildew pathogens of ornamental or wild plants in the Asteraceae. In June 2017, Solidago sphacelata plants of the cultivar ‘Golden Fleece’ were found in New Castle Co., Delaware, showing typical symptoms of downy mildew. Initial morphological observations indicated the specimen belonged to the genus Basidiophora. Phylogenetic analysis of the partial sequence of cox2 mitochondrial gene using Bayesian and maximum likelihood methods showed that the Basidiophora infecting S. sphalaceta corresponds to a previously unidentified species and is here described as B. delawarensis. This new species constitutes the fourth described species in the genus Basidiophora and can be separated from other Basidiophora species by differences in size of oogonia and oospores and nucleotide sequence divergence. This new species poses a potential threat to this ornamental plant, warranting close monitoring and the implementation of disease control programs.