Rhexocercosporidium panacis sp. nov., a new anamorphic species causing rusted root of ginseng (Panax quinquefolius)

Abstract

A new species of the anamorphic genus Rhexocercosporidium is described. Isolates of a Rhex-Rhexocercosporidium sp. were obtained from ginseng (Panax quinquefolius) roots with symptoms of rusted root. These isolates were found to be genetically and morphologically distinct from the only described species in this genus, R. carotae. Sequence data from the ribosomal DNA region spanning the internal transcribed spacers 1 and 2 and from a portion of the β-tubulin gene of the ginseng Rhexocercosporidium were compared to those of R. carotae. Parsimony analyses of sequence data showed that R. carotae and the ginseng isolates belonged to distinct but closely related clades. Conidia of a typical ginseng isolate were significantly shorter and possessed fewer septa than R. carotae but shared rhexolytic secession of conidia with R. carotae. The binomial Rhexocercosporidium panacis is proposed to accommodate isolates of this genus that are associated with the rusted root disease.

• Acrothecium
• β-tubulin
• ginseng
• ITS
• Leotiomycetes
• molecular phylogenetics
• Panax
• Pseudocercosporidium
• rusty root

The work reported here was supported in part by the Matching Investment Initiative of Agriculture and Agri-Food Canada, the Ontario Ginseng Growers Association and the Associated Ginseng Growers of British Columbia. Technical assistance was provided by SMT Hoke, Yun Zhang, JJ Miller and BB Capell. Department of Agriculture and Agri-Food, Government of Canada, ©Minister ofPUBLIC Works and Government Services Canada 2006.