Diversity of Fusarium species associated with discolored ginseng roots in British Columbia
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| Authors: | Punja, ZK; Wan, A; Goswami, RS; Verma, W; Rahman, M; Barasubiye, T; Seifert, KA; Levesque, CA |
| Year: | 2007 |
| Journal: | Canadian Journal of Plant Pathology-Revue Canadienne de Phytopathologie 29: 340-353 |
| Title: | Diversity of Fusarium species associated with discolored ginseng roots in British Columbia |
| Abstract: | Crown discoloration on roots of American ginseng (Panax quinquefolius) is a major problem that causes a reduction in quality and can be a limiting factor to ginseng production in some regions of Canada. The symptoms result from an accumulation of phenolic compounds within disorganized and disrupted cells, accompanied by the presence of fungal hyphae in affected cells. Twelve Fusarium species were recovered on isolation media during June-September of 2004 and 2005 from ginseng roots displaying root-surface discoloration in British Columbia. Many of the same species were also recovered from soil from ginseng fields and cereal-straw mulch used during ginseng production. Hybridization of labeled PCR amplicons from DNA samples from affected root tissue to a DNA array designed using oligonucleotides specific to 26 Fusarium species was used to identify the Fusarium species present in ginseng roots. Over 90% of symptomatic root samples contained F. equiseti and several other Fusarium species, including F.sporotrichioides and F. avenacemn, that were absent in nonsymptomatic tissues. An in vitro pathogenicity test was used to screen 180 Fusarium isolates originating front affected roots. Reddish brown lesions developed 10 days following inoculation with 58 isolates of F. equiseti and F. sporotrichioides and to a lesser extent with 7 isolates of F.avenacetan and F. culmorum. Greenhouse and field inoculations confirmed the pathogenicity of E equiseti and F.sporotrichioides isolates to ginseng roots. Pathogenicity tests conducted with 340 additional isolates representing 10 Fusarium species originating from wheat- and barley-straw mulch and soil from ginseng fields, as well as from cereal hosts worldwide, identified a proportion of isolates (52.5%) of F. equiseti, F. sporotrichioides, F. avenaceum, and F.culmorum that produced reddish brown lesioned areas. These cereal-infecting Fusarium species can induce a tissue response following infection that results in root-surface discoloration. |
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