title: The chemoattractant potential of ginsenosides in the ginseng - Pythium irregulare pathosystem.
abstract: Ginsenosides produced by ginseng (Panax quinquefolius L.) are mildly fungitoxic saponins; however, exposure of the ginseng root pathogen Pythium irregulare Buisman to ginsenosides enhances its growth in a dose dependent manner, leading to speculation that ginsenosides may function as chemoattractants and/or growth regulators in the context of the ginseng - P. irregulare pathosystem. In the present work, it was demonstrated that the treatment of ginseng plants with a relatively high dose of ginsenosides by dipping their roots into a solution of ginsenosides prior to planting results in delayed infection by P. irregulare in pot experiments, as monitored by non-invasive chlorophyll fluorescence imaging. In an attempt to determine whether this observation results from a protective effect of the ginsenosides, or from a modification of P. irregulare growth habit in response to ginsenosides present in the soil, standard in vitro disk diffusion assays were conducted. Here, exposure of P. irregulare to crude ginsenosides or pure ginsenoside Rb1, resulted in delayed hyphal progression, while enhancing aerial hyphae build-up around ginsenoside-treated disks. By contrast, assays with pure ginsenoside F2 resulted in clear zones of inhibition around treated disks. While it remains unclear whether ginsenosides act as chemoattractants for P. irregulare in vivo, the results here suggest that these saponins serve to alter the growth habit of this organism, both in vivo and in vitro.
authors.affiliation: Department of Biology and the Biotron, The University of Western Ontario, London, ON N6A 5B7, Canada. Electronic address: divanov2@uwo.ca.
authors.forename: Dimitre A
authors.initials: DA
authors.lastname: Ivanov
authors.affiliation: Department of Biology and the Biotron, The University of Western Ontario, London, ON N6A 5B7, Canada. Electronic address: jgeorga2@alumni.uwo.ca.
authors.forename: Jorge R C
authors.initials: JRC
authors.lastname: Georgakopoulos
authors.affiliation: Department of Biology and the Biotron, The University of Western Ontario, London, ON N6A 5B7, Canada. Electronic address: bernards@uwo.ca.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Bernards
mesh_terms: D002630:Chemotactic Factors / Q000737:chemistry / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D036145:Ginsenosides / Q000032:analysis / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology*; D015394:Molecular Structure; D005894:Panax / Q000737:chemistry*; D018517:Plant Roots / Q000187:drug effects; D011775:Pythium / Q000737:chemistry*; D012987:Soil
chemical_list: D002630:Chemotactic Factors; D036145:Ginsenosides; D012987:Soil; C407883:ginsenoside F2; C442759:ginsenoside Rb1
keywords: Araliaceae; Chlorophyll fluorescence imaging; Ginseng; Ginsenosides; Panax quinquefolius; Pythium irregulare