title: Interactions between indigenous arbuscular mycorrhizal fungi and Aphanomyces euteiches in field-grown pea.
abstract: This is the first reported study of the interactions between indigenous arbuscular mycorrhizal fungi (AMF) and Aphanomyces euteiches in pea under field conditions. A. euteiches was applied to the soil by adding oospores produced in vitro. Attempts were made to create a non-mycorrhizal control by incorporating carbendazim (Derosal Fl) in the topsoil before sowing. However, all carbendazim-treated plants showed approximately 20% root colonisation with AMF. Pea plants not treated with carbendazim showed a wide variation in AMF colonisation of 35-70% at the full flowering stage. In these control plots, root length infected with oospores of A. euteiches and colonisation by AMF were negatively correlated. Application of carbendazim increased the percent root length infected with oospores by 50-70%, depending on inoculum density of A. euteiches. Despite the lower levels of AMF colonisation in these treated plots, a negative correlation with oospore-containing root length was still observed. No correlation was found between AMF colonisation and disease severity, disease incidence or pathogen enzymatic activity (glucose-6-phosphate dehydrogenase). Thus, AMF do not seem to influence the vegetative stage of pathogen development during which cortical root rotting takes place, but rather the reproductive stage when oospores are produced. The results of this study underline the importance of field experiments for validating the significance of mycorrhizal fungi for plant health.
authors.affiliation: Department of Crop Protection, Danish Institute of Agricultural Sciences, 4200 Slagelse, Denmark. lars.bodker@agrsci.dk
authors.forename: Lars
authors.initials: L
authors.lastname: Bødker
authors.forename: Rasmus
authors.initials: R
authors.lastname: Kjøller
authors.forename: Kristian
authors.initials: K
authors.lastname: Kristensen
authors.forename: Søren
authors.initials: S
authors.lastname: Rosendahl
mesh_terms: D000935:Antifungal Agents; D001562:Benzimidazoles; D002219:Carbamates; D005954:Glucosephosphate Dehydrogenase / Q000378:metabolism; D038821:Mycorrhizae / Q000502:physiology*; D009868:Oomycetes / Q000502:physiology*; D018532:Pisum sativum / Q000502:physiology*; D010935:Plant Diseases; D018517:Plant Roots / Q000502:physiology*; D012988:Soil Microbiology
chemical_list: D000935:Antifungal Agents; D001562:Benzimidazoles; D002219:Carbamates; D005954:Glucosephosphate Dehydrogenase; C006698:carbendazim