title: The suppressive effect of a commercial extract fromDurvillaea potatorumandAscophyllum nodosumon infection of broccoli byPlasmodiophora brassicae.
abstract: A sand solution technique demonstrated the capacity for a commercial seaweed extract fromDurvillaea potatorumandAscophyllum nodosum(Seasol Commercial®) to significantly suppress infection of broccoli byPlasmodiophora brassicae. In the primary stages of infection, the extract reduced the number of plasmodia formed in the root hairs by 55 %. Later, in the secondary stages of infection, the extract reduced plasmodia in the root cortical cells by up to 84 %. The suppression of infection was found to be independent of the dilution of the extract applied (1:25 and 1:500). The basis for these results is unlikely to be a nutrient or pH effect since the extract had little impact on these parameters, particularly at the lower dilution (1:200). Rather, we hypothesise that the suppression of infection by the seaweed extract was due to its stimulation of resistance mechanisms in the host, which is possibly related to laminarins in the extract and/or the effect of exogenous growth regulators or undiscovered molecules in the extract disrupting the infection process.
authors.affiliation: Department of Environment and Primary Industries, Knoxfield, Victoria Australia.
authors.forename: D
authors.initials: D
authors.lastname: Wite
authors.affiliation: Department of Environment and Primary Industries, Knoxfield, Victoria Australia ; Victorian Strawberry Industry Certification Authority, Toolangi, Victoria Australia ; School of Botany, La Trobe University, Bundoora, Victoria Australia.
authors.forename: S W
authors.initials: SW
authors.lastname: Mattner
authors.affiliation: Department of Environment and Primary Industries, Knoxfield, Victoria Australia ; School of Botany, La Trobe University, Bundoora, Victoria Australia.
authors.forename: I J
authors.initials: IJ
authors.lastname: Porter
authors.affiliation: Seasol International, Bayswater, Victoria Australia.
authors.forename: T
authors.initials: T
authors.lastname: Arioli
keywords: Clubroot; Kelp extract; Seasol®; Seaweed extract