title: Potential for Biocontrol of Hairy Root Disease by aPaenibacillusClade.
abstract: RhizogenicAgrobacteriumbiovar 1 is the causative agent of hairy root disease (HRD) in the hydroponic cultivation of tomato and cucumber causing significant losses in marketable yield. In order to prevent and control the disease chemical disinfectants such as hydrogen peroxide or hypochlorite are generally applied to sanitize the hydroponic system and/or hydroponic solution. However, effective control of HRD sometimes requires high disinfectant doses that may have phytotoxic effects. Moreover, several of these chemicals may be converted to unwanted by-products with human health hazards. Here we explored the potential of beneficial bacteria as a sustainable means to control HRD. A large collection of diverse bacterial genera was screened for antagonistic activity against rhizogenicAgrobacteriumbiovar 1 using the agar overlay assay. Out of more than 150 strains tested, only closely relatedPaenibacillusstrains belonging to a particular clade showed antagonistic activity, representing the speciesP. illinoisensis, P. pabuli, P. taichungensis, P. tundrae, P. tylopili, P. xylanexedens, andP. xylanilyticus. Assessment of the spectrum of activity revealed that some strains were able to inhibit the growth of all 35 rhizogenic agrobacteria strains tested, while others were only active against part of the collection, suggesting a different mode of action. Preliminary characterization of the compounds involved in the antagonistic activity of two closely relatedPaenibacillusstrains, tentatively identified asP. xylanexedens, revealed that they are water-soluble and have low molecular weight. Application of a combination of these strains in greenhouse conditions resulted in a significant reduction of HRD, indicating the great potential of these strains to control HRD.
authors.affiliation: Laboratory for Process Microbial Ecology and Bioinspirational Management, Department of Microbial and Molecular Systems, KU Leuven Sint-Katelijne-Waver, Belgium.
authors.forename: Lien
authors.initials: L
authors.lastname: Bosmans
authors.affiliation: Department of Microbial Ecology, Netherlands Institute of Ecology (KNAW) Wageningen, Netherlands.
authors.forename: Irene
authors.initials: I
authors.lastname: De Bruijn
authors.affiliation: Department of Microbial Ecology, Netherlands Institute of Ecology (KNAW) Wageningen, Netherlands.
authors.forename: Saskia
authors.initials: S
authors.lastname: Gerards
authors.affiliation: Research Centre Hoogstraten vzw Meerle, Belgium.
authors.forename: Rob
authors.initials: R
authors.lastname: Moerkens
authors.affiliation: Research Centre Hoogstraten vzw Meerle, Belgium.
authors.forename: Lore
authors.initials: L
authors.lastname: Van Looveren
authors.affiliation: Research Station for Vegetable Production vzw Sint-Katelijne-Waver, Belgium.
authors.forename: Lieve
authors.initials: L
authors.lastname: Wittemans
authors.affiliation: Research Station for Vegetable Production vzw Sint-Katelijne-Waver, Belgium.
authors.forename: Bart
authors.initials: B
authors.lastname: Van Calenberge
authors.affiliation: Scientia Terrae vzw Sint-Katelijne-Waver, Belgium.
authors.forename: Anneleen
authors.initials: A
authors.lastname: Paeleman
authors.affiliation: Scientia Terrae vzw Sint-Katelijne-Waver, Belgium.
authors.forename: Stefan
authors.initials: S
authors.lastname: Van Kerckhove
authors.affiliation: Department of Microbial and Molecular Systems, Centre of Microbial and Plant Genetics, KU Leuven Leuven, Belgium.
authors.forename: René
authors.initials: R
authors.lastname: De Mot
authors.affiliation: Rega Institute, KU Leuven Leuven, Belgium.
authors.forename: Jef
authors.initials: J
authors.lastname: Rozenski
authors.affiliation: Laboratory for Process Microbial Ecology and Bioinspirational Management, Department of Microbial and Molecular Systems, KU Leuven Sint-Katelijne-Waver, Belgium.
authors.forename: Hans
authors.initials: H
authors.lastname: Rediers
authors.affiliation: Department of Microbial Ecology, Netherlands Institute of Ecology (KNAW) Wageningen, Netherlands.
authors.forename: Jos M
authors.initials: JM
authors.lastname: Raaijmakers
authors.affiliation: Laboratory for Process Microbial Ecology and Bioinspirational Management, Department of Microbial and Molecular Systems, KU Leuven Sint-Katelijne-Waver, Belgium.
authors.forename: Bart
authors.initials: B
authors.lastname: Lievens
keywords: Agrobacterium; Paenibacillus; antagonistic activity; biological control; high-throughput screening