title: Enrichment for enhanced competitive plant root tip colonizers selects for a new class of biocontrol bacteria.
abstract: Our group studies tomato foot and root rot, a plant disease caused by the fungus Forl (Fusarium oxysporum f.sp. radicis-lycopersici ). Several bacteria have been described to be able to control the disease, using different mechanisms. Here we describe a method that enables us to select, after application of a crude rhizobacterial mixture on a sterile seedling, those strains that reach the root tip faster than our best tomato root colonizer tested so far, the Pseudomonas fluorescens biocontrol strain WCS365. Of the five tested new isolates, four appeared to be able to reduce the number of diseased plants. Analysis of one of these strains, P. fluorescens PCL1751, suggests that it controls the disease through the mechanism 'competition for nutrients and niches', a mechanism novel for biocontrol bacteria. Moreover, this is the first report describing a method to enrich for biocontrol strains from a crude mixture of rhizobacteria. Another advantage of the method is that four out of five strains do not produce antifungal metabolites, which is preferential for registration as a commercial product.
authors.affiliation: Institute Biology, Leiden University, Wassenaarseweg 64, 2333 AL Leiden, the Netherlands. kamilova@rulbim.leidenuniv.nl
authors.forename: Faina
authors.initials: F
authors.lastname: Kamilova
authors.forename: Shamil
authors.initials: S
authors.lastname: Validov
authors.forename: Tatiyana
authors.initials: T
authors.lastname: Azarova
authors.forename: Ine
authors.initials: I
authors.lastname: Mulders
authors.forename: Ben
authors.initials: B
authors.lastname: Lugtenberg
mesh_terms: D000383:Agriculture / Q000379:methods; D001483:Base Sequence; D005670:Fusarium / Q000502:physiology*; D007210:Indoleacetic Acids / Q000378:metabolism; D018551:Solanum lycopersicum; D008969:Molecular Sequence Data; D030781:Organisms, Genetically Modified / Q000235:genetics / Q000502:physiology; D010572:Pest Control, Biological / Q000379:methods*; D010935:Plant Diseases / Q000382:microbiology*; D018517:Plant Roots / Q000382:microbiology*; D011551:Pseudomonas fluorescens / Q000235:genetics* / Q000502:physiology*; D017422:Sequence Analysis, DNA
chemical_list: D007210:Indoleacetic Acids