title: Root cap influences root colonisation by Pseudomonas fluorescens SBW25 on maize.
abstract: We investigated the influence of root border cells on the colonisation of seedling Zea mays roots by Pseudomonas fluorescens SBW25 in sandy loam soil packed at two dry bulk densities. Numbers of colony forming units (CFU) were counted on sequential sections of root for intact and decapped inoculated roots grown in loose (1.0 mg m(-3)) and compacted (1.3 mg m(-3)) soil. After two days of root growth, the numbers of P. fluorescens (CFU cm(-1)) were highest on the section of root just below the seed with progressively fewer bacteria near the tip, irrespective of density. The decapped roots had significantly more colonies of P. fluorescens at the tip compared with the intact roots: approximately 100-fold more in the loose and 30-fold more in the compact soil. In addition, confocal images of the root tips grown in agar showed that P. fluorescens could only be detected on the tips of the decapped roots. These results indicated that border cells, and their associated mucilage, prevented complete colonization of the root tip by the biocontrol agent P. fluorescens, possibly by acting as a disposable surface or sheath around the cap.
authors.affiliation: Scottish Crop Research Institute, Invergowrie, Dundee, UK. shumph@scri.sari.ac.uk
authors.forename: Sonia N
authors.initials: SN
authors.lastname: Humphris
authors.forename: A Glyn
authors.initials: AG
authors.lastname: Bengough
authors.forename: Bryan S
authors.initials: BS
authors.lastname: Griffiths
authors.forename: Ken
authors.initials: K
authors.lastname: Kilham
authors.forename: Sheena
authors.initials: S
authors.lastname: Rodger
authors.forename: Vicky
authors.initials: V
authors.lastname: Stubbs
authors.forename: Tracy A
authors.initials: TA
authors.lastname: Valentine
authors.forename: Iain M
authors.initials: IM
authors.lastname: Young
mesh_terms: D015169:Colony Count, Microbial; D010572:Pest Control, Biological; D018518:Plant Root Cap / Q000502:physiology*; D018517:Plant Roots / Q000166:cytology / Q000254:growth & development / Q000382:microbiology*; D011551:Pseudomonas fluorescens / Q000254:growth & development*; D012639:Seeds / Q000382:microbiology; D003313:Zea mays / Q000382:microbiology*