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.

Streptomyces lividans inhibits the proliferation of the fungus Verticillium dahliae on seeds and roots of Arabidopsis thaliana

“…As a result, they suppress a range of pathogenic microbes. Hence, their use to biocontrol various diseases, including Vertcillium wilt, has been explored (Humphris et al. , 2005).…”

“…Some studies show that Verticillium wilt is suppressed by selected Pseudomonas strains (Mercado‐Blanco et al. , 2004; Humphris et al. , 2005; Berg et al.…”

Plant growth-promoting bacteria in the rhizo- and endosphere of plants: Their role, colonization, mechanisms involved and prospects for utilization

“…strains are attracted by the root mucilage produced by maize (Mandimba et al, 1986). On the contrary, it has been reported that root mucilage prevents colonization by P. fluorescens strain SBW25 interacting with maize roots (Humphris et al, 2005). Different responses to root mucilage may further explain the spatial and temporal differences of bacterial colonization that are frequently observed along the root system.…”

Colonization of Plant Roots by Pseudomonads and AM Fungi: A Dynamic Phenomenon, Affecting Plant Growth and Health

“…This could possibly be ascribed to the intense mechanical abrasion exerted by the soil in which the root elongates (Bowen and Rovira 1976) to the presence of chemical inhibitors such as activated oxygen species or toxic compounds in root exudates (Katsuwon et al 1993), and to the high turnover of the root cap cells. In fact, as has been demonstrated by Humphris et al (2005), the production of border cells, acting as a disposable surface or sheath around the cap, may prevent root tip colonization by the biocontrol agent P. fluorescens SBW25. Besides, several components of the border cells can act as signals specifically attracting, repelling, or controlling growth and gene expression in soil microorganisms (Hawes et al 1998).…”