Endophytic Colonization of Plants by the Biocontrol Agent Rhizobium etli G12 in Relation to Meloidogyne incognita Infection

Abstract

The external and internal colonization of potato and Arabidopsis roots by the biocontrol strain Rhizobium etli G12 containing a plasmidborne trp promoter green fluorescent protein transcriptional fusion, pGT-trp, was studied in the presence and absence of the root-knot nematode Meloidogyne incognita. Plant colonization behavior and biocontrol potential of the marked strain G12(pGT-trp) was not altered compared with the parental strain. Plasmid pGT-trp was stable for more than 80 generations without selection and conferred sufficient fluorescence to detect single bacterial cells in planta. Although bacteria were found over the entire rhizoplane, they preferentially colonized root tips, the emerging lateral roots, and galled tissue caused by Meloidogyne infestation. Internal colonization of potato roots was mainly observed in epidermal cells, especially root hairs. G12(pGT-trp) colonization was also observed in inner Arabidopsis root tissues in areas of vascularization. In the presence of M. incognita, G12(pGT-trp) colonized the interior of nematode galls in high numbers. In some cases, bacterial colonization even extended from the galled tissue into adjacent root tissue. The internally colonized sites in roots were often discontinuous. Fluorescence microscopy of gfp-tagged rhizobacteria was a sensitive and a rapid technique to study external and internal colonization of plant roots by bacteria interacting with nematodes.

Effect of formulated bioorganic containing Burkholderia GanoEB2 in suppressing Ganoderma disease in oil palm seedlings

“…Bacterial Burkholderia GanoEB2 inhibited Ganoderma boninense by colonising the intracellular and intercellular tissue of plant and minimised the chances of the pathogens for both nutrient and niches without causing any harm to the host plant (Kloepper et al 1999;Hallmann et al 2001). Significant disease suppression was also reported for wheat plants endophytically colonised with Bacillus subtilis (Liu et al 2009).…”

“…They have been considered for control doi: 10.17221/26/2014-PPS of various diseases in crop plantations including BSR disease in oil palm tree due to their ability to colonise intracellular and intercellular tissue of plants at a certain time of their life cycle and minimise the chance of such pathogens to colonise the area (Kloepper et al 1999;Hallmann et al 2001), morover without causing any harm to the host or gaining benefit other than residency within the plants tissues (Azevedo et al 2000;Kobayashi & Palumbo 2000). Studies by Abdullah et al (1999), Ilias (2000), Sariah et al (2005), and Susanto et al (2005) proved that endophytic fungus, Trichoderma spp., showed high efficacy in controlling the growth of BSR disease in plant house trials and under field condition.…”

Spatial Organization of Dual-Species Bacterial Aggregates on Leaf Surfaces

“…Cultures were stored at Ϫ80°C in 15% (vol/vol) glycerol in 10 mM potassium phosphate buffer, pH 7.0, and were routinely grown on King's medium B. Plasmid DNA was isolated from Escherichia coli DH5␣(pKT-trp) (12) by using a QIAGEN DNA isolation kit (QIAGEN Inc., Valencia, CA) and was transferred into P. syringae B728a (22) and P. fluorescens A506 by electroporation using standard procedures (30). Plasmid pKT-trp consists of a green fluorescent protein marker gene (gfp) driven by the trp promoter from Salmonella enterica serovar Typhimurium (12). P. agglomerans 299R(CFP) carries plasmid pWM1009, which consists of a cyan fluorescent protein marker gene (cfp) fused to a consensus Campylobacter promoter sequence (20), yielding constitutive expression in P. agglomerans.…”

Visualization of an Endophytic Streptomyces Species in Wheat Seed

“…strain EN27, was tagged with green fluorescent protein (GFP) to study early colonization events after it was applied to wheat (Triticum aestivum L.) seeds. Expression of GFP has been used to visualize a number of unicellular bacteria-plant interactions (6,9,10,14,21), but this is the first report on a filamentous actinobacterial endophyte. For actinobacteria, gfp expression has been optimized (4,20) and coupled to a constitutively expressed promoter, ermEp (17).…”