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- Title
Risk assessment for engineered bacteria used in biocontrol of fungal disease in agricultural crops.
- Authors
Timms-Wilson, Tracey M.; Kilshaw, Kerry; Bailey, Mark J.
- Abstract
A plant growth promoting rhizobacterium (PGPR)Pseudomonas fluorescensSBW25 (WT) protects a number of crop plant species from damping-off caused byPythium ultimum. A genetically modified, phenazine-1-carboxylic acid (PCA) producing variant, 23.10, carries on its chromosome a single copy ofphzABCDEFG, under the control of the Ptacconstitutive promoter. The genetically modified biological control agent (GM-BCA), 23.10, has improved biocontrol activity when compared to wild type SBW25, and can effectively suppressPythiumspp. present at up to 100 times normal field infestations. GM-BCA inocula establish high population densities which persist well in the phytosphere of several crop plants including pea, wheat and sugar beet, effectively suppressed infection and promoted increase in total plant biomass. It also has an improved spectrum of activity over other plant phytopathogens such asFusariumspp.Gaeumannomyces graminisvar.tritici, Phytophtora cinnamomiandRhizoctonia solani. However in developing BCAs and in particular GMBCAs it is important to determine whether their use has any adverse effect in the environment. Any observed changes following inoculation with wild type BCA or GM BCA in microbial diversity (bacteria and fungi) were negligible when assessed by either quantitive selective plate count methods (CFU/g) or culture independent molecular assays (SSU rRNA based PCR-DGGE). Rhizosphere community diversity profiles (DGGE) in infected plants in the presence of inocula were highly similar to disease free systems. Histological assessment of the impact of inocula on established functional mycorrhizae associations were conducted on cores collected from an established field margin grassland pasture. No adverse impact on mycorrhizal colonization and root infection were recorded after addition of WT or GM-BCA bacterial inocula as a soil drench. This approach and the related culturable and culture independent methods have recorded only a minor, transient perturbation to microbial communities, but as far as we are aware this is the first direct demonstration that a functional, AFC producing GMM also has only a transient impact on mycorrhizal associations in established plant communities. In all instances studied the plant species, plant stage of development and disease, damping-off, had a greater impact on changes in rhizosphere diversity than the presence of an introduced GM bacterial inocula.
- Subjects
BIOLOGICAL pest control; FUNGAL diseases of plants; CROPS; PLANT growth; PSEUDOMONAS fluorescens; PLANT species; PYTHIUM ultimum
- Publication
Plant & Soil, 2004, Vol 266, Issue 1/2, p57
- ISSN
0032-079X
- Publication type
Article
- DOI
10.1007/s11104-005-2567-y