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No significant effects of the plant-growth promoting rhizobacteria were found on the insect herbivores investigated, and no significant negative effects were found on beneficial insect species, either.
Project Summary
Overview
The objective of this project was to see if both insects and pathogens of canola could be reduced with an application of one of the biological control agents. This is to optimize canola production without the use of chemicals, thus improving the plant health while protecting the environment.
The project investigated the nature of biological control of one of the most important canola pathogens, the blackleg pathogen by using naturally occurring microorganisms. The study found several bacterial agents (mostly Pseudomonas and Bacillus spp.) to be excellent biological control agents against blackleg at the seedling and adult plant stage in the field (Biocontrol. Sci. and Tech. 2006: 16:567-682). Bacteria isolated from within the plant (inside) known as endophytes were the best biological control agents.
Several of these biocontrol agents produced antibiotics such as Phenazine, Pyrollnitrin, and Zwittermycin. The identification consisted of a PCR-based marker technique to precisely identify the secondary metabolites produced by each bacterium against the Blackleg pathogen control. The researchers were then able to for the first time identify Bacillus spp. that were able to produce novel secondary metabolites (antibiotics) that are known to be antagonistic to plant pathogens, using PCR and GC/MS MALDI-TOF analysis (Canadian Journal of Microbiology 2007: 53:901-907).
Conclusions
Plant-growth promoting rhizobacteria (PGPR) are potentially important biocontrol agents because they can protect plants from pathogens through the production of various bacterial metabolites and the activation of induced systemic resistance. The use of PGPR in the control of pathogens is highly desirable because there is a decreased risk of pests developing resistance to bacterial-induced plant defences than chemical measures such as fungicides. Since the effects of these bacterial species on naturally occurring bacterial communities can be difficult to predict, research has shown that negative effects can be less, comparable to the effects of chemical fungicides.
Although no significant effects of the PGPR were found on the insect herbivores investigated, no significant negative effects were found on beneficial insect species, either. This provides additional safety information for the use of PGPR and may be important if products are registered for use in agriculture in the future, especially as these PGPR (biocontrol) agents have continuously proven to be excellent biocontrol agents agents Sclerotinia and blackleg disease pathogens of canola/rapeseed.
