Diseases and Management of Crops under Protected Cultivation

(Diseases and Management of Crops under Protected Cultivation)
microbial contaminants;
• The presence of toxins or secondary metabolites (e.g. destruxins).
• Development of genetic markers for risk assessment of BCAs: Analysis of the genetic
structure of a species can reveal information about its population structure and permit risk
analysis. Recently, genetic markers have been developed and are being used to analyze
gene flow between populations. Assessment of genetic variation is done by using
Ribosomal DNA (rDNA), mitochondrial DNA, and RAPDs. Analysis of the distribution of
markers in a fungal bioagent, Chondrostereum purpureum indicated that there were indeed
no barriers to gene flow and that the introduction of rare pathogenicity alleles from isolates
used as biological control agents would occur at a low probability.
• Tools to monitor metabolites and fungal BCAs in the environment: Species-specific
probes:
Trichoderma specific primers based on conserved regions for the species, within the IGS
region of rDNA, which were variable for a range of other soil filamentous fungi has been developed
and used for assaying gene flow. With the development of high throughput assays like ELISA and
Vito ox it becomes easy to determine cytotoxicity and genotoxicity. These assays help in the
detection/quantification of metabolites.
Recommendations for risk assessment of BCAs
• Risk assessment for biological control agents should follow the standard protocol for
ecological risk assessment with appropriate modifications.
• Potential uses of demographic elasticity analysis in risk assessment for proposed weed
biological control agents should be thoroughly explored.
• Following the problem formulation phase of the risk analysis, hazard identification and
effects analysis should be performed. If the proposed agent poses a significant hazard to
non-target species, the assessment should proceed with an exposure analysis. Individualbased
models should be given serious consideration for any exposure analysis that proves
necessary. The data required to estimate the movement parameters of such a model are
relatively easy to collect. Risk assessments should be explicitly linked with cost-benefit
analyses in a unified decision-theory framework.
Fate of BCAs in the environment- Study on fate and behaviour of plant protection products in
the environment poses quite different questions, depending on whether the product is a chemical
or a microorganism. Biocontrol product is based either on a naturally occurring biological molecule
or a living microorganism. There is an unjustified fear that an introduced microorganism will
become a pest after establishment.
In relation to biocontrol agents, till now there is no clear example of an introduced
microorganism, becoming dominant. However since it is not possible to rule out any associated
risk, it is necessary to study the fate and behaviour of bioagent in the environment.
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