Diseases and Management of Crops under Protected Cultivation

Risks of biocontrol agents:
(Diseases and Management of Crops under Protected Cultivation)
Effects inherent to the pathogen Effects due to other factors
Direct effects Pathogenicity Undesirable microbial
Toxicity/mutagenicity
contaminants during the
Irritation
production
Allergenicity Carriers, additives and
adjuvants
Indirect effects
Competitive displacement of other
organisms
Genetic instability of the fungal
biocontrol agent
Other factors limiting successful biocontrol are persistence and survival of bioagents ,
susceptibility to environmental changes and pathogens self defense. Since microorganisms are
capable to grow and multiply in many environmental conditions, clearance of microorganism has to
be studied, making the studies more difficult and costly.
Toxicity studies for the microorganism / metabolite: the toxicity tests to be conducted should
take into account the main route of exposure. There are following toxicity parameters required for
release and registration of biocontrol agents.
‣ Acute oral toxicity- acute oral toxicity refers to those adverse effects occurring following
oral administration of a single dose of a substance, or multiple doses given within 24 hours.
‣ Acute inhalation toxicity-Acute inhalation toxicity is the adverse effect caused by a
substance following a single uninterrupted exposure by inhalation over a short period of
time (24 hours or less) to a substance capable of being inhaled.
‣ Genotoxicity- Genotoxicity describes a deleterious action on a cell's genetic material
affecting its integrity. Genotoxic substances are known to be potentially mutagenic or
carcinogenic, specifically those capable of causing genetic mutation and of contributing to
the development of tumors. Similar to sensitization, genotoxicity testing poses
methodological problems.
Considering that inhalation is the most appropriate route of contamination, intratracheal
acute toxicity seems appropriate. But to test toxicity, animal (mammal) testing is costly, required
suitable facilities and equipment and specialized personnel and has ethical issues. Now
researchers have focused on the development of alternative methods for toxicity assessment.
Quantitative structure-activity relationships (QSARs), Lower organisms (bacteria, fungi, plants),
Invertebrate animals, Vertebrates at early stage of development, In vitro systems (cell and tissue
cultures) are some newly developed methods. Recently, invertebrates like Artemia salina and
Daphnia magna were used for toxicity and allergenicity analysis. Artemia salina is a sea water
organism, used for eco-toxicity testing (acute toxicity) for estuarine/marine environments and
Daphnia magna is a freshwater organism, used for eco-toxicity testing (Acute and chronic, sublethal,
toxicity) for terrestrial and freshwater environments, Accepted by international standard
organizations (ISO, OECD, and ASTM). Both of them were accepted by EU (67/548/EEC,
91/271/CEE, 91/676/CEE) and EPA for eco-toxicological assessment.
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