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Introduction to the work of the SWG
Transgenic crops expressing improved resistance or tolerance to abiotic stress are being widely tested in field trials around the world. As in any LMO risk assessment, the characterization of transgenic crops with resistance or tolerance to abiotic stress and their potential risks must be scientifically sound and sufficiently robust to allow risk assessors to make informed decisions that ensure the environmental safety of these crops, taking also into account human health.
Breeding for crops with enhanced resistance to abiotic stresses aims at expanding the cultivable area and/or season beyond those where the non-resistant crop is cultivated.
Examples of risk assessment of transgenic crops with increased tolerance to drought and salinity stress for intentional environmental release are available. One such examples is the risk assessment of wheat lines containing introduced genes that encode proteins that are intended to enable normal plant growth with reduced amounts of water (drought tolerance) either by regulating gene expression or modulating biochemical pathways in the wheat plants (OGTR, 2008). In another example, environmental risk assessment was conducted on transgenic wheat lines in which the production of the amino acid proline was altered to enable plants to grow in the presence of elevated salt levels in the soil (OGTR, 2005).
During the risk assessment of transgenic crops with resistance to abiotic stress specific questions arise in relation to the identification of potential adverse effects of such crops. For instance, resistance to abiotic stresses is likely to confer a selective advantage and the populations expressing these traits may exhibit an enhanced performance (Lu, 2008). Other factors related to the mechanism of resistance and its effects, such as on soil microorganisms (Motavalli et al., 2004), may also become relevant during the risk assessment of crops tolerant to abiotic stress.
Special consideration may also be needed with regard to the methodology used during the risk assessment. For instance, phenotypic responses of GM crops with resistance to abiotic stress may be more difficult to predict than those of GM crops that are currently being commercialized. For example, tolerance to drought is likely to be sensitive to the presence and level of water stress thus making stress a challenge to quantify across a wide geographic region (Nickson, 2008).
The aim of the guidance document being developed by the AHTEG Sub-working Group is to highlight questions and points to consider that should be taken into account while assessing the risks of crops with resistance to abiotic stress. Such points to consider may be of particular importance during the phenotypic characterization in the receiving environment, hazard identification and problem formulation steps of the risk assessment process. Taking into account the availability of scientific information, drought and salinity tolerance could be the starting point for these discussions.
(Cited references are available in the
Suggested readings)
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Draft outline of the guidance document
Draft outline of the guidance document on RA&RM of LM Crops Resistant or Tolerant to Abiotic Stress
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Guiding questions
The following questions were prepared to assist the discussions on this topic.
- Which points should be considered when characterizing an LMO with increased resistance to an abiotic stress (e.g. salinity or drought), particularly in relation to the phenotypic characterization in the receiving environment?
- Which questions should be asked during the problem formulation step of the risk assessment of a living modified crop with resistance to an abiotic stress (e.g. salinity or drought)?
- Based on the current state of knowledge, which potential hazards deserve particular attention when performing a risk assessment of a living modified crop resistant or tolerant to an abiotic stress?
- Are there other points to consider during the risk assessment process of a living modified crop with resistance to an abiotic stress that differ from those of crops which introduced traits do not change their response to abiotic stresses?
- Which risk management measures may be of particular relevance to living modified crops resistant to an abiotic stress (e.g. salinity or drought)?
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Suggested readings
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