Background and objectives

Before transgenic plants can be released into the field, approval must be obtained from regulatory authorities established to control and monitor the dissemination of genetically modified organisms (GMOs). This approval process includes an assessment of the ecological and genetic risks which may be posed by the transgenic plant. In order to standardise this assessment, there is a need for quantitative and reproducible methods to test the performance of transgenic plants in relation to their non-transgenic varieties.

This project aimed to establish a method for the quantitative risk assessment of transgenic plants before their release into the field. The second aim of the project was to test the stability of expression of a marker gene that is commonly used in transgenic plant technology to identify the presence of specific GMOs which have been re-introduced into the environment.


Approach and methodology

We investigated three separate stages in the life cycle of a transgenic plant: establishment, competition and reproduction. These stages are representative of the overall life cycle of the plants under conditions relevant to risk assessment of GMOs. To test the establishment ability of the plants, we measured the persistence of transgenic plants after exposure to different light conditions. We applied a non-linear model to describe the competitive ability of the tested plant material both in mono-cultures and in two-species combinations. The reproductive ability of the plants was quantified by counting the seed production of the test plants. We also measured the expression of the GUS-marker gene in transgenic tobacco exposed to different environmental stress conditions, i.e. low temperature and shading.
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Main findings and outcome

We detected no significant change in competitive ability during the growth season in the single species or in the two-species plant mixtures. The reproductive ability of the tested plants was closely related to the biomass production and thus to their competitive ability. The methods to test establishment ability under low light conditions gave no conclusive results. The expression of the GUS marker system (35S;GUS) was found to be affected by the environmental stress factors chilling and shading. When the environmental stress factors were removed, the normal expression pattern was re-established in the new leaves, but not in the old leaves.

These experiments allowed us to quantify the competitive ability of GM tobacco plants relative to their non-GM counterparts. This result was further examined in a follow up study “Safety assessment of the deliberate release of two model transgenic crop plants, oilseed rape and sugar beet” (BIOT-CT91-0298) to include different transgenic varieties. We noted signs of temporal changes in competitiveness, an issue that was also further addressed in the follow-up study project.
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Conclusions

The project developed a useful method to test competitive ability and seed production of transgenic plants under both greenhouse and controlled field conditions. Use of the GUS marker gene to identify transgenic plants in selection protocols and test procedures is complicated by the influence of growth conditions on expression levels and patterns.