changes in establishment ability and competitiveness of genetically modified
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.
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.
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.
Fredshavn J.R., Competition in monocultures of oilseed rape
and barley. Acta Agric. Scand., Sect. B.
Soil and Plant Sci., 43, 1993, pp. 38-44.
Fredshavn J.R., The use of substitution rates to describe
competition in mixed plant populations. Acta Agric. Scand., Sect.
Soil and Plant Sci., 44,
1994, pp. 47-54.
Fredshavn J.R., Poulsen G.S., Huybrechts I. & Rüdelsheim
P., Competitiveness of transgenic oilseed rape.
Transgenic Research, 4,
1995, pp. 142-148.
Fredshavn J.R., Poulsen G.S., Growth behavior and competitive
ability of transgenic crops.
Field Crops Research, 45,
1996, pp. 11-18.
Fredshavn J.R. & Poulsen G.S., Competitiveness of transgenic
plants, Proc. of the "Le Louverain" symposium Gene
Transfer: Are Wild Species in Danger, FOEFL, Bern, 1994, pp.
January 1989 December 1990
The Royal Veterinary and Agricultural University
The National Forest and Nature Agency
Ministry of Food Agric. & Fisheries