transgenic plants: ecological impact of gene flow
Approach and methodology
VRTP IMPACT will address the two outstanding questions concerning the potential ecological impact of virus-resistant transgenic plants: will recombination with an infecting virus lead to the creation of novel virus genomes, and will transmission of a virus resistance gene to wild relatives of the modified crop species confer a fitness advantage on the wild plants? These questions will be answered through both laboratory and field studies. In the studies of recombinational plant to virus gene flow, the particular targets will be two groups of important plant viruses, the cucumoviruses and the potyviruses. The plant to plant gene flow studies will focus on two major crop plants that are known to be able to outcross with wild relatives, beet and oilseed rape. Since it is known that gene flow between the crop and wild relatives can occur with these species, the work will focus, not on the incidence of gene flow, but on its outcome. In all cases, potential impact will be assessed relative to studies of these two forms of gene flow in the absence of transgenic plants.
findings and outcome
In the plant to virus gene flow studies, parallel experiments are being carried out with plants expressing sequences from cucumoviral or potyviral genomes. Some, but not all of these plants display some level of resistance to the viral strain from which the transgene was derived. In both systems, baseline information on the occurrence of recombinant viral genomes in doubly-infected non-transgenic plants is being obtained and compared to the occurrence of recombinant viruses in singly-infected transgenic plants. The biological properties, including relative fitness, of the recombinant viruses created will be tested. The comparison of these two data sets will make it possible to determine if the transgenic plants can promote the appearance of recombinant viral genomes that would not occur in non-transgenic plants.
In a complementary approach, a baseline study of the prevalence of recombinant viral genomes in natural cucumoviral and potyviral populations is underway. This will fill a significant gap in current knowledge, and will provide the natural biological context against which previous laboratory studies can be assessed.
In the plant
to plant gene flow studies, the prevalence of the viruses studied in the
wild plant populations will be determined, and the effects of virus infection
on the fitness of the wild species evaluated, in particular whether introgression
of a virus resistance gene from a transgenic crop relative can confer
a fitness advantage on the wild plant species.
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