Abstract

The VRTP IMPACT project 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 the transmission of a virus resistance gene to wild relatives of 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 particularly 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. In all cases, potential impact will be assessed relative to baseline studies concerning these two forms of gene flow in the absence of transgenic plants.

Objectives

Virus resistance was among the very first agronomically useful traits to be introduced into transgenic plants, and several virus-resistant transgenic cultivars have already been commercially released in the US and China. In order to provide the necessary science-based risk assessment of such plants before contemplating commercial release in Europe, it is essential to clarify several points concerning potential ecological impact. The most important potential impacts could result from two forms of gene flow, either from plant to virus by recombination, or from plant to plant by sexual outcrossing. VRTP IMPACT will study recombinational plant to virus gene flow in two extremely important groups of plant viruses, the cucumoviruses and potyviruses, and will study plant to plant gene flow in two major crops that have sexually compatible wild relatives in Europe, beet and oilseed rape. At the end of this three year project, it is expected that the results will clarify whether the currently developed types of virus-resistant cultivars can be released with acceptable risk from either of these two forms of gene flow in the absence of transgenic plants.

Description of the work

The participants have already at their disposal a considerable number of the tools and biological materials required for this programme, including numerous transgenic plant lines expressing sequences derived from viral genomes of several virus groups. In the plant to virus gene flow studies, parallel experiments will be carried out with plants expressing sequences from several different regions of 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 the cucumoviral and potyviral systems, baseline information on the occurrence of recombinant viral genomes in doubly-infected non-transgenic plants will be obtained. This will be 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 will be carried out. This will fill a significant gap in current knowledge, and will provide the natural biological context against which the previous laboratory studies will be compared. The plant to plant gene flow studies will be carried out with two crop plants, beet and oilseed rape, for which it is known that gene flow between the crop and wild relatives can occur, and will thus focus, not on the incidence of gene flow, but on the outcome of its occurrence. Here detailed studies will focus on determining the prevalence of the viruses studied in the wild plant populations, on evaluating the effects of virus infection on the fitness of the wild species, and on determining whether introgression of a virus resistance gene from a transgenic crop relative can c onfer a fitness advantage on the wild plant species.

Deliverables

The comparison of transgenic and non-transgenic plants will show if recombination in the former could lead to the appearance of novel recombinant viral genomes not occurring in the latter. The field epidemiology study of naturally-occurring recombinants in the same viral groups will tell whether the recombinants occurring under laboratory conditions correspond to those observed in the field. The gene flow studies in beet and oilseed rape and their wild relatives will allow prediction of whether introgression of a virus resistance gene into the latter will affect their fitness.

Contacts

Coordinator

• INRA-Versailles Laboratoire de Biologie Cellulaire / FRANCE

Participant

• Detlef BARTSCH / Aachen University of Technology RWTH Dept of Biology V / GERMANY
• Fernando GARCIA-ARENAL / ETSI Agronomos Ciudad Universitaria / SPAIN
• Mireille JACQUEMOND / INRA - Domaine St. Maurice Station de Pathologie Végétale / FRANCE
• René DELON / Institut du Tabac FRANCE
• Ervin BALAZS / Institute for Plant Sciences Agricultural Biotechnology Centre / HUNGARY
• Peter PALUKAITIS / SCRI UNITED KINGDOM
• University Hannover Inst. of Plant Diseases and Plant Protection / GERMANY
• Alan RAYBOULD / Winfrith Technology Centre Centre for Ecology and Hydrology / UNITED KINGDOM