Working Group meeting on "Interspecific gene flow from oilseed rape to weedy species"
Date and Location
Rennes, France, 11-13 June 2001
Report
This workshop funded by ESF was the opportunity to have large discussions between more than 30 scientists from different countries (Austria, Canada, Czech Republic, Denmark, France, Germany, Spain, Switzerland, United Kingdom and US) working on gene flow from oilseed rape to related weeds.
The question of gene flow from a crop to its wild relatives is particularly relevant for oilseed rape (Brassica napus L., AACC, 2n=38) because this species is partially allogamous and presents numerous wild relatives growing nearby in the cultivated areas. Different steps have to be examined : (1) existence of close relatives growing in sympatry with the crop, and the similarity between the crop/wild phenologies, that is necessary to ensure overlapping flowering periods, (2) the production of F1 interspecific hybrids and their survival, (3) transmission of (trans)genes from the crop through the different generations of hybridization, (4) gene introgression through recombination between the crop and wild genomes or stabilization of a new weed, (5) maintenance within the natural populations of the introgressed genes. First studies have been developed from herbicide tolerant varieties.
After a short presentation of the research activities developed on the INRA Rennes Research Center, two speakers gave the state of art concerning GMO commercialization and the related questions of regulators over Canada and Europe.
The first aspect discussed was the presentation of the main weeds and their demography over the different countries. Seven subtribes within the Brassiceae tribe were distinguished and among them 15 species can be considered as main weeds of oilseed rape. After a presentation of their demography, we tried to establish a list of the main ones according to their relative abundance into oilseed rape cultivated areas. We concluded that it is of interest to focus on 7 species.
For the assessment of interspecific hybridization, different tools of characterization were proposed either morphological markers, or molecular markers (chloroplastic markers and nuclear markers, AFLP and retrotransposons) or cytogenetical studies. The interests and limits of each of them for research and monitoring studies were discussed.
The last results concerning gene flow from oilseed rape to field mustard (B.rapa, AA, 2n=20), to wild mustard (Sinapis arvensis, SarSar, 2n=18), to hoary mustard (Hirschfeldia incana, AdAd, 2n=14) and wild radish (Raphanus raphanistrum, RrRr, 2n=18) were presented. The different weeds were classified according to the risk of production of interspecific hybrids, of fertile successive generations and of gene introgression into the genome of the weeds. First screenings among spontaneous populations growing in different agricultural conditions were described. The use of molecular markers to study such gene flow was discussed.
The studies of fitness of different generations of hybrids between B.napus and B. rapa or R. raphanistrum revealed that the ability of such plants to produce the following generations depends on the competitive situations but also on their genomic and cytoplasmic structures.
Two aspects of gene expression were presented. First, a study in progress in the Danish group on gene silencing and, secondly an experiment in progress in the American group using a construct of GFP+Bt genes to follow directly the gene flow on plants.
From experimental data, models were developed on oilseed rape pollen and seed dispersals. Further studies are needed to establish model on interspecific gene flow.
As a conclusion the group proposed different research perspectives on transgene expression, analysis of genetic mechanisms of introgression, impact of agronomic practices and monitoring. A publication summarizing the different aspects discussed could be submitted next autumn. Additionally, the group has proposed to establish a European network.
Workshop organisers
- Anne-MarieChèvreE-Mail
- Institut National de la Recherche Agronomique INRAStation d'Amélioration des PlantesLe RheuFrance
