[escepticos] Transgenicos

[josé march <15709jmf@...>]

Se trata de un documento elaborado por un grupo de expertos de la Royal
Society y titulado  *Genetically Modified Plants for Food Use*. De fecha,
Septiembre de 1998. Os envio el apartado que trata de la posibilidad de
transferencia de genes de plantas transgenicas a especies silvestres (hace
referencia a las posibilidades en el Reino Unido. Otros paises tienen una
situacion diferente).

Saludos.

Jose March


3. Will genes transfer from GM plants?

3.1 Transfer of genes from GM crop plants to wild plant species

Crop systems can be divided into three groups with respect to the possibility
>of natural transfer of genes from genetically modified (GM) crop plants
>to wild relatives:


>No sexually compatible wild relatives in the region where the crop is grown,
>therefore no gene transfer to other species can occur (e.g. GM maize or
>potatoes grown in the UK)


>Gene transfer unlikely due to the nature of the crop species (eg. Rice
>and Soya which are inbreeding species)
>

>Gene transfer likely (e.g. Oilseed rape which is an outbreeding species and
has many wild relatives in the UK)

>The likelihood of gene transfer to wild relatives therefore depends on
>the species of crop and the location in which the crop will be grown. For
>example, relatives of oilseed rape can be found growing near crops in the
>UK, whereas cereal relatives are rare. It may therefore be necessary to
>take special measures with the former.

>However, there are several steps involved in gene transfer: the pollen
>must contain a copy of the inserted gene(s); it must then move away from
>the area in which the crop plant is grown and come into contact with the
>part of a compatible plant that receives pollen; if fertilisation occurs
>successfully, it may not always result in a plant able to grow successfully,
>or if a plant is produced then it may not compete well with other species
>in the environment. In addition, if the resulting plant produces pollen
>that goes on to fertilise other plants, then the inserted gene(s) will
>become increasingly diluted in the overall population if there is no selective
>advantage for the plants that contain it. It is inevitable that some gene
>transfer will occur from certain crops, but the level of gene transfer
>to wild relatives from GM crops is likely to be exactly the same as from
>non-GM crops.

If gene transfer is judged to be likely, then it is important to assess
>what the consequences will be. This will depend on whether the inserted
>genes are likely to have a deleterious or advantageous effect as a result
>of expression in the plant to which they are transferred, if expressed
>in the wild species. The fate of crosses between crop species and wild
>relatives will be largely crop dependent. In general cultivated crop species
>or 'escapees' will not be competitive in the wild. Indeed, most crosses
>between different species will produce sterile hybrids. Hybrids produced
from crosses between most crops and wild relatives are unlikely
>to survive many generations, with the exception of oilseed rape which exists
>as wild populations in the UK. It is also notable that disease and pest
>resistant crops have been available for many years as a result of conventional
>breeding techniques, and we are not aware of any reported problems as a
>result of transfer of such traits.

>Nevertheless, we recommend that the over-arching body referred to above
>should address the question of transfer of genes between crops (whether
>GM or non-GM) and sexually compatible species, in particular genes which
>may be associated with a strong selective pressure in some environments.
>We recognise the difficulties associated with monitoring such transfer,
>but we suggest that methods of doing so be evaluated by the relevant body
>or a working group set up for the purpose. Experiments to monitor such
>transfer could be carried out using molecular markers that are unique to
>a particular species rather than using GM crops, if necessary.