The natural diversity of forage grasses: a genetic resource that needs to be better understood, preserved and utilised, from the local to the continental level

Forage grasses have been the subject of breeding programmes for several decades, with the aim of providing seed of high agronomic value for the establishment of temporary grassland. The diversity of these species found in natural grasslands has provided the genetic material that enabled the first breeding programmes to be launched and subsequently allowed the breeding pools to be regularly enriched. To this end, surveys to collect natural diversity have been carried out across vast areas. We demonstrate that the natural diversity of forage grasses remains an important genetic resource, particularly with a view to addressing new agri-environmental challenges. The spatial distribution of this diversity is outlined at three geographical scales (local, regional and continental), and the methods used to collect it are discussed. The importance of in situ conservation of this natural diversity is emphasised. It is shown that collections held by genetic resource centres can provide a basis for developing models to assess the potential risks to the in situ conservation of natural diversity. These various points are explored on the basis of two studies of the diversity of English ryegrass, one at the local scale and the other combining the regional and continental scales.