15 septembre 1996
auteur | co-auteur
Les biotechnologies permettent de contourner des difficultés rencontrées dans la sélection des plantes fourragères, souvent autopolyploïdes et allogames. Avec les techniques de culture in vitro, il est possible de modifier leur système de reproduction naturelle : la multiplication à l'identique d'un génotype, les croisements interspécifiques, le changement du niveau de ploïdie permettant de nouvelles combinaisons génétiques. Les techniques de biologie moléculaire apportent de nouvelles possibilités pour la connaissance du génotype : établissement des cartes génétiques, distinction des variétés et identification des marqueurs de caractères agronomiques (QTL). Les techniques de transformation génétique consistent à introduire des gènes étrangers, pour étudier leur fonctionnement et aussi pour améliorer les espèces. Les biotechnologies sont des outils puissants qui complètent les méthodes classiques d'amélioration et d'évaluation des variétés.
Biotechnology nowadays offers new opportunities to overcome biological constraints in breeding forage species, which are mostly autopolyploid and outbreeding. For instance, in vitro culture, by-passing the original mating system of forage plants, makes it possible to clone elite genotypes or to intercross sexually incompatible species. The ploidy level of forage species can be altered, either by doubling the whole chromosome set, or by halving it. Tetraploidization brings about some agricultural advantages in spontaneous diploid plants such as ryegrass or red clover while doubling the chromosome set is also often used for recovering fertile interspecific hybrids and for stabilizing their progenies over generations.
Molecular biology supplies now new tools with which to characterize the plant genotype. The publication of genetic maps of forage species is in progress ; the distinctiveness given to forage cultivars by the use of moleculars markers as passport data should be greatly increased I nthe future. Finally, the identification of molecular markers linked to quantitative traits of agricultural interest (QTLs) appears to be a new prospect in breeding for traits with a low heritability.
New skills in cellular and molecular biology have been applied to plant transformation. The introduction of alien genes into plant genomes is a promising tool for knowing how genes work and for considering new breeding strategies in forage plants as well.
Biotechnology is undoubtedly a powerful tool for investigating and for manipulating the plant genome. However it cannot by itself replace the usual procedures of selection and evaluation of forage varieties, and it preferably requires to be associated with them for more effective progress.
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