ANEUPLOIDY, A SOURCE OF GENETIC DIVERSITY FOR FRUIT SPECIES

Aneuploidy is reported among several plant species. Issued from open-pollinated polyploid plants and from targeted breeding, most genotypes can be saved after embryo culture that prevents plant failure due to abortion and growth abnormalities respectively. Aneuploid apple material revealed genetically stable through in vitro axillary branching and crossable after ex vitro grafting. However, certain genetic variability occurred after adventitious budding, spontaneously inducing polyploidisation and cytochimerism. Some cytochimerical clones probably sectorial chimeras, reversed to genetically uniform aneuploids after subcultures by axillary branching. Multiapexing and adventitious budding applied to these chimeras led to the regeneration of new genotypes characterized by stable and uniform ploidy or aneuploidy and mixoploidy as well. Different ploidy patterns of regenerants resulted from the hormonal balance of the shoot induction medium. The combination of the aneuploidy with the techniques of in vitro regeneration led to create new genotypes with a limited genetic variability. These are currently used for genetic analysis and the production of seedless fruit. It appears obvious that with the use of specific molecular markers, this way of genetic improvement could support the progression of innovative breeding programs.