RELATIONSHIP BETWEEN CELL PLOIDY AND REGENERATION CAPACITY OF LONG-TERM ROSA-HYBRIDA CULTURES

The present study was undertaken to characterize the ploidy level of our Rosa hybrida embryogenic cell lines with relation to their regeneration potential. Rose embryogenic calli have been established from leaf explants and are still able to give rise to plants after more than two years in culture. Embryogenic cell suspensions were initiated from these calli but could not be directly converted into embryos and plants. Flow cytometry of isolated nuclei was used to determine ploidy levels of both suspensions and calli. In calli, the majority of cells were tetraploid as were the explants from which they had originated. On the contrary in suspensions, aneuploid and polyploid cells were frequent. The relationship between ploidy and regeneration capacity is discussed.