In vitro induction of tetraploids in ornamental <Emphasis Type="Italic">Ranunculus</Emphasis>

This study investigates the capacity of the antimitotic agents colchicine, oryzalin and trifluralin for inducing polyploidisation of Ranunculus asiaticus ‘Alfa’ in vitro shoots. Flow cytometry was used to evaluate the optimal concentration of each antimitotic agent for polyploidisation. Trifluralin at a concentration of 2 μM resulted in the highest percentage of polyploidisation (27.5%), followed by a colchicine treatment of 200 μM, which induced 23.3% of polyploids. For oryzalin the highest percentage was achieved using a concentration of 1 μM. Different exposure periods were tested and turned out to be an important factor. The maximal exposure period tested (10 weeks) resulted in a significant increase in polyploidisation by oryzalin and trifluralin. In contrast, for colchicine (100 μM) exposure times of either 16 or 24 h did not significantly influence polyploidisation. Additionally the effect of the antimitotic agents on the viability was analysed. For colchicine no significant effect on the survival rate was observed, for trifluralin only a concentration of 10 μM affected viability whereas for oryzalin, concentration as well as exposure period were significant parameters. Flow cytometric data were confirmed by counting chromosomes in root tip cells.