The induction of hexaploidy in cherry rootstocks using in vitro regeneration techniques.

An in vitro regeneration technique using root callus has been combined with colchicine application to produce hexaploid plants from the sterile triploid cherry rootstock Colt. Colchicine (50 mg/l) was applied together with auxin (IBA) (3 mg/l) either before or after root primordium formation in single excised micropropagating shoots. In both cases shoots were regenerated in vitro from the putative hexaploid roots. Both methods produced hexaploid plants but more than 70% of the regenerated clones were still triploid. The hexaploid plants were distinguishable from the triploids on morphological as well as cytogenetic grounds. Quantitative characters such as leaf length/breadth ratio, stomatal length and density in the hexaploids were significantly different from both regenerated and non-regenerated triploids.