ORYZALIN AS AN EFFICIENT AGENT FOR CHROMOSOME DOUBLING OF HAPLOID APPLE SHOOTS IN-VITRO

In an outbreeding species such as apple, haploid plants may be especia lly useful in breeding programmes for the production of homozygous mat erial. However, methods must be available to induce chromosome doublin g in the haploid plants. Two antimitotic agents, colchicine and oryzal in, were compared as regards their efficiency in inducing chromosome d oubling of in vitro haploid apple shoots. Three colchicine levels (0.0 25, 0.25 and 1.25 mM) and three oryzalin levels (5, 15 and 30 mu M) we re evaluated. Three techniques were also used and compared. Survival r ate and chromosome counts were determined. Differences were observed b etween the two antimitotic agents and between the three techniques. Th is study demonstrates that oryzalin could be a better choice than colc hicine for chromosome doubling on haploid apple shoots in vitro.