How is the cabbage-rare hybrid obtained?

This hybrid was obtained by Georgy Dmitrievich Karpachenko by crossing radish and cabbage. Both species have 18 chromosomes in the diploid set, and their gametes carry 9 chromosomes (haploid set). The hybrid has 18 chromosomes, but it is sterile, since “rare” and “cabbage” chromosomes do not have compatibility when fused with each other during meiosis.
Karpachenko with the help of colchicine doubled the number of chromosomes of the resulting hybrid. As a result, 36 chromosomes were formed in the hybrid organism, which created favorable conditions for meiosis, since each chromosome had a pair for itself. “Cabbage” chromosomes merged with “cabbage”, and “rare” – with “rare”. Each gamete carried one haploid set of radish and cabbage.