Studies on the control of diploid-like meiosis in polyploid taxa of Chrysanthemum : 4. Colchiploids and the process of cytogenetical diploidization.

Chromosome pairing during meiosis was studied in colchiploids of Ch. japonense 6X and Ch. boreale 2X. In both species chromosomes paired predominantly as bivalents, even though because of complete homology they possess the ability to pair as multivalents. Multivalent formation is prevented by restriction of pairing initiation to a single site (=zygomere) per chromosome. Multivalent suppressor systems in polyploids may evolve through gradual reduction in number of zygomeres, and differentiation in their homology recognition and regulation system.