Cytogenetical studies onBougainvillea. I. a case of interchange heterozygosity

A case of interchange heterozygosity has been found inB. peruviana cv “Princess Margaret Rose” in which there is a regular formation of 15 bivalents and an interchange multiple of 4 chromosomes. The multiple is always associated with the nucleolus at diakinesis, indicating that one of the chromosome involved is nucleolar. The nucleolar pair of chromosomes shows a slight heteromorphicity which may be due to an unequal interchange. Although 80% of interchange multiples orientate non-disjunctionally, yet 65% pollen is stainable. The pollen is ineffective in self pollination, but highly effective in crosses with 2x and 3x cultivars ofB. spectabilis. The higher pollen stainability indicates that the deficiencies and duplications caused by non-disjunction do not have serious physiological offects on pollen grains and that its genome can withstand rearrangements.