Translocation Heterozygosity in Phlox drummondii

Abstract

In an individual belonging to one of the diploid garden races of Phlox drummondii Hook. (2n=14), in 30% of the cells, four chromosomes instead of forming two bivalents at meiosis form an interchange association. Except for its heterotic behaviour, the translocation heterozygote was phenotypically indistinguishable from the homozygote. The chromosome complex was both of ring and chain type, the former being preponderant. At anaphase I, in the exclusively bivalent forming cells, disjunction of two of the bivalents was consistently late. The asymmetrical nature of the interchange as well as the involvement of the long arm of two non-homologous chromosomes of second and last pair of the complement is apparent from the two heteromorphic pairs in the karyotype. Pollen fertility and seed setting were near normal. The establishment of interchange heterozygosity is correlated with a change of breeding system from out-to inbreeding.