Meiotic abnormalities of the fifth pair of chromosomes in Paeonia decomposita and P. intermedia

This study revealed that there were common meiotic abnormalities on the fifth pair of chromosomes in Paeonia decomposita and P. intermedia. Short arms had a tremendous deviation between genetic distance and physical distance, when compared with the long arms. The genetic distance of the short arm was about a twenty-eighth (P. intermedia) and fiftieth (P. decomposita) of the long arm, whereas the physical distance was about one third of the long arm and the physical distance was over nine times longer than the genetic distance. In P. decomposita, the ratio between ring bivalents (both arms formed chiasma) and rod bivalents (only one arm formed chiasma) was 1.94 : 98.06, whereas in P. intermedia the ratio was 3.42 : 96.58. In both of the species, rod bivalents were much more than ring bivalents. Occurrence frequency of anaphase I bridges was low in P. decom-posita and P. intermedia, and the length of fragments varied in a range.