Meiosis in autopolyploid Crepis capillaris. III. Comparison of triploids and tetraploids; evidence for non independence of autonomous pairing sites

Abstract

A comparison of meiotic pairing patterns in autopolyploids of Crepis capillaris reveals that the chromosomes of autotriploids form 60 per cent more pairing partner switches (PPSs) than autotetraploids. This difference is highly significant and affects all three chromosomes of Crepis capillaris to about the same extent. However, from theoretical considerations, the chromosomes of autotriploids and autotetraploids are expected to form equal numbers of PPSs provided that they have the same numbers of autonomous pairing sites (APSs) which are acting independently or showing the same degree of dependence and there are no pairing preference differences. Differences in numbers of APSs or in pairing preferences are thought to be unlikely and therefore it is considered that the difference in PPS frequencies reflects some form of interference between APSs affecting the choice of pairing partners but to different degrees in triploids and tetraploids. Such interdependence is fully consistent with the original concept of APSs as ‘regions with the capacity to initiate pairing partner exchange in an autopolyploid, regardless of the likelihood of such exchange’.