The Double Reduction Landscape in Tetraploid Potato and its Implications for the Genetic Analysis of Autotetraploids

The creation of genetic linkage maps in polyploid species has been a long-standing problem for which various approaches have been proposed. In the case of autopolyploids, a commonly-used simplification is that random bivalents form during meiosis. This leads to relatively straightforward estimation of recombination frequencies using maximum likelihood from which a genetic map can be derived. However, autopolyploids such as tetraploid potato (Solanum tuberosum L.) may exhibit additional features such as double reduction, not normally encountered in diploid or allopolyploid species. In this study we produced a high-density linkage map of tetraploid potato and used it to identify regions of double reduction in a bi-parental mapping population. The frequency of multivalents required to produce this degree of double reduction was determined through simulation. We also determined the effect that multivalents or preferential pairing between homologous chromosomes have on linkage mapping. Low levels of multivalents or preferential pairing do not adversely affect map construction when highly-informative marker types and phases are used. We reveal the double reduction landscape in tetraploid potato, clearly showing that this phenomenon increases with distance from the centromeres.