Data from: Varietal variation and chromosome behaviour during meiosis in Solanum tuberosum

Naturally occurring autopolyploid species such as the autotetraploid
potato Solanum tuberosum face a variety of challenges during meiosis.
These include proper pairing, recombination and correct segregation of
multiple homologous chromosomes, which can form complex multivalent
configurations at metaphase I, and in turn alter allelic segregation
ratios through double reduction. Here, we present a reference map of
meiotic stages in diploid and tetraploid S. tuberosum using fluorescence
in situ hybridisation (FISH) to differentiate individual meiotic
chromosomes 1 and 2. A diploid-like behaviour at metaphase I involving
bivalent configurations was predominant in all three tetraploid varieties.
The crossover frequency per bivalent was significantly reduced in the
tetraploids compared with a diploid variety, which likely indicates
meiotic adaptation to the autotetraploid state. Nevertheless, bivalents
were accompanied by a substantial frequency of multivalents, which varied
by variety and by chromosome (7-48%). We identified possible sites of
synaptic partner switching, leading to multivalent formation, and found
potential defects in the polymerisation and/or maintenance of the
synaptonemal complex in tetraploids. These findings demonstrate the rise
of S. tuberosum as a model for autotetraploid meiotic recombination
research and highlight constraints on meiotic chromosome configurations
and chiasma frequencies as an important feature of an evolved
autotetraploid meiosis.