Abstract
Polyploidy plays a pivotal role in plant evolution. However, polyploids with polysomic inheritance have hitherto been severely underrepresented in plant population genetic studies, mainly due to a lack of appropriate molecular genetic markers. Here we report the establishment and experimental validation of six fully informative microsatellite markers in tetraploid gynodioecious Thymus praecox agg. Sequence data of 150 microsatellite alleles and their flanking regions revealed high variation, which may be characteristic for polyploids with a reticulate evolutionary history. Understanding the patterns of mutation (indels and substitutions) in microsatellite flanking-sequences was a prerequisite for the development of co-dominant markers for fragment analyses. Allelic segregation patterns among progeny arrays from ten test crosses revealed tetrasomic inheritance in T. praecox agg. No evidence of frequent double reduction was detected. Polymerase chain reaction (PCR) based dosage effects allowed for precise assignment of allelic configuration at all six microsatellite loci. The quantification of allele copy numbers in PCR was verified by comparisons of observed and expected gametic allele frequencies and heterozygosities in test crosses. Our study illustrates how PCR based markers can provide reliable estimates of heterozygosity and, thus, powerful tools for breeding system and population genetic analyses in polyploid organisms.
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Acknowledgments
We thank John D. Thompson, Nike Böger and Zsófia Hock for collecting plant material from Southern France, Ireland and Hungary, respectively, and Jean-François Manen for introduction to primer design. We also thank François Felber, Hilde Nybom, John D. Thompson and two anonymous reviewers for helpful comments on the manuscript. This work was funded by the Swiss National Science Foundation (Grant No. 3100–066852.01).
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Landergott, U., Naciri, Y., Schneller, J.J. et al. Allelic configuration and polysomic inheritance of highly variable microsatellites in tetraploid gynodioecious Thymus praecox agg.. Theor Appl Genet 113, 453–465 (2006). https://doi.org/10.1007/s00122-006-0310-6
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DOI: https://doi.org/10.1007/s00122-006-0310-6