Soil seed banks can contribute to genetic restoration of threatened plants under genetic decline. To elucidate the potential of soil seed banks for the genetic restoration of threatened plants, we investigated the genetic characteristics of five existing populations and two populations derived from seed banks of Polemonium kiushianum, a critically endangered grassland herb of the Aso region, using 10 microsatellite loci.

The populations derived from seed banks harbored high allelic diversity, particularly of rare and private allelic richness as compared with existing populations. They also significantly increased the genetic diversity and effective population size of overall populations of P. kiushianum. STRUCTURE analysis revealed that one population derived from seed banks was assigned to a genetic cluster that was not known in exiting populations. This result indicates that soil seed banks restored not only genetic diversity but also a previously unknown cluster. This study demonstrates that restoring past population from soil seed banks may be an effective method for genetic restoration of threatened plants.