Ex situ conservation of Pinus koraiensis can preserve genetic diversity but homogenizes population structure

Pinus koraiensis is a conifer species of ecological and economic importance in northeast China that has been excessively exploited in recent years. A clonal seed orchard (CSO) was established including potentially genetically differentiated provenances from the whole distribution area, we applied nine simple sequence repeat (SSR) makers to study the genetic diversity and population structure of six maternal populations as well as their progeny populations. The results showed a high genetic diversity in both maternal and progeny populations, with the average expected heterozygosity of 0.617 and 0.632, respectively. The level of genetic diversity in the progeny populations was slightly higher than that in the maternal populations, and almost all diversity descriptors were correlated between maternal and progeny populations, indicating that the CSO could preserve the established species' gene pool. An overall low level of genetic differentiation of P. koraiensis (F-ST = 0.029 and 0.025 for maternal and progeny populations) was found. The six maternal populations clustered into two groups by Bayesian cluster analysis with the two northernmost populations comprising one group and the other four populations as another genetically differentiated group, potentially indicating regional adaptation. The northern group had significantly higher levels of within population diversity. Population structure was not evident anymore in the progeny populations, suggesting that mating among differentiated provenances within the CSO homogenized the different gene pools, although differences in diversity were still maintained. These results will inform efforts for the conservation and management of P. koraiensis and provide guidance for future studies of population genetics and breeding programs.