Genetic Diversity and Population Structure in Chinese Indigenous Poplar (Populus simonii) Populations Using Microsatellite Markers

Populus simonii Carr. is an important ecological and commercial breeding species in northern China; however, human interference during the last few centuries has led to the reduction and fragmentation of natural populations. To evaluate genetic diversity and differentiation within and among existing populations, we used 20 microsatellite markers to examine the genetic variation and structure of 16 natural populations. Our results indicated that the level of genetic diversity differed among populations, with average number of alleles per locus (AR) and expected heterozygosity (H (e)) ranging from 3.7 to 6.11 and 0.589 to 0.731, respectively. A marginal population from Qilian in the Qinghai-Tibetan Plateau showed the highest values (AR = 6.11, H (e) = 0.731), and the Zhangjiakou and Yishui populations showed the lowest values (AR = 4.08, H (e) = 0.589 and AR = 3.7, H (e) = 0.604). The inbreeding coefficient (F (IS)) values for all populations were positive, which indicated an excess of homozygotes. The microsatellites allowed the identification of a significant subpopulation structure (K = 3), consistent with an isolation by distance model for P. simonii populations. Additionally, molecular variance analysis revealed that 14.2 % of the variation resided among populations, and 85.8 % could be attributed to variation within populations. These data provide valuable information for natural resource conservation and for optimization of breeding programs in the immediate future.