Analysis of genetic diversity and population structure in endangered Populus wulianensis based on 18 newly developed EST-SSR markers

Populus wulianensis is an endangered tree species endemic to Shandong Province, China. Genetic diversity assessments represent the basis and a prerequisite for protecting endangered species. In our study, a total of 116 individuals of P. wulianensis from 4 extant populations (3 wild populations and 1 artificial population that covered the entire geographic distribution of the species) were analyzed using 18 expressed sequence tag-simple sequence repeat (EST-SSR) markers to assess their genetic diversity and population structure. The 18 EST-SSR markers had high levels of polymorphisms (PIC = 0.698), and 202 alleles were amplified. The present study revealed high genetic diversity at the population level (Na = 4.847, NR = 3.000, HS = 0.624, HE = 0.611, I = 1.114, and PPL = 98.6%) and the species level (HT = 0.741). Private alleles were detected in all four populations (including the artificial population JYS). Negative inbreeding coefficients (FIS