The flow cytometry was used to determine the ploidy of 469 clones of Populus tomentosa in a gene pool located at Guan County of Shandong Province.19 SSR markers were used to estimate the genetic diversity of all the diploid P. tomentosa clones. Among diploid clones, the seeds were collected from all female parents to evaluate the fertility ability and combining ability. According to pollen production measured by our group in early stage, the parental population for breeding was constructed by a comprehensiv...