Abstract: The paper identified and compared the karyotypes of 10 species(varieties) of Populus sectTacamhaca.The results were as follows:Ppseudosimonii Kitag.2n=38=27m+6sm(1SAT)+4st(2SAT)+1t(1SAT);Ptrichocarpa Torr.2n=38=2M+18m(1SAT)+8sm+10st(1SAT);Pcathayana Rehd.var.Beijing 2n=38=1M+24m+6sm+7st(2SAT);Pבpopularis’ 2n=38=3M+27m+2sm(1SAT)+4st(2SAT)+2t(1SAT);Pcathayana Rehd.var.Wutai 2n=38=5M+22m+4sm+5st+2t(2SAT);Pcathayana Rehd.var.Gansulinxiaman 2n=38=2M+28m+1sm+7st(1SAT);Pcathayana Rehd.var.Qinghai 2n=38=1M+27m+3sm+6st(3SAT)+1t(1SAT);Pcathayana×Zhongqing 10 2n=38=1M+26m+4sm+5st(2SAT)+2t(2SAT);Pcathayana×Zhongqing 48 2n=38=16m+10sm(1SAT)+10st(2SAT)+2t(1SAT).The results showed definite karyotype differences among the species of Tacamhaca.The karyotypes of most species(varieties) are made of m and sm and a few with st and t chromosomes.The karyotypes of Tacamhaca were all of 2B type of Stebbins.This study provided important basic data for taxon of Populus.

Key words: Populus