Abstract: The karyotype of 9 species ( varieties) of section Populus in the genus Popu lus have been analyzed for the first time. The resultswere as follows: P. alba L. , 2n = 28 = 1M + 30m + 4 sm (1SAT) + 1 st (1SAT) + 2 t; P. alba L. var. pyram idalis, 2n = 38 = 1M + 24m + 6 sm + 5 st (1SAT) + 2 t (1SAT) ; P. hopeiensis Hu et Chow, 2n = 38 = 1M + 25m + 8 sm + 4 st; P. tom entosa Carr. , 2n = 38 = 1M + 27m + 2 sm + 6 st + 2 st; P. trem ula L. , 2n = 38 = 27m (1SAT) + 6 sm + 5 st (2SAT) ; P. a lba bolleana, 2n = 38 = 1M + 24m + 7 sm (1SAT) + 5 st (1SAT) + 1 t; P. tom en tosa var. Ex i, 2n = 38 = 26m + 5 sm + 4 st + 3 t; P. davidiana
Dode CL alba21, 2n = 38 = 3M + 23m (1SAT) + 6 sm + 6 st (1SAT) ; P1 ×hongba inensis B14, 2n = 38 = 22m + 6 sm (1SAT) + 7 st + 3 t. Results of karyotype analysis showed that the karyotype differences among species ( varieties) in section Populus were remarkable. The results obtained indicated that their origin were different. The karyotype characteristics provided important basic data for species of section Populus.

Key words: Populus, Section Populus, Karyotype analysis