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SRAP (sequence-related amplified polymorphism) was used for the analysis of 67 sesame (Sesamum indicum L.) cultivars widely used in Chinese sesame major production areas from 1950 to 2007. A total of 561 bands were amplified using 21 SRAP random primer pairs, with 265 of them were polymorphic, resulting in a polymorphism ratio of 47.2%. The total bands and polymorphism amplified by each primer pair averaged 26.7 and 12.6, respectively. The average genetic similar coefficient and genetic distance of the 67 eultivars were 0.9104 and 0.0706, respectively, indicating limited genetic diversity and narrow genetic basis. Comparative analysis on genetic similarity and genetic distance of different classified cultivars showed that the difference of average genetic similarity coefficient and genetic distance between the landraces and cultivars bred through crosses reached significant levels (P=0.01), with the genetic basis of landraces wider than that bred cultivars. The genetic basis of cultivars used in 1990-2007 was more narrow than that of cultivars from 1950 to 1969 and from 1970 to 1989, with the differences of average genetic similarity coefficient and genetic distance reached 0.01 significant level. The genetic basis of Chinese sesame main cultivars is relatively narrow, and the genetic basis of cultivars developed through crosses in recent years is narrower than history cultivars.