Keywords: 
• Pogostemon cablin（Blanco） Benth /
• ⁶⁰Co-γ ray irradiation /
• genetic diversity /
• ISSR analysis

Abstract: A number of germfree materials were obtained from explants of the same field plant of Pogostemon cablin（Blanco） Benth.These germfree materials were irradiated by⁶⁰Co-γ ray irradiation at a respective dose of 0,45,60,75 or 90 Gy,from which 172 pieces of ⁶⁰Co-γ ray mutant material and 1 piece of germfree control material（CK;0 Gy） were produced.The genomic DNAs of 173 germfree materials were extracted and amplified by using PCR with 14 ISSR primers.A total of 297 amplified products were produced,of which there were 68 polymorphic bands,the percentage of polymorphic bands（PPB） was 43.13%,the observed number of alleles（NA）was 1.431 3,the effective number of alleles（Ne） was 1.257 3,the Nei’s gene diversity（H） was 0.146 5,and Shannon index was 0.217 5.According to the obtained genetic similarity coefficient matrix,a phylogenetic tree showing genetic relationships among the 173 materials tested was constructed by UPGMA.This phylogenetic tree diagram showed that at the genetic similarity coefficient（GS） range of 0.09＜GS＜0.42 the 173 materials could be divided into two groups:Group I and CK,that at the GS of 0.44,the Group I could be divided into two subgroups:Group II and material 90 Gy-34,and that at the range of 0.46＜GS＜0.48,the Group II could be divided into two branches:Group III and material 75 Gy-13.Although some of the mutagenic plants induced by radiation at different doses were clustered together,the mutant plants induced at the same radiation dose were generally clustered into the same group.The results showed that ⁶⁰Co-γ-ray irradiation had significant mutagenic effect on the mutants of P.cablin（Blanco） Benth.Mutation with ⁶⁰Co-γ ray could be used as an effective method for germplasm innovation of P.cablin（Blanco） Benth.