Young shoots of Dahlia pinnata Cav cultivar were irradiated by 80 MeV/u 12C6+ ions.The differences at DNA level between dwarf mutant and wild type were detected by using RAPD(Random amplified polymorphic DNA) method.The results showed that there were different polymorphic bands induced by 18 primers among the tested 25 primers

and the ratio of polymorphic bands and total bands accounted for 19.57% after 1.80×108C6+/cm2 irradiation.Meanwhile

after 1.08×108 C6+/cm2 irradiation the polymorphic bands were induced by only 6 primers and the ratio accounted for 5.76%.Using the Jaccard formula

statistic analysis of amplified bands were obtained and it showed that after 1.80×108 C6+/cm2 and 1.08×108 C6+/cm2 irradiation the similarity index were 0.65 and 0.92 respec-tively.The results suggested that DNA should prone to mutant at high doses

and high dose irradiation might be more effective in corn improving and mutagenic breeding.