Abstract: Fragan × ananassa Duch.‘Toyonoka’plants were exposed to 5，10 and 15 mg · L-1 cadmium（CdCl2 · 2.5H2O）for 6 d to investigate the influence of heavy-metal Cd on root tips，which included DNA polymorphism change and oxidation systems damage. In addition，above indexes were analyzed by physiology biochemistry methods and random amplified polymorphic DNA（RAPD）technology. Cd induced an inhibited effect on root growth and soluble protein content，which also accumulated reactive oxygen species outbreak including superoxide anion production rate increased and hydrogen peroxide content enhanced. At the same time，antioxidant enzymes（SOD，POD and CAT）activities also decreased. Moreover，DNA hyperchromic effect reduced after 6 d on 5，10 or 15 mg · L-1 Cd treatment. Finally，RAPD results showed that 8 primers gave a total of 88 RAPD bands ranging from 150 to 3 500 bp in molecular size in the normal plantlets. The changes occurring in RAPD profiles of the root tips after Cd treatment， which included loss of normal bands，appearance of new bands and variation in band intensity in comparison to which of the plantlets without treatment. It is need to point out that the RAPD band change effect was dose-dependent of Cd concentration. These results indicated that genomic template stability（a qualitative measure reflecting changes in RAPD profiles）was significantly affected by the above Cd concentrations. Reactive oxygen species outbreak and DNA cross-linking were the main reasons which causing the root tips damage. Thus，DNA polymorphisms detected by RAPD analysis could be used as an effective method for the assessment of the root tips damage by Cd in strawberry plantlets.

Key words: Fragan × ananassa Duch., Cd stress, reactive oxygen species, antioxidant enzyme system, DNA polymorphism