Analysis of cytogenetic damage in rice seeds induced by energetic heavy ions on-ground and after spaceflight

To analyze the biological effects of the space environment, we flew nine lines of rice seeds on the Chinese 20(th) recoverable satellite for a duration of 18 days. The same lines of seeds were also irradiated to low doses (2.0mGy) of Carbon, or Neon or Iron ions (with different LET value of 13.3 keV/mu m, 31 keV/mu m and 500 keV/mu m respectively) at National Institute of Radiological Sciences in Chiba, Japan. The total number of mitotic cells and chromosomal aberrations were analyzed. The mitotic index (MI) and the frequency of chromosomal aberration were evaluated in order to compare the cytogenetic damages from spaceflight and from exposure to similar doses of charged particle on the ground. The results of the present study show that the space environment and heavy energy ion can alter cell growth, and induce various chromosome aberrations including micronuclei, chromosomal bridges, fragments and laggards. With all the lines combined, the frequency of chromosome aberrations and MI in seeds flown in space are the highest. The effectiveness of cytogenetic damage from spaceflight (SP) and the heavy ion irradiations is SP > Fe > Ne > C.