ソフトエレクトロン処理した種籾のDNAコメットアッセイによる影響評価

抄録

As rice seeds are sometimes contaminated with phytopathogenic organisms such as blast disease fungi and nematodes, a novel non-chemical disinfection method for rice seeds is highly required. In order to develop a disinfection method, the effect of low energy electron (“soft-electrons”) on seed DNA was examined by using the neutral comet assay. Rice seeds (whole grain) were treated with electrons of different acceleration voltages (180kV to 1MV) at a dose of 5kGy. Nucleus suspensions were prepared from whole brown rice and subjected to electrophoresis. DNA from un-irradiated (control) seeds relaxed and produced comets with a short tail, most of the comets distributed within the range of comet length between 30μm to 70μm. In the case of seeds treated with electrons at acceleration voltages up to 190kV, cells without seed coats were not damaged and the frequency histograms of comet length showed almost the same pattern as that for control. At acceleration voltages higher than 200kV, the cells were distributed into two categories; DNA comets with a short tail (with little DNA damages, less than 70μm in the comet length, ) and DNA comets with long tails (with sever strand breaks, more than 130μm in the comet length). The ratios of damaged cells increased with increasing acceleration voltage. The growths of rice seedlings were not affected by the treatment with electrons at up to 200kV. On the contrary, the cells of gamma-irradiated seed showed small variations in the comet length, and which were depending on radiation dose. The individual cells of gamma-irradiated seeds at 1kGy showed shorter comet than the damaged cells with soft electron, seed treated with gamma rays (1-5kGy) did not shoot nor root.