Study On Bioeffects And Mechanism Of Mutagenesis Induced By Nuclear Reaction Of ～7Li Ion Beams

Compared to the ionizing irradiation such as X-rays andγ-rays etc., ion beam is one kind of the particles with mass disposition, momentum transfer and electric charge exchange except energy disposition (X-rays orγ-rays only possesses energy disposition). Ion beams showed higher biological effects than the traditional ionizing irradiation. 7Li ion beams have not only the mutagenic characteristics of common ion beams, but also the inner target nuclear reaction 1H(7Li,7Be)n in organism. 7Li ion beams could be expected to induce distinguished biological effects.The pUC18 plasmid DNA was used to study the damage effects on hydrogen bonds and the mutagenic effects of in vitro DNA which was implanted by different doses of 7Li ion beams. The dry seeds of two winter wheat varieties ZY9 and ZH7 were also implanted by the different doses of 7Li ion beams to study the changes of the DNA in M1 generation, the mutagenic effects in M2 generation and the DNA variation of mutants in M3 generation. The results were summarized as follows.1. 7Li ion beams had different damage effects on hydrogen bonds, and even low doses of 7Li ion beam could induce high damage on hydrogen bonds. The damage effects on hydrogen bonds of 7Li ion beams were higher thanγrays.2. 10 lacZ- mutants were used for sequence analysis, which indicated that the types of base changes included base transversion, transition and deletion. Among all the base changes detected, the frequency of bases transition (60%) was higher than that of bases transversion (30%) and bases deletion (10%). Adenine, thymine, guanine and cytosine all could be induced by 7Li ion beams, but the mutation frequency was not the same. It seemed that thymine was more sensitive to the irradiation than any other bases and the base changes were mainly T→C and C→T. The bases between T and C were seemed to be easily induced by 7Li ion beams.3. After the dry seeds of wheat were implanted by 7Li ion beams, many morphilogical variations were found on the wheat seedlings in M1 generation. The bands of SSR were greatly changed and the polymorphic frequency was high in wheat implanted by 7Li ion beam. The polymorphic patterns were mainly the increase and deletion of amplified fragments.4. The two wheat varieties (ZY9 and ZH7) were implanted by the 7Li ion beams with the doses of 10Gy, 20Gy, 30Gy, 40Gy, 60Gy, 100Gy and 140Gy, respectively. Mutations were found in such as plant height, spike shape, sterility, growth stage, etc. in M2 generation, The dose of 40 gray may be optimal for 7Li ion beams implantation in wheat.5. Analysis of seedling genomic DNA variation in M3 generation of mutants showed their DNA sequences had also been changed. This result further confirmed the fact that the implantation of 7Li ion beam could induce genetic mutation in wheat. 7Li ion beams could be a new mutagenic source and play a good role in crop improvement.