Rapid evaluation of effective linear energy transfer in heavy-ion mutagenesis of Arabidopsis thaliana

Heavy-ion beams are an effective mutagen for use in plant breeding and analyses of gene function. Heavy-ion beams have high linear energy transfer (LET) and thus they effectively induce DNA double-strand breaks. To rapidly evaluate effective LETs for inducing mutations, we investigated mutation frequencies in the M-1 generation using the Arabidopsis heterozygous mutant of the ALBINO PALE GREEN 3 gene. Leaves of heterozygous plants in which intact alleles were mutated showed white sectors. We irradiated heterozygous plants with heavy-ion beams with LETs ranging from 22.5 to 61.5 keV mu m(-1) and doses ranging from 0 to 450 Gy. The results showed that the effect of LETs could be classified into three types: first, the LET of 22.5 keV mu m(-1) did not effectively induce mutations, regardless of the dose; second, LETs of 30.0 or 42.5 keV mu m(-1) were not effective at low doses (100-200 Gy) but were effective at 300 Gy; third, LETs of 50.0 or 61.5 keV mu m(-1) produced comparatively high mutation frequencies at all doses. Irradiation with 42.5-61.5 keV mu m(-1) reduced seed productivity at the dose providing the highest mutation frequencies (300 Gy). We concluded that an LET of 30.0 keV mu m(-1) was optimal for obtaining Arabidopsis thaliana mutants in the M-2 generation.