PURPOSE: Proton ions are expected to be used as a discriminative radiation source to induce different kinds of mutations than those produced by γ-rays and carbon ions; however, there is little systemic information about radiosensitivity in plants. MATERIALS AND METHODS: We analyzed the LD30, LD50, and RD50 values in response to proton ions and γ-rays using 20 plant species. Plant seeds were irradiated, and growth responses were measured one month after planting, except for cymbidium, for which in vitro rhizomes were irradiated. The rhizomes were analyzed at six and nine months after subculturing. RESULTS: Resistance to proton ions and γ-rays was observed in Chinese cabbage, watermelon, and melon, while Japanese atractylodes, naked barley, and lentil were susceptible. Plants belonging to the Brassicaceae and Cucurbitaceae families were highly resistant to radiation, and plants belonging to the Compositae and Poaceae families were highly susceptible. In addition, plants with genome sizes greater than 8,000 Mbp were highly sensitive to radiation, but there was no clear relationship between radiosensitivity and genome size in plants with genomes smaller than 2,500 Mbp. CONCLUSIONS: The biological effectiveness of proton ions was greater than that of γ-rays in 16 plant species, indicating that they could be used as a discriminative radiation source to induce mutations compared with γ-rays.
PURPOSE: Proton ions are expected to be used as a discriminative radiation source to induce different kinds of mutations than those produced by γ-rays and carbon ions; however, there is little systemic information about radiosensitivity in plants. MATERIALS AND METHODS: We analyzed the LD30, LD50, and RD50 values in response to proton ions and γ-rays using 20 plant species. Plant seeds were irradiated, and growth responses were measured one month after planting, except for cymbidium, for which in vitro rhizomes were irradiated. The rhizomes were analyzed at six and nine months after subculturing. RESULTS: Resistance to proton ions and γ-rays was observed in Chinese cabbage, watermelon, and melon, while Japanese atractylodes, naked barley, and lentil were susceptible. Plants belonging to the Brassicaceae and Cucurbitaceae families were highly resistant to radiation, and plants belonging to the Compositae and Poaceae families were highly susceptible. In addition, plants with genome sizes greater than 8,000 Mbp were highly sensitive to radiation, but there was no clear relationship between radiosensitivity and genome size in plants with genomes smaller than 2,500 Mbp. CONCLUSIONS: The biological effectiveness of proton ions was greater than that of γ-rays in 16 plant species, indicating that they could be used as a discriminative radiation source to induce mutations compared with γ-rays.