Promotion of somatic embryo production from embryogenic calluses of monocotyledonous and dicotyledonous plants by heavy-ion beam irradiation

Effect of heavy-ion beam irradiation on the growth and development of embryogenic calluses was examined in the liliaceous monocotyledon Tricyrtis hirta and the umbelliferous dicotyledon Daucus carota. Embryogenic calluses of T. hirta were irradiated with 5, 10, 20 or 50 Gy of ¹²C⁶⁺, ¹⁴N⁷⁺ or ²⁰Ne¹⁰⁺ ions, and those of D. carota were irradiated with 5, 10, 20 or 50 Gy of ¹⁴N⁷⁺ ions. In both species, irradiation at 10–50 Gy inhibited growth of embryogenic calluses, and callus growth rate decreased as irradiation dose increased. Interestingly irradiation at low doses greatly promoted somatic embryo production from embryogenic calluses in both species. In T. hirta, calluses irradiated with 5 and 10 Gy ¹²C⁶⁺ ions, 10 Gy ¹⁴N⁷⁺ ions, and 5 Gy ²⁰Ne¹⁰⁺ ions produced more than twice as many embryos as the control, non-irradiated calluses. In D. carota, embryogenic calluses irradiated with 5 Gy ¹⁴N⁷⁺ ions produced more than one and a half times as many embryos as the control. Somatic embryo production in both species was inhibited by irradiation at 20 and 50 Gy.