Biological effects of offspring of maize irradiated by ¹²C⁶⁺ heavy ion beam

In order to create excellent planting materials for maize germplasm innovation and variety improvement, dry maize seeds of inbred line LY8405 were irradiated by ¹²C⁶⁺ heavy ion beams under different doses of 0 (control), 30, 60, 90, 120 Gy and the biological effects of progeny plants after irradiation were compared and analyzed in detail. The analysis results showed that with the increase of irradiation dose, the germination rate, plant height, ear position height and pollen vitality of LY8405 in M₁ generation were significantly decreased compared to the control. The physiological damage detection index of M₂ offspring irradiated with the same dose was some recovered, but was still significantly lower than that of the control. The germination rate, plant height and ear position height of M₁ and M₂ irradiated by 90 Gy and 120 Gy showed extremely significant differences from that of the control. When the radiation dose was 30 Gy, a variety of agronomic phenotype mutants were screened in M2 and M3, indicating that the biological effects by 30 Gy was the most obvious for inbred line LY8405, followed by 60 Gy. At the same time, 60 Gy was the threshod of semi-lethal dose. The mutation types of M₂ and M₃ including dwarf, lower ear position height, wrinkled leaf blade, yellowish leaf, white and mottled leaves, larger and longer spike, red cob instead of white, wine red grain color from yellow, and grain shape changing from dent corn to flint corn. Biological studies showed that 30-40 Gy is the suitable irradiation dosage for breeding maize inbred LY8405 with ¹²C⁶⁺ heavy ion irradiation within the scope of 0-120 Gy. This study will provide a method and dose reference for the creation of new germplasm resources of different maize inbred lines, and more important, it also provide some stable genetic materials for the selection and breed of new maize varieties. (authors)