Gamma-ray irradiation commonly served as a mutagenic agent to induce genetic variability in crop species. However, the appropriate gamma-ray irradiation dose requires determining before starting a mutagenesis-based breeding program. The presented study sought to determine the lethal dose (LD₅₀) and the growth reduction dose (GR₅₀) in Capsicum annuum cv. Kopay and Capsicum frutescens cv. Bara. The seeds of both cultivars sustained gamma-ray doses irradiation of 0, 200, 300, 400, and 500 Gray (Gy). This study found the seed germination percentage, survival percentage, and seedling height of the Kopay and the Bara cultivars decreased with increased gamma-ray doses compared with the control due to seed injury and impact on poor growth seedlings. The LD₅₀ and GR₅₀ values of the Bara were 257.64 and 246.10 Gy, respectively, while for Kopay, these were 333.56 and 318.61 Gy, respectively. The LD₅₀ of the gamma ray for the Kopay was higher than the Bara, indicating the Kopay variety has less sensitivity to gamma-ray irradiation than the cultivar Bara. The study results can be beneficial for mutagenesis-based plant breeding programs in Capsicum.

Keywords: Chili (C. annuum L., C. frutescens L.), cultivars, acute irradiation, gamma ray, radiosensitivity

Key findings: The LD₅₀ values of the chili (C. annuum L. and C. frutescens L.) cultivars Bara and Kopay were 257.64 and 333.56 Gy, respectively. The cultivar Kopay proved less sensitive to gamma-ray irradiation than the cultivar Bara. Chili breeders can use the LD₅₀ values in this study to obtain mutant plants with gamma rays.