Construction of mutation populations by gamma-ray and carbon beam irradiation in chili pepper (Capsicum annuum L.)

Mutagenesis using ionizing radiation has been widely used for the development of genetic and breeding resources with novel characteristics. Although mutation breeding using X- and gamma-rays has been attempted in peppers, information on the effectiveness of other ionizing radiation and a comparative analysis of mutagenic effects of different forms of radiation is limited. Therefore, we investigated and compared the biological effectiveness and mutagenesis efficiency of gamma-rays and a carbon beam (a heavy ion beam) in a chili pepper landrace of Korea, ‘Yuwol-cho’. The survival and shoot growth rate obtained by irradiation at serial doses showed that the LD50 was about 140 and 35 Gy, and the RD50 was about 80 and 32 Gy for gamma rays and carbon beams, respectively. The optimal doses for mutation breeding for these forms of radiation were estimated to be 80-100 and 15-20 Gy for gamma rays and carbon beams, respectively. We also developed M2 populations consisting of 1,836 lines by gamma-ray irradiation (100 Gy) and 154 lines by carbon beam irradiation (20 Gy). The frequency of dwarf or male sterile individuals showed that the mutagenic effect of the carbon beam was higher than that of gamma-rays. We identified individuals in each population with various developmental mutations through phenotypic analysis and categorized the mutations into four groups (mutations in plant architecture and development, leaf, flower, or fruits). This study provides basic information for mutation breeding using ionizing radiation and useful materials for the identification of genes related to the diverse characteristics in chili pepper.