Ye-Sol Kim

DNA damage and oxidative stress induced by proton beam in Cymbidium hybrid

We investigated the radiation damages caused by two types of proton beam and gamma ray in the Cymbidium hybrid RB001 [(C. sinensis × C. goeringii) × Cymbidium spp.] to characterize proton beam as a new mutagen for Cymbidium mutation breeding. The protocorm-like bodies (PLBs) of Cymbidium hybrid were irradiated with a 45 MeV proton beam [mean linear energy transfer (LET) = 1.461 keV·μm−1], a 100 MeV proton beam (LET = 0.7306 keV·μm−1), and gamma ray (LET = 0.2 keV·μm−1). The PLBs treated with radiation doses of 0–100 Gy were analyzed using the comet assay and their physiological responses as indices of radiation damage. In the comet assay, the 45 MeV proton beam caused significant damage to the DNA integrity, but the 100 MeV proton beam and gamma ray showed relatively little radiation damage between the untreated control and treated PLBs. Malondialdehyde (MDA) content, an index of the indirect effects of ionizing radiation, was increased slightly by the 45 MeV proton beam with higher-LET, but highly increased by the 100 MeV proton beam with lower-LET. These results suggested that the 100 MeV proton beam caused extreme oxidative stress. Therefore, proton beam have unique characteristics in DNA mutagenesis pattern according to its LETs. Based on these results, proton beam is expected to be a useful tool for developing new mutant varieties of Cymbidium.

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.

Genetic relationships among diverse spray- and standard-type chrysanthemum varieties and their derived radio-mutants determined using AFLPs

Gamma-ray irradiation is an important tool in ornamental plant breeding, particularly to induce flower-color variation. Standard-type chrysanthemum ‘Migok’ and spray-type ‘Argus’ have seven and four gamma-ray mutants, respectively, with novel flower colors. Genetic relationships among 26 chrysanthemum varieties or mutants were analyzed using amplified fragment length polymorphisms (AFLPs) with 20 fluorescently-labeled E+3/M+3 primer combinations (PCs). Clustering analysis was carried out using similarity coefficients and unweighted pair group method with arithmetic averages (UPGMA). The 20 PCs produced 2,837 bands, 95.6% of which were polymorphic. E-ACC/M-CAG had the most polymorphic bands (199) and high polymorphic information content, marker index, and resolving power values. Similarity coefficients ranged from 0.63 to 0.97 overall but were 0.73–0.83 in the 11 radio-mutants. The 26 varieties and radio-mutants were divided into four major UPGMA groups; the 11 radio-mutants formed two subgroups and 10 standard-type varieties or radio-mutants were closely clustered into another. The most promising mutant-specific marker candidates were PC E-ACG/M-CAG (47.5%) and E-ACA/M-CAT (44%) for the ‘Migok’ and ‘Argus’ families, respectively.