기내배양한 양란 심비디움 원괴체에 전자빔(2 MeV/n, 0.5 mA)을 10 Gy～300 Gy로 조사하여 생장 변화와 유전적 변이의 다양성을 검토하였다. 전자빔을 조사 후 배양 10주째에 선량의 증가에 따라 원괴체로부터 신초유도가 감소하였고, 200 Gy 이상의 선량을 조사한 처리구에서는 신초분화가 크게 억제되었다. 원괴체 18개체를 ISSR 분석한 결과 대조구는 12.5% 다형성을 나타내었고, 전자빔 조사구에서는 42.2%의 다형성을 나타내었다. RAPD 분석한 결과 대조구에서 13%의 다형성을 나타내었고, 전자빔 조사구에서는 43.8%의 다형성을 나타내었다. 따라서 RAPD 및 ISSR 분석 모두에서 전자빔 조사시 대조구보다 3.5배 정도 다형성이 증가한 것으로 나타났다. 유전적 유사도 지수(GSM)는 전자빔 처리가 대조구보다 낮게 나타나 전자빔 처리에 의하여 개체들 간의 유전적 다양성이 높아진 것으로 보인다. 군집분석 결과 RAPD와 ISSR 분석 모두 대조구와 전자빔 처리구가 분리되어 그룹을 이루었다. 이와 같이 전자빔 조사로 기내 배양 양란 심비디움의 유전적 다형성이 증대됨을 확인하였다.

Ionizing radiations have been effective mutagen sources to overcome the limitation of the useful genetic resources in natural environment. The study was conducted to investigate an effect of electron beam on organogenesis, growth patterns and genetic variation in the irradiated orchid organs (rhizome and protocorm). The in vitro cultured rhizomes of orchids (Cymbidium goeringii, C. kanran) were irradiated with the electron beam in the dose range of 15Gy to 2240Gy under the condition of various beam energy and beam current (10MeV/n and 0.5mA, 10MeV/n and 0.05mA, 2MeV/n and 0.5mA). Significant decreases in growth and organogenesis were observed by increase of intensity of electron beam irradiation. The irradiation intensity of lethal dose 50 (LD50) of the in vitro cultured orchid was estimated as approximately 500Gy to 1000Gy under 10MeV/n, and 1000Gy to 2000Gy under 2MeV/n. While, the optimal irradiation dose was approximately 100Gy for growth and organogenesis of the cultures under 10MeV/n with 0.05mA treatment, and 300Gy under 2MeV/n and 0.5mA electron beam condition. RAPD and ISSR analyses for the electron beam irradiated organs were performed to analyze genetic variation under the electron beam condition (2MeV/n and 0.5mA).

It was previously pointed out that mutation is the ultimate source of variation. Adequate variation is needed for plant breeding if there is a limitation in natural genetic resources. When the ionizing radiation has been known to cause chromosomal and genomic alternations, it is widely used for inducing mutagenesis. The electron beam as an ionizing radiation is the principal physical mutagens that induces mutation and effectively used in plant breeding. Since dose-response relationships of electron beam in plant species are rarely known, we investigated the seed germination rate and early seedling growth of irradiated seeds of creeping bentgrass (Agrostis palustris Huds., cv Penn-A1) with various electron beam irradiating conditions (1, 1.3, 2 MeV at both 0.03 mA and 0.06 mA with dose of 100 Gy (Gray) and 0.03, 1, 1.3, 2 MeV at 0.03 mA with dose of 200 Gy, respectively) using electron accelerator at Korea Atomic Energy Research Institute. The growth parameters in terms of shoot length, primary root length, and secondary root length showed similar response between 0.06 / 1 (mA / MeV) at 100 Gy and 0.03 / 0.3 (mA / MeV) at 200 Gy. Bentgrass seed germination was mainly affected by the intensity of irradiated dose (Gray). Germination rate was lowered as the irradiated dose increased. On the other hand, early seedling growth was mainly governed not by the dose of radiation but by voltage.

The direct use of mutation is a valuable approach to generate variability in crops. The electron beam, one of the ionizing radiations, has been applied to evaluate its effect on seed germination and early seedling growth of creeping bentgrass (Agrostis palustris Huds., cv Penn-A1). The mature dry seeds were irradiated with various electron beam energies (0.3, 1.0, 1.3, and 2 MeV) and current levels (0.03 and 0.06 mA). Although large variability was existed within each dose, distinct difference of germiability and seedling vigor were not found at 0.3 MeV / 0.03 mA and 0.3 MeV / 0.06 mA beam condition. However, 1.0 MeV / 0.06 mA application most effectively inhibited and retarded seed germination and most severely restricted cotyledon and root growth in early seedling growth. The direct use of electron beam would be a valuable supplementary approach to generate mutants suitable for breeding purposes.

Deposited road particles (DRPs) were analysed for heavy metal concentrations at four different roads in a city, Korea. The samples were collected using a roadway surface vacuum cleaning vehicle which was commonly used in collecting roadway surface particles. Six particle size ranges were analyzed separately for twelve heavy metal elements (Cd, Cr, Pb, Ni, Al, As, Co, Cu, Fe, Mn, Zn and Hg). At all sampling sites, the high concentration of the heavy metals occurred in the <74um particle size range, which conventional roadway cleaning vehicles do not remove efficiently. The Pb concentration significantly increased with decreasing particle size of DRPs, and other toxic heavy metals (Cd, Cr and Ni) also showed similar results. The heavy metal concentrations in the smaller size fraction of DRPs is important because they are contaminants that are preferentially transported by road runoff during rainfall.