In this study, the effect of pre-aging treatment for inhibition of natural aging of Al-4.8Zn-1.3Mg alloy by extrusion process was investigated. Firstly, the as-cast microstructure of Al-4.8Zn-1.3Mg alloy billet and its evolution during homogenization(460℃, 4h + 510℃, 5h) were investigated by means of optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), hardness analysis. The as-cast microstructures of Al-4.8Zn-1.3Mg alloy reveal Mg2Zn, Al5Cu, Al3Cu formed between dendrities. After homogenization, MgZn, Al4Cu, Al13Cu phases precipitated into the matrix. In addition, standard deviation of homogenized billet was improved than as-cast billet from 2.62 to 0.99. According to pre-aging(100℃, 1h) Al-4.8Zn-1.3Mg alloy by extrusion process, yield strength and tensile strength deviation improved more than condition by natural aging.

Rehmannia glutinosa is one of the most important medicinal crops in Korea. However, various plant pathogens including Fusarium sp. cause great damages and cause enormous economic losses. Therefore, this study was conducted to select Fusarium resistant plants by using mutagen-treated Rehmannia glutinosa. The plant material used was a native accession of Rehmannia glutinosa. As a result, among the Rehmannia glutinosa treated with various concentrations of EMS, R. glutinosa treated with 0. 03M EMS showed higher resistance against infection of F. oxysporum in pot tests, and Rehmannia glutinosa plants treated with 0.12M EMS showed higher resistance against infection of F. oxysporum in field tests.

The efficiency of regeneration of callus and explants from leaf and stem disks of Epimedium koreanum was examined on the MS media containing 2,4-D, NAA, Kinetin, BA and TDZ. Calli were formed on the 2mg/l 2,4-D media at the rate of 32% from leaf discs and 52% from stems. No callus was produced on the media which are containing BA or TDZ alone. The combination of 2,4-D and BA showed the effect on the formation of callus. The combination of 2mg/l 2,4-D and 0.lmg/l BA in the MS media had produced the highest percentage of callus formation, 50% from leaf discs and 40% from stems, respectively. The combination of 2mg/l 2,4-D and 1mg/1 BA in the MS media had affected the formation of callus in the rate of 40% from leaf discs and 25% from stems. The combined plant growth regulators of 2,4-D and BA increased the formation of calli from leaf discs, but single treatment of 2,4-D showed the highest callus formation from stems. Multiple shoots from leaf discs were formed on the media containing NAA, BA, kinetin, and TDZ. The highest number of multiple shoots were obtained 0.1mg/l NAA combined with 1mg/l kinetin. As a result, leaf discs or stems can be used for the mass propagation of Epimedium koreanum, but stem elongation of shoots from calli was not easy.