1. National Institute of Horticultural & Herbal Science, Rural Development Administration, 100 Jeollabuk-do, Korea
2. United States Department of Agriculture-Agricultural Research Service, United States National Arboretum, Floral and Nursery Plants Research Unit, Beltsville, MD 20705
3. Department of Applied Biology, Chungnam National University, Daejeon 305-764, Korea.