Cryopreservation has been known as an efficient method for long-term preservation of clonally propagated plants, and several cryopreservation methods have been developed. Among them, a droplet-vitrification method for potato using axillary shoot tips in vitro has been established previously. In this study, we have optimized the procedure in which explants were submitted to a step-wise pre-culture in liquid sucrose-enriched medium (0.3 and 0.7 M for 7 and 17 h, respectively). The pre-cultured explants were dehydrated with PVS3 (w/v, 50% glycerol + 50% sucrose) for 90 min or modified PVS2 vitrification solution (w/v, 37.5% glycerol + 15% DMSO + 15.0% ethylene glycol + 22.5% sucrose) for 30 min. This two dehydration solutions produced post-cryopreservation regeneration percentages of 57.2% and 80.9%, respectively. We also compared a new post-culture medium (0.1 mg L ･ -1 GA3, 0.1 mg L ･ -1 kinetin) with the conventional one (0.15 mg L ･ -1 IAA, 0.2 mg L ･ -1 zeatin, 0.05 mg L ･ -1 GA3); the shooting initiation rates were 80.9% and 43.5%, respectively. The results suggest that the modified droplet-vitrification protocol described in this study is more effective, easier to implement, and more economical than the droplet-vitrification protocols currently used for potato.

"Chuyoung" as a new double cropping potato variety was bred in 2005 for table use through a cross between "Dejima" with short tuber dormancy and HRB-31 which is a tetraploid derived from an interspecific cross between "Russet Burbank" and Solanum phureja line. It was evaluated for short dormancy, growth and tuber characteristics every twice a year from 1997 to 2001. Regional yield trials were performed from 2002 to 2004 at three locations, Jeju, Namhae and Gangneung of Korea, respectively. Its tuber shape is oblong with yellow skin and flesh colors. Its dormant periods is 60~70days. It showed less incidence of physiological disorders such as cracking or knobs on tubers, and higher resistance to common scab by Streptomyces scabies compared to "Dejima". It has tall plant height and erect growth type with green-broad leaflets and white large inflorescence. Its average yields are 29.5 and 22.6 ton/ha at 90 days after planting in spring and autumn cropping, respectively. It also showed higher marketable yield due to the lower incidence of common scab and physiological disorders compared to "Dejima".

‘Seohong’ was bred within the potato breeding program of National Institute of Highland Agriculture (NIHA). It was originated from a cross made in 1997 between ‘Jashim’ as a female and 93K65-1 as a male parent. Seohong was evaluated as a seedling number 97S05-1 for tuber characteristics, growth and yielding ability from 2001 to 2002, and than this clone was renamed as Daegwan 1-82. This clone was evaluated in the regional yield trial and the disease resistance in the five locations for three years. Finally, this clone was named as ‘Seohong’ and registered a new recommended potato cultivar in 2006. This cultivar has a round, shallow eye depth, light red-skinned tuber characteristics and low to medium dry matter content. It showed high resistance to common scab (Streptomyces scabies) and potato leaf roll virus (PLRV), however it was susceptible to potato virus Y (PVY) and late blight (Phytophthora infestans). Its mean tuber yields from the regional yield trial and winter cropping trial were 12 and 49 percent higher than that of ‘Superior’, respectively.

“Haryeong” was bred through the potato breeding program at the National Institute of Highland Agriculture (NIHA). Itin1996. It has a round, smooth, light yelow-skined tuber characteristics and high dry mater content. It showed high resistance tolate bligh

Gahwang is an excellent chipping cultivar with yellow flesh, short oval tuber shape and mid-early maturity. Its yields were a little higher than Atlantic through the regional trials with five locations. It has a lower incidence of internal brown spot comp

Shinnamjag is a round, smooth, white-skinned, and fleshed potato cultivar with erect plant shape and early maturity. It has excellent table quality. Its yields are high, especially with prominent marketable yield compared to Superior, a leading potato cul