Salt stress is one of major restrictions for the production of lettuce. In order to identify promising lettuce genotypes having tolerance against salt stress, effect of different sodium chloride (NaCl) concentrations (0, 100, and 200 mM) on electrolyte leakage and growth of thirty-two lettuce landraces from Korea was evaluated. Screening salt tolerant genotypes based on cluster analysis using data of electrolyte leakage discriminated 'IT105183' and 'IT195057' as the most salt tolerant landraces. More importantly, salinity significantly reduced growth of lettuce, but the reduction rates of growth caused by salt stress in salt-tolerant genotypes were much smaller than those in salt-sensitive genotypes. These results indicate that 'IT105183' and 'IT195057' have high potential for being used as parents to improve salt tolerance in other lettuce cultivars.

'Green King', a new green tetraploid table grape cultivar with large berries, was originated from a cross between ‘Tensyu’ and ‘Beni Fuji’ grape cultivar in 2000. The cultivar was preliminarily selected among the elite breeding lines for its superior growth characteristics in 2005. After an extensive three-year evaluation of fruit and tree characteristics as 'GWG2002-02', 'Green King' was finally selected in 2008. Under Chuncheon’s ecological conditions, the average harvest date for 'Green King' is 6 September, and the number of days from flowering to harvest is 88 days. Hence, it is 12 days shorter than 'Rosario Bianco'. The average weight of a cluster in 'Green King' is 379.6 g, and its yield is 1,852 kg/10a. It has larger fruit size and higher fruit productivity than ‘Rosario Bianco’ (Registration No. 3560).

‘Sweet Dream’(Vitis complex), a new triploid seedless grape cultivar, is developed from the grape breeding program at Gangwondo Agricultural Research and Extension Services in 2009. ‘Sweet Dream’ was obtained from a cross ‘Honey Black’(Vitis complex) and ‘Campbell Early’(Vitis labrusca), a diploid x tetraploid grape cultivar. Characteristics of fruits and vines in ‘Sweet Dream’ were observed from 2006 to 2008, and ‘Sweet Dream’ was finally selected in 2009. Its optimum harvest time in Chuncheon is September 11, 12 days later than ‘Campbell Early’. ‘Sweet Dream’ has strong vine vigor and moderate freezing tolerance, with no bud damage occurring during winter in Chuncheon. The average weight of a cluster is 440g, and its average soluble solids concentration is 16.4 °Brix. It is seedless and has larger fruit size and better fruit quality than ‘Campbell Early’. It, therefore, is expected that introduction of ‘Sweet Dream’ could contribute to the diversification and gentrification of Korean grape cultivars (Registration No. 4359).

In this study, we investigated the fruit and vine characteristics of hypo- and hyper-tetraploid grapes from which a chromosome was added or deleted. The aim of this study was to evaluate the possibility of developing seedless grapes by utilizing the characteristics of hypo- and hyper-tetraploid grapes. Both the hypo- and hyper-tetraploid grapes showed stable vine growth characteristics unlike other aneuploid plants, which displayed abnormal leaf morphology and unstable vine growth patterns, indicating that hypo- and hyper-tetraploid grapes can be used for commercial purpose. The hypo-tetraploid grapes produced 100% seedless fruits, with large berries ranging from 8.5 to 10.5 g, when the grapes were applied with 100 ppm gibberillic acid during their full bloom period. Although the fruits of the hyper-tetraploid grape were larger than those of the hypo-tetraploid grapes, it produced a lower percentage of seedless fruits. We conclude that the characteristics of hypo-tetraploid grapes may be exploited to develop seedless grapes with large berries.