Grape (Vitis vinifera L.) is a perennial fruit tree with high heterozygosity, consisting of 38 chromosomes (2n=38), and it takes a long time for grape seedlings to grow into fruit-bearing trees. Therefore, it is difficult to study grape genetics and breeding strategies. However, it has recently become possible to discover many SNPs through whole genome resequencing or genotyping-by-sequencing (GBS) analysis. In this study, we aimed to develop high-resolution melting (HRM) markers from the detected SNPs and construct a genetic linkage map using HRM markers. In a previous study, 2,553 SNPs were identified using GBS analysis. In this study, 1,336 SNPs were used to design primer sets for HRM analysis. The developed HRM markers were used for construction of a genetic linkage map in an F₁ segregating population consisting of 192 individuals from a cross between ‘Tano Red’ (V. labrusca×V. vinifera) and ‘Ruby Seedless’ (V. vinifera). A total of 805 polymorphic HRM markers were developed, of which 363 were mapped onto the genetic linkage map of grape, with a total length of 1,453.5 cM consisting of 19 chromosomes. This SNP-based genetic linkage map and HRM markers can be used for QTL identification and marker development for important fruit traits of grape.

In this study, phenotypic distribution of 15 major fruit quality traits were analyzed using 252 progenies derived from a cross between ‘Tano Red’ (seed) and ‘Ruby Seedless’ (seedless), to obtain basic data for improving the breeding efficiency of grapevine cultivars. Berry skin color was dark red-violet in 46.4% of the progenies, which is the color of ‘Tano Red’ and ‘Ruby Seedless’, and berry shape was elliptic in 48.4%. Most of the progenies were very juicy with soft flesh, and closely related to the characteristics of ‘Tano Red’. Seeds were well developed in 67.1% of the progenies, rudimentary in 30.1%, and 2.8% were seedless, with seed weight being less than 0.15 g in 84.9% of the progenies. Among the 15 fruit quality traits assessed, bunch density, ease of berry detachment from pedicel, berry weight, berry seed number, berry longitudinal diameter, berry transverse diameter, berry soluble solids, and berry acidity showed normal distributions. Heritability of berry weight, berry longitudinal diameter, berry transverse diameter, berry soluble solids, and berry acidity was 0.89, 0.82, 0.78, 0.86, and 0.93, respectively. Berry weight was positively correlated with seed weight (r = 0.486^**), presence of seeds (r = 0.483^**), and seed number (r = 0.211^**). Seed weight significantly increased with presence of seeds (r = 0.607^**) and seed number (r = 0.725^**). In addition, presence of seeds was positively correlated with seed number (r = 0.319^**). These results could be useful for the identification of quantitative trait loci associated with fruit quality to assist in grapevine breeding.

'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.