Korean markets have recently shown a strong demand for grapes with large-sized seedless fruits (Heo and Park, 2015), and several attempts to introduce world-class seedless grape cultivars, such as Thompson Seedless and Crimson Seedless, have been made. However, they are not adapted to Korea’s climate and are not recommended for commercial planting in Korea. Therefore, seedless grapes have been produced in Korea by applying gibberellins (GA3) to tetraploid seeded grape cultivars such as Kyoho. Producing seedless fruits from seeded grape cultivars generally requires two GA3 applications and cluster thinning treatments before and after blooming (Lee et al., 2013), which increase the production costs. Furthermore, fruit characteristics can be differentially expressed depending on what time the GA3 applications occur (Abu-Zahra, 2013), and it can be difficult for farmers to produce seedless grapes with uniform fruit characteristics. Therefore, the development of seedless grape varieties that can be easily produced has been regarded as an important aim of the grape breeding program in Korea.
Triploid grapes have low pollen fertility due to their unbalanced chromosome sets (Yamashita et al., 1998), and previous research has suggested that it may be possible to produce large-sized seedless fruits using one GA3 application (Heo and Park, 2016). However, it has been reported that many triploid grape cultivars require two GA3 applications to produce commercially valuable fruits (Wakana et al., 2008). Therefore, evaluating the influence of one GA3 application on fruit quality and size in a large number of triploid progenies derived from various crosses is critical when attempting to breed labor-saving triploid grapes. We made several interploid crosses using 12 diploid and seven tetraploid grape cultivars, and obtained a total of 270 triploid seedlings (Heo et al., 2007). After various screening tests, we finally developed a labor-saving triploid seedless grape called ‘Sujeong’.
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Heo, J.Y., Park, K.S., Yun, H.K. & Park, S.M. 2007 Degree of abortion and germination percentage in seeds derived from interploid crosses between diploid and tetraploid grape cultivars Hort. Environ. Biotechnol. 48 115 121
Heo, J.Y. & Park, S.M. 2016 Variation in fruit characteristics of 3x progenies obtained from a cross between 4x and 2x grape cultivars Korean J. Hort. Sci. Technol. 34 761 770
Lee, B.H.N., Kwon, Y.H., Park, Y.S. & Park, H.S. 2013 Effect of GA3 and thidiazuron on seedlessness and fruit quality of ‘Kyoho’ grapes Korean J. Hort. Sci. Technol. 31 135 140
Wakana, A., Fukudome, I., Hanada, N., Hiramatsu, M., Sakai, K. & Kajiwara, K. 2008 ‘Bei–kei’, a new triploid seedless grape cultivar derived from a ‘Muscat Bailey A’ × ‘Kyoho’ cross J. Fac. Agr. Kyushu Univ. 53 423 427