What are the main strawberry varieties bred in South Korea?

According to statistics from the Food and Agriculture Organization of the United Nations, in 2019 South Korea's total strawberry planting area was 6212 hm2, total production was 193,000 t, and export volume was 5259 t; South Korea's strawberry industry scale ranked 3rd in Asia and 7th in the world. Before 2000, most of the strawberry varieties grown in South Korea were Japanese varieties such as Toyonoka and Akihime. According to a report by Japan's agricultural news, more than 90% of South Korean strawberry varieties were bred using unauthorized Japanese varieties as parents or original parents. Japanese varieties such as Tochiotome, Red Pearl, and Akihime were introduced into South Korea without permission and used as parents to breed Seolhyang, Maehyang, and others. Japan's Ministry of Agriculture, Forestry and Fisheries assessed that from 2012 to 2017, infringement activities involving South Korean strawberries alone in export markets caused Japan losses of about 22 billion yen (about 1.3 billion yuan). Since 2000, South Korea has successively bred excellent varieties and promoted them; Seolhyang became South Korea's largest main planting variety, and in 2019 the penetration rate of South Korean domestic varieties was above 95%. In 2019, South Korea's strawberry export value was 52.6 million US dollars, three times that of 2009. South Korean strawberries ranked among the top in market share in Singapore, Malaysia, Hong Kong, China, Vietnam, Thailand, and other markets, seizing Japan's strawberry export position. According to international norms, plant variety rights must be applied for within 4 years after a new variety is marketed. South Korea only began accepting applications for strawberry new variety protection rights in 2012, so strictly speaking there was no legal obstacle in South Korea to using earlier-bred varieties as parents for breeding new varieties. South Korean strawberry breeding achieved remarkable results over 10 years, rapidly catching up with Japan in various aspects. This has important reference significance for the breeding of new strawberry varieties and the development of the strawberry industry in our country. The main strawberry varieties bred in South Korea are introduced as follows.

# Short-day varieties #

Seolhyang

Bred in 2005 by the Nonsan Strawberry Experiment Station of the Chungnam Agricultural Research and Extension Services. It is a large-fruited, high-yielding variety, easy to grow, with good flavor, but low firmness. The cross combination is Akihime x Red Pearl (Lubao). The fruit shape is short conical, with an average single fruit weight of 21 g. Flower bud differentiation is slower than Maehyang and Akihime, and slightly faster than Red Pearl. It is suitable for forcing culture; if planted in early to mid-September, it can be harvested in late November. Seedling raising is relatively easy. Its resistance to powdery mildew is higher than that of Akihime, making it suitable for green production. It is South Korea's largest main planting variety. Seolhyang's flesh is firmer than Akihime's, with a good chewy texture, fewer malformed and sunken fruits, and uniform fruit size. The soluble solids content is 10%-11%, acidity is low in winter, and the juice is abundant and refreshing. The No. 1 fruit of the first inflorescence is a large fruit of more than 60 g and may develop hollow fruit. During high-temperature periods, attention should be paid to controlling storage and transport. In some regions it is used for export during low-temperature periods.

Maehyang

Bred in 2001 by the Nonsan Strawberry Experiment Station of the Chungnam Agricultural Research and Extension Services. It has a relatively high rate of malformed fruit during low-temperature periods, but has good flavor and is tolerant of storage and transport, so it is South Korea's main strawberry export variety. The cross combination is Tochiotome x Akihime. The fruit shape is a long conical shape with narrow shoulders, with an average single fruit weight of 15 g. Flower bud differentiation is earlier than Red Pearl, and it is suitable for forcing culture; if planted in early September, it can be harvested in late November. It has poor resistance to pests and diseases, so attention should be paid to controlling anthracnose during the seedling stage and powdery mildew and gray mold during the harvest period. It is sensitive to environmental influences; under high temperature or dryness, fruiting may temporarily stop. During low-temperature periods (5°C), the incidence of malformed fruit is high, and pollen is less abundant than in other varieties. It is worth noting that during low-temperature storage, Maehyang fruit sugar content, firmness, and coloring ratio all increase, making it very suitable for export.

Kuemsil

Bred in 2016 by the Gyeongnam Agricultural Research and Extension Services. It is a medium-to-large-fruited variety used for forcing culture, with high sugar content, high firmness, and good flavor (with a peach aroma). The cross combination is Maehyang x Seolhyang. The fruit shape is short conical, with an average single fruit weight of 20.4 g. Flower bud differentiation is 1 week earlier than Maehyang. The number of flower clusters is about 15, and growth vigor is strong like Seolhyang, but it is not a high-yielding variety. It is suitable for forcing culture; if planted in early September, it can be harvested in early November. Because of flowering characteristics such as short inflorescences and low pollen viability in winter, the possibility of malformed fruit is high, so planting in southern South Korea is more favorable. The fruit shape is conical in spring and autumn, and may become shorter if low temperatures continue in winter. Fruit harvested at less than 60% coloring does not continue to color afterward (unlike Maehyang), and it is being tested for export.

Arihyang

Bred in 2017 by the National Institute of Horticultural and Herbal Science under South Korea's Rural Development Administration. It is a large-fruited variety used for forcing culture, with high firmness and uniform fruit size. The cross combination is Tochiotome x Seolhyang, with an average single fruit weight of 24 g. Flower bud differentiation is 2-3 d earlier than Seolhyang, and the trait of continuous flowering in the early stage is excellent. The main inflorescence has an average of 10.5 flowers, which can reduce the labor of flower and fruit thinning. It is suitable for forcing culture; if planted in mid-September, it sets fruit around December. Its resistance to powdery mildew, gray mold, and Fusarium wilt is weaker than that of Seolhyang, but its resistance to Phytophthora blight is slightly stronger. The proportion of malformed fruit in the No. 1 fruit of each inflorescence is high, and the proportion of malformed fruit increases at low temperatures. Fruit quality is good, but while the fruit colors quickly, it should be noted that sugar content still rises at the fully ripe stage (more than 90% coloring), and when overripe, the peel turns black-red. It is being tested for export in Chungnam, Hongseong, Yeonggye, and other places.

Ssanta

Bred in 2006 by the Seongju Melon and Fruit Vegetable Research Institute of the Gyeongbuk Agricultural Research and Extension Services. It is a large-fruited variety used for forcing culture, with good flavor, high firmness, and tolerance of storage and transport. The cross combination is Maehyang x Seolhyang, with an average single fruit weight of 23 g. When planted in mid-September (greenhouse cultivation), the harvest period is about 1 week earlier than Seolhyang. Because of its high early yield and quality, it is suitable for increasing growers' income and has already been used for export.

Berrystar

Bred in 2010 by the Seongju Melon and Fruit Vegetable Research Institute of the Gyeongbuk Agricultural Research and Extension Services. It is a medium-to-large-fruited variety used for forcing culture, with high firmness and no occurrence of hollow fruit. The cross combination is Ssanta x 07-S-28, with an average single fruit weight of 21 g. It is suitable for forcing culture; if planted in early September (greenhouse cultivation), it is harvested from December to January of the following year. It has resistance to both anthracnose and powdery mildew, is easy to manage in cultivation, and has been used for export.

Jukhyang

Bred in 2012 by the Damyang County Agricultural Technology Center of Jeonnam. It is a semi-forcing medium-to-large-fruited variety with high sugar content and firmness and few malformed fruits. The cross combination is Maehyang x Red Pearl, with an average single fruit weight of 17.2 g. It has strong resistance to powdery mildew, strong runner production and growth vigor, good continuous fruiting performance, easy flower and leaf removal operations, and easy cultivation management. It has already been used for export.

Kingsberry

Bred in 2016 by the Nonsan Strawberry Experiment Station of the Chungnam Agricultural Research and Extension Services. It is an extra-large-fruited variety used for forcing culture, with good flavor, abundant juice, and a relatively faint peach aroma. The cross combination is Akihime x NS001309, with an average single fruit weight of 30 g. Plant in early to mid-September; to promote coloring during low-temperature periods, manage the nighttime temperature 2-3°C lower than for Seolhyang. Its resistance to powdery mildew is weak, and its resistance to anthracnose is moderate. It is partly used for export.

# Day-neutral varieties #

Gangha

Bred in 2008 by the South Korea Highland Agriculture Research Institute. It has strong continuous flowering ability and adapts to high-temperature, long-day environments. It was crossed in 2004, with parents Samahberi x Elan. Regional trials were conducted in 2006-2007. The plant growth vigor is medium, the fruit is oval, the average single fruit weight is 12.0 g, the fruit is red, the soluble solids content is 11.7%, the sugar content is high, the acidity is low, the sugar-to-acid ratio is 18.9, the firmness is relatively low, and it is resistant to powdery mildew, anthracnose, and Fusarium wilt.

Yeolha

Bred in 2013 by the South Korea Highland Agriculture Research Institute. It has strong continuous flowering ability and adapts to high-temperature, long-day environments. It was crossed in 2008, with parents Goha x Elsinyo. Regional trials were conducted in 2010-2012. The plant growth vigor is strong, the fruit is conical, the average single fruit weight is 12.1 g, the fruit is pink, the soluble solids content is 8.6%, the fruit firmness is high at 37.7 g/mm2, the average yield is 117% higher than Flamenco, and it is resistant to Fusarium wilt.

Goseul

Bred in 2016 by the South Korea Highland Agriculture Research Institute. It has strong continuous flowering ability and adapts to high-temperature, long-day environments. It was crossed in 2012, with parents Albion x Seolhyang. Regional trials were conducted in 2015-2016. The plant growth vigor is medium, the leaves are round, the number of inflorescences is 1.5 times higher than Red Pearl, the average single fruit weight is 25.9 g, the soluble solids content is 12.9%, the sugar content is high, the sugar-to-acid ratio is 18.9, and the fruit firmness is high at 31.6 g/mm2.

Jangha

Bred in 2014 by the South Korea Highland Agriculture Research Institute. It has strong continuous flowering ability and adapts to high-temperature, long-day environments. It was crossed in 2008, with parents Goha x Elsinore. It was reselected in 2010-2012, and regional trials were conducted in 2013-2014. The plant growth vigor is medium, the fruit is conical, the average single fruit weight is 11.7 g, the soluble solids content is 9.6%, and the fruit firmness is high at 38.9 g/mm2.

# Seed-propagated varieties #

Seeberry, bred by the South Korea Protected Horticulture Experiment Station, is an F1 hybrid variety of short-day strawberry. In 2013 it passed review by the Crop New Variety Selection Committee of South Korea's Rural Development Administration and was named Seeberry. It is South Korea's first seed-propagated variety. The male parent is the high-firmness parent Wongyo 3115, and the female parent is the high-yielding, well-shaped parent Wongyo 3116, which are multiple selfed progenies of Benihoppe and Toyonoka, respectively. Seeberry has 12-15 flowers per inflorescence, strong plant growth vigor, conical fruit, average single fruit weight of 15-16 g, bright red color, good taste, soluble solids content of 9.7%, titratable acidity of 0.6%, and firmness of 19.0 g/mm2, higher than Akihime (13.1 g/mm2). It is resistant to anthracnose but susceptible to powdery mildew, aphids, and red spider mites. Seeberry is a seed-propagated variety, and the seedling-raising period may affect the quality and yield of strawberry seedlings. Therefore, after sowing, at least 120 d are needed to grow seedlings, that is, the crown diameter must be above 10 mm. Only by using such excellent seedlings can the characteristics of the Seeberry variety be expressed. According to South Korea's climatic characteristics, the best sowing period is late February to early March. Seeds collected in the same year have a germination rate above 90%, but long-term storage tends to reduce the germination rate, so refrigeration is necessary to maintain the germination rate to the greatest extent. When raising seedlings by sowing seeds, some plants may flower when growth vigor is insufficient; at this time, flowers should be removed to prevent weakening. In spring, problems such as a slight decrease in fruit firmness and lighter fruit color occur, so shading treatment is needed to reduce the environmental temperature during fruit development.

Source: This article is excerpted and edited from "Current Status of Strawberry Breeding in South Korea and Introduction of New Varieties" (Sun Jian, Li Shuangtao, Chang Linlin, Dong Jing, Zhong Chuanfei, Sun Rui, Gao Yongshun, Liu Huabo, Wang Guixia, Zhang Yuntao) in the 8th issue of China Fruits in 2021.