
Soybean [
Soybean [
It is generally known that distribution of the wild soybean (
Korea also has a significantly long history of domestication and cultivation of soybean, which is comparable to that of China and dates back to the ancient Chulmun period (8000-1500 BC). A recent archeological study shows that charred soybean seeds discovered in ‘Pyeonggeodong’ around the Nam River valley are as old as 4840-4650 years (Lee
Soybean is cultivated in enormous area of arable land worldwide, which accounts for 90.2 million ha, resulting in a total production of about 276 million ton (MT) in 2013 (FAO 2013). Among major producing countries, the USA is the top producer (28.2% and 32.2%), by both area and production, followed by Brazil (23.7% and 27.5%), Argentina (18.5% and 21.2%) and China (9.7% and 7.0%), respectively (Soytech Inc. 2007). In comparison to the total production of the world, Korea produced relatively small amount of soybean (0.16MT) in 2013 (FAO 2013).
Presumably, the most prominent purposes for soybean cultivation should be its high contents of protein and oil, which make up approximately 40% and 20%, respectively. In the Western world of North America and Europe, soybean is mainly regarded as oil crop or protein source for animal feed. In other countries of the Eastern World, this crop is consumed mainly by human in various forms of foods, such as bean curd (tofu), soy milk, sprout, soy paste/sauce. Soybean also has a diverse array of utilities in industry and has been used for the production of lubricants, toner ink, cosmetics and for many other purposes. In more recent years, this crop is increasingly drawing interest of scientists as a useful biofuel source.
Although soybean production in Korea has gradually decreased during the past 40 years, its importance as a major crop has not diminished probably because soybean has a long history of cultivation associated intimately with traditional food culture of Korea. Recent completion of soybean whole genome sequencing (Schmutz
According to a recent archeological study, it has been known that the cultivation and domestication of soybean in Korea was evidenced back in ancient era of the Chulmun period, which was approximately 4000 year ago. In spite of such a long history of cultivation, a memorable moment towards the development of cultivation methods and systematic crop improvement initiated officially with the first cultivar ‘Jangdanbaekmok’, which was derived from landrace through pure line selection breeding, and was recommended for farmers to grow and cultivated nationwide until the first hybridization-bred variety ‘Kwangkyo’ was developed. This cultivar was grown and used for soy sauce/paste and beared medium-to-large seeds. Before cross breeding technology was actively used, most varieties were developed by selecting pure lines or directly introduced from other countries such as the USA and Japan. At the early developmental stage of new cultivars, breeding purposes mainly focused on improvement of qualities associated with yield and easiness in cultivation. In 1960s, 6 Korean landraces (‘Haman’, ‘Chungbukbaek’, ‘Keumgangdaelip’, ‘Buseok’, ‘Iksan’, including ‘Jangdanbaekmok’) and ‘Yukwoo3’, which was introduced from Japan, were released for the purpose of cultivation. Thereafter, two cultivars, ‘Hill’ and ‘Shelby’, were introduced from the USA in 1967 and 1968, respectively. In the next year, ‘Kwangkyo’, which was the first variety developed by hybridization-based breeding, was released to farmers. ‘Kwangkyo’ was developed using ‘Jangdanbaekmok’ as maternal line and ‘Yukwoo3’ as paternal line, and thereafter was frequently employed to develop many other cross-bred varieties. In 1970s, both Korea-bred and introduced varieties were supplied for the cultivation in parallel manner, and breeding came to further focusing on development of cultivars adaptive to mechanized farming because of a social phenomenon of the rural exodus. Influenced by such change in social environment, ‘Muhankong’ (Hong
It appears that pedigree analyses for Korean soybean varieties were intermittently made by a limited number of breeding researchers. Jong
In an attempt to reconstruct the Korean soybean pedigree, previous analyses done by Jong
The data reveals that a total of 178 soybean varieties have currently been registered at the two national institutes. Fig. 1 demonstrates their basic information for all these varieties according to their uses, breeding methods and timelines at which they were developed. It is apparent that soybean varieties for soy sauce and tofu predominate in Korea while ones for vegetables are relatively minor (Fig. 1A). Of 178 registered accessions, the majority of varieties (155, 87.1%) have been developed by hybridization-based breeding methods (Fig. 1B). Since the first hybridization-bred Korean variety ‘Kwangkyo’ was released, seven more varieties were added in 1970s as recommended cultivars. These include ‘Bong-Eui’, ‘Kang-lim’, ‘Baegcheon’ (Choi
Starting from ‘Jangdanbaekmok’ the first cultivar registered in 1913 till now, we attempted to reconstruct a fully integrated pedigree including all the 178 varieties currently recorded in Korea. Thereby, it has ended up with a total of four pedigrees (Fig. 2). Of 178 registered cultivars, 10 varieties (5.6%) could not be integrated into any pedigrees because they lacked information on which they were employed as elite parental lines to cross. They include ‘Chungbukbaek’ (1948), ‘Iksan’ (1948), ‘Haman’ (1960), ‘Keumgangsorip’ (1960), ‘Buseok’ (1948), ‘Heugcheongkong’ (1999), ‘Galmikong’ (1999), which were derived from Korean landraces, and introduced accessions, such as ‘Shelby’ (1967), ‘Eundaedu’ (1970), ‘Hwasongputkong’ (1993). Of 168 varieties included in the pedigree network, 136 varieties (76.4%) and 32 varieties were involved in one or two pedigrees, respectively.
As seen in the Pedigree I (Fig. 2A), ‘Kwangkyo’, ‘Hwangkeumkong’, ‘Paldalkong’ and ‘Sinpaldalkong 2’ (Kim
‘Kwangkyo’ was intensively employed as parental line to breed other useful progenitors such as ‘Hwangkeumkong’ (1980), ‘Milyangkong’ (1983), ‘Baegunkong’ (1984), ‘Saealkong’ (Shin
‘Sinpaldalkong 2’, which occupies a significant part of the Pedigree I and is strongly resistant to soybean mosaic viruses, was developed by employing ‘Togyu’ as maternal line and ‘Paldal’-derived breeding line ‘SS79186’ as paternal line. It bears medium-sized seeds and is known as tolerant or resistant to many diseases such as soybean mosaic virus, purpura, downy mildew and necrosis. Thereafter, ‘Sinpaldal2’ was used as breeding parent to develop following varieties; ‘Daepung’ (Park
Pedigree II (Fig. 2B) shows that ‘Baegunkong’, ‘Jangyeobkong’ and ‘Keunolkong’ take central positions as basic parental lines, which comprises three pre-existing clusters 3 (‘Dongpuk-tae’ group), 5 (‘Jangyeob’ group) and 7 (‘Kwangkyo’ group) (Jong
Pedigree III was constructed by extending previous cluster 4 (‘Pangsa’ group) and cluster 6 (‘Danyeobkong’, Hill group) (Jong
Pedigree IV is a kind of orphan ones, because most varieties lack information available for breeding pathways (Fig. 2D). Actually it consist of three small pedigrees containing 6 introduced variety, 11 Korea-bred varieties, 12 breeding lines and 3 landraces. Except for ‘Jungmo3004’ and ‘jungmo2010ho’, other major varieties in the pedigree including ‘Ilpumgeomjeong2’ (2005), ‘Heugmi’ (2006), ‘Socheong’ (Baek
Pedigree for crops is truly essential to effectively manage breeding programs, and may provide breeders with pivotal information for selection of parental lines and design of crossing strategies. In this review, we intended not only to integrate all available information on currently registered Korean soybean varieties, but also to reconstruct an entire breadth of their pedigree. Such an attempt has resulted in a total of four pedigrees (Fig. 2), which is a lot more extended compared to the latest pedigree analyses (Jong
Soybean has long been cultivated for major source of protein and oil in the human history. In more recent years, it is becoming more important as a source of well-being for mankind in terms of medicinal use as well as food. Additionally its unique biological property of symbiotic nitrogen fixation is beneficial to enrich the soil, thereby protecting environment and enabling sustainable agricultural practice. Another benefit of soybean on human health has been widely explored during the last two decades (Ali 2010). Thanks to its wide range of beneficial aspects, it is likely that the cultivation and breeding of soybean will be increasingly promoted in the future.
In recent years, we are facing a transition stage in breeding technologies, from conventional (phenotype-first) breeding to genomics-driven (genomic information-based design) molecular breeding. Genome-wide understanding and its application to breeding are being significantly facilitated by cutting edge NGS technologies in conjunction with high throughput bioinformatic analyses. Such situation may lead to opening of a new phase of molecular breeding in the near future, so called ‘breeding-by-design’. In parallel with technological advancement, well-organized crop resources and information will become more and more important. In summary, as crop pedigree is one of the most important information for breeding, we anticipate that the pedigree rebuilt in this study will play a constructive role in breeding a diverse array of new soybean varieties with desirable traits when it is synergized with new findings and knowledge driven by ever advancing technologies and ‘omics’-based bioinformatic tools.
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