
Rice (
Rice breeding and varietal improvement in Korea has transformed with farmers’ requests and socio-environmental circumstances. However, there are few reports on the pedigree (Song
In Korea, rice research is conducted mainly by the NICS under the RDA. More than 40 rice varieties were developed by the NICS before 1979; however, some agronomic data were not openly accessible. Thus, we analyzed 325 Korean rice varieties released after 1980 in this study (Table 1). Agronomic and parental information were collected from the “New cultivar” section of the Korean Journal of Plant Breeding (http://www.breeding.or.kr) and Nongsaro (https://www.nongsaro.go.kr) operated by the RDA. Data descriptions, such as breeding purpose, followed by technical questionnaires were submitted to the Korean Seed and Variety Service (KSVS) when request testing. Data matrices were constructed using Microsoft Excel for detailed analyses of the parental information and agronomic traits of each variety.
Table 1 . List of rice varieties developed by Rural Development Administration in Korea from 1980 to 2017.
Year | No. of Variety | Name of variety |
---|---|---|
1980’s | 33 | Milyang42, Cheongcheong, Dongjin, Sujeong, Gaya, Samgang, Sobaek, Sinseonchal, Yeongpung, Gwangmyeong, Weonpung, Odea, Chilseong, Daecheong, Yeongdeok, Yeongsan, Yongmun, Unbong, Jangsung, Hwaseong, Namyeong, Yongju, Palgong, Hwacheong, Geumo, Donghae, Sangnambat, Tamjin, Hwajin, Gyehwa, Jangan, Jinmi, Cheongmyeong |
1990’s | 85 | Namwon, Seoan, Obong, Jinbuchal, Sinunbong, Anjung, Mangeom, Jinbu, Jinbuol, Gancheok, Yeongnam, Hwayeong, Daeya, Sangju, Hwaseonchal, Dunae, Hwajung, Daerib1, Joryeong, Nongan, Shinkeumo, Hyangmi1, Daean, Sambaek, Unjang, Juan, Geumnam, Sangsan, Hwanam, Samcheon, Ansan, Hyangnam, Dasan, Yangjo, Seojin, Ilpum, Geumo1, Namcheon, Naepung, Daejin, Dongan, Hwasin, Junghwa, Hyangmi2, Aranghyangchal, Yeonghae, Hwadong, Sangjuchal, Guru, Nampyeong, Daesan, Hwasam, Geumo2, Namgang, Heugnam, Sangmi, Sura, Inweol, Hoan, Dongjinchal, Mihyang, Gwangan, Anda, Undoo, Weonhwang, Manan, Hwabong, Nongho, Heugjinju, Hwamyeong, Seolhyangchal, Saechucheong, Areum, Munjang, Sampyeong, Sobi, Sujin, Ilmi, Jungan, Jinpum, Sindongjin, Jungsan, Goami, Manpung, Anseong |
2000’s | 115 | Haepyeong, Jeogjinju, Jinbong, Taebong, Hwaan, Junam, Hojin, Heughyang, Saegyehwa, Dongjin1, Manweol, Manchu, Saesangju, Seokjeong, Yeongan, Jongnam, Baekjinju, Seolgaeng, Manmi, Geuman, Namil, Daepyeong, Manho, Samdeok, Seogan, Taeseong, Hanareum, Goami2, Hopyeong, Samgwang, Sangok, Seopyeong, Joan, Pyeongan, Hwarang, Heugkwang, Josaengheugchal, Pungmi, Goun, Gopum, Unkwang, Cheongho, Hanmaeum, Boseogchal, Heapyeongchal, Geumo3, Manna, Baegjinju1, Seoan1, Sinunbong1, Odae1, Juan1, Pungmi1, Hanam, Onuri, Hwasin1, Dongjin2, Keunun, Nunbora, Malgmi, Junamjosaeng, Cheonga, Hwangeumbora, Gangbaek, Dami, Donghaejinmi, Keunseom, Hanganchal1, Haechanmulgyeol, Hongjinju, Hwangeunuri, Cheongdam, Hopum, Sandeoljinmi, Nogyang, Pyeongwon, Dasan1, Handeol, Goami3, Baekseolchal, Borami, Saenuri, Unmi, Jokwang, Cheongam, Hwanggeumnodeul, Heugseol, Danmi, Chilbo, Boseok, Joami, Dacheong, Boseogheugchal, Jinsumi, Haiami, Haeoreumi, Deurechan, Baekogchal, Jinbaek, Yeonghojinmi, Jinbo, Cheongnam, Goami4, Dasan2, Manjong, Mogwoo, Migwang, Boranchan, Seomyeong, Saegaejinmi, Joun, Hanseol, Geumyoung, Honong, Cheonghaejinmi |
2010’s | 92 | Geonganghongmi, Dongbo, Weolbaek, Mipum, Gangchan, Seolbaek, Suryeojinmi, Suan, Jopyeong, Cheongbaekhal, Chinong, Hanareum2, Sinbaek, Jeogjinjuchal, Mogyang, Anmi, Geonyangmi, Jungsaenggold, Daebo, Saeilmi, Seonhyangheukmi, Sodami, Sugwang, Joeunheukmi, Huimangchan, Saegoami, Seolemi, Geonyang2, Hwawang, Hyunpum, Dabo, Saeodea Subo, Jinseolchal, Cheongun, Cheongcheongjinmi, Chindeul, Heugsujeong, Sanhomi, Mimyeon, Palbangmi, Ondami, Dodam, Misomi, Sinbo, Asemi, Jinok, Haepum, Bodrami, Haedam, Baegilmi, Manbaek, Saesin, Yeongbo, Unilchal, Nunkeonheugchal, Seonpum, Anbaek, Nokwoo, Asemi1, Saemimyeon, Danpyeong, Hanareumchal, Boramchal, Yeongwoo, Jopum, Jinhan, Cheongpum, Cheonghyangheugmi, Heugjinmi, Joil, Samgwang1, Unbaegchal, Hanareum3, Miho, Jingwang, Sangbo, Sangsan, Shinpyeong, Hangaru, Hanareum4, Hyangcheola, Sinjinbaek, Aromi, Misiru, Miwoo, Saeilpum, Saechilbo, Yeachan, Cheongwoo, Keunpum, Haedeul |
Sum | 325 | - |
The NICS conducts most rice research and varietal improvements in Korea; 325 varieties have been developed since 1980. The number of varieties released per year increased continuously from 1980 to 2006, and then gradually declined (Fig. 1). The average number of varieties released in the 1980s was 3.3 variety/year, which increased to 8.5/year in the 1990s, 11.5/year in the 2000s, and then decreased to 9.2/year in the 2010s. The ideal number of yearly variety releases remains controversial. Despite the number of varieties cataloged yearly, KSVS currently produces 24 cultivars of farmer’s seed. Among 325 varieties, 232 (71.4%) were categorized as good quality for eating in rice bowls, 27 (8.3%) were high yielding, and 21 varieties (6.5%) were for waxy rice (Fig. 2). High-yielding varieties were dominant in the 1980s (36.4%) but decreased dramatically after the 1990s (7.1%). The proportion of high quality for eating varieties gradually declined as they were replaced by varieties with other purposes in the 2000s. The percentage of special-purpose varieties such as food processing, colored, fragrant, and forages almost doubled from 11.8% in the 1990s to 22.8% in the 2010s. The main reasons for the diversification of varieties were the reduction of domestic consumption per capita and changes in people’s preference trends. Colored rice then advanced to colored waxy (Song
Germplasm is an important factor for maintaining genetic diversity and hybrid vigor in plant breeding. The parental origins of 325 Korean varieties show that 66% of the varieties originate from two Korean-bred stocks and 26% of the varieties have at least one parent from Japanese stocks (Fig. 3). However, only 8% of genetic stocks were used as cross parents from other countries. Genetic stocks from the Philippines were most frequently used in the 1980s as hybrid parents for high-yielding rice. Chinese germplasms were used after the 1990s, especially in parental sources for colored rice. Decadal shifts in the origins of hybridization parent stocks show that the proportion of Korean varieties increased from 45.5% in the 1980s to 72.8% in the 2010s. Japanese genetic stocks decreased from 39.4% to 17.4% during the same period. The most frequently used Japanese varieties were “Koshihikari,” “Hitomebore,” and “Kinuhikari,” which improved the eating quality. Japanese varieties were also used to breed waxy rice varieties.
Our analysis of the crossing type revealed that the single-cross hybrid method was dominant in rice breeding programs. Single-cross varieties accounted for 79% of hybrids, and 16% were bred by double-crossing (Fig. 4). The most frequently used parental combinations for hybridization were cultivar × elite line (33%) and cultivar × entry (24%) (Fig. 5). Varieties bred from cultivar × cultivar crosses were relatively low at 19%. This suggests that higher proportions of entry and elite lines have been used extensively as cross parents by breeders.
The main shifts in agronomic traits, including culm and panicle length, seeds per panicle, flowering date, and yields of the high eating quality varieties were analyzed (Fig. 6). Among 232 varieties, culm length was continuously reduced from 79.1 cm to 74.8 cm from the 1980s to the 2010s. Culm length decreased significantly from 79.1 cm in the 1980s to 75.5 cm in the 1990s. Panicle length increased slightly from 19.7 cm in the 1980s to 20.7 cm in the 2010s. The number of panicles per hill decreased from 16.1 in the 1980s to 13.9 in the 2010s. The number of seeds per panicle increased from 91.1 to 103.3 during the same period. “Nongan” (Nongsaro, 2019) has the highest seed set per panicle among the 193 varieties with seeds. There were minor changes in the ripening ratio and 1,000-grain weight over the decades. The mean flowering date showed little variation, ranging from the 8th to the 11th of August. Milled rice yields have increased dramatically since the 1980s. The average yield increased from 491 kg/10a in the 1980s to 555 kg/10a in the 2010s. The increased number of seeds per panicle and reduced culm length are likely direct/indirect factors affecting the increase in yield. Li
The major rice diseases in Korea are blast (
Table 2 . Number of rice varieties that are disease and insect resistant.
Year | Total | 1980-1989 | 1991-2000 | 2001-2010 | 2011- |
---|---|---|---|---|---|
No. of varieties | 325 (100) | 33 (100) | 85 (100) | 115 (100) | 92 (100) |
None | 56 (17.2) | 4 (12.1) | 11 (12.9) | 30 (26.1) | 11 (12.0) |
BL | 48 (14.8) | 3 (9.1) | 18 (21.2) | 14 (12.2) | 13 (14.1) |
BLB | 9 (2.8) | - | 3 (3.5) | 5 (4.3) | 1 (1.1) |
RSV | 31 (9.5) | 3 (9.1) | 18 (21.2) | 5 (4.3) | 5 (5.4) |
BL + BLB | 19 (5.8) | - | 1 (1.2) | 13 (11.3) | 5 (5.4) |
BL + BLB + RSV | 45 (13.9) | 2 (6.1) | 12 (14.1) | 15 (13.0) | 16 (17.4) |
BL + BLB + RSV + DV | 7 (2.2) | - | 1 (1.2) | 4 (3.5) | 2 (2.2) |
BL + BLB + RSV + DV + RBSDV | 3 (0.9) | 3 (9.1) | - | - | - |
BL + BLB + RSV + DV + RBSDV + insect resist. | 3 (0.9) | 1 (3.0) | 1 (1.2) | 1 (0.9) | - |
Other combinations of resistance | 104 (32.0) | 17 (51.5) | 20 (23.5) | 28 (24.4) | 39 (42.4) |
BL: Rice blast, BLB: Bacterial leaf blight, RSV: Rice stripe virus, DV: Dwarf virus, RBSDV: Rice black-streaked dwarf virus.
Korean rice breeding shows dynamic changes according to social and economic demands over the last 40 years. The type of rice variety diversified from high eating quality rice to colored, aromatic, and processing types. Plant architecture and resistance to biotic stresses also transformed. Plant height was reduced to increase lodging resistance and the number of seeds per panicle increased continuously over the last four decades. As a consequence of extensive breeding efforts, milled rice yields increased by 13% from 491 kg/10a to 555 kg/10a. More than 80% of released varieties had resistance to single or multiple diseases and insects. However, varieties resistant to three major diseases, rice blast, bacterial leaf blight, and RSV, remained at 17.8%.
One of the potential risks in Korean rice breeding stems from the narrow pool of genetic diversity. Except for special-purpose varieties, many varieties use Korean origin germplasms as crossing parents. The limited genetic diversity has a negative influence on hybrid vigor and problems may arise in the future. The use of more Korean genetic stocks in crossing might be a double-edged sword for rice breeding. It might produce a unique Korean varietal group; however, it might also reduce the quality and genetic diversity of hybrid varieties. The genetic similarity of Korean rice has previously been calculated using phylogenetic analysis at the molecular level (Kwon
This work was supported by Korea Institute of Planning and Evaluation for Technology in Food, Agriculture, Forestry, and Fisheries (IPET) through Golden Seed Project (213009-05-4-WT311). The author would like to thank to Dr. Jun-Hyun Cho, National Institute of Crop Science, Rural Development Administration, providing pedigree information of rice varieties.
![]() |
![]() |