Developing a unique local variety that adapts well to the regional environment and consistently expresses its own characteristics provides a significant competitive advantage in the branded rice market. The aim of this study was to develop a Mid-Late Maturing Rice Cultivar with High Grain Quality adapted to the Chungnam Plain. ‘Daebang’ was developed by crossing ‘Haedamssal,’ a stable and high-yielding cultivar, with ‘Jinsumi,’ known for excellent grain appearance and eating quality, during the winter of 2013-2014. The F₁ was grown in summer 2014 to produce F₂ seeds, and promising lines were selected via the pedigree method. Under normal transplanting, ‘Daebang’ headed on August 19, about four days later than ‘Samkwang. ’ It had a culm length of 75 cm (9 cm shorter than ‘Samkwang’), indicating better lodging resistance. It had 84 spikelets per panicle, a 1,000-grain weight of 21.9 g, and a milled rice yield of 6.06 MT ha^-1, which was numerically higher but not significantly different from that of ‘Samkwang.’ The head rice ratio was 95.9%, with a protein content of 5.4%, and glossiness value 78.5, indicating a superior grain quality. ‘Daebang’ also showed similar resistance to blast and bacterial leaf blight as ‘Samkwang.’ Therefore, ‘Daebang’ is expected to serve as a promising mid-late maturing cultivar for producing premium-branded rice in the Chungnam region because of its high grain quality, lodging tolerance, and stable yield (Registration No. 9169).

In the present study, we conducted a detailed analysis of the genetic diversity and structural organization of 96 domestic Korean rice varieties (Oryza sativa L.) using 2,565 high-resolution TCS-based single nucleotide polymorphism (SNP) markers. Genetic structural variations were investigated using diversity indices, PCA, genetic similarity, and network analysis. Genetic diversity analysis revealed a significant expansion of the genetic foundation after the 1980s, marked by a sharp increase in the number of alleles (Na) from the 2000s. Despite this, high genetic homogeneity was maintained, with an average similarity of 77.7%. The observed 10% difference among same-cross varieties suggests that critical genetic variations are fixed by strong selection pressures for quality traits. Network analysis (85% similarity threshold) confirmed that the Korean rice breeding population followed a distinct core-periphery model (eight communities). The connected 84 varieties had a centrality range of 0.01 0.39. Core Variety Groups (e.g., ‘Junam’ and ‘Sindongjin’) exhibited the highest centrality (up to 0.39), indicating their extensive use as key breeding parents and their function as the central axis of the genetic network. Bridge Variety Groups (e.g., ‘Hwayeong’ and ‘Samkwang’) played an intermediary role linking clusters. Crucially, 12 ‘isolated accessions’ showed zero centrality (0.00), representing a genetic disconnect from the main pool. This quantitative network-based assessment provides essential fundamental data for breeders to select appropriate germplasms. Furthermore, the findings suggest that the current cultivar naming system, which inadequately reflects genetic relationships, requires reassessment, and that the establishment of
objective
management standards based on this research is warranted.

‘Amissal’ is a regionally specialized rice cultivar developed to strengthen the competitiveness of local rice and is characterized by its distinct long-grain japonica type. It was bred through a single backcross between ‘Boramchan’—a high-yielding japonica cultivar with excellent cultivation stability used as the recurrent parent—and ‘HR30198-AC33’ (DGS79), a breeding stock with extra-long and spindle-shaped grains used as the donor parent for japonica grain shape diversification. Population and pedigree breeding methods were used during the breeding process. During the selection stage, molecular marker-assisted selection targeting the major grain shape genes, GS3 and qSW5 was applied, enabling the identification of lines carrying the gs3-qSW5 allele combination associated with long grain shape. ‘Amissal’ was developed through yield trials, local adaptability tests, selection trials addressing regional needs, and on-farm research aimed at developing long-grain japonica rice for export. The heading date of ‘Amissal’ was August 17, two days later than that of ‘Nampyeong’. Compared to ‘Nampyeong’, ‘Amissal’ exhibited greater biomass due to longer culms, more spikelets per panicle but fewer panicles per hill, and a heavier 1,000-grain weight. It demonstrated strong resistance to bacterial blight (races K1, K2, and K3) but was susceptible to viral diseases and insect pests. In terms of yield, it outperformed ‘Nampyeong’. The average brown rice grain length was 6.14 mm, classifying it as long-grain type. The length-to-width ratio was 2.43, corresponding to a semi-spindle shape, which clearly distinguishes it from existing Korean japonica cultivars. While its milling recovery rate was similar to that of ‘Nampyeong’, a high proportion of broken rice due to its long grain shape resulted in a lower head rice. ‘Amissal’ had low protein content and provided the sticky and soft texture typical of japonica rice, with excellent scores in sensory evaluation tests. As a differentiated, regionally specialized rice cultivar featuring a long-grain japonica type and superior eating quality, ‘Amissal’ is expected to contribute to the advancement of the local rice industry, particularly through applications in rice export and the utilization of broken rice and rice straw (Registration No. 10167).

To improve resistance to planthoppers and viral diseases, a new rice cultivar named ‘Drimi9ho’ was established. The F₁ population, derived from a cross between ‘Cheongcheong’ and ‘Nagdong’, was subjected to anther culture. Subsequent generations were advanced in the field under high selection pressure for agronomic traits and disease resistance. Ultimately, the line ‘CNDH-AC63-2-2-2-1’ was selected through the pedigree method and was named ‘Drimi9ho’ after undergoing yield trials and local adaptability tests. ‘Drimi9ho’ has a heading date of August 13, which corresponds to 107 days after sowing, making it a mid-late maturing variety that heads 3 d later than ‘Cheongcheong’. The culm length of ‘Drimi9ho’ is 57.3 cm, which is 15 cm shorter than that of ‘Cheongcheong’. This reduced culm length contributes to improved tolerance to field lodging. In addition, ‘Drimi9ho’ exhibits acquired resistance to rice black-streaked dwarf virus through introgression from ‘Nagdong’. Compared to ‘Cheongcheong’, ‘Drimi9ho’ shows lower protein content and higher amylose content, which resulted in a higher score for cooked-rice palatability. ‘Drimi9ho’ shows improved milling performance compared to ‘Cheongcheong’. The 1,000-grain weight of ‘Drimi9ho’ is 22.12±0.8 g, which is heavier than that of ‘Cheongcheong’ (19.42±0.8 g). The milled rice yield of ‘Drimi9ho’ is 546.6±3.8 kg/10a, representing a 4.7% increase compared to ‘Cheongcheong’ (522.2±5.8 kg/10a). However, ‘Drimi9ho’ is resistant only to bacterial leaf blight race K₁; thus, timely disease management is required to control other races such as K₂, K₃, and K_3a (Registration No. 10610).

Early selection of grain quality traits in rice (Oryza sativa L.), is essential to improve the yield and quality of this staple crop. We analyzed four key traits—protein content, grain filling rate, height, and panicle length—in 85 Korean cultivars. Through whole- genome resequencing we identified 12,718,879 raw single nucleotide polymorphisms (SNPs); after PLINK-based quality control (bi-allelic selection, call rate≥0.90, MAF≥0.03), ~2.20 million high-quality SNPs remained for machine-learning (ML) pre-screening. To rank the features (without marker-level inference), we applied a liberal univariate PLINK case-control scan using the top and bottom 30% per trait. We also analyzed associations with a linear mixed model (GCTA v1.93.2, MLMA; fixed covariates: ecotype, PC1, PC2; random effect: GRM) to verify calibration under population structure; with n=85, no genome-wide significant hits were detected, and QQ-plots indicated adequate calibration (per-trait effective tests m≈1.54-1.57 million under stricter filters). The random forest feature importance prioritized 26, 51, 19, and 20 core SNPs for the four traits, respectively. Across the algorithms, the best models achieved mean accuracies of 81.8% (protein content), 81.0% (grain filling rate), 73.1% (height), and 94.0% (panicle length). All selected SNPs met the Fluidigm array design requirements, supporting its deployment as a compact, genotype-based panel for early selection and a practical step toward digital breeding in rice.

The intermediate breeding material ‘JJ625LG’ was developed to diversify the grain shape characteristics of Korean japonica rice cultivars. ‘JJ625LG’ was derived from a cross between ‘HR30198-AC33 (DGS79),’ a japonica breeding material with extra-long and spindle-shaped grains, and ‘Boramchan,’ a high-yielding japonica cultivar with excellent cultivation stability and medium-short and semi-round grains. By employing both bulk and pedigree breeding methods, strong selection pressure was applied to eliminate undesirable traits inherited from ‘DGS79,’ such as very late heading, long awns, and susceptibility to lodging. Consequently, elite lines with long spindle-shaped grains on a japonica background were selected. These lines subsequently underwent yield performance and local adaptability tests, during which their agronomic traits were comprehensively evaluated, leading to the final selection of ‘JJ625LG.’ The heading date of ‘JJ625LG’ was August 16th, three days later than that of ‘Nampyeong’. Its culm length was similar to ‘Nampyeong.’ ‘JJ625LG’ exhibited a higher number of spikelets per panicle, fewer panicles per plant, and heavier 1,000-grain weight than brown rice. Additionally, it showed strong resistance to bacterial blight (races K1, K2, and K3) but was susceptible to viral diseases and insect pests, indicating the need for further improvement in these areas. Its grain yield was comparable to that of ‘Nampyeong.’ With a brown rice grain length of 6.34 mm, ‘JJ625LG’ was classified as a long-grain type and had a grain length-to-width ratio of 2.64, reflecting a spindle-shaped morphology. It carried the GW2-gs3-qSW5 allele combination associated with grain shape, which is a genetic profile not found in existing Korean japonica cultivars. Although its milling recovery rate was similar to that of ‘Nampyeong,’ the presence of many broken rice due to its long grain shape resulted in a lower percentage of head rice. The eating quality of ‘JJ625LG’ was excellent, with its grains exhibiting the sticky and soft texture typical of japonica rice and receiving high scores in sensory evaluation. As the first intermediate breeding material in Korea with long and spindle-shaped grains in a japonica background, ‘JJ625LG’ is expected to contribute significantly to diversifying the traditionally narrow grain shape spectrum of Korean japonica rice cultivars (Registration No. 10166).

Bakanae disease, caused by various Fusarium species, poses a significant threat to global rice production, with its incidence increasing in major rice-producing regions. Currently, no rice varieties exhibit complete resistance to this disease. Enhancing resistance in rice cultivars could serve as a cost-effective and sustainable alternative to fungicide application. Developing resistant rice varieties may offer a practical solution to mitigate yield losses and reduce dependency on chemical treatments. ‘Jinokchal’ was derived from the cross between ‘Milyang299’, which harbors bakanae disease-resistant QTL qBK1. and ‘Baekokchal’ in 2014. A promising line, YR31624-5B-2, was then selected and designated as ‘Milyang366’ in 2019. The local adaptability test of ‘Milyang366’ was conducted at five locations from 2020 to 2022, and the cultivar was subsequently named ‘Jinokchal. ’ The heading date of ‘Jinokchal’ was August 13, classifying it as a medium-late maturing cultivar. The culm was 77 cm long and had 108 spikelets per panicle. The 1,000 grain-weight of brown rice is 22.7 g, which is heavier than that of ‘Sinseonchalbyeo’. This variety is resistant to blast, rice stripe virus, and bacterial blight, but susceptible to insect pests. The yield potential of ‘Jinokchal’ was approximately 497 kg/10a at the ordinary fertilizer level in the local adaptability test over three years. ‘Jinokchal’ is moderately resistant to bakanae disease and harbors the qBK1 gene derived from the tong-il type rice ‘Shingwang’ (Registration No. 8135).

The decrease in seed vigor and grain quality during storage has become an increasingly critical issue due to the extended storage periods resulting from declining rice consumption and climate change in Korea. Despite its importance, few studies have investigated rice seed aging in a large number of Korean rice cultivars. In this study, 53 japonica rice cultivars were evaluated for seed germination, vigor, and grain quality-related traits under accelerated-aging conditions. Seed germination rate was evaluated 7 days after imbibition, following accelerated aging treatments at 42℃ and 95% relative humidity for 8, 12, and 16 days. The average germination rates were 72.9% in the control (0 d), 71.7% after 8 days, 59.0% after 12 days, and 5.6% after 16 days of treatment. Grain quality-related traits, including texture and pasting properties, were also evaluated in rice subjected to the accelerated aging treatment. Adhesiveness and stickiness decreased, whereas hardness and toughness increased, as seed aging progressed. Cluster analysis based on germination rates after accelerated aging identified three distinct clusters, with cultivars in Cluster 3 maintaining a high germination rate of 70.6% even after 12 days of aging, showing clear differences from the other clusters. A principal component analysis (PCA) was conducted to investigate the relationship between germination rate and grain quality-related traits. The results showed that the germination rate and hardness tended to be negatively associated across all three clusters. These results suggested that cultivars with higher germination rates tend to maintain a softer cooked rice texture after aging. Our results provide insight into the relationship between seed aging and grain quality, highlighting elite cultivars that maintain both germination ability and grain quality during storage as valuable resources for breeding programs.

Genetically modified (GM) crops have been developed to enhance various agronomic traits and increase the production of functional compounds. In the present study, the major agronomic characteristics of protopanaxadiol (PPD)-enriched GM rice, which was developed by introducing dammarenediol-II synthase (PgDDS) and protopanaxadiol synthase (CYP716A47) genes from Panax ginseng into Oryza sativa cv. Dongjin, were evaluated. The stability of the introduced genes was confirmed using PCR and immunostrip tests, which showed consistent expression across multiple generations (T5-T7). Agronomic traits, including days to heading, culm length, panicle length, tiller number, and grain weight per plant, were compared between GM rice and its non-GM counterpart, Dongjin rice. No significant differences were observed for these traits, indicating that genetic modification did not affect the overall plant growth. However, seed morphology analyses revealed that PPD-enriched GM rice had significantly longer brown rice grains. In contrast, other seed traits remained within the natural range of commercial rice varieties. Furthermore, PPD was consistently detected in GM rice, whereas it was absent in non-GM Dongjin rice. These findings suggest that PPD-enriched GM rice maintains a stable agronomic performance while successfully accumulating PPD, supporting its potential as a functional crop. However, further research is required to evaluate its environmental impact, food safety, and efficacy as a functional food source.

“Jeongdami” is a specialized rice (Oryza sativa L.) variety developed to enhance the competitiveness of regional branded rice through its distinct characteristics, setting it apart from those from other regions. It is an early-maturing, semi-dwarf variety with strong resistance to rice blast and features intermediate stickiness with a low amylose content (11.6%), using “Wolbaek” as the maternal parent. The paternal parent is an F₁ hybrid created by crossing the large-grain, intermediate-maturity glutinous rice variety “Nunbora,” which is resistant to bacterial blight (K1, K2, and K3), with “Boramchan,” a high-yield, medium-late Japonica variety that is resistant to bacterial blight (K1, K2, and K3) and stripe virus. The breeding process culminated in 2020, resulting in “Jeongdami.”. Key agricultural characteristics include an average heading date of August 15, which is 6 days earlier than “Baekjinju”, an important low amylose mid-late cultivar, making it a medium-late variety when grown in the four plains regions in the central plains of Korea. Its culm length is moderately short at 77 cm, with an average of 16 panicles per hill and 96 spikelets per panicle. The 1,000-grain weight of brown rice is 20.0 g, similar to that of “Baekjinju.” There was no premature heading, leaf senescence at maturity was moderate, and the pre-harvest germination rate was 1.7%, lower than that of “Baekjinju” (7.5%). The overall cold tolerance rating was 7, indicating weak tolerance similar to “Baekjinju;” however, the variety showed strong lodging resistance in the field. “Jeongdami” exhibited strong resistance to bacterial blight (K1, K2, and K3) and moderate resistance to leaf blast but showed susceptibility to stripe virus, brown planthopper, and white-backed planthopper. The average polished rice yield was 547 kg per 10a, a 16% increase compared to that of “Baekjinju” (472 kg). The grain shape, with a paddy grain length-to-width ratio of 2.2 and a brown rice length-to-width ratio of 1.8, was similar to that of “Baekjinju,” maintaining a short and round shape. The endosperm is clearer than that of “Baekjinju,” providing superior visual quality. The protein content was 6.2%, and the amylose content was 11.5%, indicating intermediate stickiness, which was attributed to the Wx-mq gene. Due to its soft texture and stable cultivation, “Jeongdami” will contribute to increasing rice consumption by enhancing the competitiveness of regionally branded rice with its excellent eating quality and cultivation stability. (Grant No. 9168).

Risotto is an Italian rice dish cooked in broth until it reaches a creamy consistency. This is one of the most common rice preparation methods in Italy. The famous rice varieties for risotto are ‘Carnaroli,’ ‘Arborio,’ and ‘Vialone Nano.’ This study was conducted to provide essential data for breeding risotto rice varieties suitable for Korea by analyzing the agricultural traits of three risotto varieties and ‘Cheolweon96’ (Carnaroli SA-mutant line) under Korean environmental conditions. The risotto varieties and the mutant line showed early maturation, similar to ‘IS592BB.’ They had longer culm lengths and fewer panicles per hill and spikelets per panicle than to the Korean rice varieties, ‘i.e., Sindongjin’ and ‘IS592BB.’ They also exhibited lower ratios of ripened grains, brown/rough rice ratios, and lower yields. The risotto rice varieties and the mutant line other than ‘Vialone Nano,’ represented longer, wider, and heavier grain characteristics. The rice varieties and the mutants line had high levels of chalky rice, which absorbs water rapidly during cooking. Because broth absorption is important in risotto preparation, chalkiness can be considered an important characteristic of risotto rice varieties. In the analysis of pasting properties, ‘Carnaroli,’ ‘Cheolweon96,’ and ‘Vialone Nano’ showed similar characteristics, whereas ‘Arborio’ was grouped with ‘IS592BB.’ The cooked rice of ‘Carnaroli,’ ‘Cheolweon96,’ and ‘Vialone Nano’ exhibited a hard and non-sticky texture, while that of ‘Arborio’ was softer and stickier than that of the Korean rice varieties. The risotto rice varieties showed a larger grain size, higher chalkiness, pasting temperature, setback viscosity, and harder texture than the Korean rice varieties. These characteristics are expected to be useful selection indicators for breeding Korean risotto rice varieties.

The rice cultivar, ‘Dapum’, is a high-quality, late-maturing rice with low amylose content developed by the Chungcheongnam-do Agricultural Research and Extension Services (Yesan, Korea). Dapum was derived from a cross between Miho, a processed rice cultivar known for its cultivation stability and low amylose content, as the maternal parent, and Daohuaxing2, a high-quality aromatic rice cultivar, as the paternal parent. Subsequently, a pedigree breeding method was employed, and yield trials conducted from 2019-2020, followed by local adaptability tests from 2020-2021. As a result of the local adaptability test, the heading date of ‘Dapum’ was August 28^th, which is slower than the cultivars mainly cultivated in the Chungnam Province in Korea; therefore, it can be ripened at an appropriate temperature. The yield of milled ‘Dapum’ rice under standard fertilizer conditions was approximately 572 kg/10a, which was 15 kg/10a higher than that of Miho. The amylose content of ‘Dapum’ was 12.5%, similar to that of Miho, and the glossiness of cooked rice, which reflects its indirect eating quality, was 86.8, which was 7.0 points higher than that of Miho. The new rice cultivar, ‘Dapum’, is expected to be used in various ways, such as for cooked and processed rice, due to its low amylose content and good eating quality. Further, it has the potential to enhance the competitiveness of rice production in the Chungnam Province by diversifying the rice market, which has traditionally focused on mid-maturing, non-glutinous rice (Registration No. 10181).

Leaf size is closely related to photosynthesis and greatly affects rice productivity. Therefore, the search for quantitative trait Locus (QTL) that regulates leaf size is important for improving productivity through rice breeding. The F₉ recombinant inbred line (RIL) population from the cross between ‘Unbong 40’ (large leaves) and ‘Odae’ (ordinary size leaves) was grown in a test field, and the size traits of the flag leaves and 2nd leaves, along with stem and panicle length, were measured. Through QTL analysis of these traits, we detected 20 QTLs on chromosomes 1, 3, 6, 9, 11, and 12. In particular, the flag leaf length QTL qFLL3, the flag leaf area QTL qFLA3, the 2nd leaf length QTL q2LL3-2, and the 2nd leaf area QTL q2LA3 were clustered in the 149.0-161.6 cM region of chromosome 3, indicating that one QTL gene in this region may have pleiotropic effects that regulate the flag leaf length, flag leaf area, 2nd leaf length, and 2nd leaf area. In addition, the flag leaf width QTL qFLW9 and 2nd leaf width QTL q2LW9 were clustered in the 2.1-22.86 cM region on chromosome 9, which suggests that one QTL gene in this region may have pleiotropic effects that regulate both the flag leaf width and 2nd leaf width. These results serve as a valuable reference for breeding programs aiming to increase photosynthesis and yield by identifying QTLs for leaf size traits in Korean japonica rice.

‘Chamdongjin’ is a rice cultivar with a distinctively large grain size and good palatability, similar to ‘Sindongjin,’ which is a mega-cultivar in Korea. ‘Younghojinmi’ is a rice cultivar known for having the highest taste value among premium quality cultivars. In this study, we conducted quantitative trait loci (QTL) analysis of quality-related traits using recombinant inbred lines (RILs) derived from a cross between ‘Chamdongjin’ and ‘Younghojinmi’ to elucidate their genetic interactions. We analyzed 20 traits, including protein content, amylose content, glossiness of cooked rice, 7 traits related to grain appearance, 6 traits related to pasting properties, and 4 traits related to texture. Quality-related QTL were primarily detected on chromosome 3. In particular, GS3, one of the candidate genes for QTL, significantly influenced quality by affecting 14 different traits, including appearance traits such as head rice and the texture of cooked rice. Furthermore, RILs with the gs3 allele, which exhibited the large grains of ‘Chamdongjin,’ showed a lower protein content and higher amylose content than RILs with the GS3 allele. These lines also had lower head rice percentages and higher percentages of whiteness, opacity, and broken rice, indicating an inferior appearance quality. In terms of pasting properties, RILs with the gs3 allele showed a lower pasting temperature, peak viscosity, and breakdown, but a higher setback than RILs with the GS3 allele. Although the gs3 allele did not affect the glossiness, hardness, or toughness of the cooked rice, it resulted in higher adhesiveness and stickiness. Allelic alteration of the preharvest sprouting gene qLTG3-1 was found to affect seven quality-related traits, including pasting properties. Genes related to heading date (Hd18), culm length (SD1), and tiller number (OsTB1) were also associated with quality-related QTL. Alterations in the alleles of these genes caused variations in quality-related traits. Our identification of the association between quality-related traits and key agronomic genes is expected to support the effective development of rice cultivars with improved quality.

Rapid climate change has diversified the dynamics of brown planthoppers, necessitating the development of rice cultivars with enhanced resistance. Brown planthoppers contribute to reduced grain yield and quality, and the rapid ecological changes caused by global warming are expected to exacerbate this damage. In Korea, rice cultivars resistant to brown planthoppers have primarily been bred using Bph1, bph2, and Bph18. Despite the known resistance of Bph3 to brown planthoppers, this gene is underutilized in rice breeding programs. Therefore, in this study, we aimed to analyze the association between brown planthopper resistant genes and rice agronomic traits by breeding segregated populations incorporating Bph3, Bph18, and BPH26. Segregated populations were derived from crosses between ‘Jeonju686’ (carrying Bph3 and BPH26) and ‘JJ621MR’ (carrying Bph18). Our analysis revealed that Bph18 was significantly associated with a reduced fertility rate. However, Bph3 did not significantly affect fertility-related traits. As Bph3 has been reported to confer strong resistance to brown planthoppers, it is expected to be actively utilized in future resistance breeding programs. Ultimately, maximizing the efficiency of molecular breeding techniques is expected to provide valuable insights into the development of rice cultivars with enhanced resistance to brown planthoppers.

The rice cultivar ‘JJ644wx’ was developed to improve disease resistance and lodging tolerance of Korean japonica glutinous rice cultivars. ‘JJ644wx’ was derived from a cross between ‘HR27814-B-47-1-1’ (‘Sinjinbaek’), a multiple disease-resistant mid-late maturing elite line, and ‘HR29676-AC29’, a medium-maturing glutinous line with lodging tolerance. To shorten the breeding period, an anther culture method was applied to F₁ plants. ‘JJ644wx’ was selected through the pedigree method, yield trials, and local adaptability tests, with high selection pressure for disease resistance and lodging tolerance. The heading date of ‘JJ644wx’ was August 11th, four days later than that of ‘Sinseonchal’. ‘JJ644wx’ exhibited strong tolerance to lodging with a short culm length. The 1,000-grain weight of brown rice of ‘JJ644wx’ was heavier than that of ‘Sinseonchal’, and its yield was 553 kg/10a, which was 10% higher than that of ‘Sinseonchal’. ‘JJ644wx’ had a higher milling performance than ‘Sinseonchal’, but a lower head rice ratio due to a higher percentage of broken rice. ‘JJ644wx’ tended to be situated between ‘Sinseonchal’ and ‘Dongjinchal’ in terms of pasting and texture characteristics. ‘JJ644wx’ is the only Korean japonica glutinous rice cultivar resistant to the most virulent bacterial blight race, K3a; it also showed resistance to rice blast and stripe virus. ‘JJ644wx’ is expected to be a valuable resource that could contribute to improving the cultivation stability of Korean japonica glutinous rice in response to climate change (Registration No. 9606).

In Asia, where climate change is increasing the damage caused by cold stress, it is crucial to cultivate varieties with enhanced cold tolerance. In this study, the Tongil variety ‘Hanareum2’ was crossed with the Japonica variety ‘Unkwang’ to improve plant growth ability at low temperatures during the seedling stage. This led to the development of 234 recombinant inbred line (RIL) populations, and a linkage map was constructed using 249 single nucleotide polymorphism (SNP) markers. The RIL populations were transplanted to the field one month earlier than the standard transplanting period, and plant height (PH), leaf number (LN), and dry weight (DW) were measured to identify quantitative trait loci (QTL) associated with plant growth ability at low temperatures during the seedling stage. QTLs related to cold tolerance, particularly those carrying the ‘Unkwang’ allele, were identified in the PH and DW traits. For PH, the QTLs qPH1, qPH5, and qPH8 were located on chromosomes 1, 5, and 8, respectively. Regarding DW, the QTLs qDW1, qDW8, and qDW9 were identified on chromosomes 1, 8, and 9. For the LN trait, qLN3 carrying the ‘Hanareum2’ allele was located on chromosome 3. If the identified QTLs are utilized, they can be incorporated into breeding programs for plant growth at low temperatures during the seedling stage.

Recently, crossbreeding between Asian rice (O. sativa) and African rice (O. glaberrima) has become an important solution for hunger refugees and food problems in Africa by improving grain yield. O. glaberrima exhibits important traits such as stress tolerance, and genetic diversity evaluation and structural analysis of agronomic traits have been conducted. In this study, 11 yield-related agricultural traits were analyzed in 45 lines of O. sativa and 28 lines of O. glaberrima under Korean climatic conditions. Through cluster analysis using the investigated yield-related traits, O. sativa and O. glaberrima were grouped into clusters by characterizing the remaining traits, except for the number of spikelets, grain width, and grain thickness. The number of spikelets was highly influenced by the environment and had the greatest variation, whereas grain width showed the least variation. In addition, rice yield components are quantitative traits, and in breeding to improve yield, it is important to analyze the interaction of agricultural traits and the influence of the environment to maintain an optimal balance and improve plant potential. Although O. sativa was found to exhibit different agricultural traits depending on its ecotype, it still belonged to the same group when clustered. The results of this study provide basic information on the yield-related agronomic characteristics of O. sativa and O. glaberrima under Korean climatic conditions, suggesting that O. glaberrima can be used as breeding material to diversify Korean rice genetic resources.

The rice cultivar ‘Chamdongjin’ exhibits a distinctively large grain size and excellent eating quality but is weak with regard to pre-harvest sprouting (PHS), requiring genetic improvement. In contrast, the premium-quality rice cultivar ‘Younghojinmi’ exhibits strong PHS tolerance. This study conducted quantitative trait loci (QTL) analysis on PHS and low-temperature germinability (LTG) using recombinant inbred lines derived from a cross between ‘Chamdongjin’ and ‘Younghojinmi’ to elucidate the genetic factors. Thus, an elite line with improved PHS tolerance was selected. QTL analysis revealed that qPHS3 and qLTG3 were associated with PHS and LTG, respectively, and the candidate gene was identified as qLTG3-1. The loss-of-function allele qltg3-1 in ‘Younghojinmi’ enhanced PHS tolerance compared to the functional allele qLTG3-1 in ‘Chamdongjin,’ but it also showed a trade-off relationship by decreasing LTG. CY_RILs carrying qltg3-1 exhibited lower PHS and LTG rates of 17.9% and 41.6%, respectively, compared to 44.1% and 55.7%, respectively, for CY_RILs with qLTG3-1. The elite line, CY_RIL79, carrying qltg3-1, was selected from CY_RIL. This line was recognized for its PHS tolerance while maintaining the key agricultural traits of ‘Chamdongjin,’ thus designated ‘Jeonju697.’ ‘Jeonju697’ is expected to be utilized as a practical alternative for addressing the issue of enhancing PHS tolerance in ‘Chamdongjin’; however, considering its weak LTG, it is desirable to improve this trait through further breeding efforts.

Rice is a staple crop in South Korea and globally. The era of global boiling, characterized by rising temperatures and abnormal climatic conditions, significantly impacts crop production worldwide. This study examines the effects of high temperatures and rainfall on early maturing rice varieties, focusing on enhancing heat tolerance during the ripening stage and preharvest sprouting resistance. Utilizing ‘Milyang247,’ a progeny line from ‘Nampyeong,’ we developed the intermediate line ‘MY362VP.’ During 2020–2022, regional adaptability tests were conducted at five locations across Korea. Results showed that ‘MY362VP’ had a viviparous germination rate of 1.9% compared to 19.0% in the control variety ‘Jopyeong.’ Furthermore, ‘MY362VP’ maintained a head rice rate of 90.6% under high temperature conditions, outperforming ‘Jopyeong,’ which has a rate of 62.1%. ‘MY362VP’ produced an average yield of 529 kg/10a, comparable to the control’s 518 kg/10a. This study offers valuable insights for breeding climate-resilient early-maturing rice varieties, positioning ‘MY362VP’ as a promising candidate for future cultivation.

‘Saebonghwang’ was developed as a mid-late ripening rice variety with good cultivation stability and yield in transplanting and under direct seeding cultivation. It was bred by backcrossing ‘Hopum’, which has excellent cultivation stability and adaptability to direct seeding, as a repeat parent, and ‘Hitomebore,’ a Japanese rice variety with excellent taste, as a donor. The heading date of ‘Saebonghwang’ was August 11 under ordinary planting, which is two days earlier than that of ‘Nampyeong’, and August 13 under wet-direct seeding cultivation, which is the same as that of ‘Dongan’. ‘Saebonghwang’ had a culm length of 74 cm under wet-direct seeding cultivation, which is larger than that of ‘Dongan’ (69 cm), and had good cultivation stability, including lodging resistance. ‘Saebonghwang’ is resistant to bacterial leaf blight and rice stripe virus and shows moderate resistance to rice blast. Furthermore, ‘Saebonghwang’ has better grain appearance, superior taste and better milling characteristics than ‘Nampyeong’. The yield of ‘Saebonghwang’ when cultivated under ordinary planting, wet-direct seeding, and double cropping was 5.65, 5.37, and 5.37 MT/ha, respectively. Under wet direct sowing by drone cultivation, ‘Saebonghwang’ showed good initial survival rate and cultivation stability. The yield was 4.49 MT/ha, slightly lower than that obtained under transplanted cultivation (5.03 MT/ha), but was not statistically different; therefore, ‘Saebonghwang’ was adjudged to be adaptable to drone wet-direct seeding. ‘Saebonghwang’ can be used in various ways to suit the working conditions of farms, increase farm work efficiency, and expand the area of wet direct-seeding cultivation (Registration No. 9171).

The rice cultivar ‘Baekokhyang,’ a high-quality late maturing aromatic rice developed by Chungcheongnam-do Agricultural Research and Extension Services, was developed to cope with rising temperatures due to global warming and the market demand for various rice cultivars. ‘Baekokhyang’ was derived from a cross between ‘Ungwang,’ a multi-disease-resistant early-maturing rice cultivar as the maternal parent, and ‘Okhyangheugchal,’ an aromatic black rice as the paternal parent. Subsequently, a pedigree breeding method was used and yield trials were conducted from 2017 to 2018, followed by local adaptability tests from 2018 to 2019. ‘Baekokhyang’ is a late-maturing rice cultivar with the heading date of August 25th, demonstrating a slower maturation tendency compared to other medium-maturing cultivars, and this trait enables it to be ripened at an appropriate temperature after the heading date. ‘Baekokhyang’ exhibited tolerance to lodging, indicating high cultivation stability and more grains per panicle than ‘Samgwang. ’ Yield of milled rice was approximately 6.42 MT/ha under normal fertilizer levels in the local adaptability tests, which was 0.38 MT/ha higher than that of ‘Samgwang’. Additionally, the weight of 1,000 brown grains was 26 g which was 4.4 g heavier than that of ‘Samgwang’. The width/length ratio was 1.97, indicating the characteristic of long grains.The new rice cultivar ‘Baekokhyang’ is expected to enhance the competitiveness of rice production in Chungnam Province by diversifying the rice market which is currently dominated by non-glutinous and short-grain rice (Registration No. 8608).

The rice cultivar ‘Namchan’ was developed to achieve high yields under low-nitrogen fertilizer conditions and enhance cultivation stability. ‘Namchan’ was derived from a cross between ‘Nikomaru’, a Japanese rice cultivar known for its excellent ripening ability in high-temperature conditions, and ‘Saenuri’, a Korean mega rice cultivar renowned for its high cultivation stability. To shorten the breeding period, anther culture was applied to F1 plants. ‘Namchan’ was selected through the pedigree method, yield trials, and local adaptability tests, with high selection pressure for ripening ability and cultivation stability. The heading date of ‘Namchan’ was August 16, four days later than that of ‘Nampyeong’. ‘Namchan’ exhibited strong tolerance to lodging and preharvest sprouting, indicating high cultivation stability. Despite having more grains and panicles compared to that in ‘Nampyeong’, ‘Namchan’ exhibited excellent ripening ability, presumed to be inherited from ‘Nikomaru’. ‘Namchan’ showed intermediate resistance to rice blast and resistance to bacterial blight and rice stripe virus. ‘Namchan’ had excellent grain appearance, improved milling performance, and superior taste compared to ‘Nampyeong’. ‘Namchan’ exhibited a yield of 6.34 MT/ha under normal nitrogen fertilizer conditions, and its index at 115%, when compared to that of ‘Nampyeong’, is the highest among Korean japonica rice varieties. It exhibited a high yield of 5.45 MT/ha even under low-nitrogen fertilizer conditions. ‘Namchan’ is promising as an outstanding cultivar that can contribute to carbon neutrality through the reduction of nitrogen fertilizers and greenhouse gases (Registration No. 8134).

‘Dahongmi’ was developed to enhance the quality of colored rice by crossing ‘Jeogjinju’, Korea’s red-brown colored rice variety, with ‘Junam’, a variety known for excellent cultivation characteristics. ‘Dahongmi’ is a mid-maturing cultivar harvested approximately 15 days later than ‘Jeogjinju’, suitable for the mid-central plains. Each ‘Dahongmi’ plant bears 14 panicles, similar to that in ‘Jeogjinju’ but with an additional 22 grains per panicle and a heavier 1000-grain weight compared to that of ‘Jeogjinju’. ‘Dahongmi’ exhibited superior low-temperature germination rate (85.1%) and a higher percentage of fertile grains at a cold-water irrigated nursery (36.2%) compared to ‘Jeogjinju’. The stem height of ‘Dahongmi’ is 89.7 cm, similar to that of ‘Jeogjinju’. However, ‘Dahongmi’ has a third node height 9 cm shorter than that of ‘Jeogjinju’, enhancing its resistance to lodging. Furthermore, it displayed resistance to leaf blast, bacterial leaf blight (K1, K2, and K3 strains), and rice stripe virus, ensuring stability during cultivation. The protein and amylose content of ‘Dahongmi’ are 5.5% and 18.9%, respectively, similar to that of ‘Jeogjinju’ (5.9%, 18.3%). The levels of antioxidant components such as total polyphenols and flavonoids are comparable to that of ‘Jeogjinju’. However, ‘Dahongmi’ does not exhibit resistance against bacterial leaf blight strain K3a and delphacidae, underscoring the importance of timely and balanced fertilization for effective early-stage management. ‘Dahongmi’ exhibits better yield, straw strength, and plant architecture compared to ‘Jeogjinju’. It has immense potential for augmenting the yield of high-antioxidant-pigmented rice varieties. In addition, it could provide valuable foundational data for the brown rice processing industry (Registration Number: 8680).

‘Aram’ is a high-quality, medium-late maturing rice variety adapted to the Gyeongnam province. It was developed through a cross between, ‘Yeonghojinmi,’ a good quality cultivar, and ‘Saenuri,’ a disease-resistant cultivar, in 2016. Anther culture was used for developing ‘Aram’. Its average heading date was August 16, which is 2 days later than that of the check cultivar, ‘Nampyeong’. The culm length of ‘Aram’ was 82.3 cm, and it had 17 panicles per hill. The ratio of ripened grain was 85%, which was 3% higher than that of ‘Nampyeong’. ‘Aram’ shows resistance to bacterial blight and rice stripe virus and moderate resistance to bakanae disease. However, it is susceptible to the K3a race of bacterial blight, other viral diseases, and plant-hoppers. ‘Aram’ has strong resistance to viviparous germination (4.9%) before harvest, and it shows strong resistance against field lodging. ‘Aram’ has a milling ratio of 74.6%; in addition, it has a high head-rice ratio and Toyo value. In the sensory test of cooked rice, ‘Aram’ had better scores for grain appearance, texture, and other items, compared to that for the check cultivar, ‘Nampyeong’. Therefore, ‘Aram’ could be used as a raw material for brand rice in Gyeongnam province because of its improved production stability and high quality (Registration No. 9628).

To promote the expansion of rice consumption, we examined the nutritional components and qualities of five Tongil-type rice varieties. Regarding texture properties, ‘Dasan’ showed the highest viscosity at 0.43 kgf, whereas ‘Hanareum3’ displayed the lowest at 0.20 kgf. Regarding pasting properties, ‘Hanareum4’ exhibited the slowest aging speed of rice flour dough with a value of -42.34 RVU, and ‘Hanareum3’ had the slowest aging speed of cooked rice with a final viscosity of 258.62 RVU. Regarding proximate compositions, ‘Hanareum3’ had the highest crude ash content at 1.17 g/100 g, and ‘Hanareum2’ had the highest crude protein content at 8.39 g/100 g. Regarding amino acids, at 0.17–0.18%, ‘Dasan’ had a methionine content 0.13% lower than the other varieties. Regarding mineral contents, potassium, phosphorus, and magnesium contents were the highest in ‘Hanareum3’ at 263.08, 354.85, and 109.18 mg/100 g, respectively. ‘Dasan’ showed the highest contents of iron, manganese, and zinc, measured at 0.94, 2.17, and 1.43 mg/100 g, respectively. Of the 36 fatty acids measured, only 9 were confirmed. Myristic acid, linoleic acid, and alpha-linolenic acid were highest in ‘Hanareum3’ at 0.27, 9.91, and 0.48 mg/g, respectively. ‘Hanareum4’ had the highest levels of palmitic, stearic, and oleic acids, with contents of 6.69, 0.79, and 9.64 mg/g, respectively. Arachidic, eicosenoic, and lignoceric acids were detected at high levels in ‘Geumgang1,’ ‘Hanareum2,’ and ‘Dasan,’ with contents of 0.16, 0.13, and 0.3 mg/g, respectively.

‘Dabokchal, a glutinous rice variety (Oryza sativa L.) with a medium late maturation period was developed by the Department of Crops and Food, JARES in 2020. It was derived from a cross between the glutinous cultivar ‘Shinmyeongheugchal’ with the good glutinous properties and ‘Hwangkumnodeul’ as a high yielding source. The progenies of the cross were selected by bulk and pedigree breeding method until the F₈ generation. As a result, a promising line, JR53-28-4-10-5-3, was advanced and designated as the name of ‘Jeonbuk12’ in 2018. The ‘Jeonbuk12’ local adaptability test was carried out at four locations during 3 years from 2018 to 2020. This variety headed on August 13, which was eight days later than ‘Sinseonchal’ in Honam plane. The culm and panicle length of this variety was 70 cm and 22 cm, respectively. This variety has about 16 tillers per hill and 92 spikelets per panicle. The ratio of ripened grain is approximately 84.9% and 1000-grain weight was 24.9 g in brown rice. This variety has a higher amylose content compared to that of ‘Sinseonchal’. The yield performance of brown rice was 591 kg/10a in the local adaptability test. This cultivar is considered to be adaptable to the Honam plain area of Korea (Registration No. 9602).

‘Gowoo’, a mid-late flowering, high yielding rice (Oryza sativa L.) cultivar with glabrous leaf and hull and resistant to multiple diseases and insects, was developed for forage use. It was developed for use as a whole crop silage obtained from a cross between ‘Kusahonami’ with high biomass, smooth leaf and hull, lodging resistance and Japonica high yielding line ‘Iksan514,’ which showed resistance to bacterial blight (BB) (race K1, K2, K3) and rice stripe virus (RSV). In the central plain region of Suwon, ‘Gowoo’ cultivar exhibited a growth period of approximately 120 days from seeding to heading, 111 cm culm length, 22 cm panicle length, 12 panicles per hill, 140 spikelets per panicle, and 1,000-grain weight of 23.4 g as brown rice. This hairless forage rice variety was weak in response to cold stresses, similar to ‘Nokyang’. However, it was resistant to lodging in the field and showed a strong response to viviparous germination. In addition, ‘Gowoo’ was resistant to leaf and neck blast, BB, RSV, and small brown planthopper. Its average dry matter yield for three years reached 18.2 MT/ha, which was 21% higher than that of ‘Nokyang’. This glabrous cultivar had 5.3% crude protein and 68.2% total digestible nutrients, a little low compared to ‘Nokyang’. In Korea peninsular, ‘Gowoo’ grows well in central and southern plain and is good to harvest between 15 to 30 days after heading to improve its feeding value and digestion rate of livestock (Grant No. 8681).

The grain size and shape have a significant impact on the grain quality and yield of rice. Additionally, due to the globalization of the rice market, there is a demand for rice varieties of various sizes. In this study, we analyzed quantitative trait loci (QTL) associated with grain length (GL), grain width (GW), grain thickness (GT) and ratio of length-to-width (RLW) using 149 F₂ plants obtained from a cross between Hopum and Basmati 370. To construct a linkage map, we utilized 89 Fluidigm SNP markers, which covered a span of 1,116 cM of F₂ population. Nine QTLs associated with four traits were identified on chromosomes 2, 3, 5, and 7. One major QTL on chromosome 3 accounted for 43.2% of the phenotypic variation in GL. Additionally, QTLs named qGW2 and qGW5 on chromosomes 2 and 5 were detected for GW, explaining 10.4% and 18.6% of the phenotypic variation, respectively. Three QTLs for GT were found on chromosomes 2, 5, and 7, explaining 9.9%, 12.9%, and 9.9% of phenotypic variation, respectively. These QTLs offer potential applications in breeding programs using Basmati 370 to develop long and slender grain japonica varieties.

Bakanae disease, also known as the foolish seedling disease, caused by Gibberella fujikuroi, is a serious issue in Korea. Since 2007, there has been a rapid increase in the occurrence of bakanae disease; this has caused severe yield loss to rice farmers every year. The most reliable and economical solution for managing bakanae disease is to cultivate resistant varieties; however, there are only a few rice varieties in Korea that can withstand this disease. Therefore, this study aimed to evaluate the resistance of 61 major rice varieties which account for 89% of the total rice cultivation area. Only six varieties showed intermediate or higher resistance to bakanae disease; this included Anpyeong and Samkwang. The genetic inconsistency between the bioassay results and the allele types of 12 molecular markers (associated with four QTLs) ranged from 4.7% to 48.7%. Therefore, more accurate markers, such as gene-based markers, are essential for monitoring general breeding programs or gene pyramiding.