Sukwang1 is a premium-quality, mid-late maturing cultivar of japonica rice, which was developed to improve resistance to shattering and bacterial blight while maintaining the relatively high grain and eating quality of Sukwang. Derived from a cross between Sukwang and HR29177-AC70-1, the promising line Jeonju662 was evaluated through local adaptability tests (2021-2023) before release. Its average heading date was August 12, with a milled rice yield of 5.66 MT/ha. Sukwang1 exhibited improved resistance to shattering and all four Korean races (K1-K3a) of bacterial blight. Molecular marker analysis revealed the presence of Xa3 and Xa5 for bacterial blight resistance, qFfR1 for bakanae disease resistance, and a loss-of-function allele of qltg3-1 for reduced preharvest sprouting. Target capture sequencing analysis of single-nucleotide polymorphisms revealed 93.6% genetic similarity to Sukwang, indicating that most of the parental background was retained while key agronomic traits were improved. Featuring excellent grain appearance, high head-rice milling recovery, and relatively high taste, Sukwang1 has been designated as a Premium-Quality Rice cultivar by the RDA in 2025, and is recommended for the Honam and Yeongnam plains and southern coastal regions of Republic of Korea (registration number: 10667).

Bacterial grain rot (BGR), caused by Burkholderia glumae, is a major disease that reduces the yield of rice (Oryza sativa L.), thereby threatening food security. Conventional phenotypic analysis methods face limitations in objectively evaluating disease resistance and understanding the genetic basis. In this study, we integrated image-based phenotypic analysis with QTL mapping to screen for QTLs and candidate genes associated with B. glumae resistance. B. glumae was inoculated into 189 recombinant inbred lines (RILs) derived from Kele (resistant) and IS592BB (susceptible), followed by visualization and quantitative analysis using DAB staining. Phenotypic parameters, including the field resistance score, ratio of diseased spikelets (%), DAB staining intensity, and ratio of diseased area (%), were measured and used for QTL mapping. On chromosome 1, within Chr01_24592710-Chr01_37274755, four QTLs-qFRS1 [LOD: 5.98, phenotype variation explained (PVE): 15.41%], qRDS1 (LOD: 5.29, PVE: 18.56%), qQDS1 (LOD: 9.58, PVE: 22.02%), and qRDA1 (LOD: 8.44, PVE: 31.51%)-were identified as overlapping. After fine-mapping we narrow down Chr01_33472174-Chr01_33838140 and a total of 16 candidate genes were screened this region. Among which OsBGq1 was found to encode a nucleotide-binding LRR receptor (NLR) domain. OsBGq1 expression increased significantly upon B. glumae infection. Additionally, RILs Kele type of Chr01_33472174-Chr01_33838140 presented increased ROS-scavenging enzyme activity and phytoalexin accumulation upon B. glumae infection, contributing to increased resistance. The integration of DAB-based quantitative phenotyping with QTL mapping is proposed to provide a more objective indicator for identifying genes associated with resistance to BGR.

Bacterial grain rot (BGR), caused by Burkholderia glumae, is a major constraint in rice production, particularly under high temperature and humidity. However, effective molecular markers for BGR resistance remain to be developed. Thus, we aimed to identify quantitative trait loci (QTLs) associated with BGR resistance and develop molecular markers to facilitate marker-assisted selection (MAS). Kele (xa5, resistant to BGR) and IS592BB (Xa3, Xa21, susceptible to BGR), we constructed Kele/IS592BB recombinant inbred lines (KIRILs) to map QTLs associated with resistance to BGR. Based on the identified QTLs, we developed CAPS and dCAPS markers, which were subsequently validated in the Kele/IS592BB//IS592BB backcrossing inbred lines. Five QTLs were detected: qRBG(RDA)1 [logarithm of odds (LOD): 16.4, phenotypic variation explained (PVE): 37.0%] and qRBG(RDS)1 (LOD: 19.1, PVE: 44.4%) on chromosome 1; qRBG(RDS)3 (LOD: 4.2, PVE: 8.2%) on chromosome 3; and qRBG(RDA)6 (LOD: 3.5, PVE: 6.3%) and qRBG(RDS)6 (LOD: 4.7, PVE: 12.3%) on chromosome 6. Based on the flanking sequences of these loci, two cleaved amplified polymorphic sequences (CAPS) and four derived CAPS (dCAPS) markers were developed. Marker-assisted selection using these markers resulted in BGR-resistant lines with less than 30% infected grain ratio and lesion area. Among the selected lines, KIBIL84 (Kele/IS592BB//IS592BB backcross inbred line) exhibited strong resistance to BGR and harbored a pyramided gene combination (Xa3+xa5+Xa21) for resistance to bacterial leaf blight (BLB). Under BLB pressure, KIBIL84 showed reduced lesion length (1.2 cm) and lesion area (5.2%). In addition, it demonstrated improved aboveground growth under field conditions compared with its parental lines, suggesting a positive relationship with yield potential. These findings indicate that the developed markers are effective for screening BGR resistance and that KIBIL84 is a promising breeding material for improving resistance to multiple bacterial diseases in rice.

BACKGROUND:Rice milling characteristics and storage stability are critical traits influencing industrial applications. Floury endosperm rice carrying the flo4-4 allele is valuable for dry milling but exhibits reduced storage stability associated with altered starch structural characteristics. This study developed a novel rice cultivar, 'Baromi3', combining the flo4-4 allele and lipoxygenase 3 (LOX3) deficiency, and evaluated its quality and storage stability. RESULTS:To revitalize the floury endosperm rice industry, 'Baromi3' was developed through marker-assisted breeding. Compared with 'Baromi2', a commercial floury endosperm rice cultivar, 'Baromi3' exhibited a 3 day delay in heading and significantly shorter culm length. Dry-milling characteristics did not differ significantly between the cultivars, indicating that the dry-milling characteristics were preserved in 'Baromi3'. In the storage stability assessment, hexanal content increased progressively with storage duration, although its accumulation pattern varied depending on storage temperature and sample types. 'Baromi3' maintained lower hexanal content than 'Baromi2' under both low- (15 °C) and high-temperature (30 °C) storage conditions. In contrast, rice flour of 'Baromi2' showed a greater increase in hexanal content than rice grain under high-temperature storage, indicating that flour samples were more susceptible to lipid oxidation. These results suggest that LOX3 deficiency suppresses hexanal accumulation and contributes to improved storage stability even with the floury endosperm genetic background. CONCLUSION:This study demonstrates that 'Baromi3' successfully combines floury endosperm traits with improved storage stability. These characteristics highlight its potential value for dry-milled rice flour production and quality maintenance in the rice-processing industry. © 2026 The Author(s). Journal of the Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

The global rise in type 2 diabetes has intensified the need for dietary strategies that promote glycemic control, including the development of functional staple foods with a low glycemic index (GI). In this study, we assessed 16 Korean rice accessions for grain morphology, biochemical composition, starch digestibility, and glycemic response to identify promising candidates for low GI rice breeding. Substantial variation was observed in amylose (4.3–41.8%) and protein content (6.09–9.28%), both key factors influencing starch hydrolysis and postprandial glucose levels. In vitro GI assays showed that seven accessions had GI values below 60, including Dodamssal, Goami2, and Goami4, which were characterized by high resistant starch (RS) content. Interestingly, Seullomi1 and Seullomi2 maintained low-to-intermediate GI values, associated with elevated proportions of slowly digestible starch (SDS), moderate-to-high amylose content resistance to enzymatic digestion. Starch digestibility profiling confirmed that these lines retained higher SDS content even after cooking, suggesting greater resistance to enzymatic hydrolysis. In vivo murine study (n = 5 per group) further validated these findings, with Seullomi1, Seullomi2, and Dodamssal showing significantly reduced blood glucose spikes at 30 minutes compared with Sindongjin, a commercial Korean rice variety. Complementary textural analysis revealed that the Seullomi lines preserved moderate hardness and stickiness, traits favorable for consumer acceptance. Collectively, these results establish Seullomi1 and Seullomi2 as promising prototypes for the development of functional rice varieties that provide glycemic control with acceptable textural quality, thereby facilitating the breeding of rice to mitigate the risk of type 2 diabetes.

The acceleration of global warming poses a serious threat to food security, particularly affecting rice production. High temperatures during the grain-filling period deteriorate the grain quality and appearance of brown and milled rice. This study investigated meteorological changes in Korea in 2023 and 2024 and analyzed key factors influencing rice grain appearance quality. The grain appearance quality of brown rice was influenced by whole grain and immature grain levels, whereas milled rice quality was determined by perfect grain, chalky grain, and broken grain levels. In 2024, the number of days with average temperatures exceeding 30 °C increased by 12 compared to 2023, and the number of days with maximum temperatures above 35 °C increased by 8. These climatic changes significantly affected the grain appearance quality of Dongjin2, Boramchan, Sugwang, and Hwanggeumnuri. However, Asemi6 and Nampyeong showed consistent grain appearance-related traits across 2023 and 2024, identifying stable expression despite climatic changes The negative impact of high temperatures during the grain-filling period resulted in reduced 1000-grain weight and grain quality, weakening market competitiveness and decreasing farmer income. These findings highlight the increasing need for research to address the effects of climate change on rice production. This study provides a systematic analysis of the relationship between temperature variations and rice grain appearance quality. Also, we identified rice cultivars that exhibited stable grain appearance-related traits despite environmental variations. These selected resources are expected to serve as valuable parental materials for breeding high-yield cultivars with stable trait expression under future climate change.

Rice is a staple crop providing a significant portion of the global food supply. It is then crucial to develop strategies for breeding high-yield cultivars to meet global food security challenges, including the UN's zero-hunger goal. In this study, QTL mapping was employed to pinpoint key genomic regions linked to traits influencing rice yield, with a focus on panicle structure-a critical determinant of grain number. Over two consecutive years, QTLs were identified using 88 JJ625LG/Namchan Recombinant Inbred Lines (JNRILs), revealing several candidate genes. Notably, Gn1a, a known regulator of grain number, was mapped within qNS1 and qNSSr1-1, while the sd1 gene, linked to plant height, was detected across multiple QTLs. Furthermore, a novel gene, OsNSMq3 (Os03g0843800), encoding a methyltransferase, was identified in various QTLs, with haplotype and sequence homology analysis suggesting its role in enhancing yield by influencing panicle structure development. The increase in primary and secondary branches, driven by these genes, leads to a higher number of spikelets per panicle, thereby boosting yield. These findings underscore the potential of candidate genes from stable QTLs as valuable tools in molecular breeding to develop high-yield rice cultivars, addressing global hunger and aiding food supply in refugee crises.

Rice blast is a destructive fungal disease affecting rice plants at various growth stages, significantly threatening global yield stability. Development of resistant rice cultivars stands as a practical means of disease control. Generally, association mapping with a diversity panel powerfully identifies new alleles controlling trait of interest. On the other hand, utilization of a breeding panel has its advantage that can be directly applied in a breeding program. In this study, we conducted a genome-wide association study (GWAS) for blast resistance using 296 commercial rice cultivars with low population structure but large phenotypic diversity. We attempt to answer the genetic basis behind rice blast resistance among early maturing cultivars by subdividing the population based on its Heading date 1 (Hd1) functionality. Subpopulation-specific GWAS using the mixed linear model (MLM) based on blast nursery screening conducted in three years revealed a total of 26 significant signals, including three nucleotide-binding site leucine-rich repeat (NBS-LRR) genes (Os06g0286500, Os06g0286700, and Os06g0287500) located at Piz locus on chromosome 6, and one at the Pi-ta locus (Os12g0281300) on chromosome 12. Haplotype analysis revealed blast resistance associated with Piz locus was exclusively specific to Type 14 hd1 among japonica rice. Our findings provide valuable insights for breeding blast resistant rice and highlight the applicability of our elite cultivar panel to detect superior alleles associated with important agronomic traits.

Jae-Ryoung Park, Hyun-Su Park, Jeonghwan Seo, Chang-Min Lee, Songhee Park, Mina Jin, Keon Mi Lee, Keunpyo Lee, Sukyeung Lee, Ebrima Jallow, and O-Young Jeong. Korean J. Breed. Sci. 2024;56:97-111. https://doi.org/10.9787/KJBS.2024.56.2.97

Hyun-Su Park, Jeonghwan Seo, Heyonso Ji, Gileung Lee, Chang-Min Lee, Jae-Ryoung Park, Songhee Park, Keon-Mi Lee, Mina Jin, and O-Young Jeong. Korean J. Breed. Sci. 2024;56:79-95. https://doi.org/10.9787/KJBS.2024.56.2.79

Hyun-Su Park, Man-Kee Baek, Woo-Jae Kim, Jung-Pil Suh, Jeom-Ho Lee, Ji-Ung Jeung, Choon-Song Kim, O-Young Jeong, Deok-Ryeol Lee, Chang-Min Lee, Jong-Min Jeong, Young-Jun Mo, Su-Kyung Ha, Dong-Kyu Lee, Hyeonso Ji, Jeonghwan Seo, Jae-Ryoung Park, Hyun-Sook Lee, Songhee Park, Mina Jin, and Ki-Young Kim. Korean J. Breed. Sci. 2023;55:86-102. https://doi.org/10.9787/KJBS.2023.55.1.86

Rice is a major crop, providing calories and food for most of the world's population. Currently, the global population is rapidly increasing, and securing a yield of rice that can satisfy everyone is an ongoing challenge. The yield of rice can be increased by controlling 1000-grain weight as one of the important determining factors. Grain length, grain width, grain thickness, and 1000-grain weight, which determine grain size, are controlled by QTLs. To identify QTLs related to grain size, we screened and then mapped 88 RIL individuals derived from a cross between JJ625LG, which has a long grain size, long spindle-shaped grains, and low 1000-grain weight, and Namchan, which has short grains with round shape and heavy 1000-grain weight. In 2021 and 2022, 511 SNP markers were used to map QTLs related to grain size to a physical map. The QTLs found to be related to grain size are evenly distributed on chromosomes 2, 3, 5, 10, and 11. The mapping results also show that the QTLs qGl3-2, qRlw3, and qRlw3-2 of chromosome 3, and qGt5 and qRlw5 of chromosome 5 are, respectively, associated with GS3 and qSW5, which are the major genes previously cloned and found to be related to grain size. In addition, qGw10 and qGw10-1, which were additionally detected in this study, were found to be associated with Os10g0525200 (OsCPq10), a potential candidate gene involved in controlling grain size. This gene codes for a cytochrome P450 family protein and is reported to have a positive effect on grain size by interacting with proteins related to mechanisms determining grain size. In particular, OsCPq10 was screened in the same identified QTL region for 2 consecutive years, which is expected to have a positive effect on grain size. These results will be helpful for breeding elite rice cultivars with high yields through additional fine mapping related to grain size.