‘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).

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).

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.

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.

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.

‘Chamdongjin’ is a near-isogenic line with enhanced disease resistance compared to ‘Sindongjin,’ a mega-cultivar in Korea. ‘Younghojinmi’ is the rice cultivar with the highest taste quality among the premium cultivars. This study conducted quantitative trait loci (QTL) analysis on yield-related traits using the recombinant inbred lines derived from a cross between ‘Chamdongjin’ and ‘Younghojinmi’ to elucidate genetic interaction. We utilized KASP markers and a target-capture sequencing SNP genotyping platform to address the insufficient genetic diversity of the population using Korean japonica cultivars. A QTL associated with heading date (HD), qHd8, was detected, and the candidate gene Hd18 was identified. The hd18 allele delayed HD by 3 days and reduced the brown/rough rice ratio (BRR) by 0.3%. QTLs associated with culm length (CL), panicle length (PL), and yield (g/plant), namely qCL1, qPL1_2023, and qYield1_2023, respectively, were detected, and the candidate gene SD1 was identified. The sd1 allele shortened CL and PL by 11 and 0.8 cm, respectively, and reduced the yield by 2.3 g. It also reduced the number of spikelets per panicle (NS) by 10 and decreased the ratio of ripened grains (RRG) by 2.6 %. QTLs associated with 1,000-grain weight (TGW), NS, and BRR, namely qTGW3, qNS3, and qBRR3_ 2023, respectively, were detected, and the candidate gene GS3 was identified. The gs3 allele increased TGW and BRR by 3.8 g and 0.4%, respectively, and reduced NS by 12. It also reduced RRG content by 1.9% and increased the yield by 1.7 g. The QTL associated with the number of panicles per hill (PN), qTN3, and the candidate gene, OsTB1, were identified. The OsTB1^TGTG allele reduced PN by 1.3 and affected the increase in NS and RRG by 10 and 1.4%, respectively. The allele combinations of SD1, GS3, and OsTB1 were analyzed to assess their effects on yield-related traits. NS and RRG were influenced by trait variations, depending on the combination background of other alleles during allele substitution. ‘Jeonju 697,’ an elite breeding line exhibiting improved lodging resistance with shortened CL, was selected by substituting SD1 with sd1 while maintaining the Hd18-gs3-OsTB1^TGTG allele combination of ‘Chamdongjin.’ This is expected to be a practical alternative for addressing the lodging problem in ‘Chamdongjin.’

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).

The cultivated area of glutinous rice in the Homan Plain of Korea is increasing to diversify the cropping system. Depending on the time of transplanting, glutinous rice can be divided into early, ordinary, and late cultivation. Eight glutinous rice cultivars (Baegseolchal, Baekogchal, Boramchal, Boseogchal, Dongjinchal, JJ644wx, Nunbora, and Sinseonchal) were used to evaluate yield, pasting properties, and texture according to cultivation time and to analyze the genotype-environment relationship. There were nine yield-related, six pasting-related, and four texture-related traits studied. Heading date and culm length were shortened as cultivation time increased, while panicle length, number of spikelets, and 1,000-grain weight increased. Furthermore, late cultivation time also reduced pasting properties, peak viscosity, trough viscosity, and final viscosity. Hardness and adhesiveness among the texture properties increased with cultivation time, but stickiness decreased. The variation in 1,000-grain weight is mostly dominated by genotype, whereas heading date and yield are heavily influenced by environmental factors. All pasting property characteristics varied with environment changes, and genotype variation was dominant for all texture properties. Boramchal yielded the most in early and ordinary cultivation and Sinseonchal, together with Boramchal, yielded the most in late cultivation. Cultivars with excellent grain quality were Sinseonchal in early cultivation and Baegseolchal and Baekogchal in ordinary and late cultivation. A comparative analysis of characteristics based on cultivation time can assist in the selection of glutinous rice suitable for the Honam Plain and in the breeding of cultivars with improved yield and excellent grain quality.

The rice cultivar ‘Chamdongjin’ was developed to enhance the disease resistance of ‘Sindongjin’. ‘Sindongjin’, developed by the RDA in 1999, is a mega-variety with a unique grain size and excellent taste, and has been cultivated in the largest area in Korea since 2018. As ‘Sindongjin’ has been cultivated in a large area recently, problems such as pest damage are increasing, and the necessity to develop alternative cultivars is emerging. Accordingly, the multiple disease-resistant, mid-late maturing rice cultivar ‘Chamdongjin’, carrying the bacterial blight resistance gene Xa21 into the genetic background of ‘Sindongjin’, was developed. ‘Chamdongjin’ was developed by the backcrossing method using the donor parent ‘HR27195-59-3-5-5’, harboring the bacterial blight resistance genes Xa3+Xa21 and the recurrent parent ‘Sindongjin’. ‘Chamdongjin’ was selected through the pedigree method, yield trials, and local adaptability tests, with a high selection pressure for agronomic trait similarities with ‘Sindongjin’. In order to effectively improve the disease resistance, marker-assisted selection for disease resistance genes and bioassays for bacterial blight, blast, and stripe virus were performed in parallel. ‘Chamdongjin’ was confirmed to have three disease-resistance genes, Xa3+Xa21+Stvb-i. Most of agronomic traits of ‘Chamdongjin’ were similar to ‘Sindongjin’, while ‘Chamdongjin’ showed enhanced disease resistance against bacterial blight and panicle blast compared to ‘Sindongjin’. ‘Chamdongjin’, like ‘Sindongjin’, possessed a grain size-related gene, the gs3 allele, and exhibited larger grains than general Korean japonica cultivars. In addition, ‘Chamdongjin’ showed a similar or higher level of palatability compared to ‘Sindognjin’, indicating the excellent quality characteristics. In the genetic background analysis using 787 KASP markers, ‘Chamdongjin’ showed 96.3% homozygosity with ‘Sindongjin’, indicating that it had a more similar genetic background to ‘Sindongjin’ than to other existing cultivars. ‘Chamgdongjin’ is expected to be widely cultivated as an alternative to ‘Sindongjin’, which could maintain the brand value while preventing the disease damage caused to ‘Sindongjin’ (Registration No. 9310).

Soybean (Glycine max (L.) Merr.) is one of the most important crops with economic value as a source of protein and vegetable oil for human food and animal feed. In recent years, rapidly developed genome editing techniques have shown widespread application prospects for gene function studies and for improving important agronomic traits in many crops. Therefore, it is important to establish a highly efficient method for protoplast isolation and transient expression systems in soybeans. In this study, we established an efficient method for protoplast isolation and its application to transient gene expression in Korean soybean cultivars. The protoplasts were isolated from leaves, epicotyls, hypocotyls, cotyledons, and etiolated hypocotyls using various combinations of enzyme mixtures. We found that high-quality and large amounts of protoplasts were isolated from the etiolated hypocotyls when incubated for 8 h under conditions of 0.5% cellulase, 0.5% pectinase, and 1% viscozyme. In addition, we observed a high transfection efficiency of green fluorescent protein using etiolated hypocotyl protoplasts. Taken together, our protoplast isolation and transfection method is highly efficient and can be used for gene function and molecular analysis to better understand the biological and physiological processes in soybean.

Salt stress is a significant factor limiting growth and productivity in crops. However, little is known about the response and resistance mechanism to salt stress in maize. The
objective
of this research was to develop an enhanced salt-tolerant silage maize by mutagenesis with gamma radiation. To generate gamma radiation-induced salt-tolerant silage maize, we irradiated a KS140 inbred line with 100 Gy gamma rays. Salt tolerance was determined by evaluating plant growth, morphological changes, and gene expression under NaCl stress. We screened 10 salt-tolerant maize inbred lines from 2,248 M₂ mutant populations and selected a line showing better growth under salt stress conditions. The selected 140RS516 mutant exhibited improved seed germination and plant growth when compared with the wild-type under salt stress conditions. Enhanced salt tolerance of the 140RS516 mutant was attributed to higher stomatal conductance and proline content. Using whole-genome re-sequencing analysis, a total of 328 single nucleotide polymorphisms and insertions or deletions were identified in the 140RS516 mutant. We found that the expression of the genes involved in salt stress tolerance, ABP9, CIPK21, and CIPK31, was increased by salt stress in the 140RS516 mutant. Our results suggest that the 140RS516 mutant induced by gamma rays could be a good material for developing cultivars with salt tolerance in maize.