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.

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.

Submergence is becoming a major problem in decreasing rice production. This study conducted a QTL analysis for submergence tolerance on germination stage using 165 recombinant inbred lines (RILs) derived from crosses between ‘Milyang 23’ and ‘Tong 88-7’. An integrated genetic linkage map consisting of 1,313 SNPs was constructed, which covered a total length of 1,254.59 cM, with an average distance of 0.96 cM between adjacent markers. Four QTLs were detected on chromosomes 1, 3, 4, and 7. In qSUB1 and qSUB3, the allele of ‘Tong88-7’ improved survival rates, while in qSUB4 and qSUB7 the allele of ‘Milyang 23’ improved the same. Phenotypic variance explanations for qSUB1, qSUB3, qSUB4, and qSUB7 were 9.44%, 14.62%, 9.74%, and 7.09%, respectively. The average survival rate of the lines with all four QTLs was 93.33±6.67%.

Root development at the seedling stage is an important trait for the early growth of rice. In this study, the root length and weight of 211 Korean landrace rice at the seedling stage were evaluated, and the average root length and weight were 6.94 cm and 48.18 mg, respectively. Principal component analysis (PCA) of 211 accessions based on 70,849 SNPs presented three subgroups. Two quantitative trait loci (QTLs) associated with root length were detected on chromosomes 3 and 6 using genome-wide association study (GWAS). Four haplotypes were identified using associated SNPs for the two root length QTLs. The average root length of Hap2 and Hap 3 was 7.32 cm and 6.56 cm, respectively, and were significantly different. Gene expression analysis in the candidate regions of QTLs for root length at the seedling stage showed that several genes were expressed in the root. QTLs associated with root length at the seedling stage identified in this study may be applied to improve the root length trait and detect candidate genes.

‘Golden queen 3’, an aromatic rice variety, was developed by Seedpia inc. (Suwon, Korea) breeding company in 2014. This cultivar was derived from a cross between ‘HJ-11’, a high-yield, aromatic line, and ‘JCH33M-15-1-9-1’, which has a low amylose content. During the F₃-F₈ generation, breeding lines were selected using a pedigree breeding method. The most promising line (JS9-3-73-15-5-1-5-3-1-1) was advanced and named ‘SP005’ in 2013. This variety was headed on August 13, two days later than ‘Hwayeong’ in the ‘in middle plane’ is commonly used to distinguish rice cultivation areas in Korea, so I think it's no problem to the understanding for readers (including farmers). The culm and panicle lengths of this variety were 75.7 cm and 20.1 cm, respectively. It has approximately 14.7 tillers per hill and 104.8 spikelets per panicle, and the 1000-grain weight was 21.8 g. The yield performance was 5.47 MT/ha in the local adaptability test, and the amylose content of this variety was 12.5%. 2-Acetyl-1-pyrroline was detected as the major volatile ingredient in aromatic rice, and a 1 bp insertion on the 14th exon (badh2.7 allele) was identified in the Badh2 gene. (Registration No. 7308).

Rice blast caused by the fungus Magnaporthe grisea (anamorphic: Pyricularia oryzae) is an important disease in rice and development of resistant varieties to blast is one of the most important goals in rice breeding programs. A japonica rice variety, Palgong, has shown resistance to the Korean blast pathogen since it was developed in 1996. Nine blast resistance quantitative trait loci (QTLs) in Palgong alleles were identified on chromosomes 2, 4, 7, and 11. Four QTLs of qBn2.3, qBn4.2, qBn11.1, and qBn11.2 explained 28–56.7% of total phenotypic variation, while five QTLs of qBn2.2, qBn2.4, qBn4.1, qBn7.1, and qBn7.2 explained 9.7–18.8%. In a previous study, one to four resistance genes were located on the loci qBn2.2, qBn2.3, qBn4.2, qBn11.1, and qBn11.2, however, resistance genes were not located on the loci qBn2.4, qBn4.1, and qBn7.1. A major QTL, qBn11.2, explaining 56.7% of total phenotypic variation was related to the durable resistance of Palgong. Additionally, rice stripe virus resistance of Palgong was assumed to be based on the Stvb-i gene, which is located on a major QTL qBn11.2.

Rice landrace germplasms are highly valuable because of their wide genetic variation. Their traits have not been selected by modern breeders but by nature, thus, these traits and the gene associated with them have tremendous potential to improve modern rice cultivars. The first step to utilize this potential is to conduct a thorough evaluation of the target traits to select superior germplasm for a breeding program. Here, with 386 Korean landrace germplasms, we evaluated mesocotyl elongation traits which possibly promote direct seedling cultivation in rice. Mesocotyl length ranged from 0 mm to 28 mm. Among the tested landraces, we selected and reported the top 20 performing landraces whose mesocotyl length were larger than 16 mm. The previously reported agronomic traits for the selected 20 landraces were also listed for breeders to promote the utilization of these germplasms in breeding programs.

‘Superhongmi’, a reddish brown rice cultivar, was derived from a cross between CG2-3-5-1-6-1 (Heugjinju/Suwon 425) producing blackish purple rice and ‘Daeribbyeo 1’ producing large white grains. A promising line, SR28721-7-5-2-1-2-1, was obtained using the pedigree breeding method from 2003 to 2015 and designated as ‘KNOU6R’. This variety headed on September 5, and its culm length is 94.7 cm. The panicle length of ‘Superhongmi’ is 19.8 cm. The number of panicles per hill and grain per panicle is 5.4 ea and 154.9 ea, respectively. The fertility ratio of ‘Superhongmi’ is approximately 91.0% and 1000-grain weight (TGW) is approximately 26.8 g, which is similar to that of ‘Superjami’; however, the number of panicles per hill is half of that of ‘Superjami’. The content of taxifolin and total polyphenol extracted from whole grains of ‘Superhongmi’ is 67.7 and 248 mg/100g seed weight, respectively (Registration No. 7365).

‘Hyowon 3’, a medium-maturing glutinous rice variety was developed by the rice breeding team of Pusan National University in 2013. This cultivar was developed from a cross between ‘Hongna’ which is a landrace from the Korean peninsula showing good glutinous properties, and ‘Junam’, which has stable productivity. During the F₃–F₈ generations, breeding lines were selected using a pedigree breeding method. As a result, the promising line (JS24-6-95-11-5-2-1-1-1-B) with good glutinous properties was advanced and designated as ‘SP 107’. This variety headed on Aug. 16, which is 3 days later than ‘Dongjinchal’ in the middle plane. The average culm length and panicle length of this variety were 80.7 cm and 20.1 cm, respectively. This variety yielded approximately 14.1 tillers per hill and 104 spikelets per panicle. The ratio of ripened grain was about 93.0%, and the 1,000-grain weight was 19.30 g in brown rice. The yield performance was 492 kg/10a in a local adaptability test.

Hyowon6, a mid-late maturing, good eating quality rice variety with multi-resistance, was developed by the rice breeding team of Pusan National University in 2013. This variety was derived from a cross between Hwayeong (as a multi-resistant parent) and Koshihikari (as a good eating quality parent). Selection by the pedigree breeding method was carried out until the F₈ generation. A promising line, JS14-12-36-8-5-3-1-1-1, was developed and designated as HY103 in 2013. This variety headed on August 22, which was 11 days later than that of Hwayeong. The culm length and panicle length of Hyowon6 was 85.7 cm and 21.1 cm, respectively. The number of panicles per hill was 14.5 and the number of grains per panicle was 101.7. The ratio of ripened grain was approximately 92% and the 1,000-grain weight was approximately 21.36 g for brown rice, which were similar to those of Hwayeong. Hyowon6 was moderately resistant to lodging and also to neck blast, leaf blight, and stripe virus. The glossiness value of Hyowon6 was 83, which was considerably higher than that of Hwayeong.

The Jinsang 2 cultivar is a new late-maturing, low amylose rice variety with a medium to short culm created by the Seedpia Inc. breeding company in 2012. This variety was derived from a cross between Junam, a high-yield and lodging tolerant source, and DM3-8-72-9, which was derived from a cross between Donjinchal and Milkyqueen, with a low amylose content and superior agronomic traits. A general single seed descent method was applied to develop Jinsang 2 in the F3-F4 generations. During the F5-F8 generations, the breeding lines were selected through a pedigree breeding method. A promising line, JS6-B-52-8-3-5-1-B-B-B, was selected and named HJ-6 in 2011. This variety headed on the 25^th of August, which was 14 days later than Hwayoung. The culm and panicle length of the variety was 71.6 cm and 19.9 cm, respectively. The milled rice from the variety had a dull and medium- to short-grain, and the 1,000-grain weight was around 20.0 g. It had a low amylose content of 12.2% and a low protein content of 6.8%. The yield performance of Jinsang 2 milled rice was about 5.36 MT/ha from the ordinary culture replicated yield trial test.

Cymbidium goeringii of ‘Arihyang’ was developed for a fragrant Korean Cymbidium variety by Semangeum Bio Center. ‘Arihyang’ was developed from the cross between ‘Daebugui’ as a good fragrant source and ‘SC-005’, a collected Korean Cymbidium collected in 2001, which shows short plant-type and round flower. The selected seed was germinated and cultivated in 2007. Through continuous cultivation and checking the fixed phenotype from 2007 to 2008, the fixed phenotype of none boundary line jade color flower and moderate fragrance was confirmed. In 2010, ‘Arihyang’ was cultivated in field and evaluated the phenotype to be confirmed the fixed phenotype. ‘Arihyang’ has length of 20~25cm plain leaves with dark green color. The flower has a moderate fragrance with jade color. The length and width of flower are 2.5cm, 3cm, respectively.

‘Hyowon 4’, a new medium maturing glutinous rice variety was developed by the rice breeding team of Pusan National University in 2013. This cultivar was derived from a cross between ‘Boseokchal’ and ‘Donna’ with good glutinous property. During F3~F8 generation, breeding lines were selected by a pedigree breeding method. As a result, the promising line (JS23-4-39-14-5-1-1-1) with good glutinous property was advanced and designated as the name of ‘SP 106’ in 2012. This variety headed on Aug. 15, which is 2 days later than ‘Dongjinchal’ in middle plane. The culm length and panicle length of this variety was 82.4 cm and 21.1 cm, respectively. This variety has about 13.9 tillers per a hill and 100 spikelets per a panicle. The ratio of ripened grain is about 92.0% and 1000-grain weight was 20.9 g in brown rice. The yield performance was 5.03 MT/ha in local adaptability test.

"Hyowon 5’, a new aromatic rice variety with high yield was derived from a cross between 'Dasan’ as a high yield source and ‘IR841-1-1-2’ as a donor for aroma. A general pedigree breeding method was applied to develop Hyowon 5. In F₈ generation, a promising line, JS14-12-36-8-5-3-1-1-1, was selected and designated as the name of ‘SP 102’ in 2012. This variety headed on Aug. 14 , which is 3 days later than ‘Hwayoung’ in middle plane. The brown rice of this aromatic variety ‘Hyowon 5’ exhibited 51 odor-active volatiles including a pop corn-flavoring 2-acetyl-1-pyrroline which is exclusively detected in aroma rice varieties. The Culm length and panicle length of this variety was 83.2 cm and 26.4 cm, respectively. This variety has about 14.9 tillers per hill and 124.5 spikelet numbers per panicle. The 1000-grain weight was 20.9 g in brown rice. The yield performance of brown rice was 6.27 MT/ha in local adaptability test.

'Hyowon 2’, a new medium-late maturing glutinous rice variety with short clum and lodging tolerance was developed by the rice breeding team of Pusan National University in 2013. This cultivar was derived from a cross between 'Junam’ as a short clum source and ‘Donna’ with a good glutinous properties. During selected by the pedigree breeding method, until F8 generation. As a result, a promising line, JS22-3-24-1-6-2-1-1-1, was advanced and designated as the name of ‘SP 105’ in 2012. This variety headed on Aug. 22 is 9 days later than ‘Dongjinchal’ in middle plane. The Culm length and panicle length of this variety was 65.6 cm and 22.5 cm, respectively. This variety has about 14.4 tillers per hill and 113 spikelet numbers per panicle. The ratio of ripened grain is about 93.0% and 1000-grain weight was 18.4 g in brown rice. This variety has higher α-tocotrienol content compared to that of ‘Hwasunchal’. The yield performance of brown rice was 4.81 MT/ha in local adaptability test.

Cymbidium goeringi of ‘ Julie’ was developed from the cross between the accession of SC-017 and Daeyeophyeran by Semangeum Bio Center in 2004. The harvested seed was germinated and cultivated. During the cultivation, a individual plant showing marginal stripe pattern was selected in 2008. Through continuous cultivation and checking the special patterns in the leaf, the phenotype was fixed in 2009. From field cultivation in 2010, the fixed phenotype of marginal stripe pattern was confirmed. Julie shows clear marginal stripe patterns with yellow-green color. This pattern is more cleared as it grows. The leaf color is dark green with 35 ~ 40 cm length. The flower has fragrance with 4 cm width and 2.7 cm length.

Cymbidium goeringi of ‘Ariul’ was developed from the cross between Daebugui and SC-005 by Semangeum Bio Center in 2001. The harvested seed was germinated and cultivated. During the cultivation, an individual plant showing unique marginal stripe pattern was selected in 2006. Through continuous cultivation and checking the special patterns in the leaf, the phenotype was fixed through 2007 ~ 2008. From field cultivation in 2009, the fixed phenotype of marginal stripe pattern was confirmed. Ariul shows clear marginal stripe patterns with yellow color. The leaf color is dark green with 20 cm ~ 25 cm length. The flower of jade color has fragrance with 3 cm width and 2.5 cm length.

‘Jinsang’ is a new japonica rice variety was derived from a cross between ‘Yumetsukushi’ as a high grain quality and ‘Milky queen’ with low amylose content and good eating quality in 2000, and selected by pedigree breeding method until M8 generation. As a result, a promising line, JCH33M-15-1-9-1-5-1-1-1, was advanced and designated as the name of ‘HJ-2’ in 2009. This variety has about 111 days to heading after sowing and has 75.2 cm culm height. Milled rice of that shows dull and medium short grain and 1,000-grain weight was about 20.9 g. It has low amylose content of 11.9% and lower protein content of 6.8%. The yield potential of ‘Jinsang’ in brown rice was about 4.57 MT/ha by ordinary culture in replicated yield trial test.