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.

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.

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%.

‘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 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.

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.

‘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 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.