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.

Saemimyeon, a Tongil type, medium-late maturing rice variety, is especially used for preparing rice noodles. Its high amylose content was developed to fit market demands and to be affordable for rice processing industries. One of the high yielding lines, Milyang181 (Hanareum), was used in the final three-way cross of IR50*2/YR18241-B-B-115-1-1 for yield improvement and cultivation stabilization, including disease resistance. YR24235-10-1-3, a high yielding and compact plant type, was selected and named Milyang278 after yield test at NICS (RDA, Miryang) in 2010. It was subjected to regional yield test at six sites in the middle and southern plain areas of South Korea. Saemimyeon heading occurs on August 12 and is a mid-late maturing cultivar, with resistance to leaf blast, rice stripe virus, and bacterial blight (K1-K3a), but it is susceptible to major diseases and insect pest infestation. Saemimyeon showed a high amylose content of 26.7%, with a relatively low KOH digestion value of 3.5, which are key factors in rice noodles and pasta processing. In the local adaptability tests, the yield of Saemimyeon was 7.08 MT/ha—an increase of approximately 106% compared to that of Dasan. Thus, Saemimyeon is suitable for cultivation in the southern and middle plain areas of South Korea.

This study was conducted to identify DNA markers related to resistance to herbicide containing mesotrione in Tongil type rice. Two Tongil type elite lines; Milyang154 and Suweon382, showed resistance to mesotrione, whereas the others were susceptible at 20 days after mesotrione application, and severe growth inhibition was observed in the remaining 13 lines. As a result of analysis of mesotrione resistance using 190 F₂ populations derived from a cross of Hanareum2 (susceptible) and Milyang154 (resistant), the mesotrione resistance locus was shown to be a single dominant gene with a 3:1 segregation ratio (X²=1.19, P=0.31). To identify a DNA marker closely linked to the mesotrione resistance gene, bulked segregant analysis (BSA) was adopted. The DNA marker RM3501 was identified on chromosome 2 with a recombinant value of 0.53 to the mesotrione resistance gene. Mst1(t) was located between SSR (simple sequence repeat) markers RM3501 and RM324 with a physical map distance of 10.2 Mb–11.4 Mb on chromosome 2. The band pattern of agarose gel electrophoresis of the SSR marker RM3501 showed the same segregation pattern with respect to mesotrione treatment in 20 Tongil type varieties and a BC₂F₂ segregation population derived from a cross between Unkwang (resistant) and Hanareum2 (susceptible). Thus, the RM3501 DNA marker could be used in breeding programs for Marker Assisted Selection in mesotrione resistant rice breeding.