Bakanae disease, caused by various Fusarium species, poses a significant threat to global rice production, with its incidence increasing in major rice-producing regions. Currently, no rice varieties exhibit complete resistance to this disease. Enhancing resistance in rice cultivars could serve as a cost-effective and sustainable alternative to fungicide application. Developing resistant rice varieties may offer a practical solution to mitigate yield losses and reduce dependency on chemical treatments. ‘Jinokchal’ was derived from the cross between ‘Milyang299’, which harbors bakanae disease-resistant QTL qBK1. and ‘Baekokchal’ in 2014. A promising line, YR31624-5B-2, was then selected and designated as ‘Milyang366’ in 2019. The local adaptability test of ‘Milyang366’ was conducted at five locations from 2020 to 2022, and the cultivar was subsequently named ‘Jinokchal. ’ The heading date of ‘Jinokchal’ was August 13, classifying it as a medium-late maturing cultivar. The culm was 77 cm long and had 108 spikelets per panicle. The 1,000 grain-weight of brown rice is 22.7 g, which is heavier than that of ‘Sinseonchalbyeo’. This variety is resistant to blast, rice stripe virus, and bacterial blight, but susceptible to insect pests. The yield potential of ‘Jinokchal’ was approximately 497 kg/10a at the ordinary fertilizer level in the local adaptability test over three years. ‘Jinokchal’ is moderately resistant to bakanae disease and harbors the qBK1 gene derived from the tong-il type rice ‘Shingwang’ (Registration No. 8135).

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.

Rice is a staple crop in South Korea and globally. The era of global boiling, characterized by rising temperatures and abnormal climatic conditions, significantly impacts crop production worldwide. This study examines the effects of high temperatures and rainfall on early maturing rice varieties, focusing on enhancing heat tolerance during the ripening stage and preharvest sprouting resistance. Utilizing ‘Milyang247,’ a progeny line from ‘Nampyeong,’ we developed the intermediate line ‘MY362VP.’ During 2020–2022, regional adaptability tests were conducted at five locations across Korea. Results showed that ‘MY362VP’ had a viviparous germination rate of 1.9% compared to 19.0% in the control variety ‘Jopyeong.’ Furthermore, ‘MY362VP’ maintained a head rice rate of 90.6% under high temperature conditions, outperforming ‘Jopyeong,’ which has a rate of 62.1%. ‘MY362VP’ produced an average yield of 529 kg/10a, comparable to the control’s 518 kg/10a. This study offers valuable insights for breeding climate-resilient early-maturing rice varieties, positioning ‘MY362VP’ as a promising candidate for future cultivation.

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.

Bakanae disease, also known as the foolish seedling disease, caused by Gibberella fujikuroi, is a serious issue in Korea. Since 2007, there has been a rapid increase in the occurrence of bakanae disease; this has caused severe yield loss to rice farmers every year. The most reliable and economical solution for managing bakanae disease is to cultivate resistant varieties; however, there are only a few rice varieties in Korea that can withstand this disease. Therefore, this study aimed to evaluate the resistance of 61 major rice varieties which account for 89% of the total rice cultivation area. Only six varieties showed intermediate or higher resistance to bakanae disease; this included Anpyeong and Samkwang. The genetic inconsistency between the bioassay results and the allele types of 12 molecular markers (associated with four QTLs) ranged from 4.7% to 48.7%. Therefore, more accurate markers, such as gene-based markers, are essential for monitoring general breeding programs or gene pyramiding.

Bakanae disease is caused by several species of Fusarium and imposes serious limitations to rice production worldwide. The incidence of this disease is increasing in the top rice-growing countries. No rice variety has been found to be completely resistant to this disease. Thus, higher resistance to the disease may be a cost saving solution preferable to the application of fungicides. ‘Anpyeong’ was derived from the cross between ‘YR24982-9-1’ and ‘Saeilmi’ in 2012 and selected as the promising line, ‘YR30389-B-2GH-103’; it was further selected and designated as ‘Milyang 313’ in 2016. The local adaptability test for ‘Milyang 313’ was conducted at five locations from 2016 to 2018 and the cultivar was named ‘Anpyeong’. The heading date for the medium-late maturing cultivar ‘Anpyeong’ was August 13. The ‘Anpyeong’ culm was 77 cm long and had 115 spikelets per panicle. The brown rice 1,000 grain-weight was 22.2 g, which is higher than that of ‘Nampyeong’. This variety is resistant to blast disease and rice stripe virus, but susceptible to bacterial blight and insect pest. The potential ‘Anpyeong’ yield was approximately 562 kg/10 a at ordinary fertilizer level in the local adaptability test and for three years. ‘Anpyeong’ harboring the qBK1 gene derived from a tongil type rice ‘Shingwang’ is moderately resistant to bakanae disease (Registration No. 8135).

A total of 285 Korean rice cultivars were used for amylose content and genetic analyses using KASP markers related to the amylose content. We used three polymorphic KASP markers targeting the Waxy (Wx) gene and compared the genotyping efficiency with previously reported molecular markers. The rice cultivars were raised in Miryang, Korea, for one period. Genetic analysis of the rice cultivars revealed that the three KASP markers on the Wx gene were functional for genomic selection of SNPs related to amylose content variation. Therefore, the three KASP markers targeting different Wx alleles can be used for genomic selection. In addition, KASP markers were more efficient than previously reported molecular markers that target the same alleles. These findings can be beneficial for the breeding and genomic selection of high-quality rice in Korea.

The rice variety ‘Youngjin’ is a japonica rice (Oryza sativa L.) with good eating quality, lodging tolerance, and resistance to the rice stripe virus (RSV) and bacterial blight disease (BB). It was developed by the rice breeding team of the Department of Southern Crop, NICS, RDA, in 2016. This variety was derived from a three-way cross between ‘Iksan486’, ‘YR22722-B-B-B-25-1’, and ‘Chengmu,’ with good eating quality, in the summer of 2007. The pedigree of ‘Youngjin’ was YR27874Acp46-1, and was designated as ‘Miyang283’ in 2012. After local adaptability tests at five different locations from 2014 to 2016, it was released under the name ‘Youngjin’ in 2016. ‘Youngjin’ is a mid-late maturing ecotype with a short culm length of 67 cm. This variety was found to be resistant to the K1, K2, and K3 races of BB, and RSV, and moderately resistant to leaf blast disease. The milled rice kernels of ‘Youngjin’ were translucent and clear, without white core and belly, and had good eating quality, according to a panel test. This variety showed a lower percentage of cracked kernels compared to other susceptible cultivars. The milled rice yield of ‘Youngjin’ was 568 kg/10a, under normal levels of fertilization, determined by the local adaptability tests. This cultivar is adaptable to the Yeongnam plain area (Registration No. 7653).

‘Sangbo’ is a japonica rice (Oryza sativa L.) variety with high head rice grain ratio and good ripened grain color, as well as resistance to rice dwarf virus (RDV) and bacterial blight disease (BB). It was developed by the rice breeding team of the Yeongdeok Branch of the National Institute of Crop Science, RDA, Korea, in 2015. This variety was derived in the 2002 summer season from a cross between ‘Yeongdeog32’, with high eating quality, and ‘Nampyeong’, with a high milling ratio. In 2012, a promising line, YR24256-142-5-3-1-1-2, selected by the pedigree breeding method, was designated the name, ‘Yeongdeog59’. After performing a local adaptability test at nine locations from 2013 to 2015, ‘Yeongdeog59’ was released with the name ‘Sangbo’ in 2015. ‘Sangbo’ has a culm length of 77 cm and a medium-late growth duration. This variety was resistant to K1, K2, and K3 races of bacterial blight, along with the dwarf virus, and was moderately resistant to leaf blast disease. Based on the results of a panel test, ‘Sangbo’ has translucent and clear milled rice kernel without white core and belly rice, and good eating quality. The yield potential of ‘Sangbo’ in milled rice was approximately 6.21 MT/ha at the ordinary fertilizer level of the local adaptability test (LAT). This cultivar would be adaptable to the middle plain, south plain, Yeongnam plain, east coastal area, and south mid-mountainous areas of Korea (Registration No. 7284, 2018.06.25).

Bakanae disease is an important fungal disease caused by Gibberella fujikuroi. Incidence of rice bakanae disease creates serious problems in the foremost rice producing countries, affecting more or less all known rice cultivars. Breeding rice cultivars resistant to bakanae disease will thus be a cost-effective alternative to the application of fungicides. ‘MY299BK’ was derived from a cross between YR24982-9-1 and ‘Ilpum’ in 2008. A promising line, YR28297-1-38-1-1, was selected from among the progeny and designated ‘Milyang299’ in 2013. The local adaptability test of ‘Milyang299’ was carried out at five locations from 2014 to 2016 and named ‘MY299BK’. The heading date of ‘MY299BK’ was Aug. 15, typical for a medium-late maturing cultivar. Its culm was 71 cm long, there were 114 spikelets per panicle, and 1,000 grain-weight of brown rice was 23.4 g; these parameters were similar to those of ‘Nampyeong’. ‘MY299BK’ cultivar was resistant to blast and rice stripe virus, but susceptible to bacterial blight and insect pests. Its yield potential was about 566 kg/10 a at ordinary fertilizer level in a three-year-long local adaptability test. ‘MY299BK’ resistance to bakanae is conferred by the qBK1 gene derived from a tong-il type rice ‘Shingwang’ (Registration No. 7651).

Limitation of genetic diversity in japonica rice breeding populations is often identified as a potential obstacle for the development of high yielding cultivars. The use of diverse germplasm in rice breeding has been suggested as one way of combating this problem. This study was conducted to improve the genetic diversity for rice, by developing an advanced backcross population derived from a backcross ‘Junam’ as recurrent parent and ‘IR72’ as a donor parent. Among them, we selected a promising line ‘YR24438-B-B-B-B-132’ containing bacterial blight resistance gene Xa4. Testing in the replicated yield trial in 2009, the ‘YR24438-B-B-B-B-132’ line was selected, and it was designated as ‘Milyang298’. The local adaptability test of ‘Milyang298’ was carried out at three locations from 2014 to 2016 and it was named ‘MY298BB’. The average culm length in the replicated yield trials was 87 cm, which is 15 cm taller than recurrent parent ‘Junam’. Number of spikelets per panicle was significantly lower than in ‘Junam’ but the number of tillers per hill was higher. This variety is resistant to bacterial blight race K1, K2, K3, and K3a.However ‘MY298BB’ showed early leaf senescence at the mature stage and the chlorophyll content of ‘MY298BB’ was significantly lower than that of the recurrent parent ‘Junam’. Moreover the grain filling ratio and yield were significantly lower in ‘MY298BB’ than those of recurrent parent ‘Junam’. Therefore, understanding the leaf senescence mechanism would be useful for improving yield potential in rice.

‘Haedamssal’ is an early maturing and rice stripe virus disease-resistant cultivar adaptable for early-transplanting cultivation that was developed by the rice breeding team of the Department of Southern Crop, NICS, RDA, in 2014. This cultivar was derived from the cross YR25869 (YR21247-B-B-B-49-1/Sasanishiki BL4//Koshihikari) and YR25868 (Unkwang//YR21247-B-B-B-49-1/Sasanishiki BL4) made in the 2005/2006 winter season and was advanced to the F₅ generation by a bulk breeding method using rapid generation advance. To incorporate rice stripe virus resistance, marker-assisted selection on the RSV gene was conducted in 3-way and 6-way cross F₁ generation using the tightly linked marker RM6897. From testing in the replicated yield trial in 2011, a promising line YR26258-B-B-B-33-3 was selected and it was designated as ‘Milyang276’. A local adaptability test of ‘Milyang276’ was performed at three locations from 2012 to 2014 and it was named as ‘Haedamssal’, which was a good eating quality variety. The culm length was 67 cm in yield trials, which was 4 cm shorter than ‘Jopyeong’. The number of spikelets per panicle was lower than ‘Jopyeong’, whereas the number of tillers per hill was higher. This variety was resistant to RSV disease, bacterial blight, and leaf blast disease. The milled rice yield of ‘Haedamssal’ was 5.48 MT per ha at the early transplanting in the local adaptability test. ‘Haedamssal’ is well adapted to early transplanting cultivation in the southern plain area (Registration No. 6811).

‘Yeongbo’ is a variety of japonica rice (Oryza sativa L.) with good eating quality, resistance to rice stripe virus, rice dwarf virus, and bacterial blight disease. It was developed by the rice breeding team of the Yeongdeok Branch, National Institute Crop Science, Rural Development Administration in 2014. This variety was derived from a cross between ‘Yeongdeog35’ with good eating quality and ‘Saekyehwa’ with good plant type in the 2002 summer season. A promising line selected through the pedigree breeding method, YR24269-1-2-1-2-3-3, was designated as ‘Yeongdeog57’ in 2011. After a local adaptability test at nine locations from 2012 to 2014, ‘Yeongdeog57’ was released under the name of ‘Yeongbo’ in 2014. ‘Yeongbo’ had a short culm length of 66 cm and medium growth duration. This variety was resistant to K1, K2, and K3 races of bacterial blight, rice stripe virus, and dwarf virus, and moderately resistant to leaf blast disease. ‘Yeongbo’ had translucent and clear milled rice kernel without white core and belly, and good eating quality according to a panel test. The yield potential of ‘Yeongbo’ in milled rice was approximately 5.75 MT/ha at an ordinary fertilizer level in the local adaptability test. This cultivar would be adaptable to middle plain area, south plain area, Yeongnam plain area, east costal area, and south mid-mountainous area. (Registration No.6804)

The rice recombinant inbred lines derived from Hanareum2 and Unkwang (HURILs) cross were used in genetic mapping and QTL analysis studies using the inclusive composite interval mapping (ICIM) method. In this study, we constructed the genetic map using 241 SNP markers based on the SNPs in the whole genome region between these varieties. As a result, the total genetic distance and average distances were 1,142 cM and 4.7 cM, respectively. Both heading date and plant height are important traits related to grain yield in rice. Twelve heading date QTLs were detected under natural condition in Korea. A major QTL qDTH3-2 for heading date and qCL1-2 for plant height explained 25.8~27.4% and 30.8~56.9% of the phenotypic variations in the HURIL populations. Four panicle traits, grain number (GN), panicle length (PL), number of panicle per plant (NPP), grain filling ratio (GFR) were evaluated for QTL effects in HURILs population during two years. Results showed that a total of twelve QTLs for GN, PL, NPP, and GFR were detected on chromosome 2, 3, 4, 6, 7, 8. A major QTL qGNP4 for GN was detected in HURIL populations with LOD score 7.7-19.3 and explained 6.7-17.69% of phenotypic variations. Twenty-five QTLs for the four traits TGW, GL, GW, and GT were identified in the HURIL populations for two years (2014~2015). The three QTLs, qTGW8, qGL8-2, and qGW8-2, shared the same interval between id8007093 and id8007764 on chromosome 8 with explained 4.8-4.1%, 4.2-6.8%, and 5.3-10.5% of phenotypic variations, respectively. Furthermore, two QTLs, qTGW3-2 and qGL3-2, were detected in the same chromosomal interval at the same position. These findings will benefit breeding design for development of high yielding variety in rice.

Rice stripe virus (RSV) is one of the major constraints in rice production which is transmitted by the small brown plant hopper, Laodelphax striatellus. Identifying new resistance genes from diverse sources is important for rice breeding programs to enhance the resistance level and/or to overcome the breakdown of resistance genes. This study was conducted to identify novel sources of resistance against RSV. We used five RSV resistant varieties that do not harbor Stv-bⁱ. The presence of known genes for RSV resistance was identified using the InDel7 marker for Stv-bⁱ, two Indel (Sid primer set) markers for Stv-b, and DNA sequence analysis for OsSOT1. We revealed that two varieties, 02428 (IT236925) and Tung Ting Wan Hien 1, are novel RSV resistance sources.

Oryza sativa ‘Sinbo’ is a cultivar of japonica rice with good eating quality as well as resistance to rice dwarf virus (RDV) and bacterial blight disease (BB). It was developed in 2013 by the rice breeding team of Yeongdeok Branch, National Institute of Crop Science, RDA, Korea. This cultivar was derived from a cross between ‘Yeongdeog34‘, a cultivar with good eating quality, and ‘Saekyehwa’, a cultivar of a good plant type, in summer of 2002. A promising line (YR24264-25-3-2) selected using the pedigree breeding method was designated as ‘Yeongdeog55’ in 2010. After carrying out the local adaptability test at nine locations from 2011 to 2013, ‘Yeongdeog55’ was published under the name of ‘Sinbo’ in 2013. ‘Sinbo’ is a medium-late maturing cultivar with a short culm length of 70 cm. This cultivar is resistant to K1, K2, and K3 races of bacterial blight as well as to dwarf virus, and it is moderately resistant to leaf blast disease. The results of the panel test indicated that ‘Sinbo’ has translucent and clear milled rice kernel without white core and belly rice as well as good eating quality. The yield potential of ‘Sinbo’ was approximately 5.67 MT/ha at the ordinary fertilizer level in the local adaptability test (LAT). This cultivar could be adaptable to the middle plain, south plain, Yeongnam plain, east costal area, and south mid-mountainous area of South Korea. (Registration No. 5643)

Rice tungro disease is a serious threat to rice production in South and Southeast Asian countries. Rice production in these countries has been intensified, often through continuous cultivation of rice. We conducted a screen of the resistance to tungro virus disease in Korean japonica rice. Dongjin, Hwaseong, and Sangju were varieties resistant to Rice tungro spherical virus (RTSV) but susceptible to Rice tungro bacilliform virus (RTBV). RTSV-resistant variety Sangju was crossed with RTSV-susceptible variety Unkwang to conduct a genetic analysis for RTSV resistance originating from Sangju. Evaluation of 201 F2 plants from the cross between Unkwang and Sangju showed that there were 85 plants showing resistance, and that 116 plants were susceptible, indicating a ratio fitting a 7:9 ratio ratio (χ² = 0.54; p = 0.46). Thus, the resistance to RTSV in Sangju might be controlled by two recessive genes. This result indicates that Sangju might serve as a useful genetic source for diversification of RTSV resistance and stabilization of resistance through gene pyramiding.

‘Hwawang’ is an early maturing and short statured rice cultivar adaptable to the rice–cash crop rotation system that was developed by the rice breeding team of the Department of Southern Crop, National Institute of Crop Science (NICS), Rural Development Administration (RDA), Korea, in 2012. This cultivar was derived from the cross of YR25867 (Hitomebore//YR21247-B-B-B-49-1/Sasanishiki BL4) and YR25866 (Akidagomachi//YR21247-B-B-B-49-1/Sasanishiki BL4) during the 2005/2006 winter season and was fixed as a homozygous line by a doubled haploid breeding system. In the replicated yield trial in 2009, a promising line (YR26253Acp26-1) showed a good phenotype and high yield potential, and so it was selected and designated as ‘Milyang256’. The local adaptability test of ‘Milyang256’ was carried out at three locations from 2010 to 2012. It was named ‘Hwawang’ and had a high head rice ratio and good eating quality. The culm length of ‘Hwawang’ averaged 62 cm during the yield trials and was 10 cm shorter than that of ‘Keumo’. The number of spikelets per panicle of ‘Hwawang’ was significantly lower than that of ‘Keumo’, but the number of tillers per hill was higher. This variety showed resistance to bacterial blight disease but was moderately susceptible to both leaf and neck blast. The milled rice yield of ‘Hwawang’ was 452 kg/10 a at the late transplanting stage of the local adaptability test. Thus, ‘Hwawang’ is well adapted to the rice–cash crop rotation system in the southern plain area. (Registration No. 5106)

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.

Rice production is largely affected by various environmental conditions such as cold, heat and flooding. Here, to identify cold tolerant QTLs at seedling stage in rice, we generated RIL population derived from a cross between Hanareum 2 and Unkwang which are a highly cold sensitive and cold tolerant, respectively. We observed cold phenotype of this population in the growth chamber conditions and natural field conditions. For observation of cold tolerant phenotype of RIL population in the growth chamber, we treated cold stress (5~13°C) for 14 days and recovery for 4 days. When we examined the phenotype of RIL in the field conditions, temperature range in the field conditions was about 6 to 25°C in 2015~2016. We named QTLs as Seedling Cold Tolerant (SCT) in growth chamber and Cold induced Yellowing Tolerant (CYT) in the field, respectively. Three QTLs for SCT and 5 QTLs for CYT were detected on chromosome 1, 6, 7, 8, 10, 11 and 12. Among these QTLs, qSCT12 on chromosome 12 showed 26.3 LOD score with 25.5% of phenotypic variation. When qSCT11.1 and qSCT12 were combined, cold tolerant was most strongest in our experimental conditions. qCYT10 on chromosome 10 was identified in field experiment on both 2015 and 2016. These results may provide useful information for a marker-assisted breeding program to improve cold tolerance in rice.

To fit the market demands for functional rice such as black and red color rice, ‘Sugary’a high free sugar content line was backcrossed to the black rice ‘Milyang152. The pedigree method was adapted in selection and generation advance. A high polyphenol content line, YR19646-3-2-1-1-2-2 showing red pericarp was selected and designed as ‘Milyang234’ followed by variety name ‘Geonganghongmi’ in 2010. Heading date of ‘Geonganghongmi’ was Aug. 19, medium-late maturing cultivar. ‘Geonganghongmi’ showed resistance to leaf blast and rice stripe virus while susceptible to major diseases and insects. The total polyphenol content of ‘Geonganghongmi’ was high as much as 24.2mg/g compare to that of 4.9mg/g of ‘Nampyeongbyeo’ and 17.2mg/g of a red pericarp rice ‘Jeogjinju’ at 70% ethanol extraction conditions. In local adaptability tests, yield of ‘Geonganghongmi’ was 4.5MT/ha about 86% of ‘Nampyeongbyeo’ and 102% of ‘Jeogjinju’, respectively. ‘Geonganghongmi’ is suitable for southern and middle plain area of Korea.

The amylose contents of rice determine eating quality which is one of the major traits in rice breeding program. To identify the low-amylose gene of the japonica rice cultivar Baegjinju, genetic analysis was conducted using 200 F₂ population derived from a cross between the japonica cultivars, Saeilmi and Baegjinju. Individual F₂ plants were classified as wild type (translucent grain) and mutant type (dull grain) based on the grain appearance of brown rice. Two hundred F₂ plants were segregated into 155 wild type plants and 45 mutant type plants, which fit the 3:1 ratio (x² = 0.667, df = 1, p = 0.414) and this result indicated the low-amylose gene of Baegjinju is a single recessive gene which controls the amylose contents. Linkage analysis was conducted to localize the low-amylose gene of Baegjinju and fine mapped within an 800-kb interval between 17.5 to 18.8Mb on short arm of chromosome 10. Co-segregated SSR marker, RM25648 was developed and it could be useful for marker-assisted selection and determination of the genetic resource related with amylose contents in rice breeding.

Bakanae (foolish seedling) disease caused by Gibberella fujikuroi creates serious problems in the foremost rice growing countries. This study was conducted to identify new resistance genetic sources to Bakanae disease. Bioassay showed that 11 varieties including Gwangmyeongbyeo, Hawn, Wonseadaesoo, Erguailai etc. were resistant to bakanae disease among 254 rice germplasm. Mismatch ratio between phenotype on bakanae disease bioassay and allele type of RM9, a SSR marker closely linked the bakanae disease resistant QTL, qBK1, were 38.3%. These results suggest that RM9 might be used for selecting qBK1, but it cannot be used for wide range of rice germplasm. Resistant germplasm in this study might be have resistant genes different from qBK1. The eleven varieties resistant to selected in this study will be used to identify new resistant alleles or genes to improve bakanae disease resistance in rice.

In chronic renal failure, to reduce the burden on the kidneys, it is necessary to provide patients with therapy based on a low-protein diet. To cope with this situation, low and easy to-digest protein rice variety is helpful. ‘Geongyang2’, low glutelins rice cultivar, was developed by the National Institute of Crop Science (NICS), RDA, Miryang, Korea in 2012. ‘Geongyang2’was derived from a cross between ‘Junambyeo’and‘Chugoku 173’ as a source of low glutelin and amylose. The pedigree of ‘Geongyang2’was YR24174-B-B-B-B-46 and designated as the ‘Milyang262’ in 2009. The local adaptability test of ‘Milyang262’ was carried out at six locations from 2010 to 2012. ‘Geongyang2’ is a mid-maturing ecotype with 65cm in culm length and the number of spikelet/panicle and 1,000 grain weight of brown rice were slightly lower compared to those of ‘Nampyeongbyeo’. ‘Geongyang2’ is resistant to bacterial blight and virus disease while susceptible to major insect and pest. The glutelin and amylose contents of ‘Geongyang2’ were 63.1% and 11.5%, respectively. The milled rice yield of ‘Gyeongyang2’ is 4.61MT/ha at the ordinary transplanting of the local adaptability test. This cultivar would be adaptable to the plain paddy field of middle, honam and yeongnam province of Korea under ordinary cropping system.

A rice variety ‘Dabo‘ is a japonica rice (Oryza sativa L.) with good eating quality, lodging tolerance, and resistance to rice stripe virus (RSV) and blight bacterial disease(BB). It is developed by the rice breeding team of Yeongdeog Substation, National Institute Crop Science, RDA in 2012. This variety derived from a cross between ‘Yeongdeog31’ with good plant type and ‘Milyang165’ with good eating quality conducted in 2001/2002 winter season. A promising line, YR23160-31-2-1-5-B-3, selected by pedigree breeding method was designated as the name of ‘Yeongdeog53’ in 2009. After the local adaptability test was carried out at seven locations from 2010 to 2012, ‘Yeongdeog53’ was released as the name of ‘Dabo’ in 2012. ‘Dabo’ is short culm length as 69 cm and medium-growth duration. This variety is resistant to races, K1, K2, and K3 of bacterial blight and stripe virus and moderately resistant to leaf blast disease. ‘Dabo’ has translucent and clear milled rice kernel without white core and belly rice, and good eating quality as a result of panel test. The yield potential of ‘Dabo’ in milled rice is about 5.90 MT/ha at ordinary fertilizer level of local adaptability test. This cultivar would be adaptable to south plain, east-south costal area, and south mid-mountainous area.

Nunkeunheugchal (registration No. 01-0001-2014-4), a black waxy giant embryo rice cultivar, was developed by the rice breeding team of National Institute of Crop Science (NICS), RDA in 2012. This cultivar was derived from the cross between ge^t and Josaengheugchal in 2004/2005 winter season, and selected by a promising line, YR25277-B-B-314-2, was selected and designated as the line of Milyang263 in 2009. The local adaptability test of Milyang263 was carried out at four locations from 2010 to 2012 and it was named as Nunkeunheugchal. This variety is a early maturity cultivar. It has 65 cm in culm length and 72 spikelets per panicle, and 1,000 grain-weight of brown rice is 17.8 g which is less than that of Josaengheugchal. This variety is resistant to leaf blast, but susceptible to bacterial blight, neck blast, virus disease and insect pest. The yield potential of Nunkeunheugchal was about 3.54 MT/ha as brown rice at ordinary fertilizer level in local adaptability test for three years. Nunkeunheugchal possesses benefits to rice consumers because of high amounts of GABA, anthocyanin, calcium and iron. This variety would be adaptable to the paddy field of middle and southern plain region of Korea.

A rice variety ‘Daebo’ is a japonica rice (Oryza sativa L.) with good eating quality, lodging tolerance, and resistance to rice stripe virus (RSV) and blight bacterial disease (BB). It is developed by the rice breeding team of Yeongdeog Substation, National Institute Crop Science, RDA in 2011. This variety derived from a cross between ‘YR21247-68-1’ with good plant type and ‘Yeongdeog35’ with good eating quality conducted in 2002 summer season. A promising line, YR23940-B-17-1-2, selected by bulk and pedigree breeding method was designated as the name of ‘Yeongdeog51’ in 2008. After the local adaptability test was carried out at seven locations from 2009 to 2011, ‘Yeongdeog51’ was released as the name of ‘Daebo’ in 2011. ‘Daebo’ is short culm length as 63 cm and medium-growth duration. This variety is resistant to races, K₁, K₂, and K₃ of bacterial blight and stripe virus and moderately resistant to leaf blast disease resistance. ‘Daebo’ has translucent and clear milled rice kernel without white core and belly rice, and good eating quality as a result of panel test. The yield potential of ‘Daebo’ in milled rice is about 5.93 MT/ha at ordinary fertilizer level of local adaptability test. This cultivar would be adaptable to middle plain, south plain, mid-west costal area, and south mid-mountainous area.