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‘Haedeul’ is a high-quality rice variety with early maturing that adapts to the central region of Korea. This cultivar was crossed between ‘Gopum’, which has excellent taste, and ‘Hoban’, which has a low viviparous germination rate and is moderately tolerant of cold, by the rice breeding team of the Department of Central Area Crop Science, NlCS, RDA, in 2017. In early-transplanting cultivation, the heading date of ‘Haedeul’ was July 24 in central area of Korea, which was seven days later than that of ‘Jopyeong’. ‘Haedeul’ had a culm length of 75 cm and 99 spikelets per panicle. The viviparous germination rate of ‘Haedeul’ was 7.7%. It showed resistance to blast and bacterial blight (K1, K2, K3 race), but was susceptible to the K3a race of bacterial blight, stripe virus, dwarf and black streak dwarf viruses, and plant-hoppers. The milled rice of this variety exhibited a translucent and medium short grain shape. The cooked rice grains of ‘Haedeul’ had an excellent palatability index (0.61) and lower amylose content (18.0%) than that of ‘Jopyeong’. The grain milling characteristics were better than those of ‘Jopyeong’, especially the head rice milling recovery ratio and head rice ratio (94.9%). ‘Haedeul’ milled rice productivity averaged 5.32 MT/ha at five sites under ordinary cultivation. [ABSTRACT FROM AUTHOR]

Early maturing rice cultivars grown in plain areas have an undesirable appearance due to high temperatures during the grain-filling stage. Therefore, developing early maturing rice cultivars with desirable appearance traits in plain areas is the primary goal of rice breeding programs. This study aimed to develop an early maturing rice cultivar adaptable to early transplanting cultivation in the Chungnam plain area. To develop “Yeoreumi,” two breeding materials were used, good-quality “Joami” from the Chungnam plain area and “Hokuto” having the fastest heading date among the genetic resources and originating from Japan. These two resources were crossed in 2010 to develop the “Yeoreumi” cultivar using the pedigree method. A yield trial was conducted in 2015-2016, and a local adaptability test was conducted in 2017-2019. The heading date of “Yeoreumi” was July 10, when it was transplanted early in the Chungnam plain area, and it could be harvested at August end, which was sufficient to produce a fresh stock of rice before “Chuseok, which is the Korean Thanksgiving Day.” The yield of milled rice was approximately 5.29 MT/ha in the local adaptability test, which was 0.47 MT/ha higher than that of “Jinbuolbyeo.” Additionally, its grain quality was good, with 89.9% head rice and 67.6 glossiness of cooked rice. Overall, the results of this study indicated that “Yeoreumi” was suitable for early transplanting cultivation in the Chungnam plain area for “Chuseok,” and could be used as a representative early maturing rice cultivar in Chungcheongnam-do (Registration No. 8597). [ABSTRACT FROM AUTHOR]

“Baromi2” is an improved resistant early maturing rice variety with floury endosperm, and is suitable for dry milling. This variety was developed in 2019 by crossing “Suweon542,” which is ideal for dry milling, and “Jopyeong” by the rice breeding team at the National Institute of Crop Science, Rural Development Administration. The heading date of “Baromi2” was July 27 in the Honam Plains, 17 d earlier than that of “Seolgaeng.” The culm length of “Baromi2” was 76 cm, which was almost the same as its check variety “Seolgaeng”; additionally, its panicle length, panicle number, and 1,000 grain-weight of brown rice were 23 cm, 11, and 18.4 g, respectively. “Baromi2” showed strong resistance against rice blast, bacterial blight, and stripe virus disease, but was susceptible to dwarf and brown and small brown planthoppers. The milled rice yield of “Baromi2” was approximately 475 kg/10a in the local adaptability test for 3 years in the late planting culture. The grain hardness of “Baromi2” with a floury endosperm was 2 and 3 times lower than that of “Seolgaeng” with opaque endosperm and “Jopyeong” with transparent endosperm, respectively. The rice flour of “Baromi2” exhibited superior physicochemical characteristics with respect to granule size and damaged starch content compared with any other check varieties. These results inferred that “Baromi2” was suitable for dry milling and for the processed rice industry, owing to its lower milling costs and eco-friendly milling methods (Registration No. 9052). [ABSTRACT FROM AUTHOR]

Rice blast is one of the most serious agricultural diseases in the world. Rice blast can be managed using low nitrogen fertilizers, treatment with chemical fungicides, and the most effective resistant varieties. Many genetic resources have been investigated and used along with molecular markers to breed blast-resistant rice varieties. In this study, the genetic diversity of blast resistance genes using 27 functional/linked markers and rice blast incidence over three years was investigated in 296 Korean rice varieties. Blast incidence was determined using a 0-9 scoring system (0=no lesions to 9=dead leaves) in nursery tests. The blast incidence of 296 rice varieties showed a significant correlation between years (r>0.64, p<0.001). The 261 Japonica varieties showed blast resistance compared to 114 mid-late maturing varieties or 96 medium-maturing varieties. 35 Tongil-type varieties also exhibited greater resistance than Japonica varieties. DNA marker-trait association analysis was conducted using 27 DNA markers linked to 19 blast resistance genes. Twelve DNA markers showed significant associations with the average blast incidence over 3 years. The ‘9871.T7E’ marker linked with Pi40 was strongly associated with blast disease, with a phenotypic variance of 24% over 3 years (p<0.001). Among the varieties harboring the Pi40 allele, early maturing varieties accounted for 87%. These results imply that the blast resistance of early maturing Korean varieties is associated with the Pi40 gene. These results will be beneficial for breeding blast-resistant rice in Korea. [ABSTRACT FROM AUTHOR]

This study was performed to determine the optimum transplanting dates of ‘Bbareumi’ in the Chungnam Plain area. ‘Bbareumi’ was transplanted into a rice research field of Chungnam Agricultural Research and Extension Services at intervals of approximately 15 days from April 17th to August 1st in 2019 and 2020. The heading dates of ‘Bbareumi’ were June 23rd to September 2nd depending on transplanting dates. The highest milled-rice yield was 5.61 MT/ha on May 1st and the lowest was 3.65 MT/ha on August 1st. As the transplanting date was delayed, protein content increased; however, the number of days from transplanting to heading decreased. Protein content and the number of days from transplanting to heading showed a highly significant correlation (R² = 0.802**). Therefore, it was found that early transplanting was beneficial to produce lower protein content because head rice percentage was 84-87% for early (April 17th to May 16th), 74-80% normal (June 1st to June 16th), and 86-95% for the late transplanting date (July 1st to August 1st). The mean temperature during the ripening stage differed according to the transplanting dates, and early transplanting showed a lower temperature than the normal one (May 16th to June 15th) and a higher head rice percentage. Therefore, extremely early maturing rice cultivars should be transplanted between late April and early May to obtain lower protein content and higher head rice percentage. These results will be useful for rice breeding programs, as it is generally recognized that early transplanting results in poor rice quality; however, this study revealed contrasting results. [ABSTRACT FROM AUTHOR]

Temperate japonica is used as the parent for crossing in the breeding of new rice cultivars in Korea, and the grain shape of the developed lines or cultivars is a semi-round and medium-short grain length. To overcome the current low quantity of japonica cultivar germplasm and deterioration in quality caused by climate change, it is necessary to diversify the grain characteristics of japonica. Most of the United States (US) cultivars are classified as medium, long, extra-long, and half spindle- and spindle-shaped grains. The qSW5 allelotype, a major gene involved in grain width, is found in all US cultivars. In addition, the US cultivar ‘Saber’ has both qgl3 and GS3_B alleles, which have low allele frequencies among Korean rice cultivars, and ‘A020’ had gw8, an allele with a reduced grain width. The pasting properties and texture of medium-grain length and half-spindle-shaped cultivars were relatively similar to those of the Korean rice cultivar, but different from those of long-grain and long spindle-shaped cultivars. Therefore, grain shape is associated with pasting properties and texture traits. Among the rice cultivars in the US, tropical japonica belongs to the same japonica as the Korean rice cultivar; however, its grain shape is similar to that of indica. As grain shape is also related to grain quality, US cultivars can be used as a useful genetic resource for diversifying the grain characteristics of Korean japonica cultivars and breeding new cultivars. [ABSTRACT FROM AUTHOR]

Interspecific and intersubspecific crosses have been an important strategy for rice breeding programs to obtain useful characters by expanding genetic diversity. However, the wide cross routinely causes undesirable characters in rice, such as spikelet sterility and poor quality. In this study, we developed near-isogenic lines of R-gene (Xa4+xa5+Xa21+Pi40+Bph18) introgression population to investigate the genetic relationship between the occurrence of poor characters and R-genes induced by MAS. The ANOVA analysis revealed that Pi40, Bph18, and Xa4 were associated with spikelet fertility (SF), ratio of ripened grain (RRG), third internode length (TIL), panicle extraction (PE), and protein content (Pro), whereas others showed no association with the 14 traits tested. In the three-way ANOVA, the impact of two R-genes (Pi40 and Bph18) on the poor characters was independent, with no interaction with others. Quantitative trait locus (QTL) analysis identified QTLs for PE and TIL traits near Pi40, and in particular, QTLs for five traits (SF, RRG, TIL, PE, and Pro) were negatively affected around Bph18. The occurrence of a poor character in R-gene pyramiding lines could be associated with linkage drag caused by the Bph18 gene. We speculate that the development of DNA markers that effectively eliminate poor characters will not only improve breeding efficiency using MAS, but will also help improve traits of japonica rice through wide crossing. [ABSTRACT FROM AUTHOR]

Rice is the most important staple food in Korea. Rice blast, caused by Magnaporthe oryzae, is one of the most devastating diseases in the rice-growing world and in Korea. Eighteen major blast resistance genes were screened in 33 leading Korean japonica varieties using 44 DNA markers. The 33 leading japonica varieties are cultivated in 659,642 ha (90.4%), and a variety of Samkwang is cultivated widely on a nation-wide scale. Four resistance genes, Pia, Pib, Pi19, and Pb1, were detected in 10-21 varieties, and the R-genes of Pii, Pish, Pita/Pita-2, Piz/Piz-t, Pi35, and Pi65(t), were present in 2-5 varieties. Five R-genes, Pit, Pi5, Pi9, pi21, and Pi40, were not detected in the Korean japonica rice varieties. A total of six varieties, two mid-late flowering varieties, Ilmi and Saeilmi, a medium flowering variety Gopum; and three early flowering varieties Jopyeong, Haedamssal, and Haedeul; were resistant to blast nursery screening over 12 years. A variety of Gopum harbored alleles for Piz/Piz-t, and three early flowering varieties, Jopyeong, Haedamssal, and Haedeul, had extensive loci of the multiple-gene family Piz/Piz-t, Pi9, and Pi40 on chromosome 6. Two mid-late flowering varieties, Ilmi and Saeilmi, harbored the Pita-2 gene, and Gopum had Pita. In the japonica rice breeding program, an effective means for enhancing stable resistance to blast would be introduced to 2-3 R genes among resistance genes Pit, Pi5, Pi9, pi21 and Pi40 which were not identified in Korean japonica rice varieties, and resistance genes Pita/Pita-2, Piz-t/Piz-5, to 2-3 R genes among and Pi20 that showed stable resistance in monogenic IRBL lines. [ABSTRACT FROM AUTHOR]