• Korean Journal of Breeding Science
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• v.51 no.3
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• pp.190-200
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• 2019

It is reported that the absence of lipoxygenase-3 (LOX-3) may contribute to a reduction in stale flavor after the storage of rice. To improve the quality of stored rice of the Korean japonica rice cultivar, we conducted a breeding program to develop near-isogenic rice without LOX-3 in the genetic background of Saenuri, a mega variety of Korea. In the first step of the breeding program, we used a donor parent of LOX-3 null, Daw Dam, and a recurrent japonica parent, Sindongjin, to develop HR27873-AC12 by backcross (BC₁), color test for introgression of lox-3, and anther culture for rapid fixation. In the second step, we used the donor parent, HR27873-AC12, and the recurrent parent, Saenuri, to develop HR28896-31-3-1-1 by backcross (BC₁), marker-assisted selection (MAS) for lox-3, and phenotypic selection (PS) for agronomic traits. Finally, in the third step, we developed HR30960-186-2-1-2-1 (Jeonju624), derived from a cross between Saenuri and HR28896-31-3-1-1, by MAS for lox-3 and PS with high selection pressure for agronomic characteristics. Jeonju624 was confirmed with the introgression of lox-3 by molecular marker. Jeonju624 was a mid-late maturing rice with similar agronomic characteristics to Saenuri, lodging tolerance with short culm, erect plant architecture, and resistance to bacterial blight and rice stripe virus. The yield components of Jeonju624 were mostly similar to Saenuri, except for the 1,000-grain weight of brown rice. The appearance of the grain of Jeonju624 was better than that of Saenuri, and the characteristics of cooked rice were similar to those of Saenuri. In the genetic background analysis using 406 KASP (Kompetitive Allele-Specific PCR) markers, Jeonju624 was confirmed to be the near-isogenic line (NIL) of Saenuri with a 95.8% recovery rate. Jeonju624 is the NIL of Saenuri without LOX-3, and overcomes the linkage drag of Daw Dam with similar agronomic characteristics and genetic background to Saenuri. Jeonju624 can be utilized as a practical cultivar to improve the quality of stored rice, breeding material for the introgression of lox-3, and genetic material to elucidate the effect of introgressed genes.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.56 no.2
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• pp.124-133
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• 2011

Bacterial blight (BB), cuased by the vascular pathogen Xanthomonas oryzae pv. oryzae, is one of the major threats in rice fields worldwide. In Korea, two resistance genes against BB, Xa1 and Xa3 had been intensively used for developing high quality japonica rice cultivars. Those traditional resistance sources have being rapidly ified by the adopting of BB pathogen through mutations of the corresponding avr-genes, such as K3a exhibiting high compatibility to both Xa1 and Xa3. To expanding genetic resource against BB in Korea, the Suweon506, an introgression line between a Korean japonica cultivar, Hwaseong and a wild relative, Oryza minuta, was be subjected for genetic analysis owing to the BB resistance. Through association analyses between the pathotyping and genotyping results for each $F_2$ progenies, derived from a cross between Suweon506 and a Tongil type cultivar, Milyang23, a major resistant dominant gene is localized on the subterminal region of rice chromosome 4, where at least three BB resistancde genes, Xa1, Xa2, and Xa22, were reported previously.

• Korean Journal of Breeding Science
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• v.40 no.4
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• pp.414-421
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• 2008

We conducted a QTL analysis of agronomic traits using 117 $BC_3F_5$ and $BC_3F_6$ lines developed from a cross between Ilpumbyeo and Moroberekan. Genotypes of 117 $BC_3F_5$ lines were determined using 134 simple sequence repeat (SSR) markers. A total of 832 Moroberekan chromosome segments with 410 homozygous and 422 heterozygous, respectively, were detected, and the genetic distance of introgression segments ranged from 0.5 cm to 112.1 cm. A linkage map constructed using 134 SSR markers was employed to characterize quantitative trait loci (QTL). The 117 $BC_3F_5$ and $BC_3F_6$ lines were evaluated for seven agronomic traits at two locations in 2006 and 2007 and at one location in 2007. A total of 26 QTLs were identified for seven traits including days to heading, and the phenotypic variance explained by each QTL ranged from 9.2% to 24.2%. Moroberekan alleles contributed positive effects in the Ilpumbyeo background at eleven QTL loci including panicle length and spikelets per panicle. Five QTLs, two for days to heading and one each for culm length, panicle length and spikelets per panicle were consistently detected in every occasions indicating that these QTLs are stable. Among them, two QTLs, spp6 for spikelets per panicle and pl6 for paniclel length were localized in the similar region. Increase in spikelets per panicle at this locus might be due to the increase in panicle length, because both traits were associated with increase in spikelets per panicle and panicle length due to the presence of the Moroberekan allele. These Moroberekan QTLs might be useful in breeding programs to develop high-yielding cultivars.

• Korean Journal of Breeding Science
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• v.43 no.4
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• pp.304-310
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• 2011

In previous studies, we reported QTLs for grain weight (GW), qGW3 and for spikelets per panicle (SPP), qSPP3 linked to RM60 on chromosome 3 using advanced backcross lines derived from a cross between Oryza sativa ssp. Indica cv. Milyang 23 and O. glaberrima. The O. glaberrima alleles at this locus increased GW and spikelets per panicle in the Milyang 23 background. To further confirm and narrow down the position of the QTLs on chromosome 3, substitution mapping was performed using five lines containing the target O. glaberrima segment on chromosome 3. The size and position of the O. glaberrima segment on chromosome 3 were different in each line. These lines possessed 3-10 non-target O. glaberrima introgressions in the Milyang 23 background. These five lines were evaluated for seven agronomic traits including 1,000 grain weight and spikelets per panicle and also genotyped with seven SSR markers. Four lines were informative in delimiting the position of QTLs, qGW3 and qSPP3. Two lines with the O. glaberrima segment flanked by SSR markers, RM60 and RM523 displayed significantly higher values than Milyang 23 in GW and SPP whereas two lines without that O. glaberrima segment displayed no difference in GW and SPP compared to Milyang 23. The result indicates that two QTL, qGW3 and qSPP3 are located in the interval between RM60 and RM523 which are 1.2-Mb apart. Introgression lines having QTLs, qGW3 and qSPP3 would be useful materials not only to indentify the relationship between these two yield QTLs, but also to develop high yielding variety via marker-aided selection technology.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.65 no.3
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• pp.161-171
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• 2020

Direct seeding is one of the rice seedling establishment methods that is increasingly being practiced by farmers to save labor and reduce costs. However, this method often causes poor germination under flooding conditions after sowing. In this study, we developed japonica elite lines with quantitative trait loci (QTL) associated with anaerobic germination (AG) tolerance to overcome poor germination and seedling establishment in wet direct seeding. The QTL introgression lines were developed from a cross between weedy photoblastic rice as the AG donor and the Nampyeong variety via phenotypic and genotypic selection. Compared to Nampyeong, the survival rates of the selected lines were improved by approximately 50% and 240% under field and greenhouse conditions, respectively. To improve selection efficiency by marker assisted selection, the QTL markers associated with AG tolerance were converted to cleaved amplified polymorphic sequence markers designed based on next-generation sequence analysis. These lines retained similar agronomic traits and yield potential to the parent, Nampyeong. Among these lines, we selected the most promising line, which exhibited high survival rate and good agricultural traits under flooding conditions and named the line as Jeonju643. This line will contribute to breeding programs aiming to develop rice cultivars adapted to wet direct seeding. This study demonstrates the successful application of marker-assisted selection to targeted introgression of anaerobic genes into a premium quality japonica rice variety.

• Proceedings of the Korean Society of Crop Science Conference
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• 2017.06a
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• pp.21-21
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• 2017

Severe lodging has recurrently occurred at strong typhoon's hitting in recent climate change. The identification of quantitative trait loci (QTLs) and their responsible genes associated with a strong culm and their pyramiding are important for developing high-yielding varieties with a superior lodging resistance. To identify QTLs for lodging resistance, the tropical japonica line, Chugoku 117 and the improved indica variety, Habataki were selected as the donor parent, as these had thick and strong culms compared with the temperate japonica varieties in Japan such as Koshihikari. By using chromosome segment substitution lines (CSSLs) in which chromosome segments from the japonica variety were replaced to them from Habataki, we identified the QTLs for strong culm on chrs. 1 and 6, which were designated as STRONG CULM1 (SCM1) and STRONG CULM2 (SCM2), respectively. By using recombinant inbred lines (BILs) derived from a cross between Chugoku 117 and Koshihikari and introgression lines, we also identified the other QTLs for strong culm on chrs. 3 and 2, which were designated as STRONG CULM3 (SCM3) and STRONG CULM4 (SCM4), respectively. Candidate region of SCM1 includes Gn1 related to grain number. SCM2 was identical to APO1, a gene related to the control of panicle branch number, and SCM3 was identical to FC1, a strigolactone signaling associated gene, by performing fine mapping and positional cloning of these genes. To evaluate the effects of SCM1~SCM4 on lodging resistance, the Koshihiakri near isogenic line (NIL) with the introgressed SCM1 or SCM2 locus of Habataki (NIL-SCM1, NIL-SCM2) and the another Koshihikari NIL with the introgeressed SCM3 or SCM4 locus of Chugoku 117 (NIL-SCM3, NIL-SCM4) were developed. Then, we developed the pyramiding lines with double or triple combinations derived from step-by-step crosses among NIL-SCM1 NIL-SCM4. Triple pyramiding lines (NIL-SCM1+2+3, ~ NIL-SCM1+3+4) showed the largest culm diameter and the highest culm strength among the combinations and increased spikelet number due to the pleiotropic effects of these genes. Pyramiding of strong culm genes resulted in much increased culm thickness, culm strength and spikelet number due to their additive effect. SCM1 mainly contributed to enhance their pyramiding effect. These results in this study suggest the importance of identifying the combinations of superior alleles of strong culm genes among natural variation and pyramiding these genes for improving high-yielding varieties with a superior lodging resistance.

• Korean Journal of Breeding Science
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• v.43 no.1
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• pp.81-91
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• 2011

Rice wild relatives have been recognized as reservoirs of genetic reinforcements to improve cultivating rice against biotic and abiotic stresses. A wild relative, Oryza. minuta(BBCC; Acc. 101141), was hybridized with a Korean Japonica cultivar, 'Hwaseong'(AA), followed by ovule culture and several times of back crossings to overcome high level of sterility. During evaluation of the introgression lines, breeding line exhibited resistance to bacterial blight with reasonable agronomic performances, and nominated as an elite breeding line, the 'Suweon497'. A mapping population, to dissect genetic basis of the resistance, was constructed by using $F_2$ progenies of the 'Suweon497' ${\times}$ 'Milyang23'. Association analysis between SSR marker genotypes and pathogenisity levels of each $F_2$ progeny revealed the end terminal region of rice chromosome 11 as the nesting place for the wild rice derived bacterial blight resistance gene, where at least four other genes, Xa3, Xa4, Xa26 and Xa31, have been reported.

• International Journal of Industrial Entomology and Biomaterials
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• v.13 no.1
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• pp.7-14
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• 2006

A breeding programme was initiated during 2001 to introduce sex-limited larval markings to a productive multivoltine breed - BL67 from an inbred sex-limited line, MY1 (SL) maintained at Central Sericultural Research and Training Institute, Mysore. Introgressive hybridization, recurrent backcrossing for six generations followed by sib-mating resulted in synthesis of a new multivoltine silkworm breed BL67 (SL) with sex-limited larval markings. The new breed was studied for combining ability by crossing with eight bivoltine breeds viz., $NB_4D_2,\;CSR_2,\;CSR_2 (SL),\;CSR_2,\;CSR_4,\;CSR_8,\;CSR_{18}\;and\;CSR_{19}$. General combining ability effects of the new breed showed its superiority over the popular Pure Mysore by expressing significant GCA effects for six out of twelve characters whereas the results are on par with the original multivoltine breed. The hybrid $BL67(SL){\times}CSR2(SL)$ excelled in several quantitative characters such as pupation rate (90.2%), cocoon weight (1.97 g), cocoon shell weight (40 cg), cocoon shell ratio (20.3%), filament length (918 m), denier (2.96), raw silk percentage (14.96%) and neatness (90 p). Studies on cocoon size variability revealed that the cocoons of $BL67(SL){\times}CSR2(SL)$ were found comparatively uniform showing less standard deviation of 6.55 and co-efficient of variation of 3.91 %. The suitability of newly developed breed for easy grain age operation and commercial exploitation with promising hybrid have been discussed.

• Proceedings of the Korean Society of Crop Science Conference
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• 2017.06a
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• pp.116-116
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• 2017

Low-temperature is one of the environmental stress factors that affect plant growth and development and consequently limit crop productivity. The control of seed germination under low-temperature is organized by many genes which are called quantitative trait loci (QTLs). High germination rate for low-temperature is an important factor of growing rice. Previously, we identified a major QTL controlling low-temperature germinability in rice using 96 introgression lines (ILs) derived from a cross between Oryza rufipogon (Rufi) and the Korean japonica cultivar, 'Hwaseongbyeo (HS)'. A $BC_3F_7$ line (TR5) showed better low-temperature germinability than its recurrent parent. TR5 was crossed with HS to develop a segregating F2:3 populations for the target QTL. Six SSR markers polymorphic between HS and Rufi were used to screen and fine map the qLTG1. The qLTG1 on chromosome 1, which accounted for 55.5% of the total phenotypic variation, confirmed that Rufi allele enhanced the low-temperature germinability. Intervals between markers CRM16 and CRM15, four candidate genes were identified. The identified candidate genes, which are encoded by a protein of unknown function, showed their direct involvement on seed germination at low-temperature. To identify genes targeted by qLTG1, we investigated the expression profiles of these candidate genes and germination behavior of qLTG1 under different stress conditions and compared to HS, Rufi, and TR5 at $13{\pm}2^{\circ}C$ for 3 days after incubation. Furthermore, transgenic rice plants will also be developed to conduct a detailed investigation on low-temperature germinability. Hence, the QTL for low-temperature germinability would be useful in rice breeding programs especially in the development of lines possessing low-temperature germinability.

• Korean Journal of Breeding Science
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• v.40 no.3
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• pp.243-249
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• 2008

In the previous study, 141 $BC_3F_2$ lines from a cross between the Oryza sativa cv. Milyang 23 and O. glaberrima were used to identify favorable wild QTL alleles for yield component traits. In this study, we carried out QTL analysis of four grain morphology as well as four yield component traits using 141 $BC_3F_5$ lines from the same cross and compared QTLs detected in two different generations. The mean number of O. glaberrima segments in the 141 $BC_3F_5$ lines ranged from 1 to 13 with 2.69 and 5.71 of the average means of homozygous and heterozygous segments, respectively. There was a three-fold difference in the number of QTLs detected for four traits commonly evaluated in two generations (seven QTLs in the $BC_3F_5$ vs 21 in the $BC_3F_2$ population). The percentages of the phenotypic variance explained by QTLs in the BC3F5 population were similar to or less than those in the $BC_3F_2$ population. This is probably due to the difference in the genetic composition of two populations and the environmental effects. The locations of the QTLs commonly detected in both generations were in good agreement except for one QTL for spikelets per panicle. The yield QTL, yd3 was colocalized with the spikelets per panicle, spp3. Yield increase at this locus is due to the increase in spikelets per panicle, because both traits were associated with increase in spikelets per panicle and yield due to the presence of an O. glaberrima allele. Clusters of QTLs for grain morphology traits were observed in two chromosome regions. One cluster harboring five QTLs near SSR markers RM106 and RM263 was detected on chromosome 2. This population would serve as a foundation for development of the introgression line population from a cross between Milyang 23 and O. glaberrima.