Myeong-Ki Kim

Identification of Quantitative Trait Loci Associated with Rice Eating Quality Traits Using a Population of Recombinant Inbred Lines Derived from a Cross between Two Temperate japonica Cultivars

Improved eating quality is a major breeding target in japonica rice due to market demand. In this study, we performed genetic analysis to identify quantitative trait loci (QTLs) that control rice eating quality traits using 192 recombinant inbred lines (RILs) derived from a cross between two japonica cultivars, ‘Suweon365’ and ‘Chucheongbyeo’. We evaluated the stickiness (ST) and overall evaluation (OE) of cooked rice using a sensory test, the glossiness of cooked rice (GCR) using a Toyo-taste meter, and measured the amylose content (AC), protein content (PC), alkali digestion value (ADV), and days to heading (DH) of the RILs in the years 2006 and 2007. Our analysis revealed 21 QTLs on chromosomes 1, 4, 6, 7, 8, and 11. QTLs on chromosomes 6, 7, and 8 were detected for three traits related to eating quality in both years. QTLs for ST and OE were identified by a sensory test in the same region of the QTLs for AC, PC, ADV, GCR and DH on chromosome 8. QTL effects on the GCR were verified using QTL-NILs (near-isogenic lines) of BC3F4–6 in the Suweon365 background, a low eating quality variety, and some BC1F3 lines. Chucheongbyeo alleles at QTLs on chromosomes 7 and 8 increased the GCR in the NILs and backcrossed lines. The QTLs identified by our analysis will be applicable to future marker-assisted selection (MAS) strategies for improving the eating quality of japonica rice.

Suppression of NS3 and MP is important for the stable inheritance of RNAi-mediated Rice Stripe Virus (RSV) resistance obtained by targeting the fully complementary RSV-CP gene

Rice stripe virus (RSV) is a viral disease that seriously impacts rice production in East Asia, most notably in Korea, China, and Japan. Highly RSV-resistant transgenic japonica rice plants were generated using a dsRNAi construct designed to silence the entire sequence region of the RSV-CP gene. Transgenic rice plants were inoculated with a population of viruliferous insects, small brown planthoppers (SBPH), and their resistance was evaluated using ELISA and an infection rate assay. A correlation between the expression of the RSV-CP homologous small RNAs and the RSV resistance of the transgenic rice lines was discovered. These plants were also analyzed by comparing the expression pattern of invading viral genes, small RNA production and the stable transmission of the RSV resistance trait to the T3 generation. Furthermore, the agronomic trait was stably transmitted to the T4 generation of transgenic plants.

Development of Resistant Gene-Pyramided Japonica Rice for Multiple Biotic Stresses Using Molecular Marker-Assisted Selection

Advances in plant molecular techniques have dramatically widened the applicability of gene identification and pyramiding valuable genes. This study was carried out to pyramid five resistance genes for biotic stress into the japonica rice cultivar using marker-assisted selection (MAS) and marker-assisted background analysis of selected progenies using SSR markers. The Pi40, Xa4, xa5, Xa21 and Bph18 genes were combined in Jinbubyeo, a Korean japonica rice variety using MAS. Gene specific co-dominant PCR-based markers were used to select for homozygous recombinant lines in a segregating population derived from a cross between the parental homozygous resistant gene introgression lines. We had successfully developed multiple gene pyramided breeding lines (GPLs) for bacterial blight, blast, and brown planthopper using MAS in rice. The GPLs exhibited high resistance against biotic stress and had around 93% of the genetic background of the recurrent parent Jinbubyeo based on SSR graphical mapping. The yield and agronomic traits of the GPLs were similar to those of the recurrent parent, indicating that there is no apparent agronomic trait penalty associated with the presence of the resistance genes. The strategy of simultaneous foreground and phenotypic selection to introduce multiple R genes is very useful to reduce the cost and the time required for the isolation of desirable recombinants with target resistance genes in rice. The GPLs could be useful to enhance effective resistance for biotic stress and produce stable grain yield in japonica rice breeding programs.

SSR Analysis of Genetic Diversity and Cold Tolerance in Temperate Rice Germplasm

A total of 23 elite rice cultivars from eight countries were evaluated for cold tolerance using two screening methods at Chuncheon Substation, National Institute of Crop Science (NICS), Republic of Korea. The rice cultivars Jinbu, Mustaqillik, and Avangard showed cold tolerance and high spikelet fertility (63-79%) in cold-water irrigation screening. Under greenhouse screening, five cultivars (Giza 177, Avangard, Mustaqillik, Jinbu, and Jungan) showed high cold tolerance and high spikelet fertility (71-81%). Simple sequence repeat (SSR) marker analysis of 21 genotypes revealed two major clusters, the japonica and indica groups, with a genetic similarity of 0.69. Out of 21 rice cultivars, only four (Giza 178 from Egypt, Attey and Zakha from Bhutan, and Millin from Australia) fell under the indica cluster. The cold-tolerant varieties Jinbu, Mustaqillik, and Avangard were clustered with the japonica group, which had genetic similarity of 0.83. These varieties are considered as potential germplasm that will help diversify the japonica gene pool for cold-tolerant rice breeding. A one-way linear analysis of variance identified a significant relationship between individual alleles and traits. Three SSR markers were significantly associated with spikelet fertility under cold-water irrigation on chromosomes 1, 2, and 7. Five SSR markers were associated with spikelet fertility under a cool-environment greenhouse on chromosomes 8, 9, 10, and 12. The SSR markers associated with cold tolerance may also be useful as selection markers in indica/japonica cross combinations to improve cold tolerance.

A high biomass yield and whole crop silage rice cultivar 'Mogyang'.

‘Mogyang’, a new high biomass yield and whole crop silage rice (Oryza sativa L.) cultivar, is developed by the rice breeding team of National Institute of Crop Science, R.D.A., Suwon, Korea, during the period from was to 2010 and released in 2011. It was derived from a cross between SR24592-HB2319/IR73165-B-6-1-1. This cultivar has about 118 days of growth duration from seeding to heading and has long and erect leaves (culm length 93 cm). It has tough thick culm with strong lodging tolerance. This cultivar has a few less tillers per hill and markedly more spikelet numbers per panicle. ‘Mogyang’ has wide and stay green leaf compared other whole crop silage varieties. This new variety has grain shattering resistance and disease resistance for blast and dwarf virus. This variety has good qualities for whole crop silage with high TDN (Total Digestive Nutrient) yield and low NDF (Neutral Detergent Fiber) and low ADF (Acid Detergent Fiber) compared to common high grain yield varieties. The biomass and TDN yield performance of ‘Mogyang’ was 59.5% (chemical properties), 17.7 MT/ha (biomass yield), individually in local adaptability test for three years. ‘Mogyang’ is adaptable to central plain area, southern plain area of Korea.

A Late-Maturing and Whole Crop Silage Rice Cultivar `Mogwoo`

`Mogwoo`, a new high yield and whole crop silage rice (Oryza sativa L.) cultivar, was developed by the rice breeding team of the National Institute of Crop Science, RDA, Suwon, Korea, from 1999 to 2009, and was released in 2010. It was derived in 1999 from a cross between Dasanbyeo, having a high yield, and Suweon431/IR71190-45-2-1. A promising line, SR25848-C99-1-2-1, selected by the pedigree breeding method, was designated the name of `Suweon 519` in 2007. This cultivar has about 155 days of growth period from seeding to heading, and is tolerance to lodging, with erect pubescent leaves as well as a long and thick culm. This cultivar has the same number of tillers per hill and higher spikelet numbers per panicle compared to Nokyang. `Mogwoo` has longer leaves compared with other Tongil-type varieties. This new variety is resistant to grain shattering, leaf blast, bacterial leaf blight, and small brown planthopper. The biomass yield of `Mogwoo` was 1,956 kg/10a in a regional test over three years. The result shows that `Mogwoo` is adaptable to central and south-east plain areas of Korea.

Rice Blast Control and Race Diversity by Mixed-Planting of Two Cultivars (`Hopyeongbyeo`/`Nampyeongbyeo`) with Different Susceptibility to Magnaporthe oryzae

Mixed-planting of two rice cultivars, HP (`Hopyeongbyeo`) and NP (`Nampyeongbyeo`), having a dissimilar susceptibility to rice blast was practiced for chemical-free control of rice blast in the field. The HP/NP combination was selected for applying under mechanized agricultural conditions. Because they have similar genetic characteristics such as seed germination and heading time, culm length, rice quality and size of rice grains except susceptibility to blast. Incidence of panicle blast was reduced 50.4 % compare with supposed blast incidence by HP/NP mixed-planting when the seeds of two cultivars were combined 1 to 1 as weight. Supposed blast incidence was estimated from reduction of rice blast caused by addition of a resistant cultivar NP. Race diversity of Magnaporthe oryzae was examined for correlation with control effect of HP/NP mixed-planting on rice blast. The population of dominant race KJ-101 was diminished and replaced with various co-existing races and eleven new races were appeared in mixed-planting plot. Total number of race isolated from mixed-planting plot was not largely different from mono-culture. However, detection frequency of the new race was increased and variation of the population size of each race was decreased in mixed-planting plots. It was shown that a biased community with a dominant race (KJ-101 or KI-181) was altered to a balanced one of coexisting races. From these results, it was supposed that the balanced diversity among co-existing races within a community might be correlated to control effect by HP/NP mixed-planting on rice blast. Further more, it should be studied that genetic characteristics of the individual race including a virulence on cv. HP and NP was examined for verifying a correlation of mixed-planting effect and race diversity.

Lodging and Pre-harvest Sprouting Tolerant, High Quality and Suitable for Processing Cooked Rice ‘Jungmo1017’

The ‘Jungmo1017’ is a japonica rice variety developed from a cross between Suweon462 which has a good plant architecture, cold tolerance, moderately tolerant to leaf blast and bacterial blight and medium maturing habit, and Yeongdeog34 which has translucent milled rice and good milling properties, by the rice breeding team at NICS, RDA in 2011. The heading date of ‘Jungmo1017’ is August 16 and it is six days later than ‘Hwaseong’. ‘Jungmo1017’ has 65 cm of culm length which is 18 cm shorter than those of ‘Hwaseong’ and 93 spikelet per panicle. The pre-harvest sprouting rate of ‘Jungmo1017’ is 8.6% that is lower than 27.7% of ‘Hwaseong’ on local adaptability test (LAT). It showed resistance to blast diseases and moderately resistant to bacterial blight (K1 race) and stripe virus, but susceptible to other races (K2, K3 and K3a) of bacterial blight, viruses and planthoppers. The milled rice of this variety exhibits translucent, clear non-glutinous endosperm and medium short grain shape. It has better palatability index of cooked rice (0.53) than that of ‘Hwaseong’. ‘Jungmo1017’ showed lower protein content (6.4%) and amylose content (18.0%). ‘Jungmo1017’ could use aseptic-packaged cooked rice or processing cooked rice because its hardness of cooked rice is soft, setback and balance is low and palatability of cold and aseptic rice showed high score. The characters related to milling is better than those of ‘Hwaseong’. ‘Jungmo1017’ showed 5.01 MT/ha of milled rice productivity at 7 sites of middle plain, southern mid-mountainous and south-east coastal area in ordinary cultivation. ‘Jungmo1017’ could be adaptable to the middle plain area in Korea.

A Medium-Maturing, Black Pericarp and Aromatic Rice Variety ‘Sheonhyangheukmi’

Sheonhyangheukmi, black pericarp and aromatic rice (Oryza sativa L.) variety, was developed by the rice breeding team of National Institute of Crop Science (NICS), RDA in 2011. This variety was derived from the cross between Suweon477 and CG2-2-75-4-1-22-3 in 2002 summer season, and selected by a promising line, SR28684-9-2-2-2, was selected and designated as the line of Suweon532 in 2009. The local adaptability test of Suweon532 was carried out from 2009 to 2011 and it was named as Sheonhyangheukmi in 2011. This variety is medium matured with heading date of August 11 in central plain area of Korea. This variety is about 89 cm tall culm length and 122 spikelets per panicle. Its 1,000 grain-weight of brown rice is 17.0 g. This variety is susceptible to leaf blast and and insect pest, but resistant to bacterial leaf blight and moderately resistant to stripe virus disease. This variety has tolerance to unfavorable environment such as cold. Milled rice of Sheonhyanghuekmi is non-glutinous and aromatic endorsperm. This variety has higher anthocyanin content compared to black pigmented variety Heukjinju. The yield potential of Sheonhyangheukmi in brown rice was about 4.75 MT/ha at ordinary fertilizer level in local adaptability test for three years. This variety would be adaptable to the southern plain and middle plain of Korea.