Bong-Choon Lee

G7H, a new Soybean mosaic virus strain: its virulence and nucleotide sequence of CI gene.

A new Soybean mosaic virus (SMV) strain was isolated in Korea and designated as G7H. Its virulence on eight differentials and 42 Korean soybean cultivars was compared with existing SMV strains. G7H caused the same symptoms as G7 did on the eight differential cultivars. However, it caused different symptoms on the G7-immune Korean soybean cultivars; G7H caused necrosis in Suwon 97 (Hwangkeumkong) and Suwon 181 (Daewonkong), and a mosaic symptom in Miryang 41 (Duyoukong), while G7 caused only local lesions on those varieties. The nucleotide sequence of the cylindrical inclusion region of G7H was determined and compared with other SMV strains. G7H shared 96.3 and 91.3% nucleotide similarities with G2 and G7, respectively; whereas G7 shared 95.6% nucleotide similarity with G5H.

Occurrence and Detection of Rice black-streaked dwarf virus in Korea

Until now, occurrence of Rice black-streaked dwarf virus (RBSDV) is observed in Gyeongsang provinces, southeastern part of Korea. However, recently, the occurrence of RBSDV is increasing and spreading in Jeonra provinces including Gochang-gun, southwestern part of Korea. RBSDV infected plants showed typical symptoms including stunted, deformed leaves with white waxy or black-streaked swelling along the veins. We extracted viral genomic dsRNA from infected leaves and analyzed dsRNA pattern by polyacrylamide gel electrophoresis. Ten genomic segments with similar sized dsRNAs were observed. We also detected RBSDV by reverse transcription (RT)-PCR using specific primers for S10 from genomic dsRNA and observed amplified DNA fragment specific for RBSDV S10.

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.

A systems approach for identifying resistance factors to Rice stripe virus.

Rice stripe virus (RSV) causes disease that can severely affect the productivity of rice (Oryza sativa). Several RSV-resistant cultivars have been developed. However, host factors conferring RSV resistance in these cultivars are still elusive. Here, we present a systems approach for identifying potential rice resistance factors. We developed two near-isogenic lines (NIL), RSV-resistant NIL22 and RSV-susceptible NIL37, and performed gene expression profiling of the two lines in RSV-infected and RSV-uninfected conditions. We identified 237 differentially expressed genes (DEG) between NIL22 and NIL37. By integrating with known quantitative trait loci (QTL), we selected 11 DEG located within the RSV resistance QTL as RSV resistance factor candidates. Furthermore, we identified 417 DEG between RSV-infected and RSV-uninfected conditions. Using an interaction network-based method, we selected 20 DEG highly interacting with the two sets of DEG as RSV resistance factor candidates. Among the 31 candidates, we selected the final set of 21 potential RSV resistance factors whose differential expression was confirmed in the independent samples using real-time reverse-transcription polymerase chain reaction. Finally, we reconstructed a network model delineating potential association of the 21 selected factors with resistance-related processes. In summary, our approach, based on gene expression profiling, revealed potential host resistance factors and a network model describing their relationships with resistance-related processes, which can be further validated in detailed experiments.

Selection of Bactericides for Controlling Soybean Bacterial Pustule

Bacterial pustule of soybean (Glycines max) caused by Xanthomonas axonopodis pv. glycines is one of the most prevalent bacterial diseases of soybean. This bacterium shows strong pathogenicity to the plants and distributes throughout Korea. However, no good control measures including bactericides and resistant cultivars are available to control the disease in Korea. Therefore, this study was conducted to develop chemical control method against soybean bacterial pustule. The present study was undertaken to find out the growth inhibitory effect bactericides (8 antibiotics, 2 copper compounds, quinoline, 18 agro-chemicals) on bacterial pustule pathogen. Antibiotics test showed that tetracycline and streptomycin sulfate significantly suppressed the growth of bacterial pustule pathogen. Also, application of oxolinic acid was found to be effective for pathogen inhibition. However, vancomycin, polymyxin B sulfate and copper compounds did not show the positive suppressive effect on growth of the pathogen. Among the eighteen agro-chemicals, streptomycin sulfate + oxytetracyclin (18.8 + 1.5%) WP, oxytetracycline (17%) WP and oxolinic acid (20%) WP were found to be effective for the inhibition of the pathogen in vitro. The selected 5 agro-chemicals were also applied on soybean in field and their control effects against the soybean bacterial pustule were tested. The foliar application of streptomycin sulfate + oytetracyclin WP and oxytetracycline WP on the naturally infected soybean (Taekwangkong) showed high control value (above 70%). Therefore, it is concluded that the bactericides used in this study showed strong inhibitory effect to soybean bacterial pustule and they can be recommend to farmers to control the disease.

New Alternate Host of Rice stripe virus - `Deulmuksae`

Rice stripe virus (RSV) is one of Tenuivirus Group, which is carried by small brown planthopper. There is an outbreak of RSV in South Korea at 20Ot, and 2007. The infection caused by RSV had been investigated on weeds around the rice cultivated areas 13 region and 26 site including Jeonbuk Buan and Chungnam Seocheon. There have a doubt as to alternate host of RSV is total 15 Family and 50 Species including Gramineae 24 species of Duksaepul (Alopecurus aequalis), H. sativum var. vulgare etc.. There is identified the infected RSV in Festuca myuros, Alopecurus aequalis, Hordeum sativum var. vulgare, Trisetum bifidum, Echinochloa crus-galli var. crus-galli, Digitaria ciliaris among this species. Deulmuksae is the overwintering exotic weed which sprout in Autumn and wither in Spring and commonly growed as green manure crop or cover crop. In order to identify the infection rate furthermore, 111 samples which were collected at Buan Gyehwa-myeon region, and 50 samples from Seocheon Maseo-myeon in June, 2008, were ELISA tested. The results are 32 positives from Buan, 28.8% infection rate, 8 positives from Seocheon 16.0% infection rate. RSV infection of Deulmuksae is not reported currently, and follow report first describes the Deulmuksae as an alternate host of RSV.

Viruliferous Rate of the Small Brown Planthopper in the Maize Field Infected with Rice black-streaked dwarf virus

The Rice black-streaked dwarf virus (RBSDV) infected 99-100% of a -maize field in Mungyeong City in 2007. Adjacent to the area is a Persimmon orchard where barley crops were grown under the trees as green manure crops and for soil amendments. The barley acted as winter host to the small brown plant hoppers (SBPH) enabling the insects to survive and pass the winter season. The existence of RBSDV was detected and confirmed by RT-PCR using S9 specific primer. Samples of the insect vector SBPH were collected in the area on May 3, June 7 and, August 4 and the results of the RT-PCR analysis revealed viruliferous insect rates of 2.9, 4.8, and 4.4%, respectively. These observed viruliferous insect rates were similar with those detected in RBSDV infected rice fields.

Influence of Disease Severity of Bacterial Pustule Caused by Xanthomonas axonopodis pv. glycines on Soybean Yield

Crop Environment Research Division, National Institute of Crop Science, Rural Development administration, Suwon 441-707, Korea(Received on November 4, 2011; Revised on December 4, 2011; Accepted on December 8, 2011)Bacterial pustule of soybean (Glycine max) caused by Xanthomonas axonopodis pv. glycines is one of the mostprevalent bacterial diseases of soybean in Korea, where it causes considerable yield loss. This study was carriedout to develop yield prediction model for bacterial pustule by analyzing correlation between the percentage ofdiseased leaf area and yield. The severe disease incidence of soybean bacterial pustule caused yield losses by19.8% in 2006 and 16.8% in 2007, respectively. Severity of bacterial pustule greatly affected on 100 seed weightand yield, but did not on stem length, number of branches per plant, number of pods per plant, number of seedsper plant. On the other hand, correlation coefficients between diseased leaf area and yield were −0.93

Detection of Xanthomonas axonopodis pv. glycines and Survey on Seed Contamination in Soybean Seeds Using PCR Assay

Xanthomonas axonopodis pv. glycines is the causal agent of bacterial pustule of soybean(Glycine max. (L.) Merr), which is one of the most prevalent bacterial diseases in Korea. In this study, Polymerase Chain Reaction (PCR) assay was applied to detect Xanthomonas axonopodis pv. glycines and to survey on seed contamination in 36 soybean cultivars of Korea. And we have to compare PCR assay with dilution-plating assay of detection and identification. We confirmed detection of pathogen from artificial infected seeds and natural Infected seeds using PCR assay. This assay gave results similar to a seed-wash dilution plating assay and proved more effective than classical methods. Results of survey on seed contamination by X. axonopodis pv. glycines from 36 cultivar seeds showed that the pathogen was detected from Pungsan-namulkong, Mallikong, Taekwangkong, Daemangkong, Ajukkarikong using PCR assay. Therefore, The PCR assay provides a sensitive, rapid tool for the specific detection of X. axonopodis pv. glycines in soybean seeds.

Detection of Rice Stripe Virus using RT-PCR

Until now, occurrence of rice stripe virus (RSV) is limitted in southern part of Korea. However, recently the occurrence of RSV is increased and spreaded in central part of Korea including Chungcheong and Kyonggi province. It is very difficult to distinguish RSV symptoms on virus symptom physiological damage of rice. We detected RSV viral RNA from infected rice and its insect vector Laodelphax striatellus using specific primer of RSV-polymerase and coat protein gene with reverse transcription (RT)-PCR. The result of RT-PCR, we observed specific band including RSV-polymerase (1,,023 bp) and CP (969 bp) in both host of rice and insect vector.