Dong Bum Shin

One-step multiplex reverse transcription-polymerase chain reaction for the simultaneous detection of three rice viruses.

Rice stripe virus (RSV), Rice black-streaked dwarf virus (RBSDV), and Rice dwarf virus (RDV) are major rice-infecting viruses in Korea that can cause serious crop losses. A one-step multiplex reverse transcription-polymerase chain reaction (mRT-PCR) was developed for the simultaneous detection of these rice viruses. Three sets of specific primers targeted to the capsid protein coding genes of RSV, RBSDV, and RDV were used to amplify fragments that were 703 bp, 485 bp, and 252 bp, respectively. The one-step mRT-PCR assay proved to be a sensitive and rapid method for detecting the three rice viruses. This method could be used to facilitate better control of rice viruses.

Change in Occurrence of Rice stripe virus Disease

We surveyed the occurrence of Rice stripe virus (RSV) disease in 672 fields from 29 rice representative area in July 2012 as nationwide survey for RSV occurrence since 2008. We confirmed occurrence of virus disease in 18 areas, in west coast region including Secheon, Taean, Buwan and Cheorwon. RSV incidence rates of plant in Sacheon and Buan were less than 0.01% and 0.15%, respectively, showing similar rate with the nationwide survey carried out in 2008, whereas incidence rate of field declined from 19.9% in 2008 to 4.9% in 2012. Earlier, RSV occurred largely across the southern region of Korea. In 2001, RSV disease was found in Gangwha and Gyeonggi-do, the northern region of Korea. In 2007, RSV appeared in west coast; Buan in Jeollabuk-do and Seocheon in Choongnam-do. After migration of the vector, small brown plant hopper, from China in 2009, RSV is becoming a pandemic.

Distribution of Rice Blast Disease and Pathotype Analysis in 2014 and 2015 in Korea

벼는 쌀을 주식으로 하는 아시아 및 여러 국가에서 가장 중요한 작물이다. 이러한 쌀의 생산량에 가장 큰 영향을 미 치는 병해는 벼 도열병으로, 벼의 전 생육기에 걸쳐 발생하 며 환경요인에 따라 피해 수준이 심각하게 늘어나는 것으로 알려져 있다. 병 발생에 관여하는 환경요인으로 기상요인, 비료관리, 토양, 그리고 약제방제 등을 들 수 있다. 최근의 기 상 조건 및 비료관리는 벼 도열병 발생에 부적합하였다. 특 히, 지구 온난화에 의한 생육기간 중 기온 상승 및 7월 장마 가 사라지는 현상(Lee 등, 2010), 그리고 질소 비료를 적게 사 용하는 재배기술 보급이 잎 도열병이 감소하는 주요 원인으 로 생각되고 있다. 또한, 1960년대부터 시작된 벼 도열병 저 항성 품종의 육성 및 보급은 벼 도열병의 감소에 가장 크게 기여한 것으로 여겨진다(Cho 등, 2007). 그러나 매년 새로운 벼 도열병 저항성 품종을 보급하고 있 음에도 불구하고, 몇 년 이내에 저항성 품종이 감수성 품종 으로 바뀌어 병이 발생하는 사례들이 다수 보고되어 왔다 (Han 등, 1995). 이러한 저항성 역전 현상은 주로 벼 도열병균 의 유전적 변이 및 친화성 균주 집단의 급격한 증가에 의해 일어난다 (Han 등, 2001). 이에 대비하여 국립식량과학원에

Incidence of Wildfire Disease on Soybean of Korea during 2014-2015

나이며, 특히 우리나라를 비롯한 동북아시아 지역은 콩의 원산지로 식량안보차원에서 안전한 생산기반 확충이 필요 하다. 콩 생산에는 다양한 요인들이 영향을 미치지만, 병 발 생에 의한 콩 생산량의 감소와 품질 저하는 수량의 주요 제 한요인이 되어왔으며 기후변화에 따른 봄 기온 상승, 강우 량의 증가 및 감소 등은 세균병 발생 증가에 직접적인 영향 을 미치고 있다(Schaad, 2008). 콩 들불병은 담배들불병과 같은 병원균인 Pseudomonas syringae pv. tabaci에 의한 것으로 국내에는 2009년 콩에 처음 으로 보고되었고(Myung 등, 2009), 최근 게놈 시퀀스 및 분 자분류학적 분석을 통해 Pseudomonas amygdali pv. tabaci로 재분류되었다(Jeong 등, 2015). 특히 병원균이 내는 tabtoxin 이라는 독소로 인해 주위에 노란색 둘레무리가 생기는데 (Turner와 Taha, 1984), 이 독소를 분비하지 못하는 변종은 모 무늬병(angular leaf spot)으로 구분되며 국내에서는 잎담배 에 그 발생이 보고되어진 바 있다(Yi 등, 1990). 지금까지 국내 콩 포장에서 잎마름병(Kim 등, 2005), 검은 뿌리썩음병(Park 등, 2006), 콩 위축바이러스병(Kim 등, 2006) 등 신규 병 발생이 지속적으로 보고되고, 콩 불마름병의 경

Use of Sodium Hypochlorite for the Control of Bakanae Disease in Rice

For application of sodium hypochlorite as a seed disinfectant to the control of bakanae disease caused by Gibberella fujikuroi in rice, we investigated the effects of sodium hypochlorite for antifungal activity, eliminating fungus from seeds and reducing disease occurrence in vitro and greenhouse. The viability of the pathogen was significantly reduced at 80 ml/l concentration of sodium hypochlorite, and the pathogens did not grow at over 100 ml/l concentration of sodium hypochlorite. The effect of eliminating fungus was 90% at treatment of 0.3% sodium hypochlorite solution to infected rice seeds for eight hours. When the rice seeds were soaked into 0.5% and 0.3% sodium hypochlorite solutions for twelve hours, the disease incidences of rice seedling were remarkably reduced to 4.3% and 4.7%, respectively, compared to 97.3% of non-treatment control. The rates of seedling stand were 29.1% and 26.9% higher with the sodium hypochlorite treatment than that of non-treatment control. When prochloraz and sodium hypochlorite was treated to naturally severely infested rice seeds with bakanae disease, the disinfection effect was higher than that of prochloraz alone treatment. When the seeds were soaked in sodium hypochlorite before or after prochloraz, the rate of seed contamination was low as 4.0% or 6.3%, respectively, compared to prochloraz alone as 13.7%. The disease incidence was low as 3.7% or 8.3%, respectively, compared to prochloraz alone as 14.3%. The disinfection effect of treatment with prochloraz after sodium hypochlorite was higher than that of treatment with prochloraz before sodium hypochlorite.

Corn Cultivation to Reduce the Mycotoxin Contamination

The effects of insecticide and fungicide treatment were investigated to reduce mycotoxin contamination of corn (Zea mays L.) seeds. Deoxynivalenol and zearalenone contents were reduced in the treated seeds, but aflatoxin, ochratoxin A, fumonisin, and T-2 toxin were not effective by chemical treatments. The chemical treatment did not affect the growth of saprophyte, but inhibited the pathogenic fungi such as Fusarium verticillioides, F. graminearum and F. equiseti. Myotoxin contents at different harvesting time were compared. As the harvest time was delayed, both levels of deoxynivalenol and zearalenone and frequency of Fusarium spp. increased. However, the major nutrient contents of corn seeds were not affected by harvesting period. These results show that chemical treatments are necessary to reduce the fungal contamination of corn and harvest without delay is important as well.

Survey of Fungal Infection and Fusarium Mycotoxins Contamination of Maize during Storage in Korea in 2015

Maize is one of the most cultivated cereals as a staple food in the world. The harvested maize is mainly stored after drying, but its quality and nutrition could be debased by fungal spoilage and mycotoxin contamination. In this study, we surveyed mycotoxin contamination fungal infection of maize kernels that were stored for almost one year after harvest in 2015. The amount of deoxynivalenol and zearalenone detected were higher than the other mycotoxin, such as aflatoxin, ochratoxin, fumonisin and T-2 toxin. In particular, level of deoxynivalenol was detected as 1200±610 mg/kg in small size kernels, which was four to six times higher than the large and the medium size kernels. Moreover, the amount of deoxynivalenol, zearalenone, and fumonisin were increased with discolored kernels. 10 species including Fusarium spp., Aspergillus spp. and Penicillium spp. were isolated from the maize kernels. F. graminearum was predominant in the discolored kernels with detection rates of 60% (red) and 40% (brown). Our study shows that the mycotoxin contents of stored maize can be increased by discolored maize kernels mixed. Therefore elimination of the contaminated maize kernels will help prevent fungal infection and mycotoxin contamination in stored maize.

In Vitro Expression and Antibody Preparation of Rice black-streaked dwarf virus Coat Protein Gene

cc This is an open access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/ licenses/by-nc/4.0/), which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. Research Article Open Access Res. Plant Dis. 22(1): 32-37 (2016) http://dx.doi.org/10.5423/RPD.2016.22.1.32

Assessing Frogeye Leaf Spot Resistance on Recommended Soybean Cultivars

Soybean frogeye leaf spot caused by the fungus Cercospora sojina Hara, has known to lead a severe reduction of crop yield. Since frogeye leaf spot on soybean has recently become a serious problem in Korea, the susceptibility of recent recommended cultivars against C. sojina had been tested. To standardize the disease severity of soybean, the optimum sporulation condition of C. sojina and the disease index were established in this study. Sporulation was maximized on the 10% V8 juice agar with 12 h light and 12 h dark at 25C. Spore suspension (10 spores/ml) was sprayed on the leaves of soybean (V6 stage), and the disease responses to each isolate were evaluated on 28 days after inoculation. As a result, Daepung, Shinpaldal2ho, Yeonpung and Cheonga showed the resistance reaction to 8, 7, 6, 6 isolates of C. sojina, respectively, whereas Cheongja, Hwangkeum, Taekwang, Daewon, Cheonsang and Sinhwa showed the susceptible reaction to 8 isolates of C. sojina. Breeding the resistant soybean cultivars against C. sojina requires a uniform resistance for screening technique. The disease index of frogeye leaf spot on soybean developed in this study can be effectively used for the accurate field assay to select the frogeye leaf spot resistant soybean.

Evaluation of Sequential Planting Method for Screening of Durable Resistance against Rice Blast in Rice Breeding Program

A sequential planting method was developed to screen rice plants with durable resistance against rice blast in a short time, and applied for several years in Korean rice breeding program. In this study, we showed the advantages of a sequential planting method compared to other pathogenicity tests. The correlation analysis among three pathogenicity tests and other factors demonstrated that durable resistance depended on the average of diseased leaf area and the number of compatible pathogens. Significant correlations were found in the nursery test but not in the field test result. In addition, we traced changes in the pathogen population during sequential planting stages through re-isolation of the pathogen. The portion of compatible pathogens was increased during sequential planting. Through this study, we provide an effective sequential planting method and direction of durable resistance in a breeding program.