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Citrus vein enation virus (CVEV), which was regulated as a quarantine virus in Korea, was firstly found on Jeju Island in 2017. In February 2018, a survey was carried out to determine the distribution of CVEV in the main commercial areas growing Citrus spp. and Poncirus trifoliata. The survey was performed at 203 groves in the southern Korean Peninsula and Jeju Island. CVEV infection was determined by reverse transcription polymerase chain reaction detection and sequencing. The coat protein (CP) gene sequences obtained from the CVEV-infected samples showed high similarities (more than 98%) to the previously reported CVEV CP sequences. In summary, CVEV was detected in 136 groves (67%), in which 85.4% of Citrus junos and 77.8% of Citrus unshiu were infected by CVEV. In Jeju Island, the infection rate of CVEV was relatively higher (90.6%). Our result revealed that CVEV has spread widely in Citrus and Poncirus in Korea. Based on the result, the Korean quarantine agency decide to exclude CVEV from quarantine in Korea.

Apple chlorotic leaf spot virus (ACLSV), Apple stem pitting virus (ASPV), Apple stem grooving virus (ASGV), and Apple scar skin viroid (ASSVd) are economically important viruses that infect pear tree species worldwide. To evaluate the prevalence of these viruses in Korea, we investigated infection degree of three viruses and one viroid for the commercial nursery trees of the pear cultivars, Niitaka, Chuwhang, Wonwhang, and Whasan in 2017 and 2018. The results showed that the infection ratio of ACLSV, ASPV, ASGV, and ASSVd for the scion of pear cultivar Niitaka was 10%, 45%, 77%, and 50%, respectively. From the scion of pear cultivar Chuwhang, infection ratios of ASPV, ASGV, and ASSVd were found to be 70%, 50%, and 60%, respectively. From the scion of pear cultivar Whasan, infection ratios of ACLSV, ASPV, ASGV and ASSVd were found to be 40%, 60%, 93%, and 20%, respectively. From the root stock of pear cultivar Wonwhang, infection ratios of ACLSV, ASPV, ASGV, and ASSVd showed 28%, 57%, 100%, and 14%, respectively. ASGV had the highest recorded infection rate, and ACLSV was characterized by the lowest infection rate. The mixed infection ratio of Niitaka, Chuwhang, Whasan, and Wonwhang was 45%, 60%, 70%, and 85%, respectively.

A multiplex reverse transcription-polymerase chain reaction (mRT-PCR) assay was developed for the detection of Clover yellow vein virus (ClYVV), Peanut mottle virus (PeMoV), and Tomato spotted wilt virus (TSWV), which were recently reported to infect soybean and azuki bean in Korea. Species-specific primer sets were designed for the detection of each virus, and their specificity and sensitivity were tested using mixed primer sets. From among the designed primer sets, two combinations were selected and further evaluated to estimate the detection limits of uniplex, duplex, and multiplex RT-PCR. The multiplex RT-PCR assay could be a useful tool for the field survey of plant viruses and the rapid detection of ClYVV, PeMoV, and TSWV in leguminous plants.

In 2010, foliar symptoms were observed in the paprika leaves in Jinju city, Korea. Beet western yellows virus (BWYV) was identified in paprika by using the large-scale oligonucleotide chip assay. To investigate the occurrence of BWYV, a survey was performed on various crops, including paprika, from 2011 to 2014. Further, the presence of BWYV was consistently verified through literature survey from 2015 to 2017. BWYV infection has been identified in Solanaceae crops (bell pepper, hot pepper, and paprika), various weeds, and green peach aphids and it occurs on a nationwide scale. Cultivation using organic methods involved natural enemies and showed a high BWYV infection rate, which was more than that for conventional cultivation methods in greenhouse. The complete genome sequence of BWYV isolated from paprika was determined for the first time. The genome of the BWYV-Korea isolate consists of 5750 nucleotides and has six open reading frames. Sequence identity results showed maximum similarity between the BWYV-Korea isolate and the BWYV LS isolate (identity ＞ 90%). This study is the first report of BWYV infecting paprika in Korea. The survey revealed that BWYV is naturalized in the domestic ecology of Korea.

Throughout year 2015 to 2016, 101 proso millet and 200 sorghum samples were collected from five provinces in South Korea. The samples were subjected to paired-end RNA sequencing and further analyzed by RT-PCR. The results indicated that Rice black-streaked dwarf virus (RBSDV) was detected from sorghum collected in Gyeongsang province. The other four viruses, including RBSDV, Rice stripe virus (RSV), Barley virus G (BVG), and Cereal yellow dwarf virus (CYDV), were detected from proso millet. Among four viruses, both RSV and RBSDV were identified high frequency from proso millet collected from Gyeongsang province. Otherwise, BVG was nearly equally identified from five provinces, suggesting that the virus was supposedly widespread nationwide. RBSDV was first identified from both proso millet and sorghum in South Korea. The other virus annotated CYDV identified proso millet was shown to have relatively low identities compared to CYDV previously reported, suggesting that the virus might be new member of Polerovirus.

During 2012 to 2014, a survey for the presence of viral diseases in yam plants was carried out in a field of the Institute for Bioresources Research in Gyeongsangbuk-do, Korea. A total of 88 leaf samples were collected and tested by reverse transcription polymerase chain reaction using specific primer sets. Eighty-one samples were positive for Broad bean wilt virus 2 (BBWV2), Chinese yam necrotic mosaic virus (ChYNMV), Cucumber mosaic virus (CMV), Japanese yam mosaic virus (JYMV), and Yam mild mosaic virus (YMMV), whereas Yam mosaic virus (YMV) was not detected. Additionally, seven samples were negative for all viruses. Several samples exhibited mixed (double and triple) infections. Three viruses (CMV, JYMV, and YMMV) were detected for the first time in yam plants in Korea. A BLAST search showed that three viruses shared nucleotide identities with CMV-Ca (98%), JYMV-O2 (91%), and YMMV-TG_NH_1 (86%). Thus, our findings confirmed that yam plants cultivated in Korea were infected with multiple viruses with three of these viruses reported for the first time in Korea.

In 2015, a nationwide survey was carried out to investigate about occurrence pattern of virus infecting foxtail millet. A total 100 foxtail millet leaf samples showing virus-like and abnormal symptoms were collected in the seven main cultivated regions of Korea. Four viruses were identified using reverse transcription polymerase chain reaction and RNA sequencing. Of the collected 100 foxtail millet samples, 10 were Barley virus G (BVG), 4 were Rice stripe virus (RSV), 1 was Northern cereal mosaic virus (NCMV), and 1 was Sugarcane yellow leaf virus (ScYLV) infection. To our best knowledge, this is the first report of BVG and NCMV infecting foxtail millet in Korea and ScYLV is expected as new Polerovirus species. This research will be useful in breeding for improved disease-resistant foxtail millet cultivars.

In May 2016, 24 peach samples showing abnormal and virus like symptoms were collected in one of major peach producing area, Yeongcheon-si, Gyeongsangbuk-do, Korea. We performed RT-PCR diagnosis for confirmation of viral infection. The diagnostic targets are 17 species of viruses and viroids that quarantine and high risk pathogens when it occur. As a results, seven species of viruses and viroids, including an unreported (Apricot pseudo-chlorotic leaf spot virus, APCLSV) and a quarantine (Peach latent mosaic viroid, PLMVd) species in Korea, were detected. For the sequence analysis of unreported virus, APCLSV, the sequence of coat protein gene were amplified and cloned. The sequence showed 97% nucleotide identity with other APCLSV isolates and compared with other seven species of reported Trichoviruses. This virus was classified as APCLSV based on the sequence and phylogenetic analysis. This isolate was named Yeongcheon. As patterns of APCLSV occurrence, all samples that APCLSV detected were co-infected with Apple chlorotic leaf spot virus (ACLSV). As properties of ACLSV, APCLSV has high possibility of wide spread disease in fruit tree farms in Korea. Therefore, it is necessary to do related researches, such as infection route and influence of disease in commercial orchards.

Cymbidium mosaic virus (CymMV) is a major virus infecting orchid plants and causing economic loss. In this study, the incidence of viral infection in Calanthe spp. at the Korean Institute of Calanthe was investigated using reverse transcription polymerase chain reaction. The CymMV infection rate was 42%, and the two viruses Odontoglossum ringspot virus and Cucumber mosaic virus had frequencies of 8% and 2%, respectively. Additionally, we characterized an isolate of CymMV, CymMV-GW, using biological tests and examined the nucleotide sequence properties of its complete genome. CymMVGW induced chlorotic ringspots and chlorotic spot symptoms in inoculated leaves of Chenopodium amaranticolor and Nicotiana benthamiana, respectively. In this study, we have for the first complete genome sequence of CymMV-GW in Korea. The CymMV-GW genome was 6,225 nucleotides in length, excluding the poly-(A) tail, and showed whole-genome nucleotide and amino acid sequence identities of 97.7% and 100%, respectively, with the NJ-1 isolate of CymMV. Here, we report the complete genome sequence of the CymMV-GW isolate and viral infection rates for Calanthe spp. in Korea.

)은 상록활엽관목으로 늦겨울과 이른 봄에 꽃을 피워 그 향기를 천리까지 보낸다고 하여 천리향이라는 이름으로 잘 알려져 있다(Garibaldi 등, 2009; Ro 등, 2009). 원산지가 중국으로 알려진 서향은 내한성이 약하여 제주도를 포함하여 일부 남부 지역에 자생하고 있으며(Liang 등, 2010; Ro 등, 2011), 관상가치가 뛰어나 정원, 길거리 및 아파트 조경용으로 많이 심겨지고 있는 정원수 중 하나이다(Kwon 등, 2005). 또한, 한의학에서 서향의 뿌리와 나무껍질은 관절염, 고열, 피부염 등의 치료를 위한 한방재료로 이용되기도 한다(Chen 등, 2009; Kim 등, 2005). 2009년, 국내에서 재배되는 서향에서 바이러Open AccessRes. Plant Dis. 22(1): 59-63 (2016)http://dx.doi.org/10.5423/RPD.2016.22.1.59

Soybean mosaic virus (SMV) is a prevalent pathogen that causes significant yield reduction in soybean production worldwide. SMV belongs to potyvirus and causes typical symptoms such as mild mosaic, mosaic and necrosis. SMV is seed-borne and also transmitted by aphid. Eleven SMV strains, G1 to G7, G5H, G6H, G7H, and G7a were reported in soybean varieties in Korea. A reverse transcription loop-mediated isothermal amplification (RT-LAMP) method allowed one-step detection of gene amplification by simple procedure and needed only a simple incubator for isothermal template. This RT-LAMP method allowed direct detection of RNA from virus-infected plants without thermal cycling and gel electrophoresis. In this study, we designed RT-LAMP primers named SML-F3/B3/FIP/BIP from coat protein gene sequence of SMV. After the reaction of RT-LAMP, products were identified by electrophoresis and with the detective fluorescent dye, SYBR Green I under daylight and UV light. Optimal reaction condition was at 58°C for 60 min and the primers of RT-LAMP showed the specificity for nine SMV strains tested in this study.

In May 2013, an angel’s trumpet leaves showing mosaic and malformation symptoms were collected from Suwon city, Gyeonggi-do. An analysis of the collected sample by transmission electron microscopy observation showed filamentous rod particles of 720-800 nm in length. On the basis of the these observations, we performed PCR against three reported Potyviruses (Brugmansia mosaic virus, Colombian datura virus and Brugmansia suaveolens mottle virus), and the sample was positive for BruMV. Pathogenicity and host range test of BruMV was determined by mechanical inoculation. Solanaceae (tobacco, tomato and eggplant) and Amaranthaceae (ground cherry) appeared typical virus symptoms. To determine coat protein of this virus, we designed specific primer pairs, and performed PCR amplification, cloning, and sequencing. Phylogenetic analysis showed that BruMV-SW was most closely related to BruMV isolate SK. Comparison of the BruMV-SW coat protein nucleotide sequences showed 92% to 99% identities to the other BruMV isolates.

A disease, supposedly caused by a virus, was observed from Insam (Panax ginseng) fields of Punggi in year 2006. It has long believed to be a physiological disorder. However, the incidence of the disease has increased every year. When several samples were observed under electron microscope, filamentous virus-like particles were observed. The nucleotide sequences of the virus were analyzed by RT-PCR with specific primer sets derived from the results of DNA chip. The results indicated that the disease was caused by Watermelon mosaic virus (WMV). It revealed that the result of the biological assay by the virus was different from that of WMV previously found in other crops. Therefore, this is the first report that WMV causes the disease in P. ginseng and the virus is named to be WMV-Insam.

In surveys of weed occurrence undertaken from 2006 to 2007, near to the Daegu experimental fields of theNational Institute of Crop Science, plants belonging to 31 families, 74 genera and 96 species were found. Forthe investigation of the natural or alternative hosts of Soybean yellow mottle mosaic virus (SYMMV), 495 plantsamples belonging to 26 families 84 species were subjected to RT-PCR. SYMMV was detected only fromlegume plants such as Glycine soja, Vigna angularis var. nipponensis, Trifolium repens, and Lespedeza cuneata.Among legume plants tested, more than a third of G. soja (wild soybean) contained SYMMV, indicating thatthe wild soybean played an important role as a reservoir of SYMMV. Wild soybeans may be infected withSYMMV as early as mid-July. Considering the results of early infection and the high infection rate of seedand seed transmission of SYMMV in G. soja , wild soybeans may have played an important role in thecompletion of disease cycle of the virus.Keywords : Disease cycle, Natural hosts, Soybean, Soybean yellow mottle mosaic virus , Wild soybean

For quarantine purpose, we developed the RT- and nested PCR module of Tomato black ring virus (TBRV), Arabis mosaic virus (ArMV), Cherry leafroll virus (CLRV) and Grapevine fanleaf virus (GFLV). The PCR modules, developed in this study make diagnosis more convenient and speedy because of same PCR condition. And also, the methods are more accurate because it can check whether the result is contamination or not using the mutation-positive control. We discard or return the 27 cases of Nepovirus infection seed by employing the module past 3 years. This study provides a rapid and useful method for detection of four quarantine plant viruses.

National Institute of Horticultural and Herbal Science, Horticultural and Herbal Environmental Division,Suwon 441-707, Korea(Received on September 11, 2012; Revised on October 11, 2012; Accepted on October 12, 2012)The total number of requests and associated specimens for the diagnosis of virus infection were 573 and 2,992,respectively, on crops from agricultural places of farmers, Agricultural extension services and so forth for 5years from 2007. The total number of virus tests was 13,325. The number of species of viruses infected on thesubmitted crops was 21 in 2007, 15 in 2008, 23 in 2009, 21 in 2010 and 17 in 2011. The newly recorded viruseswere Tobacco leaf curl virus (TbLCV) in 2007, Tomato yellow leaf curl virus (TYLCV) in 2008, Impatiencenecrotic spot virus (INSV) and Radish mosaic virus (RaMV) in 2009, and Beet western yellows virus (BWYV) in2010. Forty virus species including Alfalfa mosaic virus were detected over 5 years. The ten most frequentlydetected virus species were Cucumber mosaic virus (CMV), Tomato spotted wilt virus (TSWV), Tomato leaf curlvirus (TYLCV), Cucumber green mottle mosaic virus (CGMMV), Broad bean wilt virus 2 (BBWV2), Zucchiniyellow mosaic virus (ZYMV), Melon necrotic spot virus (MNSV), Pepper mild mottle virus (PMMoV),Watermelon mosaic virus (WMV) and Pepper mottle virus (PepMoV). The types of crops submitted fromagricultural places were 51 in total and the ten most frequently submitted crops were red pepper, tomato,paprika, watermelon, melon, rice, cucumber, corn, radish and gourd. The total request rate for the top 10crops and top 20 crops was 81.6% and 94.2%, respectively. Eight pepper infecting virus species includedCMV, and the average infection rate was 24.6% for CMV, 18.9% for PMMoV and 14.7% for TSWV. Sevenkinds of double infection were detected in pepper including BBWV2+CMV at 14.7% on average, and fourtypes of triple infection including BBWV2+CMV+PepMoV at 0.9% on average. Six virus species detected ontomato including TYLCV, and the average infection rate was 50.6% for TYLCV, 14.5% for TSWV and10.9% for Tobacco leaf curl virus (TbLCV). The mixed infection of CMV+TSWV on tomato was 3.9% onaverage and of Tomato mosaic virus (ToMV)+TYLCV was 0.4% on average. Five viruses detected onwatermelon included MNSV and the average infection rate was 37.0% for MNSV, 20.4% for CGMMV,18.1% for ZYMV and 17.8% for WMV. The mixed infection rate on watermelon was CMV+MNSV andWMV+ZYMV having an average infection rate of 0.7% and 5.0%, respectively. The average infection rateson melon were 77.6% for MNSV, 5.6% for CMV and 3.3% for WMV. Mixed infections of CMV+MNSVoccurred on melon with an average infection rate of 13.5%. Keywords : BBWV2, BWVY, CGMMV, CMV, MNSV, Plant virus, TYLCV, ZYMV

The kinds of crop requested from agricultural actual places of famers, Agricultural extension services and soforth was 8 including red pepper for vegetables, 4 including apple for fruit trees and 6 includingchrysanthemum for flowers in 2010. The important vegetables in clinical diagnosis of viral diseases weretomato, watermelon and red pepper having the requested rate of 31.8%, 21.4% and 19.5%, respectively. Onfruit trees, grape and apple were most common with the requested rate of 63.6% and 33.0%, orderly. Onfloral crops, tulip and cactus were damaged by viral diseases with the requested rate of 60.0% and 20.0%,orderly. On peppers and tomatoes, six viruses including Cucumber mosaic virus (CMV) and Broad bean wiltvirus 2 (BBWV2) infected. Five viruses including Melon necrotic spot virus (MNSV) and CMV were identifiedfrom watermelons. On grapes, six viruses including Grapevine fleck virus (GFkV) infected. CMV wasidentified from six vegetables including pepper out of 8 kinds of vegetables and tulip plant. Total agents ofvirus and viroid species were 32 and 4 species, respectively, in 2010. Tomato yellow leaf curl disease by Tomatoyellow leaf curl virus and Tobacco yellow leaf curl virus was occurred newly at 18 Si/Gun areas including Buan,Jeonbuk province in 2010 and the total areas were increased up to 58 Si/Gun from the first incidence in 2008.Tomato spotted wilt virus (TSWV) occurred newly at two areas of Jinan, Jeonbuk and Jeju in Jeju province in2010, and the incidence areas were expanded to 25 Si/Gun areas from severe occurrence at Anyang area in2004. No incidence of TSWV was recorded only in Gyeongbuk and Chungbuk province. Tomato bushy stuntvirus occurred newly at Jinju, Gyeongnam, and it had the total incidence areas of 5 Si/Gun after firstobservation at Sacheon, Gyeongnam in 2004.

Throughout the years 2008 to 2010, we analyzed approximately two thousand oriental melon samples collected from Seongju, using electron microscopy and testing by RT-PCR using primers specific for eight cucurbit-infecting viruses. Data from RT-PCR indicated that Cucumber green mottle mosaic virus (CGMMV), Watermelon mosaic virus 2 (WMV2) and Zucchini yellow mosaic virus (ZYMV) were present and the other viruses were not detected. Among them, CGMMV and WMV2 were the most prevalent pathogens. CGMMV was thought to infect oriental melon from the early growing season, and reached nearly 100% in the later of growing period. Otherwise, WMV2 emerged from June, several months later compared to CGMMV. CGMMV was detected from all aerial parts of the oriental melon including seeds, but not from the roots of the grafted pumpkin rootstock. Seed of two out of five commercial varieties were shown to be CGMMV positive. Nine varieties of pumpkins used as rootstocks were not infected with CGMMV. When the seedlings of grafted oriental melon were transplanted into pots mixed with the oriental melon debris infected with CGMMV, they were not infected by CGMMV. Cutting of pruning shear and the contact of tendrils contributed 48% and 30% to the transmission of the virus, respectively.

Virus diseases occurring on cucumber was surveyed at main plantation areas of ``Sangju`` and ``Gurye`` in 2006 and 2007. Viral infection rate on cucumber was ranged from 14% to 90% in fields and the average infection rate was 46% at Sangju area. Cucumber cultivated at Gurye area had viral incidence ranged 9-100% and averaged 48%. The majorly infected viruses were Cucumber green mottle mosaic virus, Zucchini yellow mosaic virus, Papaya ring spot virus and Watermelon mosaic virus-2, and their infection rates were 23.5%, 13.0%, 9.0% and 2.0%, respectively in 2006 and 2007. Mixed infection rate of duplex, triplex and tetraplex was 31.5%, 7.5% and 2.5%, respectively. The rate of infection type was 47.7% by single infection, 31.5% by double infection and 88.7% by both infection types. Important viruses involved in mixed infection types were Zucchini yellow mosaic virus, Cucumber green mottle mosaic virus, Papaya ring spot virus and Broad been wilt virus2, orderly. Symptom in single infection was almost same on ``Dadagi`` line and ``Chicheong`` line of cucumber cultivars. Cucumber green mottle mosaic virus produced various symptoms of chlorotic spot, vein chlorosis and vein wrinkle and so on. Main symptoms of vein chlorosis, and severe mosaic and malformation were induced by Zucchini yellow mosaic virus. Mild symptoms were occurred relatively by Papaya ring spot virus and Watermelon mosaic virus2.

In 2005, a survey was conducted to identify virus diseases on victory onion, Allium victorialis var. platyphyllum grown in Ulleung island located in the East Sea. A total of 61 samples were collected from victory onion in the neighborhood of Seonginbong. The identification of viruses from the samples were carried out by electron microscopy and RT-PCR using primers species specific to GCLV, LYSV, SLV, OYDV and genus specific to Allexivirus, respectively. From sixty-one samples, filamentous rod particles (600-900 nm) were detected from four victory onion samples in EM, three samples containing SLV and one sample containing both SLV and Allexivirus in RT-PCR analysis, respectively. Victory onions naturally infected by the viruses were asymptomatic apparently. The viruses detected by RT-PCR were further characterized by the nucleotide sequence analysis of the coat protein region. Three isolates of SLV showed approximately 99% identities in the nucleotide and amino acid sequences, suggesting that they were likely to be the same strain. On the other hand, they showed approximately 75.7~83.7% identities in the nucleotide and 89.2~97.0% in amino acid sequences compared with the previously reported SLV isolates in Allium. The CP gene of the Allexivirus showed approximately 99.2% nucleotide identities and 98.8% amino acid identities with Garlic virus A. However, there was relatively low homology ranging from 60.6% to 81.5% compared with other Allexiviruses (GarV-C, GarV-E, GarV-X, GMbMV, and Shal-X). These data suggested that two viruses, SLV and GarV-A identified from victory onion, are named SLV-Ulleungdo and GarV-A-Ulleungdo, respectively. This is the first report of viruses infecting victory onion.

Among the plant specimens requested from agricultural actual places of farmers, Agency of agricultural extension services and so forth for the diagnosis of plant virus diseases in 2009, the rate of crop types was 87.5% for vegetables, 4.0% for upland crops and 3.5% for orchids. In vegetables, the crops damaged severely by viral diseases were red pepper and tomato by the infection rate of 51.6% and 26.5%, orderly. Virus species occurring vegetables were 19 and the economically important viruses were Cucumber mosaic virus (CMV), Tomato spotted wilt virus (TSWV), Tomato yellow leaf curl virus (TYLCV), Pepper mild mottle virus (PMMoV) with the infection rate of 33.2%, 16.9%, 16.1% and 7.4%, respectively. Rice stripe virus (RSV) occurred at the whole areas of west coast in Korea in 2009, and its incidence was 14.2% mainly on the susceptible cultivars and yield loss was estimated up to 50%. TYLCV was spread at 34 areas of Si and/or Gun, 22 areas in 2009 and 12 in 2008. Distribution of TSWV was expanded newly in 6 areas of Si and/or Gun including Gangryung, Gangwondo in 2009, and its occurrence areas were 23 Si and/or Gun after first incidence at Anyang area in 2004. Tomato bushy stunt virus (TBSV) was incited newly at Gimcheon area in 2009 with the infection rate of 65.2%, and its soil transmission rate was 55.0% in average.

Genetic diagnosis method of Virion Captured (VC)/RT-PCR for Rice stripe virus (RSV) and Rice black-streaked dwarf virus (RBSDV), Korean major rice viruses transmitted by small brown plant hopper, Laodelphax striatellus, was developed. Virion extraction buffer for rice plant was 0.01M potassium phosphate buffer, pH 7.0, containing 0.5% sodium sulfite. However, the extraction buffer for L. striatellus was 0.01M potassium phosphate buffer, pH 7.0, containing 0.5% sodium sulfite and 2% polyvinylpyrrolidone wt 40,000 (PVP-40). Specific primers for detection of RSV and RBSDV were selected for VC/RT-PCR method. The specific primers were used as a duplex primer to detect viruliferous small brown plant hopper collected from Gimpo, Pyeongtaek and Siheung areas in Gyeonggi province. The genetic diagnosis methods of single and duplex VC/RT-PCR for RSV and RBSDV could be used easily and economically, especially on the diagnosis of L. striatellus. The rate of viruliferous insect (RVI) for RSV was compared with ELISA and VC/RT-PCR for L. striatellus collected from fields. RVI by ELISA was same as 9.2% with RVI by VC/RT-PCR. However, there were some different detection results between the methods. It could be suggested that there is a possibility of serological and/or genomic differences among RSV isolates. The portion of RVI detected simultaneously by ELISA and VC/RT-PCR was 71.0%, and the detection rate from VC/RT-PCR was higher as 3.2% than that from ELISA, which had a reason of simultaneous detection ability both RSV and RBSDV of VC/RT-PCR.

Viruses diagnosed on crops including rice plants from farmers or agricultural extension agencies cover the country were 11 species including Broad bean wilt virus 2 (BBWV2) in 2008. Tomato spotted wilt virus (TSWV) was the most important virus having the detection rate of 22.9%. Two viruses of Tomato yellow leaf curl virus (TYLCV) and Tobacco leaf curl virus (TLCV) inducing leaf yellow and curl diseases on tomatoes were occurred newly with the detection rate of 12.2% and 4.0%, respectively, in 2008. Rice stripe virus (RSV) was occurred on 869.5 ha mainly at Jindo and Haenam areas in Jeollanamdo province. At Jindo area, 12 plots were damaged severely with the infected hill rate of 83.8%. At the main production area of oriental melon at Seongju, almost all fruits from whole sale market at Seongju were infected with Cucumber green mottle mosaic virus (CGMMV) as the detection rate of 87%. The areas occurred TSWV in Korea were 25 totally from 2003 including 7 areas newly reported in 2008 including Naju in Jeoallanamdo. TSWV could be reduced as 0.1 % from 5.3% by covering insect proof net in vinyl house after chemical soil sterilization. Tomato yellow leaf curl disease was occurred on April in 2008 at Tongyoung area in Kyeongsangnamdo, and detected continuously at 13 areas, 7 in Kyeongsangnamdo, 4 in Jeollabukdo and 2 in Jejudo. Potato spindle tuber viroid (PSTVd) was occurred abruptly in a confined space of a civil breeding greenhouse and a cultivar evaluation field followed by disuse 17.4 M/T of potato tubers. No PSTVd was detected at 17 fields cultivated the related potatoes to the bred company by RT-PCR.

The severe damage induced by the important viruses of Rice stripe virus (RSV), Cucumber green mottle mosaic virus (CGMMV), Melon necrotic spot virus (MNSV), Tomato spotted wilt virus (TSWV) and Tomato bushy stunt virus (TBSV) was described on major crops in Korea. In 2007, the plot incidence rate of RSV was 100% on the precocious rice cultivars at the Western coastal provinces of Gyeonggido, Chungcheongnamdo, Jellabugdo and Jellanamdo, and Jejudo. RSV occurred in 2,441 ha with incidence rate of 70% over at 5 areas of Seocheon, Seosan, Boryung, Hongsung and Buyou in Chungcheongnamdo. At 4 areas of Buan, Gimje, Gunsan and Gochang in Jellabukdo, RSV occurred in 2.016 ha. CGMMV occurred on watermelon in 4.6 ha at Cheongyang area, and its outbreak was also 890 ha on oriental melon for 120 farmers with the incidence area of 23% against total cultivation areas of Seongju. MNSV was recorded firstly on watermelon in 2006 at Andong and it spread to 3 areas of Hapcheon, Gochang and Yanggu. TSWV occurred firstly at Danggin in Chungcheongnamdo in 2005. TSWV in 2006 spread to 6 areas; Taian, Hongsung and Seosan in Chungcheongnando, Namwon in Jellabukdo, and Sunchon and Kwangju in Jellanamdo. In 2007, TSWV covered 17 areas of western and southern parts; the 5 area including Taian in Chungcheongnamdo, Kwangju in Jellanamdo, Bucheon in Gyunggido, and so forth. TBSV was described firstly on table tomato at Sacheon in Kyungsangnamdo in 2004. TBSV occurred on cherry tomato at Chungju in 2006 and on table tomato at Busan area.

In year 2003, a soybean(Glycine max) sample showing severe dwarfing symptom was collected from a farmers` field in Cheongsong in Korea. The results from the diagnosis of the sample by RT-PCR revealed that it was infected by Soybean dwarf virus(SbDV), SbDV-L81. This study could be the first report of the occurrence of the virus in Korea. To further characterize the virus, the partial nucleotide sequence of the genomic RNA of SbDV-L81 was determined by RT-PCR using species-specific primers. The sequences were analyzed and subsequently compared to previously characterized strains of SbDV based on the pattern of symptom expression and vector specificities. The intergenic region between ORF 2 and 3 and the coding regions of ORF 2, 3 and 4 were relatively similar to those of dwarfing strains(SbDV-DS and DP) rather than those of yellowing strains(SbDV-YS and YP). Likewise, the result from the analysis of 5`-half of the coding region of ORF5 indicated that SbDV-L81 was closely related to strains(SbDV-YP and DP) transmitted by Acyrthosiphon pisum. These data from the natural symptom and the comparisons of five regions of nucleotide sequences of SbDV suggested that SbDV-L81 might be closely related SbDV-DP.

In 2004, average temperature was higher, and rainfall was less than those of previous year, The diseases of rice, barley, pepper, chinese melon, apple and oriental pear were surveyed. Seedling diseases, leaf blast, sheath blight and bacterial blight of rice, phytophthova blight, virus diseases and anthracnose of pepper, and sudden wilt syndrome and powdery mildew of chinese melon grown in plastic greenhouse were severe. Especially, sheath blight and bacterial blight of rice occurred two times higher than those of previous year, Panicle blight of rice decreased about 4 times, compared with the previous year, presumed that the lower rainy days, rainfall and RH suppressed spread of the fungal pathogens to panicles of rice. Lower rainfall during mid- and late Aug caused three-times less occurrence of phytophtora blight of red-pepper than that of the previous year, Another diseases surveyed occurred similar or less than those of the previous year.

In the year of 2002 annual nationwide survey of virus diseases occurring in the pepper fields and greenhouses in Korea, the distribution and the incidence of viral diseases was investigated. The pepper samples from both greenhouses (155 samples) and open fields (227 samples) were collected and further analyzed to detect eleven different viruses by RT-PCR. The results indicate that no sample collected from both greenhouse and open field seems to be infected by TMV, RMV, PVY, AMV, and TSWV. On the other hand, CMV, BBWV2, PepMoV, PMMoV, TMGMV and ToMV are readily identified from greenhouse and open field samples by RT-PCR. The infection rates of the collected samples between greenhouse and open field are largely different. Comparing with 10% of virus-infected pepper samples grown in greenhouse, approximately one third of pepper samples collected from open field are infected. The mixed-infection rates in the virus-infected greenhouse and open field samples are 16% and 61%, respectively. The dominant virus occuring in greenhouse is PMMoV, indicating that virus-infected seed stocks and infected plant debris in the growing area may be important sources of inocula. On the other hand, both CMV and BBWV2 are dominant viruses in open field. This may indicate that the migration of viruliferous insect vectors into pepper fields may be the most important source of inoculum. Also, the survey shows that BBWV2 is newly immerging virus to be controlled in Korea. The discrepancies on the distribution and the occurrence of viral diseases between field and greenhouse may provide a fact that the accumulation and distribution of inoculum by successive cultivation and the migration of viruliferous vectors into growing areas are likely to be important factors to determine the incidence of viral diseases. Therefore, the further studies on epidemiology and the consideration of new breeding program of pepper are essential to minimize virus diseases.

Recent occurrence of virus diseases on watermelon plants cultivated in Jeonnam province was investigated from 1998 to 2002. While virus diseases were severely occurred on watermelon cultivated in green house in 1998, those of open field were severer than in green house since 2000. When 128 samples collected from different fields were examined by electron microscopy, 87.8％ of the samples contained rod-shaped or filamentous virus particles. RT-PCR analysis of the samples revealed that Cucumber green mottle mosaic virus (CGMMV) was only detected from collected samples at May. Watermelon mosaic virus (WMV) was most frequently found and CGMMV and Zucchini yellow mosaic virus (ZYMV) were slightly at June and July. However Cucumber mosaic virus (CMV) and Papaya ringspot virus (PRSV) have not been detected.

Field disease incidences of squash virus diseases in Jeonnam province were estimated to be 76.1% and of delayed planting on August-September (retarding culture) and on February-March (semi-forcing culture) on glass house were 55.0% and 0%, respectively, in 2000. Disease incidences of individual squash plant within a field were 100% and 3.6%, respectively, in wild culture and retarding culture. Total of 61 samples suspected to be infected with viruses were collected in 2000 and tested by RT-PCR using specific oligonulceotide primer sets designed for the detection of Cucumber green mottle mosaic virus (CGMMV), Kyuri green mottle mosaic virus (KGMMV), Zucchini yellow mosaic virus (ZYMV), Papaya ring spot virus (PRSV), Watermelon mosaic virus (WMV), and Cucumber mosaic virus (CMV). Each specific primer set for WMV, ZYMV, and PRSV amplified expected size of DNA fragments from 16, 10, and 2 samples in wild culture, respectively. Double or triple infection were observed in 7 samples tested. In contrast, each specific primer set for WMV, ZYMV, and PRSV confirmed virus infection from 7, 6, and 6 samples, respectively, in samples collected from semi-forcing culture. Double infection of WMV and PRSV was observed in only one sample. However, no DNA fragment was amplified from RT-PCR using CGMMV, KGMMV, and CMV specific oligonucleotide primer sets indicating no CGMMV, KGMMV, or CMV infection in squash fields in Jeonnam province in 2000.