Jeom-Deog Cho

Complexity of dsRNA mycovirus isolated from Fusarium graminearum.

Fusarium graminearum is the causal agent of a serious scab disease of small grains in Korea. We screened 827 isolates of F. graminearum from diseased barley and maize and tested for the presence of double-stranded RNA (dsRNA) mycovirus. Of them, 19 isolates contained various sizes of dsRNAs. A dsRNA associated with pronounced morphological changes including reduction in mycelial growth, increase in dark orange to red pigmentation, reduced sporulation and virulence was previously observed in nine dsRNA-containing Fusarium isolates (Chu et al., Appl Env Microbiol 68, 2529–2534, 2002). Ten additional isolates were found infected with dsRNA mycoviruses. These mycoviruses contain 2–4 different segments of dsRNAs with the size-range of approximately 1.7–10 kbp in length. The presence of dsRNAs did not affect colony morphology and were transmissible through conidia and ascospore with incidence of 30–100%. Interestingly, dsRNA mycovirus found in F. graminearum isolates, JB33 and JNKY19, that show the pattern of mixed infection of two different viruses were transmitted to all progeny conidia and ascospores. These results indicate that there is genomic diversity of dsRNA mycoviruses that infect F. graminearum isolates and that impact of virus infection on hosts morphology and virulence is determined by the interaction between dsRNAs and the fungal host, not by the mere presence of the dsRNAs.

Survey of Viral Diseases Occurrence on Major Crops in 2007

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.

Viruses and Symptoms on Peppers, and Their Infection Types in Korea

The incidence of virus disease on peppers was investigated at the 52 areas in the whole country in 2002, 2004 to 2006. Among the six viruses, Cucumber mosaic virus (CMV), Pepper mottle virus (PepMoV), Pepper mild mottle virus (PMMoV), Broad bean wilt virus 2 (BBWV2), Tobacco mild green mosaic virus (TMGMV) and Tomato spotted wilt virus (TSWV), infecting peppers in Korea, the incidence of CMV, PepMoV, PMMoV and BBWV2 was 29.4%, 13.6%, 14.3%, 25.6%, orderly. TMGMV and TSWV had the same low infection rate of 1.0%. The infection rate of CMV was higher as 53.3% and 34.2% in 2002 and 2004, but it was decreased to 18.2% and 11.9% in 2005 and 2006, respectively. The infection rate of BBWV2 was lower as 1.3% in 2002 and 1.8% in 2004, but it was increased abruptly to 41.3% in 2005 and 58.2% in 2006. For the types of mixed infections of pepper viruses, the incidence of CMV+PepMoV was 62.6% in 2002 and 50.0% in 2004, and that of CMV+BBWV2 was increased suddenly from 33.3% in 2005 to 83.2% in 2006. The triplex infection of CMV+BBWV2+PepMoV was 6.4% in average. CMV caused severe mosaic and BBWV2 induced ring spots, and the two mixed virions caused chlorosis on the leaves of red peppers. TSWV induced the typical symptoms of multiple ring spots on the leaves and fruits of red peppers.

2007?2011 Characteristics of Plant Virus Infections on Crop Samples Submitted from Agricultural Places

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

Biological Characteristics and Nucleotide Relationships in Korean Tomato spotted wilt virus Isolates

Tomato spotted wilt virus (TSWV) was identified from seven plants at two areas, Anyang and Dangjin, in Korea. The isolates of TSWV were seven as TSWV-KATm from tomato, TSWV-KAPo from potato, TSWV-KABal from balsam, TSWV-KACTm from cherry tomato and TSWV-KAIxe from Ixeris dentata at Anyang area, and TSWV-KDSe from sesame and TSWV-KDRP from red pepper at Dangjin area. Pathogenicity of seven TSWV isolates was various on the assay plants, and could not be grouped definitely. Three isolates of TSWV-KAIxe, TSWV-KACTm and TSWV-KABal had relatively narrower host ranges among the seven isolates. Percentage of nucleotide substitution in nucleotide sequences encoding nucleocapsid protein (NCP) was 1.2-1.7% among seven TSWV isolates and TSWV-KP. Korean TSWV isolates were divided into three groups by nucleotide homology or amino acid compositions. From the analysis of nucleotide sequences of Korean TSWV isolates compared with those of TSWV reported from other 5 countries including Japan, the Korean seven isolates of TSWV was grouped with German TSWV (D13926). No Korean TSWV isolates were grouped with those from The Netherlands, Brazil and USA.

Reduction of Tomato spotted wilt virus on Table Tomatoes in Greenhouses by Soil Fumigation

Tomato spotted wilt virus (TSWV) has occurred on fields annually disease occurrence rates were 73.3% in 2005, 53.3% in 2006 and 41.6% in 2007 at Anyang area in Gyeonggi Province. Seasonal occurrence pattern of TSWV showed a dramatic increase from 8.7% in late May to 30.1 % in early June in 2007 at Anyang area, coincided with the high population of a thrip, Frank-liniella occidentalis at that time. The rate of viruliferous thrips with TSWV on lettuce and red pepper was 20.2% and 52.1%, respectively, in greenhouses. Dazomat, soil fumigation pesticide, reduced TSWV disease incidence drastically on table tomato as treatment the chemical into the soil with humidity in early spring in 2006 and 2007. Spraying insecticide periodically after treatment with Dazomat was more effective to control TSWV than spraying if on plants or applying into the soil of the insecticide during growing season. Control efficiency through treatments both of the soil fumigation and of spraying insecticide was significantly high with 85.3% in 2006 and 87.8% in 2007. Removing the potential vector from the soil of TSWV infested area can be an effective strategy for reducing TSWV disease.

Ribgrass Mosaic Tobamovirus Occurred on Chinese Cabbage in Korea

A tobamovirus, Ribgrass mosaic virus (RMV), was identified newly from chinese cabbage (Brassica campestris L. pekinensis) in Korea. Virus disease incidence of RMV on chinese cabbage was 37.9% in alpine area on August in 1993. RMV induced the symptoms of necrotic ring spots, necrotic streak on midrib and malformation. RMV, Ca1 and Ca3 isolate, could infect 35 species out of 45 plants including Chenopodium amaranticolor. Physical properties of RMV Ca1 isolate were very stable as 10.8 over for dilution end point, for temperature inactivation point and 18 weeks for longevity in vitro. RMV had the soil transmission rate of 75.0% for the chinese cabbages, `Chunhawang` and `Seoul` cultivars. The purified virions of RMV had the typical ultraviolet absorption spectrum of maximum at 260 nm and minimum at 247 nm. RMV of Ca1 isolate was related serologically with antisera of Tobacco mosaic virus (TMV)-Cym, TMV-O and Pepper mottle virus, but not related with antiserum of Odontoglossum ring spot virus. coat protein gene of RMV-Ca1, sized 473 nucleotides, encoded 158 amino acid residues. Nucleotide identity of RMV-Ca1 CP gene was 96.4% with RMV-Shanghai (GenBank accession No. of AF185272) from China and 96.0% with RMV-Impatiens (GenBank accession No. of AM040974) from Germany. Identity of amino acids between RMV-Ca1 and the two RMV isolates was 96.8%. Specific three primers were selected for rapid and easy genetic detection of RMV using Virion Captured (VC)/RT-PCR method.

Occurrence of Chrysanthemum chlorotic mottle viroid in Chrysanthemum(Dendranthema grandiflorum) in Korea

Chrysanthemum chlorotic mottle viroid(CChMVd) isolates have been identified from chrysanthemum showing yellow spots or infected without symptom. They were 399-400 nucleotides length of RNA. CChMVd-SSHA6(GenBank accession no. DQ450682) revealed a GAAA to DUUC substitution in positions 82-85 of CChMVd-MSIN34(GenBank accession no. DQ402041). In vitro RNA transcripts with the complete CChMVd sequence were infectious and induced the typical CChMVd infection symptom of yellow spots in chrysanthemum cv. Sharotte. CChMVd caused reduction in growth in some cultivars, whereas some cultivars were not affected. This is the first report on the occurrence of CChMVd in chrysanthemum in Korea.

Strawberry mild yellow edge potexvirus from Strawberry in Korea

National Academy of Agricultural Science, RDA, Suwon 441-707, Korea(Received on March 23, 2011; Accepted on April 25, 2011) Symptoms induced in the leaves of strawberry (Fragariax ananassa Duch.), ‘Seolhyang’ and ‘Eyeberry’, weremosaic, distortion and black colored edge on leaves atNonsan area, one of the important production areas inKorea. Electron microscopy by quick-dip revealed theflexuous rod-shape particles having about 550-600 nmlength. Cytoplasmic inclusion bodies composed of aggre-gated virus particles were observed frequently in meso-phyll parenchyma and epidermal cells for the leaves ofstrawberry. The specific primers amplifying products of635 bp and 729 bp were developed for RT-PCR detec-tion of Strawberry mild yellow edge virus (SMYEV).Nucleotide identity of the CP gene of SMYEV was 92.8-99.2% with those of other SMYEV isolates from Gen-Bank database.Keywords : nucleotide identity, RT-PCR, SMYEV,strawberry, ultrastructureStrawberry, the genus Fragaria, is one of the fruit veget-ables producing about 200 metric tons for the five yearsfrom 2001 in Korea (naqs.go.kr/statistics). The Koreanconsumption of strawberry is shared to 6% of world and13% of Europe production (Babini et al., 2004). More than30 kinds of virus are known to infect strawberry, but thesymptoms are not described well. Viral infection instrawberry may cause stunting under continuous croppingand a loss of vigor, and resulted up to 80% yield loss fromthe synergistic symptom expression with the mixedinfection of two or more viruses. The disease by Strawberrymild yellow edge virus (SMYEV) was first described inCalifornia in 1922 and it has occurred with an infection rateof over 30% (Converse et al., 1987). SMYEV is transmitted by the strawberry aphid in apersistent manner. Five European countries including Italy,three aphid-transmitted viruses, Strawberry mild yellowedge virus (SMYEV), Strawberry mottle virus (SMoV) andStrawberry crinkle virus (SCV) without Strawberry veinbanding virus (SVBV) occurred with the infection rate of1.3%, 1.6% and 1.2%, respectively, and SMoV occurredonly regionally in Poland and Lithuania (Babini et al.,2004; Karesova et al., 2004). The viral infection can bedetermined by the diagnostic methods of bioassay, sero-logical test of ELISA and genetic test of RT-PCR. Thebioassay using indicator plants by grafting has been usedclassically. The ELISA and RT-PCR have been developedrecently against strawberry infecting viruses (Thompsonand Jelkmann, 2004a), but those methods need to beverified for the purpose of certification or quarantine in theworld (Martin, 2004). The multiplex RT-PCR for the 4aphid transmitting viruses was proposed (Thompson, Wittzeland Jelkmann, 2004), however, three viruses (SCV, SMYEVand SMoV) could be detected in every possible combi-nation, excluding with SVBV. In Korea, there is no reportfor the viruses infecting strawberry to date in spite of massproduction of strawberry fruits from the mass multiplicationof strawberry clones. Strawberry cultivar ‘Seolhyang’ was collected from Nonsanarea and ‘Eyeberry’ cultivar was acquired at greenhousemaintaining genetic resources in Nonsan strawberry experi-ments station. Mosaic symptom was produced typically onthe newly developed leaves of strawberry ‘Seolhyang’(Fig. 1). The leaves showing mosaic symptom were develop-ed distortion later. On ‘Eyeberry’ cultivar of strawberry, thetypical symptom of black colored edge on the leaves wasproduced. Electron microscopy was conducted through LEO 902A.Quick leaf dip method was used for the observation of virusparticles after staining with 2% PTA. Potexvirus particles offlexuous rod having 550-600 nm length were observedfrequently from the leaves of strawberry showing the symp-toms of mosaic, distortion and black leaf margin (Fig. 2).For the ultrastructural studies of the infected cells, theleaves of strawberry were cut into 1 × 1-2 mm and fixedwith Karnovsky’s fixative for 30 min. The fixed specimenswere dehydrated with ethyl alcohol gradually from 30% to100% with 8 steps. For infiltration medium of the dehydratedspecimens, LR White resin was used. Hardening of theresin blocks was done at 60 for 24 hr. Sections of 80 nmthickness were stained with uranyl acetate and lead citrate

Convenient Genetic Diagnosis of Virion Captured (VC)/RT-PCR for Rice Viruses (RSV, RBSDV) and Small Brown Plant Hopper

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.