• Korean Journal of Breeding Science
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• v.43 no.5
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• pp.464-469
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• 2011

Virus diseases often cause serious damage to rice production in Asia. The lack of information on virus resistance genes has been a major obstacle for the breeding of resistant varieties. In order to identify DNA marker associated with resistance against rice stripe virus (RSV), the quantitative trait locus (QTL) was carried out using advanced backcross population developed from a cross between RSV-resistant tongil type cultivar Shinkwang and susceptible japonica cultivar Ilpum. A RSV resistance QTL $qSTV11^{SG}$ explaining 44.2% of the phenotypic variation was identified on chromosome 11 of Tongil type rice cultivar 'Shingwang'. $qSTV11^{SG}$ was tightly linked to DNA marker RM6897. The RM6897 divided as resistance type allele and susceptible type alleles. Twenty seven resistant varieties showed the resistant-type allele and 23 susceptible varieties were susceptible-type allele to the marker of RM6897. This results and the molecular markers presented here may be useful in rice breeding for improving RSV resistance in japonica rice.

• Korean journal of applied entomology
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• v.23 no.4 s.61
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• pp.197-202
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• 1984

Two soybean cultivars Hanan and Kwanggyo were used to monitor SMV spread in the field. The Haman producing mosaic symptoms by infection with SMV strain G7 was planted in $2.2m^2$ at the coater of $320.7m^2$ field and Kwanggyo producing necrosis by infection with SMV-G7 was planted around the Haman one day after inoculation of Heman with SMV-G7. The most severe incidence of the necrotic disease in soybean cultivar Kwanggyo occurred on 43 days after planting(July 13) whereas aphid population reached peak around 22 days after planting(June 22). Total incidence of the necrotic disease was $20.4\%$, in the whole field and $56\%$, in eight $mall plots around the spreader of SMV. The spread of S MV outward from the spreader source was greater downwind than it was upwind. Spread also showed a signigicant gradieut pattern leeward from the infection focus.

• Research in Plant Disease
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• v.20 no.4
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• pp.303-306
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• 2014

Tomato yellow leaf curl virus (TYLCV) disease survey of tomato plants cultivated at Youngam, Changseong and Hwasun in Jeonnam Province was conducted in 2012 to 2013. To detect TYLCV in the field, PCR assay was performed using genomic DNAs extracted from tomato samples. According to cropping pattern, 23 and 59.4% of TYLCV infections were shown in semi-forcing and retarding cropping systems, respectively, and the frequencies of diseased plants were 0.4 and and 13.1% in the two cropping systems, respectively. Especially, TYLCV incidences in the susceptible varieties were 24.3 and 83.0% in semi-forcing and retarding cropping systems, respectively. Resistant varieties showed 9.1% infection in retarding cropping system but did not in semi-forcing cropping system. Also, TYLCV was occurred on early June after transplanting on April and at approximate 20 days after transplanting on August or September.

• Research in Plant Disease
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• v.15 no.3
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• pp.175-182
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• 2009

We investigated the effect of the infection times and infection degrees at transplanting time of Zucchini yellow mosaic virus (ZYMV) on the growth and yield of cucumber plants at the semi-forcing and the retarding culture in 2007. When cucumber was inoculated with ZYMV at transplanting time, 15, 30, 45, 60, and 75 days after transplanting, vine length, internode length, number of leaf of the plants and marketable yield largely decreased as the cucumber infected earlier. The regression models were obtained between the disease incidence levels at 20 days after transplanting as the inoculation degrees and the marketable yield of cucumber: y = $9333.1e^{-0.0317x}$ ($R^2$ = 0.8946) at the semi-forcing culture and y = $14695e^{-0.0303x}$ ($R^2$ = 0.8735) at the retarding culture. And the cucumber yield loss regression models between the symptoms incidence days from the final harvesting time and the rates of yield decrease were expressed as y=1.0851x - 6.7067 ($R^2$ = 0.9567) at the semi-forcing culture andy=1.0439x + 2.1321 ($R^2$ = 0.9674) at the retarding culture.

• The Korean Journal of Pesticide Science
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• v.15 no.4
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• pp.490-494
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• 2011

Rice stripe virus (RSV) has been the main viral disease of rice plant in western coastal region of Korea since 2000. The control of the vector insect, small brown planthopper (Laodelphax striatellus), is the most effective management method of the persistently-transmitted viral disease. Thus, ecological study between RSV and the vector insect was needed and investigated in order to make effective control plan, especially about study on the feeding and transmission of the virus by the vector insect. Each larval stage of vector insect differed in vector competence; larvae over 4th stage were shown as higher transmission after feeding on RSV-infected rice plant. These 4th and 5th larvae had higher transmission rates, 69.2% and 67.9% respectively, than 44.8% of the adult stage. The vector competence, however, was changed according to temperature; the highest transmission rate was 93.3% on $30^{\circ}C$ in comparison to 70.6% on $25^{\circ}C$ and 43.8% on $20^{\circ}C$.

• Korean Journal of Poultry Science
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• v.46 no.2
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• pp.127-136
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• 2019

Three strains of infectious bronchitis viruses (IBVs), designated VNUA3, VNUA8 and VNUA11, were isolated from diseased/infected chickens in Hanoi, Thainguyen, and Haiphong provinces of Vietnam. These birds had received a live IBV vaccination but still suffered from infectious bronchitis. VNUA3, VNUA8 and VNUA11 harbor cleavage sites (RRTGR, HRRRR, and HRRKR, respectively) within the S protein. A BLASTN search revealed that the S gene of VNUA3, VNUA8, and VNUA11 showed the highest nucleotide identity with those of IBV strains CK/Italy/I2022/13, CK/CH/LHLJ/08-6, and GX-NN120084, respectively. Phylogenetic analyses based on the S gene nucleotide sequences revealed that VNUA3, VNUA8 and VNUA11 clustered with Q1-like, QX-like and TC07-2-like genotypes, respectively, and were closely related to reference IBV strains from China. However, the Vietnam IBVs showed high divergence from vaccine strains 4/91 and Ma5, which are used in the Vietnamese farms from which the isolates were obtained. Taken together, these results indicate that at least three genotypes of IBV are circulating among chickens in North Vietnam. This is the first report of the molecular epidemiology of IBV in Vietnam.

• Research in Plant Disease
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• v.17 no.3
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• pp.351-357
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• 2011

Occurrence of Rice stripe virus (RSV) was investigated in Jeonnam province from 2008 to 2011. Incidence of RSV was surveyed in paddy fields during growth stage. In western and southern coast parts of 5 districts, Jindo, Wando, Shinan, Haenam and Muan, rice was severely damaged by RSV from 2008 to 2009. But, RSV didn't almost occur in 2010. Viruliferous ratio (VIR) of RSV from overwintered small brown plant hopper (SBPH, Laodelphax striatellus) showed 4.7%, 11.3%, 8.7%, and 2.8% from 2008 to 2011. It was highly recorded in Jindo, Wando, and Shinan of southwestern area. SBPH was collected by sucking machine at 1 $m^2$ with 3 replications per paddy field in March. The density of SBPH was high on March, but low on April in non-cultivated barley field from winter to spring. Farmer's plowing this season assumed to be a cause of SBPH density decrease. The number of SBPH was 7.7, 5.4, and 4.0 per $m^2$ during three years, respectively.

• Research in Plant Disease
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• v.10 no.1
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• pp.48-52
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• 2004

We investigated the effect of infection time of CGMMV on the growth and quality of watermelon and cucumber plants. The effect (damages by CGMMV) was estimated on the watermelon where CGMMV had been inoculated at different growth stages, vegetative (transplanting stage, vegetative growth stage) and reproductive growth stage (fruiting stage and fruit hypertrophy stage). In the case of cucumber, CGMMV was inoculated at transplanting stage and Erst flowering stage, respectively. When watermelon was infected with CGMMV at vegetative growth stage, vine length, internode length, leaf area, and fruit weight of the plants largely decreased compared with control plants, while the infected plant growth was not very different from control plants when it was infected at reproductive growth stage. Brix of the fruit of watermelon also decreased when the plants was infected with the virus earlier than fruiting stage. The occurrence of 'Pisubag', internal discoloration and decomposition of watermelon fruits, tended to be increased as earlier infection time with CGMMV In the case of cucumber infection time with CGMMV did not influence earlier growth of the plants, but did later growth showing that plant height, vine length, internode length, number of leaf, leaf wide, and leaf length of the plants decreased as infection time became to be earlier.

• Journal of Microbiology and Biotechnology
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• v.31 no.4
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• pp.529-539
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• 2021

The beet armyworm, Spodoptera exigua, is a serious insect pest infesting various vegetable crops. Two infectious insect viruses, baculovirus and iflavirus, are known to induce epizootics in S. exigua populations. Indeed, some laboratory colonies have appeared to be covertly infected by these viruses. Diagnostic PCR tests detected two different viruses: Spodoptera exigua multiple nucleopolyhedrosis virus (SeMNPV) and iflaviruses (SeIfV1 and SeIfV2). Viral extract from dead larvae of S. exigua could infect Sf9 cells and produce occlusion bodies (OBs). Feeding OBs to asymptomatic larvae of S. exigua caused significant viral disease. Interestingly, both SeIfV1 and SeIfV2 increased their titers at late larval stages. Sterilization of laid eggs with 1% sodium hypochloride significantly reduced SeMNPV titers and increased larval survival rate. Double-stranded RNA (dsRNA) specific to SeIfV1 or SeIfV2 significantly reduced viral titers and increased larval survival rate. To continuously feed dsRNA, a recombinant Escherichia coli HT115 expressing SeIfV1-dsRNA was constructed with an L4440 expression vector. Adding this recombinant E. coli to the artificial diet significantly reduced the SeIfV1 titer and increased larval survival. These results indicate that laboratory colony collapse of S. exigua is induced by multiple viral infections. In addition, either suppression of SeMNPV or SeIfV infection significantly increased larval survival, suggesting a cooperative pathogenicity between baculovirus and iflavirus against S. exigua.

• Research in Plant Disease
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• v.17 no.1
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• pp.66-74
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• 2011

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.