• Journal of the Korean Society of Tobacco Science
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• v.20 no.1
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• pp.50-56
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• 1998

The complementary DNA (cDNA) of potato virus Y- vein necrosis strain (PVY-VN) replicase gene (Nlb) was transformed into tobacco (Nicotiana tabacum cv. Burley 21) plants. Out of 25 putative transformants regenerated, 3 were resistant to PVY-VN, one highly resistant plant with no symptom until seed harvest time and the other two with mild chlorotic spot symptoms at late stages after infection. No symptom was observed in the highly resistant plant, while mild vein necrotic symptoms were developed on suckers of the moderately resistant plants after seed harvest time, In the first generation (T1) via self fertilization, resistance to susceptibility frequency in transgenic plants from the highly resistant transformant was about 3 : 1, while it was lowered much (about 1:2 and 1:19) in T1 of the moderately resistant transformants. In the second generation (T2) of the highly resistant plant, resistance frequencies were similar to T1, but resistance levels varied greatly and appeared to be decreased. Key words : potato virus Y, viral replicate gene, transgenic tobacco plants, resistance.

• Journal of the Korean Society of Tobacco Science
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• v.18 no.1
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• pp.54-59
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• 1996

Erwinia carotovora subsp. Carotovora (Ecc), a pathogen of tobacco hollow stalk disease, was isolated for testing susceptibility to streptomycin from diseased plants in burley tobacco growing area. Of 157 isolates tested, 17 isolates (108%) were resistant to the antibiotic at the antibiotic from field soils, which streptomycin had been used continuously for three years for control of the disease was three times higher than those of non-used. There was no difference in virulence and generation time between streptomycin-sensitive and resistant strains.

• Journal of the Korean Society of Tobacco Science
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• v.18 no.1
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• pp.21-29
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• 1996

Tobacco plants resistant (cvs. Xanthi-nc and Samsun-NN) and susceptible (cv. NC 82) to tobacco mosaic virus (TMV) were inoculated with TW to obtain basic information about the characteristics of resistance expression in tobacco plants by examining the viral populations, symptom development and gene expression of pathogenesis-related proteins (PR-proteins) such as PR-1 and $\beta$-1, 3-glucanase in different temperature conditions. TMV populations in resistant plants increased more at 37$^{\circ}C$ than at 27$^{\circ}C$, while the viral populations increased continuously and were not significantly influenced by the temperature conditions in the susceptible tobacco plants. Infection sites of resistant tobacco leaves were remarkably expanded in proportion with increased time at the high temperature.

• Journal of the Korean Society of Tobacco Science
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• v.30 no.1
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• pp.1-7
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• 2008

Bacterial wilt caused by Ralstonia solanacearum has become a severe problem on tobacco in Korea. No effective single control measure is available at present time. One of the most potential way for controlling the bacterial wilt on tobacco is growing tobacco cultivars resistant to the bacterial wilt. In this study, optimal conditions for screening tobacco cultivars resistant to the bacterial wilt were examined to provide reproducible and efficient methods in growth chamber testing and field experiments for evaluating plant disease resistance. For this, already-known inoculation methods, inoculum densities, and incubation temperature, and plant growth stages at the time of inoculation were compared using tobacco cultivars resistant (Nicotiana tabacum cv, NC95), moderately resistant (N. tabacum cv. SPG70), and susceptible (N. tabacum BY4) to the bacterial disease. It was determined that root-dipping of tobacco seedlings at six true leaf stage into the bacterial suspension with inoculum level of $10^8$ colony-forming units (CFU)/ml for 20 min before transplanting was simple and most efficient in testing for resistance to the bacterial wilt of tobacco caused by R. solanacearum, for which disease incidences and severities were examined at 2 weeks of plant growth after inoculation at $20{\sim}25^{\circ}C$ in a growth chamber. These experimental conditions could discriminate one tobacco cultivar from the others by disease severity better than any other experimental conditions. In field testing, the optimum time for examining the disease occurrence was late June through early July. These results can be applied to establishing a technical manual for the screening of resistant tobacco cultivars against the bacterial wilt caused by R. solanacearum.

• Journal of the Korean Society of Tobacco Science
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• v.17 no.1
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• pp.57-61
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• 1995

Black shank(Phytophthora parasitira roar. nicotianae) resistant burley tobacco (Nicotiana tabacum L.) germplasms, KB 104 and KB 106, were developed by Korea Ginseng & Tobacco Research Institute. KB 104 was developed from the single cross of Burley 21$\times$Newton 77, using a modified pedigree method. KB 104 was highly resistant to black shank, and its agronomic characteristics and chemical contents were comparable to those of Burley 21, and value per 10a was slightly higher than Burley 21, KB 106 is a maternally derived doubled haploid made by N. africana method from the single cross of Burley 21$\times$ Va 509. KB 106 was also highly resistant to black shank, had two more harvestable leaves per plant and flowered three days later than Burley 21 did. Total alkaloid and nicotine contents of KB 106 were significantly lower than those of Burley 21. But its nornicotine content was higher than Burley 21 5. Key wads : Burley tobacco germplasm, Black shank resistance.

• Journal of the Korean Society of Tobacco Science
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• v.20 no.1
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• pp.66-70
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• 1998

TMV resistant lines (TRLs) originated from the Blo plant of Nicotiana tabacum cv. NC82 transformed with TMV coat protein cDNA which initially showed delayed disease symptom were selected for increased resistance in each subsequent generation. The result of field experiment of the transgenic tobacco lines in the fifth generation for TMV resistance and their response to other tobacco diseases (black shank, bacterial wilt, and powdery mildew) is described in this report. When fifteen TRLs of the fifth generation were tested for TMV resistance by mechanically inoculating the individual plants, over 95 percent of the plants of 6 lines showed complete resistance even 8 weeks after the inoculation. Average frequency of the resistant plants in TRLs of the fifth generation 8 weeks after the inoculation was 87%. Stable insertion and expression of TMV coat protein cDNA in the fifth generation of the transgenic tobacco plant were confirmed by PCR and immunoblot hybridization, respectively. All TRLs were resistant to the black shank but were susceptible to the bacterial wilt disease and the powdery mildew to the same degree as non-transgenic NC82 was. Therefore, it was indicated that the phenotypes related at least to disease resistance were not changed in the transgenic tobacco. Key words : TMV CP cDNA, TMV resistant tobacco plant, transformation.

• Journal of the Korean Society of Tobacco Science
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• v.21 no.1
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• pp.70-76
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• 1999

KF 116 was TMV resistant tobacco plant and KB 301 was PVY resistant plant transformed with TMV CP gene and PVY CP gene, respectively. These resistant plants were cross-fertilized and the 4 lines of the TMV-PVY resistant plants were selected from F1 hybrid plants. The rate of PVY-resistant plant in these hybrids was 100 percent and that of TMV-resistant plants including delay type was 90-98 percent at 4 weeks after virus inoculation. It was confirmed that the TMV and PVY CP genes were integrated into the genome of hybrid plants by genomic PCR, and Southern blot hybridization. The genome of F1 hybrid plants had one copy and 4 copies of PVY-CP gene and TMV-CP gene, respectively, and CaMV 35S promoters were not methylated, regardless of the difference symptom development to TMV.

• Journal of the Korean Society of Tobacco Science
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• v.19 no.1
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• pp.11-17
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• 1997

A flue-cured tobacco variety (Nicotiana tabacum cv. Wisconsin) was used for Plant transformation with the complementary DNA (cDNA) of potato virus Y-necrosis strain (PVY-VN) replicase gone (Nb) which was synthesized through reverse-transcription Primed with oligo(dT) and Polymerization using RNase H-digested template. The cDNA was cloned into Plant expression vector Plasmid (PMBP2), and introduced into tobacco plants by co-culturing tobacco leaf disks with Agrobacterium tumefaciens LBA4404 containing the plasmid before Plant regeneration. Eight Plants, in which the inserted cDNA fragment was detected by Polymerase chain reaction (PCR), out of 70 putative transformants inserted with sense-oriented Mb cDNA showed no symptom at 3 weeks after inoculation, while the other 62 plants, and all plants with vector gone only and antisense-oriented NIb cDNA had susceptible vein-necrosis symptoms. However, only 2 of the 8 resistant plants were highly resistant, which remained symptomless up to 10 weeks after inoculation. Among the first progenies (T1) from self-fertilized seeds of the two resistant transgenic plants, less than 10 % of 71 plants appeared highly resistant (with no symptom), 70% moderately resistant (with mild symptoms on 1 - 2 leaves), and about 20% susceptible (with susceptible symptoms on 3 or more leaves) at 3 weeks after inoculation. These results suggest that the PVY resistance was inherited in the 71 generation. Key words : potato virus Y. viral replicase gene, transgenic tobacco Plants, resistance.

• Journal of the Korean Society of Tobacco Science
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• v.18 no.1
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• pp.60-65
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• 1996

Chemicals including antibiotics and bactericides were screened for suppression of streptomycin-resistant Erwinia cmutouom subsp. cmutovom (Ecc) strains in laboratory and field conditions. Oxytetracycline, ethoquinolac and dichlorophen suppressed the growth of streptomycin-resistant Ecc strains in vitro. Fractional inhibitory concentration (FIC) indices of oxytetracycline and ethoquinolac mixed with streptomycin against the Ecc strains were equal to and less than one, respectively. Consequently the efficacy of those chemicals in mixture with sorptomycin were non-antagonistic But that of dichlorophen mixed with streptomycin was more than one, therefore the efficacy of the mixture was antagonistic. Spray of oxyteoucycline, ethoquinolac and agrimycin-100 on the topped burley tobacco plants was efficacious in reducing tobacco hollow stalk at the same level of sorptomycin treatment in three-year field trials, which suggests that those are promising chemicals to be alternative to streptomycin for control of tobacco hollow stalk.

• The Plant Pathology Journal
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• v.16 no.4
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• pp.222-226
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• 2000

In disease surveys from 1986 ti 1998, disease incidence of tobacco black shank was gradually increased in burley tobacco from 1996. To study the causes of the disease occurrence, one hundred and fourteen isolates of Phytophthora parasitica var. nicotianae (Ppn) were collected from burley tobacco-growing areas in the southern part of Korea during 1996-1997, and tested in vitro for meatlaxyl sensitivity which was determined by measuring the mycelial growth on corn meal agar (CMA) amended with metalaxyl. Of the tested isolates, 78.1% showed sensitive to metalaxyl, having $\textrm{ED}_{50}$ values less than 1.0 $\mu\textrm{g}/$\textrm{ml}, while 1.7% was resistant weth $\textrm{ED}_{50}$ greater than 100 $\mu\textrm{g}/$\textrm{ml}. Ppn isolates from three provinces, Chungnam, Chonbuk and Chonnam showed similar distributions of metalaxyl sensitivity. Metalaxyl-resistant isolates were not significantly different from metalaxyl-sensitive ones in mycelial growth rate, chlamydospore formation capacity and size of the spore, and pathogenicity on tobacco plant (cv. Burley 21). These results suggest that the metalaxyl-resistant Ppn in burley tobacco may be one of the major factors to cause the higher occurrence of the tobacco black shank in the burley tobacco-growing area.