• Korean Journal Plant Pathology
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• v.1 no.1
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• pp.17-21
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• 1985

Microbial antagonism between virulent and avirulent isolates of Pseudomonas solanacearum was studied in relation to the control of bacterial wilt of tobacco. In nutrient broth media or in soil, the avirulent isolate of P. solanacearum grew faster than did the virulent one. Inhibitory effect of avirulent isolate against growth of virulent one was negligible in mixed culture of the two isolates. The disease severity of bacterial wilt was significantly reduced when the roots of cultivar BY 4 susceptible to bacterial wilt was dipped in suspension of an avirulent isolate for 6 hours prior to transplanting to the soil infested with virulent bacteria. When the seedlings of tobacco were poured with the suspension of an avirulent isolate onto the soil in pre-planting pots 24 hours before ransplanting, there was a significant reduction in disease severity in the field. However, the reduction was noticed until early July, but after middle of July, no difference between the avirulent isolate-treated and non-treated plants was found in severity of the bacterial wilt.

• The Plant Pathology Journal
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• v.25 no.2
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• pp.121-127
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• 2009

Since July 2005, survey of chestnut ink disease was carried out in chestnut stands located at southern parts of Korea. Dead chestnut trees showing inky ooze on necrotic trunks were found in two different locations. In order to isolate and identify the causal fungus, infected tissues and soil samples around dead or dying trees were collected and placed on Phytophthora-selective medium. Rhododendron and chestnut tree leaves were used as a bait to isolate the fungus from soil samples by attracting zoospores in soil suspensions. On V-8 culture medium, the isolates produced homothallic oogonia with protuberances ($34.0-46.2{\times}21.9-26.7{\mu}m$) abundantly, but did not produced sporangia. Mass production of sporangia was possible by immersing agar plugs with actively growing mycelium in the creek water at $18^{\circ}C$ for 3 days. Sporangia were papillate, and ovoid to obpyriform ($17.0-38.9{\times}14.6-29.2{\mu}m$) in shape. Comparison of the ITS sequences revealed that the isolates had 100% identity to the P. katsurae isolates from Japan and New Zealand and 99.6% identity to other P. katsurae isolates. All of the examined isolates from Korea were completely identical to each other in ITS sequence. Numerous sporangia were formed in filtered as well as unfiltered creek water, but no sporangia formed in sterilized distilled water. Light induced sporangia formation, but has no influence on oospore formation. Amendments of ${\beta}$-sitosterol in culture media have no significant effect on mycelial growth but significantly stimulate oospore and sporangia formation.

• The Plant Pathology Journal
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• v.35 no.6
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• pp.575-584
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• 2019

Colletotrichum acutatum is a species complex responsible for anthracnose disease in a wide range of host plants. Strain C. acutatum KC05, which was previously isolated from an infected pepper in Gangwon Province of South Korea, was reidentified as C. scovillei using combined sequence analyses of multiple genes. As a prerequisite for understanding the pathogenic development of the pepper anthracnose pathogen, we optimized the transformation system of C. scovillei KC05. Protoplast generation from young hyphae of KC05 was optimal in an enzymatic digestion using a combined treatment of 2% lysing enzyme and 0.8% driselase in 1 M NH₄Cl for 3 h incubation. Prolonged incubation for more than 3 h decreased protoplast yields. Protoplast growth of KC05 was completely inhibited for 4 days on regeneration media containing 200 ㎍/ml hygromycin B, indicating the viability of this antibiotic as a selection marker. To evaluate transformation efficiency, we tested polyethylene glycol-mediated protoplast transformation of KC05 using 19 different loci found throughout 10 (of 27) scaffolds, covering approximately 84.1% of the entire genome. PCR screening showed that the average transformation efficiency was about 17.1% per 100 colonies. Southern blot analyses revealed that at least one transformant per locus had single copy integration of PCR-screened positive transformants. Our results provide valuable information for a functional genomics approach to the pepper anthracnose pathogen C. scovillei.

• Journal of Plant Biology
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• v.35 no.4
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• pp.393-401
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• 1992

A new species of Dictyostelium, isolated from the subalpine coniferous forests of Halla mountain, was described. The most noteworthy morphological characteristics of this new species were broad petal-like aggregates, concentrated long branches near the bases, typically clustered and delicate sorocarps. DictyosLeLium jloridurn sp. novo was also characterized by 1) elliptical spores with distinctive polar granules, 2) strongly tapering and rough surface of sorophores, 3) frequent occurrence of expanded conical bases, 4) the congealed slime substrate where the several bases were anchored into, 5) compound and c1avata tips. It was quite sensitive to environmental conditions, particularly temperature. Macrocysts and microcysts were not observed. This species can be cultured satisfactorily in assosiation with Esch'||'&'||'pound;richia coLi upon agar media of weak nutrient content, 0_1% lactosepeptone, under diffuse light and darkness. Optimum temperature for growth and develoi)ment was about $18-22^{\circ}C$, below that of most other species of the family.

• Research in Plant Disease
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• v.10 no.1
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• pp.17-20
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• 2004

A disease causing blights on leaves, stems, flowers, and pods of Vinca (Catharanthus roseus L.) was occurred in Aug. 2003 in Chengdo Peach Experiment Station. A species of Phytophthora was isolated from the diseased tissues. The causal fungus was identified as Phytophthora nicotianae on the basis of mycological characteristics and pathogenicity. Sporangia were ovoid to spherical, noncaducous, prominently papillate and averaged 38.0${\times}$31.0 ${\mu}{\textrm}{m}$ in dimension. Chlamydospores were abundantly produced on agar media and sized about 30.5 fm in diameter, The fungus was heterothallic and Al mating type. Oospores were measured 23.1 ${\mu}{\textrm}{m}$ in size. Optimum temperature for growth of the fungus was 25 to 3$0^{\circ}C$. This is the first report of occurrence of foliage blight of Vinca caused by P. nicotianae in Korea.

• Korean Journal of Plant Tissue Culture
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• v.25 no.6
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• pp.525-530
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• 1998

These studies were carried out to select the active grow hairy root lines induced from various ginseng(Panax ginseng C. A. Meyer) parts. Hairy roots were induced in root explants, stem and petiole in vitro by A. rhizogenes R1000 or A. rhizogenes $A_4$. These hairy roots could be grown on the phytohormone free medium, and PCR analysis of rol C and vir C gene fragments confirmed that hairy roots were transgenic tissues. We have selected 11 hairy root lines with active growing characters among 300 hairy root lines selected based on growth and morphological characteristics on 1/2MS solid media with 250 mg/L carbenicillin. Morphological characteristics of selected 11 hairy root lines were thickness and thiness of main roots, and many projection for lateral roots, active grow of lateral roots. Among selected 11 hair root lines prominent characteristics of hairy roots with active growing characters were thiness of main roots and active grow of lateral roots. But characteristics of low growing hairy roots were thickness of main roots and low grow of lateral roots. Finally we have selected actively growing hairy roots, KGHR-1, KGHR-5, KGHR-8 among 11 hairy root lines.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.12 no.2
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• pp.285-291
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• 1992

The purpose of this research, through kinetic analyses and pilot plant experimentation of biofilm filtration reactor, is to study the theoretical equation of head loss in the Biofilm Reactor. The Head loss in the biofilm reactor has occurred due to the biofilm growth and the adhesion to the media surface and stagnation of upflow air bubble, which have caused the pore spaces to become smaller. On a basis of the head loss theory of sand filtration, therefore, the following equation of head loss for the biofilm reactor was proposed from this research results and proved to be possible to apply the equation for practical design of the biofilm filter. $h={\frac{h_o}{L}}{\int}^L_00.58\exp[-4.5){\sigma}_B)][{\frac{1-{\varepsilon}_o+({\sigma}_B)}{1-{\varepsilon}_o}}]^2{[\frac{{\varepsilon}_o}{{\varepsilon}_o-({{\varepsilon}_B)}}]^3dz$ here ${\sigma}_B=0.130+0.001{\theta}$.

• Journal of Plant Biotechnology
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• v.43 no.1
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• pp.110-118
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• 2016

We compared germination efficiency for somatic embryos (SE) of Liriodendron tulipifera using semi-solid (SS), temporary immersion bioreactors (TIB), and continuous immersion bioreactors (CIB) to produce vigorous plants. The bioreactors were designed to be immersed in liquid media with plantlets with an adjustable immersion time. TIB and CIB improved germination rates up to 80.86% and 95.21%, respectively, however, CIB produced more hyperhydric plantlets than TIB. The height of plantlets in TIB was significantly higher than for those in CIB. Fresh weights of plantlets grown in CIB of were significantly lower than for those grown in TIB. The lowest chlorophyll concentration was found in in vitro plantlets from CIB. We examined abnormally developed leaves, stems, and apical zones of in vitro plantlets that were produced in CIB. Among the three types, SS showed the highest stomatal density and the shortest stomatal length in in vitro plantlets. After acclimatization, plants from CIB exhibited the lowest values in biomass, such as height, root collar diameter, leaf fresh weight, leaf length, leaf width, petiole length, petiole diameter, and leaf area. Photosynthesis and transpiration rates of ex vitro plants were not significantly different among the three culture types, but stomatal conductance was higher in TIB than in the SS and CIB. Therefore, the results suggest that TIB is the preferable bioreactor to improve in vitro plantlet regeneration of L. tulipifera. TIB-originated plants showed higher growth rate than SS and CIB after transferring to soil.

• The Plant Pathology Journal
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• v.16 no.3
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• pp.125-129
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• 2000

A rapid and efficient assay to determine melanin biosynthesis inhibition of Magnaporthe grisea, a causal agent of the rice blast, by chemicals was developed. Wells in 24-well plates were loaded with spore suspension of the fungus and three known melanin biosynthesis inhibitors of KC10017, tricyclazole, and carpropamid. Subsequent color changes of mycelia and culture media in the wells were observed 7 days after incubation. The wells treated with KC10017 (an inhibitor of polyketide synthesis step and/or pentaketide cyclization step) became colorless, whereas tricyclazole (an inhibitor of 1, 3, 8-trihydroxynaphthalene reductase) or carpropamid (an inhibitor of scytalone dehydratase)-treated wells exhibited red color. They did not show any inhibitory effect on fungal growth. The inhibition of reaction steps prior to 1, 3, 6, 8-tetrahydroxynaphthalene formation was easily determined by colorless medium and mycelia. However, it was impossible to distinguish between inhibition of reduction steps and inhibition of dehydration steps by colors of the cultures. It was accomplished through HPLC analysis of the melanin biosynthesis-involving pentaketide metabolites accumulated by the inhibitors. Through screening of a number of synthetic chemicals using the in vitro assay, we could find a novel chemical group of melanin biosynthesis inhibitor.

• Korean Journal of Plant Tissue Culture
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• v.24 no.6
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• pp.357-360
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• 1997

Multiple shoot formation was obtained from excised axillary buds of Achyranthes japonica NAKAI cultured on MS media containing various growth regulators such as auxin and cytokinin. The highest average number of shoots was obtained in 1 mg/L NAA and 2 mg/L BA after 6 weeks (25.8 adventitious shoots per node). Although the regeneration rate was less than the former condition, optimal combination for the production of more shoots with a suitable size was 0.5 mg/L NAA and 1 mg/L BA (19.7 adventitious shoots per node). Roots were induced from regenerated shoots after 3 weeks culture, transferred to 1/2 MS medium supplemented with 0.1 mg/L IBA. Micropropagated plants were successfully transferred to soil.