• Korean Journal Plant Pathology
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• v.14 no.6
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• pp.583-588
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• 1998

This study was conducted to investigate the potential of nitrate-nonutilizing mutants (nit mutants) in ecological studies of Fusarium disease of strawberry. Nit mutants of Fusarium oxysporum from strawberry were easily formed on chlorate-containing media. Nit mutants were assigned to three phenotypic classes, nit1, nit3, and NitM, on the basis of their growth on media containing one of the following five different nitrogen sources ; nitrate, nitrite, hypoxanthine, ammonium and uric acid. Frequency of nit mutation and proportion of three phenotypes of nit mutants depended on the isolate. Mutation rate was 45.6% and ranged from 15.0% to 95.0%. The frequency of nit1 mutants was higher than that of nit3 or NitM. The complementary reaction between nit1 and NitM was higher than that of other combination. There has been no complementary response observed between nit3 and nit3. The nit mutants showed similar growth pattern as the that of wild type isolate on potato sucrose agar and potato sucrose liquid media. Most of the mutants retained pathogenicity, and maintained their phenotypes even after two year preservation through subculture on slanted PSA at room temperature. Nit mutants were selctively isolated from infested soil and infected plants on the selective medium (MMCPA) containing potassium chlorate with their original phenotypes, while naturally occurring isolates of Fusarium oxysporum were not grow on the medium. On the contrary, nit mutants showed very slight growth on the medium (MMPA) containing nitrate as a sole nitrogen source, and therefore could be distinguished from wild type isolate.

• The Plant Pathology Journal
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• v.30 no.3
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• pp.279-287
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• 2014

KYC 3262 was selected as a biocontrol agent against anthracnose on hot pepper from 813 extracts of myxobacterial isolates. Dual culture with Colletotrichum acutatum and 813 myxobacterial extracts was conducted, and 19 extracts were selected that inhibited germination and mycelial growth of C. acutatum. All selections were Sorangium cellulosum, which are cellulolytic myxobacteria from soil. With the infection bioassay on detached fruits in airtight containers, KYC 3262, KYC 3512, KYC 3279, and KYC 3584 were selected. The listed four myxobacteria were cultured in CSG/1 liquid media, and harvested filtrates were sprayed on the infected fruits. KYC 3262 was selected from the studies of attached fruit in a greenhouse study. KYC 3262 filtrate was applied for 3 years (from 2011 to 2013) in a field study in Asan, Republic of Korea. Control values of the KYC 3262 in the field were 31%, 89%, and 82% in 2011, 2012, and 2013, whereas values of the fungicide spray treatment were 19%, 97%, and 91%, respectively. Yields (kg/20 plants) of the KYC 3262 were 2.66 kg and 18.6 kg in 2011 and 2013, respectively, and those of the fungicide treatment were 2.0 kg and 20.2 kg, in 2011 and 2013, respectively.

• Journal of Plant Biotechnology
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• v.6 no.3
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• pp.151-156
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• 2004

Soil-borne fungal pathogens such as Verticillium and Rhizoctonia can colonize in the stem tissue of plant through root and lead to wilting symptoms of plant by blocking. water transportation. During the colonization of Rhizoctonia solani in the vascular tissue of tomato stems, particularly, phenylalanine ammonia-lyase (PAL) gene induction pattern was cyclized showing peak induction at two different time points (10 and 80 h) after fungal spores inoculation in vivo. In leaves or roots, however, no such cycling pattern was observed. The first induction peak may be due to an initial sporulation events leading to a second induction peak by a proliferation of fungal spores to the upper stems or other tissues from an initial spore trapping sites. Tomato PAL gene was also dramatically induced by wounding, light illumination and mercury chloride treatment but was not cyclized. Mercury chloride showed the earliest induction with all tissues even at half an hour after treatment.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2000.10a
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• pp.96-113
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• 2000

Coleus forskohlii Briq. of the family Lamiaceae yields a valuable secondary metabolite known as forskolin which is a labdane diterpenoid. Coleus forskohlii is the only known source of this compound. Forskolin is used in medicine for the treatment of glaucoma, congestive cardiomyopathy and asthma. Morphogenic callus was induced from young leaves on MS medium augmented with NAA and BA. These calli, when subcultured on MS with KN alone gave rise to shoots. The regenerated shoot developed good root system on MS medium fortified with NAA. The fully grown plantlets were transferred to soil for acclimatization. Coleus plant is mainly infected by a fungi Lasiodiplodia theobromae which causes root of disease. The fungal culture filterate (FCF) of Lasiodiplodia theobromae, has been used in regeneration media to find the MIC and further to select resistant plants to the pathogen. In the present study 40% FCF in the medium showed maximum inhibition and is there fore considered as the MIC level of Coleus forskohlii. This data could prove to be useful for the future for selecting a resistant C,forskohlii plant against the root disease caused by L.theobromae.

• The Korean Journal of Mycology
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• v.37 no.2
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• pp.198-200
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• 2009

From 2008 to 2009, the stem rot of Astragalus sinicus L. caused by Sclerotium rolfsii occurred sporadically in Gyeongnam area, Korea. The typical symptom is water-soaking, rotting and wilting on the stem. The infected plants were eventually died. White mycelial mats were spread over lesions, and then sclerotia were formed on stems and near soil line. The sclerotia were globoid in shape, white to brown in color, 1-3 mm in size and the hyphal width was 3-9 μm. The optimum temperature for mycelial growth and sclerotial formation on PDA was 30oC. The typical clamp connections were observed in the hyphae of the fungus grown on PDA. On the basis of mycological characteristics and pathogenicity to host plants, this fungus was identified as Sclerotium rolfsii Saccardo. This is the first report on the stem rot of A. sinicus caused by S. rolfsii in Korea.

• Microbiology and Biotechnology Letters
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• v.38 no.2
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• pp.117-123
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• 2010

BT toxin is produced by a soil bacterium Bacillus thuringiensis and has long been used as a biological insecticide without any competition. Recently, Photorhabdus, a symbiotic bacterium from entomopathogenic nematodes, family Heterorhabditae, has been researched and discussed as alternatives to B. thuringiensis. Photorhabdus, which lives in the gut of entomopathogenic nematodes, is a highly virulent pathogen of a wide range of insect larvae. When an insect is infected by the nematodes, the bacteria are released into the cadaver, and produce a number of insecticidal toxins. The biological role of the different Photorhabdus toxins in the infection process is still unclear. Photorhabdus toxin complex (Tc) is highly secreted gut-active toxin and has been characterized as a potent three-component (A, B and C) insecticidal protein complex. These components are necessary for full oral activity against insect larvae. The Photorhabdus PirAB binary toxins exhibit a potent injectable activity for Galleria mellonella larvae, and have oral toxicity against mosquitoes and caterpillar pest Plutella xylostella. Other toxin, 'makes caterpillars floppy' (Mcf) showed injectable activity on caterpillars. Recombinant Mcf triggers apoptosis in both insect hemocytes and the midgut epithelium and carries a BH3 domain. In this review, the relationship between the Photorhabdus and the nematode is discussed and recent important insecticidal toxins from Photorhabdus are described.

• Research in Plant Disease
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• v.28 no.1
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• pp.51-53
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• 2022

In January 2021, unusual outbreak of shoot rot symptoms was observed in young spikenard (Aralia cordata) plants growing in vinyl greenhouses located in Chuncheon and Yanggu, Gangwon Province, Korea. The symptoms initially appeared on young shoots of the plants at or above the soil surface level. Later, the infected shoots wholly rotted and blighted. The incidence of diseased plants in the vinyl greenhouses investigated ranged from 5% to 30%. Eight isolates of Rhizoctonia sp. were obtained from shoot lesions of the diseased plants. All the isolates were identified as Rhizoctonia solani AG-2-1 based on the morphological characteristics and anastomosis test. Three isolates of R. solani AG-2-1 were tested for pathogenicity on young shoots of spikenard plants using artificial inoculation. All the tested isolates induced shoot rot symptoms on the inoculated plants. The symptoms were similar to those observed in spikenard plants from the vinyl greenhouses investigated. This is the first report of R. solani AG-2-1 causing shoot rot in spikenard.

• The Korean Journal of Mycology
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• v.50 no.4
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• pp.319-329
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• 2022

In July 2020, wilting symptoms were observed among adzuki bean plants (Vigna angularis var. angularis L.) in the fields in Yeosu, Korea. Infected plants showed yellowing of leaves, browning inside the stems, splitting of stem bark, and wilting. When these plants were uprooted, their roots were found to be brown. The fungal pathogens NC20-737, NC20-738, and NC20-739 were isolated from symptomatic stem and root tissues. These pathogens were identified as a Fusarium fujikuroi species complex based on their morphological characteristics. Molecular identification was performed using the DNA sequence of translation elongation factor 1 alpha and the RNA polymerase II second largest subunit regions. The nucleotide sequences of all three isolates were similar to the F. fujikuroi reference isolates NRRL 13566 and NRRL 5538 of the National Centre for Biotechnology Information GenBank. A pathogenicity test was conducted by the soil inoculation method with cornmeal sand inoculum. Approximately 3 weeks after inoculation, symptoms were observed only in the inoculated adzuki bean seedlings. To the best of our knowledge, this is the first report of Fusarium root rot caused by F. fujikuroi in adzuki beans, both in Korea and worldwide.

• Korean journal of applied entomology
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• v.47 no.1
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• pp.9-15
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• 2008

This study was conducted to investigate the seasonal occurrence of chestnut weevil, Curculio sikkimensis. The chestnuts infected by the weevils were collected from Gongju, Buyeo, and Cheongyang in Chungnam Province, Republic of Korea. Investigation was focus on the escape period of chestnut weevil larvae from the fruits, invading time and vertical distribution in soil, survival rates of larvae during overwintering, emergence period, emergence rate, and sex ratio and longevity of adults. For precocious species, larvae escaped the chestnut from the mid-September to the early-October, middle species and slow species, were escaped from the late-September to the mid-October and from the early-October to the mid-November. After escaping from the chestnut fruits all of the larvae burrowed into the soil within 35 minutes. Overwintering larvae inhabited in the range of $0{\sim}48cm$ from the soil surface and highly distributed in the range of $18{\sim}36cm$. The 74.1 % of wintering chamber were distributed within $18{\sim}36cm$ from the surface. Survival rates observed were 38.0% in 1st year, 16.0% in 2nd years, and 2% in 3rd years, respectively. Seasonal occurrence period of C. sikkimensis was from the early-Aug. to early-Oct. and the optimal occurrence period was the early and mid-Sept. Emergence rate decreased to 8.4% in 1st year, 3.6% in 2nd years, and 0.8% in 3rd years, respectively. Sex ratio was showed in the range of 0.51-0.55. It is female biased ratio. Longevity of adults was 9.9 days for female and 8.9 days for male.

• Korean journal of applied entomology
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• v.47 no.1
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• pp.101-105
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• 2008

Effects of different application of nematicides (fosthiazate 5% G, ethoprophos 5% G, and diazinon 34% EC) for the control of Aphelenchoides fragariae in strawberry were evaluated in a greenhouse experiments. Mother strawberry (Fragaria grandiflora) cv. Yeohong were dipped in solution of nematicides (fosthiazate or ethoprophos at 2.5 g a.i./liter in $20^{\circ}C\;or\;46^{\circ}C$) for 10 min. and planted in a greenhouse for dipping treatment. For the compare, mother strawberry were dipped in hot water for 10 min. without chemicals. For soil treatment, fosthiazate or ethoprophos at 3 kg a.i./ha were mixed into soil. For foliar spray, diazinon at 3.4 g a.i./liter was sprayed at foliage until runoff. At 40, 80, and 100 days after planting, runners were harvested from each treatment and the rate of nematode infestation and the number of nematodes per plant were examined. After 100 days of planting, mother strawberry plants dipped in fosthiazate solution (2.5 g a.i./liter, $20^{\circ}C$) for 10 min. produced more number of healthy runners and reduced % of infected runner as much as 90% and also had fewer nematodes per runner. Fosthiazate was more effective than ethoprophos. Foliar application of diazinon was reduced A. fragariae populations only in early season. Hot water treatment and nematicide soil treatment were less effective.