• The Plant Pathology Journal
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• v.32 no.3
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• pp.228-241
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• 2016

In our previous study, we reported that a novel endophytic bacterium Bacillus oryzicola YC7007 has suppressed bacterial diseases of rice via induced systemic resistance and antibiotic production. This endophytic strain, B. oryzicola YC7007 was used as a biological control agent against bakanae disease of rice caused by Fusarium fujikuroi, and its mechanism of interaction with the pathogen and the rice was further elucidated. Root drenching with B. oryzicola YC7007 suspension reduced the disease severity of bakanae significantly when compared with the untreated controls. The treatments of B. oryzicola YC7007 suspension ($2.0{\times}10^7cfu/ml$) to the rice rhizosphere reduced bakanae severity by 46-78% in pots and nursery box tests containing autoclaved and non-autoclaved soils. Moreover, in the detached rice leaves bioassay, the development of necrotic lesion and mycelial expansion of F. fujikuroi were inhibited significantly by spraying the culture filtrate of B. oryzicola YC7007. Drenching of ethyl acetate extracts of the culture filtrate to the rhizosphere of rice seedlings also reduced the bakanae disease severity in the plant culture dish tests. With the root drenching of B. oryzicola YC7007 suspension, the accumulation of hydrogen peroxide was observed at an early stage of rice seedlings, and a hormonal defense was elicited with and without pathogen inoculation. Our results showed that the strain B. oryzicola YC7007 had a good biocontrol activity against the bakanae disease of rice by direct inhibition, and was also capable of inducing systemic resistance against the pathogen via primed induction of the jasmonic acid pathway.

• The Plant Pathology Journal
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• v.26 no.3
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• pp.216-222
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• 2010

Fusarium proliferatum is the causal agent of stalk and root rot disease of maize, foot rot disease of rice, basal and root rot disease of onion and knife cut disease of sugarcane in Iran. In recent years, incidence and severity of these diseases have been increased in Iran. Fifty seven F. proliferatum single-spore isolates collected from diseased maize, rice, onion and sugarcane plants at different areas were used to study genetic diversity by determination of vegetative compatibility groups (VCGs). Chlorate-resistant nitrate non-utilizing (nit) mutants were recovered from selected isolates of F. proliferatum and used in complementation tests. All isolates in which both nit1 and NitM (or nit3) mutants were recovered, demonstrated self-compatibility. Vegetative compatibility tests by pairing nit mutants identified 30 VCGs among 57 isolates. Twenty-three isolates belonged to singlemember VCGs and the remaining 34 isolates, belonged to other seven multimember VCGs. Segregation of F. proliferatum isolates obtained from various area and host plants into different VCGs in Iran is reported for the first time. In this study, none of isolates obtained from rice complemented with any other isolates from onion and sugarcane and, non complementation occurred between onion and sugarcane isolates. Also, only one complementation occurred between one isolate of maize and one isolate of sugarcane and rice. Thus, a correlation between VCGs grouping and host preferences was founded. It is concluded that natural populations of F. proliferatum in Iran are probably genetically divergent and include isolates representing a potential risk for disease development.

• Research in Plant Disease
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• v.7 no.1
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• pp.20-24
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• 2001

As stand-missing rate (SMR) of ginseng plants in fields are directly related to the ginseng root rot, the forecasting model for the root rot progress in ginseng fields was developed, using the estimated SMRs by disease incidence (DI) of ginseng seedling in the soil-indexing bioassay and the estimate of DI derived from soil environmental factors or rhizoplane microflora. For fitness analysis of the forecasting model, simple correlation and linear regression between SMRs at different planting ages in fields and their estimates by 3 factors of the model were evaluated.The SMR estimated from the factor of DI in the bioassay had much higher fitness to the SMR observed in fields than that from the factors of soil environments and rhizoplane microflora. The estimated SMRs in young and aged ginseng fields by DI in the bioassay were significantly correlated with the observed SMRs in 3- and 5-year-old ginseng fields, respectively (p=0.01). this implicates that indexing preplanting field soils with the forecasting model using DI in the bioassay can provide an information to determine the suitability of the fields for ginseng cultivation, and that indexing cultivating field soils can be helpful to determine the time of harvesting to reduce further yield loss by root rot in continuous cultivation in the next year.

• Research in Plant Disease
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• v.13 no.1
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• pp.6-14
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• 2007

Root and basal stem rot disease occurred on moth orchid (Phalaenopsis spp.), Pung-nan (Neofinetia falcata) and Nadopung-nan (Aerides japonicum) grown in the farmers' greenhouses located in Namyangju Kyonggi province, Korea during 2005 to 2006. Wilting symptoms occurred on these orchard plants at initial stage and the infected plant leaves turned yellow to red. The discolored leaves were fallen down to lead to eventual death of the entire plant. A total of 59 isolates of Fusarium spp. was obtained from roots and leaf bases of the diseased plants. The cultural and morphological characteristics of isolated Fusairum spp. were identified as Fusarium oxysporum, F. proliferatum and F. solani. F. oxysporum and F. proliferatum were isolated from all these orchard plants but F. solani was isolated only from Phalaenopsis spp. Pathogenicity of the three Fusarium spp. was confirmed by artificial inoculation. Although F. oxysporum, F. proliferatum and F. solani cusing root rot disease in Phalaenopsis spp. have been reported in Korea, the pathogens in N. falcata and A. japonicum were not reported yet. Therefore, this is the first report on the root and stem rot of N. falcata and A. japonicum caused by F. oxysporum and F. proliferatum in Korea.

• The Plant Pathology Journal
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• v.18 no.4
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• pp.225-227
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• 2002

Moth orchid plants with yellowing blight and root rot symptoms were collected, and a total of 54 isolates of Fusarium spp. was obtained from roots and leaf bases of the diseased plants. The isolates were identified based on their morphological characteristics. Out of the 54 isolates of Fusarium spp., 42 isolates were identified as F. solani, 5 isolates as F. oxysporum, and 7 as F. proliferatum. Isolates of the three Fusarium spp. were tested for pathogenicity to moth orchid plants by artificial inoculation. All the Fusarium spp. induced root rot of the host plants. The symptoms progressed up to the basal part of the leaves, which later caused yellowing blight. The symptoms induced on the plants by artificial inoculation with the Fusarium spp. isolates were similar to those observed in greenhouses. The present study reveals that F. oxysporum, F. proliferatum, and F. solani cause root rot of moth orchid, and that F. solani is the main pathogen of the disease.

• Research in Plant Disease
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• v.26 no.2
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• pp.88-94
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• 2020

Recently, the severe dieback of apple trees resulting from soil-borne diseases has occurred in South Korea. The casual agents of dieback were surveyed on 74 apple orchards that had been damaged nationwide in 2016-2019. The number of apple orchards affected alone by Phytophthora rot, violet root rot, and white root rot was 31, 34, and 3, respectively. Also, the total number of mixed infection orchards was 6. Out of 9,112 apple trees affected by dieback, the trees damaged by Phytophthora rot, violet root rot, and white root rot were 3,332, 3,831, and 44, respectively. Moreover, the total number of mixed infection apple trees was 1,905. The provinces mainly affected were Gyeongnam, Gyeongbuk, Chungbuk, and Jeonbuk. The survey on these infected apple orchards will be available to form management strategy for the dieback that had been increased by soil-borne fungal pathogens.

• Research in Plant Disease
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• v.19 no.1
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• pp.25-30
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• 2013

Root-knot nematodes (Meloidogyne spp.) are among the main pathogens of greenhouse crops worldwide. Plant resistance is currently the method of choice for controlling these pests. To select resistant tomato against two common species of root-knot nematodes, M. incognita and M. arenaria, 36 commercial tomato (Lycopersicon esculentum Mill.) cultivars were screened. Seventeen tomato cultivars were resistant to both root-knot nematodes: six in cherry tomato, 'Tenten', 'Cadillac', 'Cutti', 'Sweet', 'Ppotto', 'Lycopin-9', eight in globe tomato, 'Lovely 240', 'Dotaerang Dia', 'Cupirang', 'Dotaerang Master', 'Super Dotaerang', 'Dotaerang Season', 'Miroku', 'Hoyong', and three in root stock, 'Special', 'Fighting', and 'Magnet'.

• Journal of Periodontal and Implant Science
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• v.24 no.1
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• pp.109-119
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• 1994

An essential fact in the regeneration of new periodontal tissue after periodontal therapy is the reattachment of collagen fibers to the tooth. Two phenomena play a fundamental role in preventing new connective tissue attachment to the exposed root surface ; 1) The apical migration of the junctional epithelium 2) The contamination of cementum by toxic substances, especially endotoxins. Authors have used rat submucosal implantation of root sections to study the connective tissue healing to periodontally diseaed root, previously planed and demineralized with citric acid and tetracycline- HCl. The results were obtained as follows. 1. The connective tissue attachment was increased in tetracycline, citric acid, non disease, scaling and root planing order and inflammatory reaction was seen in the rat teeth, no treatment group. 2. Collagen fiber attachment at the dentin surface was more increased than cementum surface 3. In 2 week of citric acid and tetracycline-HCl specimens, osteoid was seen near the fibrotic band. 4. In the MT view, collagen fiber formation was increased with time and the numerous collagen fiber and connective tissue was more densly attached to the tooth surfaces in the tetracycline-HCl group than the citric acid group.

• Korean Journal of Agricultural Science
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• v.37 no.2
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• pp.255-260
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• 2010

Rusty root, the browning disease on ginseng, decreases quality and value. Recent studies indicated that endophytic bacteria could be a possible cause of rusty root. Actinomycetes antagonistic to the rusty-root-causing bacteria were isolated from soil. Twenty nine out of 932-isolates of Actinomycetes from soil showed antibacterial activity against Agrobacterium tumefaciens and Pseudomonas veronii an endophytic isolate in ginseng. The strongest antibacterial strain(ATO4O104) was classified based on 16S rDNA sequence. The Actinomycetes strain, ATO4O104, isolated in soil of USA volcano national park was identified as Streptomyces adephospholyticus. To test plant toxicity, radish seeds were sprouted with the culture of S. adephospholyticus and it did not show any harmful effect. The butanol partition out of n-hexane, ethyl acetate, butanol, and water partions showed the highest antibacterial activity.

• Korean journal of applied entomology
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• v.22 no.3 s.56
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• pp.181-185
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• 1983

Ditylenchus destructor Thorne 1945 was found to be the causal organism of the new root rot disease of Panax ginseng, which occurred extensively in Dongseong area of Cheolweon-gun, Gangweon Province, Korea in 1982. Thirty-six percent of the investigated fields was damaged due to the potato rot nematode. Infected roots showed brown discoloration of cortex and suberization outside the cambium. Cortex of the severly infected roots became sponge-like in texture and cavity was produced in the central portion of the root. Only the severely infected ginseng plants exhibited sympotoms of sudden wilting of leaves. The number of potato rot nematode in such field soils was $8.5\~222/30g$ soil, while there was no such symptoms on leaves if the number was less than 7.