• Applied Biological Chemistry
• /
• v.35 no.5
• /
• pp.382-388
• /
• 1992

Mycelial growth inhibition activity of forty-one N-substituted phenyl 5-chloro-1,3-dimethylpyrazole-4-carboxamides against Rhizoctonia solani was analysed quantitatively by multiple regression analysis using physicochemical parameters of substituents as independent variables and $pEC_{50}$ as dependent variable. As a result, a quantitative structure-activity relationship was formulated using eight physicochemical parameters, which explains 83% of variance of the fungicidal activity. The most important parameter for the biological activity was log k', as related to the penetration and transport processes in the biological system. The activity also correlated with other hydrophobic parameters$({\pi}_2,\;{\pi}_3)$, an electronic parameter$({\Sigma}{\sigma})$, and steric parameters$(STERIMOL\;parameters\;L_3,\;L_4)$.

• Asian Journal of Turfgrass Science
• /
• v.23 no.2
• /
• pp.209-218
• /
• 2009

Bacterial isolates collected from rhizosphere of turfgrass showed strong in vitro antagonistic activities against a number of turfgrass soilborne pathogens such as Rhizoctonia cerealis, R. solani AG-1(1B), Sclerotinia homoeocarpa and Typhula incarnata. In vivo study, four bacterial isolates selected have control values over 60% against one or more turfgrass pathogenic fungi. The antagonistic effects of the bacterial isolates varied depending on fungal species, host plant, and disease pressure, indicating that control effects of the antagonists could be variable depending on field conditions. They were classified as belonging to the genus Pseudomonas species, based on morphological and biochemical characteristics as well as 16S rRNA analysis. The four bacterial isolates are under a study for finding proper cultural conditions and determination formulation type.

• Journal of Plant Biotechnology
• /
• v.43 no.4
• /
• pp.450-456
• /
• 2016

Rhizoctonia leaf blight (large patch) has become a serious problem in Korean lawn grass, which is extremely hard to treat and develops mostly from the roots of lawn grass to wither it away. Rhizoctonia leaf blight (large patch) is caused by Rhizoctonia solani AG2-2 (IV). To develop zoysia japonica with strong disease tolerance against this pathogenic bacterium, ${\beta}-1,3-glucanase$ was cloned from zoysia japonica, which is one of the PR-Proteins known to play a critical role in plant defense reaction. ${\beta}-1,3-glucanase$ is known to be generated within the cells when plant tissues have a hypersensitive reaction due to virus or bacterium infection and secreted outside the cells to play mainly the function of resistance against pathogenic bacteria in the space between the cells. This study utilized the commonly preserved part in the sequence of corn, wheat, barley, and rice which had been researched for their disease tolerance among the ${\beta}-1,3-glucanase$ monocotyledonous plants. Based on the part, degenerate PCR was performed to find out the sequence and full-length cDNA was cloned. E.coli over-expression was conducted in this study to mass purify target protein and implement in vitro activation measurement and antibacterial test. In addition, to interpret the functions of ZjGlu1 gene, each gene-incorporating plant transformation vectors were produced to make lawn grass transformant. Based on ZjGlu1 protein, antibacterial activity test was conducted on 9 strains. As a result, R. cerealis, F. culmorum, R.solani AG-1 (1B), and T. atroviride were found to have antibacterial activity. The gene-specific expression amount in each organ showed no huge difference in the organs based upon the transformant and against 18s gene expression amount.

• Journal of Life Science
• /
• v.20 no.8
• /
• pp.1254-1260
• /
• 2010

Microorganisms near the plant rhizosphere usually inhabit the surface or the inside of the plant roots and have a direct effect on plant growth by secreting plant growth promoters or antagonistic materials which protect the root zone system from various pathogens. This study was carried out to identify and isolate the antagonistic materials after isolation of microorganisms showing high antagonistic activities, in hopes of contributing to the development of sustainable agriculture and the preservation of agricultural environments. A number of antagonistic bacteria were isolated from paddy soil. Among isolates, RRj 228 showed plant growth promotion and antagonistic activity. RRj 228 was identified as Pseudomonas sp. according to the results of physiological properties and genetic methods. On the basis of the results of anti-fungal spectrum against several pathogens by RRj 228, the antagonistic effect of the isolate against Botrytis cinerea, Pythium ultimum, Phytopthola capsici, and Rhizoctonia solani, especially against red-pepper anthracnose caused by Colletotrichum acutatum, was remarkable. The experiment evaluating the biological control effect by RRj 228 revealed that the $ED_{50}$ value by the RRj 228 culture against C. acutatum, R. solani and P. ultimum were 0.14 mg/ml, 0.16 mg/ml and 0.29 mg/ml, respectively. An antagonistic substance was isolated and purified by several chromatographies from the RRj 228 culture. The $^1H$ and $^{13}C$ assignment of the antagonistic substance was achieved from two-dimensional $^1H-^1H$ COSY, HMQC, and HMBC. Finally, the antagonistic substance was identified as Phenazine-1-carboxylic acid ($C_{13}H_8N_2O_2$, M.W.=224).

• Journal of Applied Biological Chemistry
• /
• v.59 no.3
• /
• pp.173-178
• /
• 2016

Phenyllactic acid (PLA), which is a known antimicrobial compound, can be synthesized through the reduction of phenylpyruvic acid (PPA) by lactate dehydrogenase of lactic acid bacteria (LAB). PLA-producing LAB was isolated from coffee beans, and the isolated LAB was identified as Lactobacillus zeae Y44 by 16S rRNA gene sequence analysis. Cell-free supernatant (CFS) from L. zeae Y44 was assessed for both its capability to produce the antimicrobial compound PLA and its antifungal activity against three fungal pathogens (Rhizoctonia solani, Botrytis cinerea, and Colletotrichum aculatum). PLA concentration was found to be 4.21 mM in CFS when L. zeae Y44 was grown in MRS broth containing 5 mM PPA for 12 h. PLA production could be promoted by the supplementation with PPA and phenylalanine (Phe) in the MRS broth, but not affected by 4-hydroxy-phenylpyruvic acid, and inhibited by tyrosine as precursors. Antifungal activity assessment demonstrated that all fungal pathogens were sensitive to 5 % CFS (v/v) of L. zeae Y44 with average growth inhibitions ranging from 27.8 to 50.0 % (p<0.005), in which R. solani was the most sensitive with an inhibition of 50.0 %, followed by B. cinerea and C. aculatum. However, pH modification of CFS to pH 6.5 caused an extreme reduction in their antifungal activity. These results may indicate that the antifungal activity of CFS was caused by acidic compounds like PLA or organic acids rather than proteins or peptides molecules.

• Korean journal of applied entomology
• /
• v.20 no.2 s.47
• /
• pp.112-116
• /
• 1981

This study was conducted to investigate the seasonal occurrence of aphids and to evaluate their efficacy in the field for the control of some aphids on soybean when Carbofuran, Disulfoton and Ortran were applied infurrow at the planting time in 1976. Foxglove aphid (Aulacorthum solani) and soybean aphid (Aphis glycines) were dominat species in soybean field and there were two peaks in the year. The patterns of occurence of aphids were different between in field and yellow-pan. Carbofuran and Disulfoton showed a good effect for the control of aphids but Ortran was less effective.

• Korean Journal of Environmental Agriculture
• /
• v.28 no.3
• /
• pp.289-294
• /
• 2009

Concerning about the negative impact of chemical pesticides on human health and the environment has been leading to dramatic increase of research in natural product-based pesticides. An antagonistic bacterium Streptomyces sp. S-1110 was isolated from apple farm soil. The culture filtrate of the strain showed growth inhibition effects to apple pathogenic fungi, Botryosphaeria dothidea, Colletotrichum gloeosporioides and Rhizoctonia solani. The unidentified antibiotic substances from the strain kept antagonistic activity either after heat treatment at $121^{\circ}C$ for 1 h or pH treatment at range of pH 3 - pH 12 for 24 h. The substances also prevented apple fruit from spoiling by inoculated two pathogenic molds, B. dothidea and C. gloeosporioides. These results suggested that the isolated strain would be useful as a biocontrol agent to control apple spoiling occurred from mold.

• Research in Plant Disease
• /
• v.7 no.1
• /
• pp.11-15
• /
• 2001

Root rot of Cucurbitaceae plants, caused by Monosporascus cannonballus, is one of the recently described diseases in Korea. The distribution and pathogenicity of M. cannonballus were examined by field and in vitro experiments. Root rot caused by M. cannonballus occurred on melon, oriental melon, watermelon and cucumber plants. In two years of disease survey, the disease occurred at 10 and 32 fields in 1997 and 1998, respectively, which were located at Kimhae, Chinju, and Namhae in Kyeongnam province, at Kwangyang in Chonnam province, at Kwangju city, and at Yeoju and Inchon in Kyeonggi province. The disease progress in a melon field at Namhae was not observed until the middle stage of plant growth, but rapidly increased at the fruit maturing stage, resulting in more than 50% yield loss. Isolation rate of M. cannonballus was 36.7% from wilted hosts. Fusarium oxysporum and Rhizoctonia solani were also frequently isolated. In vitro test, seedlings wilted after 7∼14 days of inoculation, and perithecia were formed in infected roots 21 days later. Two cucumber cultivars, Baekbong and Eunhwa, were resistant to the disease.

• Korean journal of applied entomology
• /
• v.22 no.1 s.54
• /
• pp.21-25
• /
• 1983

To develop forecasting methods of rice sheath blight caused by Rhizoctonia solani, two rice cultivars Jinheung (Japonica type) and Yushin (Tongil type) were used from 1976 to 1981. Severity of rice sheath blight disease at maturing stage was estimated by top lesion height, percentage of top lesion height vs. plant height in July and lesion index on September 11. The relationship between top lesion height on July 11 and degree of damage at maturing stage for a cultivar Yushin was represented by the equation of Y=4.64x-13.2, and $r=.840^{**}$, where Y is degree of damage by shea4h blight at maturing stage and x is top lesion height on July 11. Considering the percentage of infected hills/stems was rapidly increased from July 11 to August 1, the most effective period and time for fungicide spray were considered July 15 and July 25 or July 25 and August 5.

• The Korean Journal of Mycology
• /
• v.16 no.4
• /
• pp.220-225
• /
• 1988

This study was carried out to investigate the effect on the system of crop rotation of sesame(Sesamum indicum L). The results of infected plant percentage and yield of sesame wilting disease, fluctuation of density of Fusarium oxysporum and Actinomycetes, and their pathogenicity test on Fusarium spp isolated from sesame cultural soil were investigated. Density of F. oxysporum was the highest in a sesame continuous cropping soil but that of Actinomycetes was the lowest in that soil. And that of F. oxysporum and Actinomycetes according to investigation date was the highest at June. 30 and July. 30, respectively. Their pathogenicity of F. oxysporum and F. solani isolated from sesame cultural soil to sesame, peanut and green gram were recognized to all isolates except one isolate among F. oxysporum 8 isolates and one isolate to sesame, 2 isolates to peanut and all isolates to green gram among F. solani 4 isolates. F. oxysporum density and infected plant of wilting disease were increased as a result of replanted cultivation of sesame, and yield of that was prominantly reduced. Relation between density of F. oxysporum in cultural soil and infected plant percentage showed positive correlation and yield index highly negative. There was little difference between sesame-upland rice and sesame-peanut in the system of crop rotation.