• Journal of agriculture & life science
• /
• v.50 no.4
• /
• pp.27-34
• /
• 2016

Sclerotium rolfsii is a well known broad host range soil borne plant pathogenic fungus and caused serious damage to various vegetable crops. To develop an effective biological control agent for S. rolfsii, an isolate which showed strong inhibitory effect on the mycelial growth of S. rolfsii was selected among the antagonistic bacterial isolates collected from vinyl-house soil. The bacterial isolate was identified as Bacillus amyloliquefaciens KBC1009 based on the morphological, physiological characteristics and by 16S rRNA sequence analysis. The growth conditions for B. amyloliquefaciens KBC1009 were optimized in LB media(pH7) by culturing at 30℃ for 72 hrs. Glucose and yeast extract were confirmed as the best carbon and nitrogen sources, respectively. In order to test the inhibitory effect of B. amyloliquefaciens KBC1009 to stem rot of pepper, green house experiment was conducted. Drench of 1/500 diluted bacterial suspension of B. amyloliquefaciens KBC1009(5×108 cfu/ml) to each pepper plant 3 times with 10 days interval showed 66.7% control effectiveness. These results suggest that B. amyloliquefaciens KBC1009 is one of promising biocontrol agent to control stem rot caused by Sclerotium rolfsii.

• The Korean Journal of Pesticide Science
• /
• v.11 no.3
• /
• pp.186-193
• /
• 2007

Characteristics and control activity of copper hydroxide against pepper phytophthora blight caused by Phytophthora capsici were investigated in a greenhouse and a pepper field Copper hydroxide strongly inhibited the germination of zoosporangia and zoospores of P. capsici JHCS 2-5, showing $EC_{50}$ value by 0.6 and 0.3 ${\mu}g\;mL^{-1}$. With 1,040 ${\mu}g\;mL^{-1}$ of copper hydroxide in a greenhouse it showed 80% of the control value by soil-drenching application, while 16% by leaf-spraying. However, when it was treated enough to runoff to soil by leaf-spraying application with 50 ml per a pepper plant, it controlled a pepper phytophthora blight by 94.6 % of control value. Copper hydroxide showed a high protective activity at 1 and 3 days before application, while no curative activity. In a field it showed a high activity of 91%, when pepper plants were treated with copper hydorxide 4 times with a intervals of 10 days.

• Research in Plant Disease
• /
• v.26 no.2
• /
• pp.79-87
• /
• 2020

Fusarium wilt caused by Fusarium oxysporum f. sp. fragariae (Fof) is the most important diseases of a strawberry field in Korea. We surveyed phylogenetic analysis, pathogenicity test, and fungicide response about Fof isolates isolated from Korea. Twenty-seven isolates of F. oxysporum isolated from strawberry plants were conducted in this study. Specific amplification by Fof specific primer was confirmed in all 26 isolates except Fo080701 isolate. The nuclear ribosomal intergenic spacer region and the translation elongation factor EF-lα gene sequences of isolates revealed three main lineages. Most of all isolates were contained DNA lineage group 1, but 2 and 3 group was shown only one and three isolates, respectively. All isolates were shown in pathogenicity with cv. Seolhyang. The EC₅₀ mean values of prochloraz ranged 0.02-0.1 ㎍/ml except for Fo080701 and effectively inhibited mycelial growth at low concentrations. The EC₅₀ value of metconazole was also 0.04-0.22 ㎍/ml, showing a similar inhibitory effect to that of prochloraz. The EC₅₀ value of pyraclostrobin was 0.23-168.01 ㎍/ml, which was different according to the strain. In the field trial, boscalid+fludioxonil, fluxapyroxad+pyraclostrobin, and prochloraz manganese were selected as the effective fungicides for controlling Fusarium wilt.

• Research in Plant Disease
• /
• v.17 no.2
• /
• pp.121-128
• /
• 2011

Bacteriolytic myxobacteria have been known to secrete various antifungal metabolites against several soilborne phytopathogens including Phytophthora. Among the three isolates of Myxococcus spp., KYC 1126 and KYC 1136 perfectly inhibited the mycelial growth of Phytophtora capsici in vitro. In order to show the biocontrol activity on Phytophthora blight of hot pepper, we tried to find the best way of application of a myxobacterial isolate. Although KYC 1126 fruiting body was easily grown on the colony of Escherichia coli as a nutrient source, it did not control the disease when it was pre-applied in soil. Before the bioassay of a liquid culture filtrate of KYC 1126 was conducted, its antifungal activity was confirmed on the seedlings applying with the mixture of the pathogen's zoospore suspension and KYC 1126 filtrate. On greenhouse experiments with five and four replications, the control value of KYC 1126 on phyllosphere and rhizosphere was 88% and 36%, respectively. Whereas, the control value of dimetnomorph+propineb on phyllosphere was 100% and that of propamorcarb on rhizosphere was 44%. There was a phytotoxicity of the myxobacterial filtrate when seedlings were washed and soaked for 24 hours. Gummy materials were covered with roots. And stem and petiole were constricted, then a whole seedling was eventually blighted.

• Journal of Life Science
• /
• v.20 no.3
• /
• pp.403-410
• /
• 2010

In order to produce high-quality fermenting composts, a microorganism was isolated from the natural world. The bacterium has not only in high enzyme activities but also had good antimicrobial activities against phytopathogenic microorganisms. Its cultivating characteristics were then investigated. Bacterium KJ-9, which contains high CMCase, protease and chitinase activities and excellent antimicrobial activities against phytopathogenic microorganisms, was separated from leaf mold and identified as Bacillus licheniformis by two methods: Bergey's Manual of Systematic Bacteriology and API 50 CHL Carbohydrate Test Kit (Bio Merieux, France) using an ATB (Automated Identification) computer system (Bio Merieux, France). Optimal medium for cultivation of B. licheniformis was 2% soluble starch as a carbon source, 0.5% yeast extract as a nitrogen source and 0.05% $MgSO_4{\cdot}7H_2O$. Optimal growth conditions of pH, temperature and shake speed were pH 7.0, $50^{\circ}C$ and 180 rpm, respectively. Culture broth of B. licheniformis KJ-9 cultured for 36~60 hr was effective in fungicidal activities against plant pathogens including Botrytis cinerea, Corynespora cassicola, Fusarium oxysporum, and Rhizoctonia solani.

• Weed & Turfgrass Science
• /
• v.1 no.4
• /
• pp.69-75
• /
• 2012

In response of fungicides for control of gray snow mold, isolates of Typhula incarnata were collected from three golf courses in 2012 Yongpyeong, Korea and tested for sensitivity to propiconazole, tebuconazole and azoxystrobin fungicides. Four discriminatory concentrations were used to detect in vitro sensitivity of 50 isolates. Mean 50% effective concentration inhibiting mycelial growth ($EC_{50}$) values for tebuconazole was the lowest among the three fungicides. The $EC_{50}$ value of tebuconazole ranged from 0.0005 ${\mu}g\;ml^{-1}$ to 0.014 ${\mu}g\;ml^{-1}$ with a mean of 0.0048 ${\mu}g\;ml^{-1}$. The mean $EC_{50}$ values of propiconazole in triazole family was 0.5825 (0.78-1.651) ${\mu}g\;ml^{-1}$. $EC_{50}$ value of azoxystrobin ranged from 0.0017 ${\mu}g\;ml^{-1}$ to 0.131 ${\mu}g\;ml^{-1}$ with a mean of 0.0278 ${\mu}g\;ml^{-1}$. There was no correlation among $EC_{50}$ values for propiconazole, azoxystrobin and tebuconazole indicating no cross-resistance relationships with each other. Results of this study were confirmed no resistance isolates in vitro sensitivity of T. incarnata of three fungicides in Yongpyeong.

• Research in Plant Disease
• /
• v.21 no.1
• /
• pp.12-19
• /
• 2015

Antimicrobial activities of nano-materials were tested against several plant pathogens. Twelve different nano-materials were used to observe the antagonistic activity against three kinds of mold and sixteen different kinds of watermelon fruit rot pathogens (Acidovorax citrulli). According to the results, no antagonism have been found against the pathogen, Cylindrocarpon destructans. However in the case of Pythium ultimum, combination of Brass/Glucose 1,000 ppm confirmed the mycelial growth reduction by 94%. In addition, little effect was found against Rhizoctonia solani by Ag/Glucose 3,000 ppm. The remaining other nano-materials have different antimicrobial effect depending on the strains of A. citrulli. But in the case of lime (Cu/Salt 1,000 ppm) highest antimicrobial activity was observed with 97%. Moreover growth of five different strains of A. citrulli was checked by 99% with the combination of Ag/Glucose 1,000 ppm. 92% reduction of A. citrulli growth was observed with $Brass/CaCO_3$ 3,000 ppm. Tested nano-materials against different plant pathogens in this study showed the antimicrobial activity at the range of 24-70%.

• The Korean Journal of Mycology
• /
• v.44 no.4
• /
• pp.330-337
• /
• 2016

Streptomyces sp. A75 and A501 inhibited the mycelial growth of pathogenic Rhizoctonia solani and Pythium sp., which cause the ginseng disease known as damping-off. Three methods were evaluated for the control of these pathogens, using a mixture of the culture broths from Streptomyces sp. A75 and A501. The methods tested were seed dipping with 50-fold diluted broth, drenching of soil with 100-fold diluted broth after sowing, and combined seed dipping and drenching. These methods reduced the incidence of ginseng damping-off caused by R. solani by 81.3%, 84.8%, and 32.2% and that caused by Pythium sp. by 51.0%, 52.1%, and 75.3%, respectively. Based on these results, the combination of seed dipping and soil drenching after sowing using a mixture of the culture broths from Streptomyces sp. A75 and A501 effectively reduced the incidence of damping-off in ginseng.

• The Korean Journal of Mycology
• /
• v.30 no.2
• /
• pp.157-165
• /
• 2002

Of 125 isolates collected from 35 golf courses, sensitivity of 44 isolates of Pythium species to metalaxyl was determined on corn meal agar with various concentrations of metalaxyl (0.1, 1.0, 10.0, 50.0, 100.0, and $250.0{\mu}g\;a.\;i/ml$). The isolates were able to be categorized into the sensitive and resistant groups based on hyphal growth measured in terms of colony diameters on the medium with $1.0\;and\;10.0{\mu}g\;a.\;i./ml$. When compared with hyphal growth on the medium without metalaxyl, hyphal growth of the sensitive group which included 31 isolates was inhibited by $66{\sim}98%$ on the medium with $1.0{\mu}g\;a.\;i./ml$, whereas that of the resistant group which included 13 isolates grew well and the hyphal growth was inhibited only by $6{\sim}26%$. When $10.0{\mu}g\;a.\;i./ml$ of metalaxyl was included in the medium, hyphal growth of the sensitive and resistant groups was inhibited by $82{\sim}99%\;and\;27{\sim}47%$, respectively. Occurrence of metalaxyl-resistant isolates of Pythium spp. not only from turfgrasses on golf courses but also from other crops was observed for the first time in Korea. Metalaxyl-resistant isolates occurred most frequently in P. graminicola. Control effects of metalaxyl were determined by applying metalaxyl after and before inoculation of 4 and 3 isolates of sensitive and resistant isolates of P. graminicola, respectively, to creeping bentgrass in pots. The minimum concentration of metalaxyl to control metalaxyl-sensitive isolates was $6.25{\mu}g\;a.\;i./ml$, whereas the disease caused by the metalaxyl-resistant isolates could not be controlled with $12.50{\mu}g\;a.\;i./ml$ of metalaxyl. The disease was controlled more effectively by an application of metalaxyl prior to inoculation than after occurrence of the disease.

• Research in Plant Disease
• /
• v.17 no.2
• /
• pp.142-147
• /
• 2011

In order to develop a environmentally friendly control protocol for managing tomato leaf mold disease in the field, we employed bacteria- and fungi-based commercially available microbial preparations. The field experiment was conducted from April to July in 2010. Average incidence rates tomato leaf mold caused by Fulvia fulva were 13.1% at the two plastic houses located in Jangsung, Jeonnam area. Initially 11 microbial preparations were tested for antifungal activity against F. fulva in vitro. Among them, 7 selected preparations showed to be inhibited the mycelial growth of the fungal pathogen over 50%. Four microbes suppressed disease incidence as much 50% under greenhouse condition. Eventually in the field two microbial products including Bacillus subtilis GB-0365 and B. subtilis KB-401 respectively were showed control value up to 71.8% for four times sprays from 20 days to 70 days after transplanting. Furthermore, the control value of three times spray program demonstrated 79.3%. Efficacy of the three and four spray programs was more effective than that of non-spray control treatment. Our results indicated that adjustment of application method of commercially available microbial preparation could be used to control a target plant disease as an effective and efficient crop protection system for organic farming.