• Journal of Applied Biological Chemistry
• /
• 제50권3호
• /
• pp.136-143
• /
• 2007

Despite the increased interests in biological control of soilborne diesease for environmental protection, biological control of bacterial wilt caused by Ralstonia solanacearum have not provided consistent or satisfying results. To enhance the control efficacy and reducing the inconsistency and variability, combinations of specific strains of microorganisms, each having a specific mechanism of control, were applied in this study. More than 30 microorganisms able to reduce the activity of pathogen by specific mechanism of action were identified and tested for their disease suppressive effects. After in vitro compatibility examinations, 21 individual strains and 15 combinations were tested in the greenhouse. Results indicated three-way combinations of different mode of control, TS3-7+A253-16+SKU78 and TS1-5+A100-1+SKU78, enhanced disease suppression by 70%, as compared to 30-50% reduction for their individual treatments. This work suggests that combining multiple traits antagonizing the pathogen improve efficacy of the biocontrol agents against Ralstonia solanacearum.

• The Plant Pathology Journal
• /
• 제22권4호
• /
• pp.348-352
• /
• 2006

Barley mild mosaic virus(BaMMV) is a soilborne Bymovirus vectored by root-infecting fungus, Polymyxa graminis. Mechanism of cultivar's resistance to BaMMV in field tests are difficult to assess since resistance could be either due to the virus or to P. graminis, or both. Whereas, available mechanical inoculation methods for BaMMV and other related viruses are labor intensive, give inconsistent results and generally result in low infection rates. Inoculation method using stick with gauze(SWG) was developed for BaMMV. The improved method proved to be simple, efficient, and reliable. The infected leaf tissues were preserved by drying in a frozen state under high vaccum(freeze dried barley infected leaves) to circumvent reduction of virus infectivity during storage. Five Korean barley cultivars were mechanically inoculated with BaMMV-infected sap by the improved method. Infection rates obtained were compared with natural infection. Cultivar Naehanssalbori showed resistance to BaMMV in the field trials but was found highly susceptible in the greenhouse tests by mechanical inoculation, indicating that the field resistance may be possibly due to resistance to P. graminis.

• Journal of Microbiology and Biotechnology
• /
• 제26권10호
• /
• pp.1755-1764
• /
• 2016

The application of Bacillus sp. in the biological control of plant soilborne diseases has been shown to be an environmentally friendly alternative to the use of chemical fungicides. In this study, the effects of bioorganic fertilizer (BOF) fortified with Bacillus amyloliquefaciens SQY 162 on the suppression of tomato bacterial wilt were investigated in pot experiments. The disease incidence of tomato wilt after the application of BOF was 65.18% and 41.62% lower at 10 and 20 days after transplantation, respectively, than in the control condition. BOF also promoted the plant growth. The SQY 162 populations efficiently colonized the tomato rhizosphere, which directly suppressed the number of Ralstonia solanacearum in the tomato rhizosphere soil. In the presence of BOF, the activities of defense-related enzymes in tomato were lower than in the presence of the control treatment, but the expression levels of the defense-related genes of the plants in the salicylic acid and jasmonic acid pathways were enhanced. It was also found that strain SQY 162 could secrete antibiotic surfactin, but not volatile organic compounds, to suppress Ralstonia. The strain could also produce plant growth promotion compounds such as siderophores and indole-3-acetic acid. Thus, owing to its innate multiple-functional traits and its broad biocontrol activities, we found that this antagonistic strain isolated from the tobacco rhizosphere could establish itself successfully in the tomato rhizosphere to control soilborne diseases.

• 한국식물병리학회지
• /
• 제14권3호
• /
• pp.253-259
• /
• 1998

Effects of soil disinfection, fungicide application, and narrow ridge cultivation on ginger rhizome rot development were examined in two naturally-infested fields at Seosan, Choongnam province. Soil disinfection treatments were assigned to main plots, and fungicide and ridge treatments to sub-plots in a split plot design with three replications. The rhizome rot started in late July, and progressed rapidly until late September with the peak incidence in mid-august to early September. Soil disinfection by dazomet application showed the most prominent inhibition effects in both fields, where the disease was reduced by the treatment from 17.5% to 4.8% in one field, and from 51.0% to 2.2% in the other field. Three to five applications of fungicide metalaxyl-copper during the growing season inhibited the disease by 89.7% in one field, but less effectively in the other field. Narrow ridge cultivation reduced the disease effectively by 78.1% and 63.9%, compared to the unridged control plots in each field, respectively. Germination rate of seed-rhizomes and growth of ginger plants were similar between treatments, except when the plots received improper aeration after applying dazomet, and then the germination rate was significantly reduced. The greatest yields were obtained in the disinfected plots, regardless of rhizome rot incidence, except one control plot with very little disease. Ginger yield was negatively correlated with disease severity. However, the yield of ridge plots averaged 58∼59% compared to those of the unridged plots, due mainly to the half planting rate of the ridge plots. In spatial progress, the disease in the disinfected plots started from a single focus of the inoculum, and spread into the adjacent areas only, whereas in the untreated plots, the disease started from many foci that were distributed over the plot, and rapidly progressed to make an epidemic during the season. The soil density of P. myriotylum in the disinfected plots was not changed or, if not, increased slightly during the season. However, in the untreated plots it increased rapidly to reach the density 3 to 5 times greater by the end of the season.

• The Plant Pathology Journal
• /
• 제34권3호
• /
• pp.163-170
• /
• 2018

Strawberry Fusarium wilt disease, caused by Fusarium oxysporum f. sp. fragariae, is the most devastating disease in strawberry production. The pathogen produces chlamydospores which tolerate against harsh environment, fungicide and survive for decades in soil. Development of detection and quantification techniques are regarded significantly in many soilborne pathogens to prevent damage from diseases. In this study, we improved specific-quantitative primers for F. oxysporum f. sp. fragariae to reveal correlation between the pathogen density and the disease severity. Standard curve $r^2$ value of the specific-quantitative primers for qRT-PCR and meting curve were over 0.99 and $80.5^{\circ}C$, respectively. Over pathogen $10^5cfu/g$ of soil was required to cause the disease in both lab and field conditions. With the minimum density to develop the wilt disease, the pathogen affected near 60% in nursery plantation. A biological control microbe agent and soil solarization reduced the pathogen population 2-fold and 1.5-fold in soil, respectively. The developed F. oxysporum f. sp. fragariae specific qRT-PCR protocol may contribute to evaluating soil healthiness and appropriate decision making to control the disease.

• 한국미생물·생명공학회지
• /
• 제23권2호
• /
• pp.236-242
• /
• 1995

Biological control of soilborne plant pathogens by the addition of antagonistic microorganisms to the soil may offer a practical supplement or alternative to existing disease management strategies that depend heavily on chemical pesticides. Soil amendment with antagonistic microbes was non-effective because of high cost, low efficacy, and inconvenient usage on the treatment course. Therefore, seed coating formulation for the application of biological seed treatments has been being to apply successful disease suppression for many important crops. The objectives of this study were to investigate the optimal condition for the spore production of biocontrol agent Bacillus subtilis YBL-7 and the liquid coating formulation that contained a suspension of a proper aqueous binder, as well as a ground fine solid particulate material. The maximum yield has been obtained from 60 hrs-old culture at 30$\circ$C in spore forming (SF) medium containing 0.8% nutrient broth, 0.05% yeast extract, 10$^{-1}$ M MgCl$^{2}$, 10$^{-4}$ M MnCl$^{2}$, 10$^{-5}$ M dipicolinic acid, and pH 6.5. The optimal condition of dried spore preparation was achieved when cells of B. subtilis YBL-7 was heat-dried with 50$\circ$C for 2 hrs.

• 식물병연구
• /
• 제8권4호
• /
• pp.245-249
• /
• 2002

검은점뿌리썩음병의 병원균에 감염된 참외의 광합성 및 생육 반응을 측정한 결과, 수확기 참외의 광합성 속도는 이병주가 건전주에 비해 현저하게 낮았고, 기공저항은 이병주에서 큰 것으로 나타났다. 목부일비액은 이병주에서 전혀 분비되지 않았다. 수확기 참외의 잎과 줄기에서 무기양분함량은 이병주와 건전주 간에 차이를 보여주지 않았다. 참외의 생육특성은 이병주가 건전주에 비해 엽면적이나 생체중및 건물중에서 건전주에 비해 낮았으며, 평균 과중도 같은 경향을 보였다.

• The Plant Pathology Journal
• /
• 제25권3호
• /
• pp.263-269
• /
• 2009

Bacterial wilt, Fusarium wilt and Foot rot caused by Ralstonia solanacearum, Fusarium oxysporum, and Phytophthora capsici respectively, continue to be severe problems to tomato, potato and black pepper growers in Vietnam. Three bio-products, Bacillus vallismortis EXTN-1 (EXTN-1), Bacillus sp. and Paenibacillus sp. (ESSC) and Bacillus substilis (MFMF) were examined in greenhouse bioassay for the ability to reduce bacterial wilt, fusarium wilt and foot rot disease severity. While these bio-products significantly reduced disease severities, EXTN-1 was the most effective, providing a mean level of disease reduction 80.0 to 90.0% against bacterial wilt, fusarium wilt and foot rot diseases under greenhouse conditions. ESSC and MFMF also significantly reduced fusarium wilt, bacterial wilt and foot rot severity under greenhouse conditions. Bio-product, EXTN-1 with the greatest efficacy under greenhouse condition was tested for the ability to reduce bacterial wilt, fusarium wilt and foot rot under field condition at Song Phuong and Thuong Tin locations in Ha Tay province, Vietnam. Under field condition, EXTN-1 provided a mean level of disease reduction more than 45.0% against all three diseases compared to water treated control. Besides, EXTN-1 treatment increased the yield in tomato fruits 17.3% than water treated control plants.

• 한국유기농업학회지
• /
• 제30권3호
• /
• pp.409-422
• /
• 2022

본 연구에서는 흰비단병에 대한 길항 미생물과 유기농업자재를 선발하여 혼합 처리 시 방제 효과를 확인하고자 하였다. 토양에서 분리한 39균주 중 균사 생장 억제력이 가장 높은 JJ2-01 균주를 길항 미생물로 선발하였다. 또한, 유기농업자재의 흰비단병 발병도를 확인하여 병 억제 효과가 있는 유기농업자재로 마늘 오일을 선발하였다. 선발 미생물과 마늘 오일을 혼합하거나 마늘 오일을 단독으로 사용할 경우 병 억제 효과는 유사하게 나타났지만, 마늘 오일을 단독으로 사용할 경우 토양의 acid phosphatase의 활성이 감소하였다. 반면, 마늘 오일과 선발 미생물 JJ2-01 균주를 혼합 처리하였을 때 urease 활성이 증가하였다. 본 실험의 결과를 종합하면, 선발 미생물 JJ2-01 균주와 마늘 오일을 혼합하여 사용하면 고추 흰비단병을 효과적으로 억제하고 토양의 질과 건전성을 유지 또는 향상하는데 도움이 될 수 있을 것이라 판단된다.

• The Plant Pathology Journal
• /
• 제27권4호
• /
• pp.390-395
• /
• 2011

Fusarium wilt caused by Fusarium oxysporum has become a serious problem world-wide and relies heavily on chemical fungicides. We selected Pseudomonas sp. NJ134 to develop an effective biocontrol strategy. This strain shows strong antagonistic activity against F. oxysporum. Biochemical analyses of ethyl-acetate extracts of NJ134 culture filtrates showed that 2,4-diacetylphloroglucinol (DAPG) was the major compound inhibiting in vitro growth of F. oxysporum. DAPG production was greatly enhanced in the NJ134 strain by adding mannitol to the growth media, and in vitro antagonistic activity against F. oxysporum increased. Bioformulations developed from growth of NJ134 in sterile bean media with mannitol as the carbon source under plastic bags resulted in effective biocontrol efficacy against Fusarium wilt. The efficacy of the bioformulated product depended on the carbon source and dose. Mannitol amendment in the bean-based formulation showed strong effective biocontrol against tomato Fusarium wilt through increased DAPG levels and a higher cell density compared to that in a glucose-amended formulation. These results suggest that this bioformulated product could be a new effective biocontrol system to control Fusarium wilt in the field.