• The Plant Pathology Journal
• /
• 제28권2호
• /
• pp.172-184
• /
• 2012

An infection risk model for Phytophthora blight on chili pepper was developed to estimate the first date of disease occurrence in the field. The model consisted of three parts including estimation of zoosporangium formation, soil water content, and amount of active inoculum in soil. Daily weather data on air temperature, relative humidity and rainfall, and the soil texture data of local areas were used to estimate infection risk level that was quantified as the accumulated amount of active inoculum during the prior three days. Based on the analysis on 190 sets of weather and disease data, it was found that the threshold infection risk of 224 could be an appropriate criterion for determining the primary infection date. The 95% confidence interval for the difference between the estimated date of primary infection and the observed date of first disease occurrence was $8{\pm}3$ days. In the model validation tests, the observed dates of first disease occurrence were within the 95% confidence intervals of the estimated dates in the five out of six cases. The sensitivity analyses suggested that the model was more responsive to temperature and soil texture than relative humidity, rainfall, and transplanting date. The infection risk model could be implemented in practice to control Phytophthora blight in chili pepper fields.

• Journal of Microbiology and Biotechnology
• /
• 제26권9호
• /
• pp.1542-1550
• /
• 2016

This is the first report that paromomycin, an antibiotic derived from Streptomyces sp. AG-P 1441 (AG-P 1441), controlled Phytophthora blight and soft rot diseases caused by Phytophthora capsici and Pectobacterium carotovorum, respectively, in chili pepper (Capsicum annum L.). Chili pepper plants treated with paromomycin by foliar spray or soil drenching 7 days prior to inoculation with P. capsici zoospores showed significant (p < 0.05) reduction in disease severity (%) when compared with untreated control plants. The disease severity of Phytophthora blight was recorded as 8% and 50% for foliar spray and soil drench, respectively, at 1.0 ppm of paromomycin, compared with untreated control, where disease severity was 83% and 100% by foliar spray and soil drench, respectively. A greater reduction of soft rot lesion areas per leaf disk was observed in treated plants using paromomycin (1.0 μg/ml) by infiltration or soil drench in comparison with untreated control plants. Paromomycin treatment did not negatively affect the growth of chili pepper. Furthermore, the treatment slightly promoted growth; this growth was supported by increased chlorophyll content in paromomycin-treated chili pepper plants. Additionally, paromomycin likely induced resistance as confirmed by the expression of pathogenesis-related (PR) genes: PR-1, β-1,3-glucanase, chitinase, PR-4, peroxidase, and PR-10, which enhanced plant defense against P. capsici in chili pepper. This finding indicates that AG-P 1441 plays a role in pathogen resistance upon the activation of defense genes, by secretion of the plant resistance elicitor, paromomycin.

• The Plant Pathology Journal
• /
• 제23권3호
• /
• pp.180-186
• /
• 2007

The biocontrol agent, Serratia plymuthica A21-4, has been developed for controlling pepper Phytophthora blight. Serratia plymuthica A21-4 strongly inhibits the mycelial growth, zoospore formation, and cyst germination of Phytophthora capsici in vitro. The application of a cell suspension of strain A21-4 to pepper plants in pot experiments and in greenhouse successfully controlled the disease. The bacteria produced a potent antifungal substance which was a key factor in the suppression of Phytophthora capsici. The most active chemical com-pound was isolated and purified by antifungal activity-guided fractionation. The chemical structure was identified as a chlorinated macrolide $(C_{23}H_{31}O_8Cl)$ by spectroscopic (UV, IR, MS, and NMR) data, and was named macrocyclic lactone A21-4. The active compound significantly inhibited the formation of zoosporangia and zoospore and germination of cyst of P. capsici at concentrations lower than $0.0625{\mu}g/ml$. The effective concentrations of the macrocyclic lactone A21-4 for $ED_{50}$ of mycelial growth inhibition were $0.25{\mu}g/ml,\;0.25{\mu}g/ml,\;0.30{\mu}g/ml \;and\;0.75{\mu}g/ml$ against P. capsici, Pythium ultimum, Sclerotinia sclerotiorum and Botrytis cinerea, respectively.

• The Plant Pathology Journal
• /
• 제29권4호
• /
• pp.418-426
• /
• 2013

Pseudomonas isolates from different crop plants were screened for in vitro growth inhibition of Phytophthora capsici and production of biosurfactant. Two in vivo experiments were performed to determine the efficacy of selected Pseudomonas strains against Phytophthora blight of pepper by comparing two fungicide treatments [acibenzolar-S-methyl (ASM) and ASM + mefenoxam]. Bacterial isolates were applied by soil drenching ($1{\times}10^9$ cells/ml), ASM ($0.1{\mu}g$ a.i./ml) and ASM + mefenoxam (0.2 mg product/ml) were applied by foliar spraying, and P. capsici inoculum was incorporated into the pot soil three days after treatments. In the first experiment, four Pseudomonas strains resulted in significant reduction from 48.4 to 61.3% in Phytophthora blight severity. In the second experiment, bacterial treatments combining with olive oil (5 mL per plant) significantly enhanced biological control activity, resulting in a reduction of disease level ranging from 56.8 to 81.1%. ASM + mefenoxam was the most effective treatment while ASM alone was less effective in both bioassays. These results indicate that our Pseudomonas fluorescens strains (6L10, 6ba6 and 3ss9) that have biosurfactant-producing abilities are effective against P. capsici on pepper, and enhanced disease suppression could be achieved when they were used in combination with olive oil.

• 환경생물
• /
• 제38권4호
• /
• pp.724-732
• /
• 2020

본 연구에서는 기 선발한 Enterobacter asburiae ObRS-5 균주를 1×10⁸ cfu mL^-1 농도로 고추에 관주 처리했을 때 Phytophthora capsici에 의한 고추역병을 74.6% 방제하는 효과가 있었다. E. asburiae ObRS-5 균주에 의한 고추역병 방제 메커니즘을 확인하기 위해 고추의 PR1, PR4 및 PR10 유전자를 특이적으로 증폭하는 프라이머를 이용하여 quantitative PCR을 수행하였다. 그 결과 E. asburiae ObRS-5 균주를 처리한 고추에서 대조구와 비교하여 상기 세 가지 유전자의 발현이 모두 높은 수준을 유지하였다. 또한 E. asburiae ObRS-5 균주는 고추의 생육을 억제하지 않으면서 ISR 반응을 유도하는 것으로 나타났다. 이러한 결과를 통하여 P. capsici이 침입할 때 E. asburiae ObRS-5 균주가 매개하는 ISR 메커니즘을 통해 Phytophthora 역병의 제어가 가능한 것으로 사료된다.

• 한국미생물·생명공학회지
• /
• 제21권4호
• /
• pp.322-328
• /
• 1993

During the screening of antifungal compounds from microbial secondary metabolites to control phytophthora blight of red pepper caused by Phytophthora capsici, a soil isolate, strain 38D10 was selected. Based on taxonomic studies, this strain was identified as Streptomyces neyagawaensis. The antifungal compound was purified from culture broth by HP-20 column chromatography, ethyl acetate extraction, silica gel column chromatography, HPLC and identified as concanamycin B by UV. $^1H$-NMR, $^{13}C$-NMR, SIMS analysis. Concanamycin B has strong antifungal activity against some phytopathogenic fungi but not antivacterial activity and preventive value were 50% and 100% at 125ppm and 250ppm in pot assay.

• 생명과학회지
• /
• 제24권11호
• /
• pp.1187-1192
• /
• 2014

고추는 한국, 중국, 멕시코를 포함한 온대 및 아열대 지역을 중심으로 전세계적으로 전형적인 향신료로 식용되고 있으며 그 생산량 및 사용량은 해마다 증가하는 추세에 있다. 고추역병균인 Phytophthora capsici는 고추의 생산에 있어, 질적, 양적으로 많은 피해를 야기하는 식물병원균으로 알려져 있다. 난균강에 속하는 이 병원균은 기주식물의 뿌리, 줄기, 잎과 함께 과실에 이르기까지 식물체 전체를 가해한다. 고추역병의 발병을 분자수중에서 이해하기 위해서는, 발병과정에서 발현되는 유전자에 대한 연구분석이 필수적이며, 이를 위해 최근 개발되어 응용되고 있는 발현서열표지(expressed sequence tags, ESTs)의 분석을 시도하였다. 고추역병균을 접종한후 3일째 발병초기의 고추잎으로부터 추출한 total RNA를 이용하여 고추-고추역병균 발병초기 cDNA library를 구축하였다. 이 cDNA library에서 무작위로 선발된 5,760 clone에 대하여 말단 염기서열 분석을 수행하여 5,148개의 양질의 염기서열을 확보하고 contig assembly에 적용한 결과, 2,990개의 unigenes을 확보하였다. 이들 2,990개의 unigenes에 대한 BLASTX를 이용한 상동성 분석결과, 2,409개가 기존에 알려진 서열과 matching을 보였으며, 이중 606개가 기능적으로 구분되었다.

• The Plant Pathology Journal
• /
• 제25권1호
• /
• pp.62-69
• /
• 2009

In this study, we characterized the bacterial strain KJ2C12 in relation with its biocontrol activity against Phytophthora capsici on pepper, and identified this strain using morphological, physiological, biochemical, fatty acid methyl ester, and 16S rRNA gene sequence analyses. Strain KJ2C12 significantly (P=0.05) reduced both final disease severity and areas under the disease progress curves of 5-week-old pepper plants inoculated with P. capsici compared to buffer-treated controls. As for the production of antibiotics, biofilms, biosurfactant, extracellular enzyme, HCN, and swarming activity, strain KJ2C12 produced an extracellular enzyme with protease activity, but no other productions or swarming activity. However, Escherichia coli produced weak biofilm only. Strain KJ2C12 could colonize pepper roots more effectively in a gnotobiotic system using sterile quartz sand compared to E. coli over 4 weeks after treatments. However, no bacterial populations were detected in 10 mM $MgSO_4$ buffer-treated controls. Strain KJ2C12 produced significantly higher microbial activity than the $MgSO_4$-treated control or E. coli over 4 weeks after treatments. Bacterial strain KJ2C12 was identified as Bacillus luciferensis based on morphological, physiological, and biochemical characteristics as well as FAME and 16S rRNA gene sequence analyses. In addition, these results suggested that B. luciferensis strain KJ2C12 could reduce Phytophthora blight of pepper by protecting infection courts through enhanced effective root colonization with protease production and an increase of soil microbial activity.

• 한국미생물·생명공학회지
• /
• 제29권3호
• /
• pp.186-193
• /
• 2001

경북 경주지역의 저병해 고추경착지역의 토양으로부터 생물학적 방제기작중의 하나인 항생물질을 생산하는 길항미생물을 분히하기 위하여 70여종의 세균을 분리하였으며 이들을 대상으로 고추역병균 Phytophthora capsici를 가장 강력하게 길항하는 균주를 최종 선발하였다. 선발균주는 Chryseomonas luteola로 동정되었고 방제 기작은 약한 siderophore 생산성과 cellulase 생산성도 기인되었으나 항생물질 생산성이 주요 기작임을 확인하였다. 항진균성 항생물질의 대량생산의 기초자료로 활용하고자 항생물질 생산의 최적배지 조건 및 배양조건을 조사하였는데 길항균주의 항생물질 생산에 미치는 탄소원의 영향은 0.45% N-acetyl-D-glucosamine과 0.15% D(+) cellobiose에서 81%와 89%의 P. capsicivh자의 성장 억제율을 나타냈다. 질소원의 경우는 0.55% $NH_4$CI 첨가시 69%의 억제율을 나타냈고 무기염의 영향에 있어서는 0.01% KCI을 사용했을 때 63%의 억제율을 나타냈다. 또한 배양 조건에 있어서는 pH 7.0m $30^{\circ}C$에서 84시간 배양시 가장 높은 항진균성 항생물질 생산성을 나타내었다. 토양내에서 실제로 생물방제력을 발휘하는지를 확인하기 위하여 고추를 이용한 in vivo pot test를 실시한 결과 P capsici 만 처리한 것은 고추역병 현상을 나타냈고, P capsici 와 길항균 C luteola 5042를 함께 처리한 것은 역병 현상이 나타나지 않았다. 이것으로 길항균주는 C luteola 5042 P capsici 의 성장을 저해하여 고추 역병의 발병을 억제한다는 사실을 확인할수 있었다.

• 환경생물
• /
• 제18권1호
• /
• pp.47-51
• /
• 2000

Phytophthora capsici에 의한 고추 역병은 세계적으로 피해가 심할 뿐만 아니라 방제도 매우 어려운 병으로서 효과적인 병 방제를 위해 새로운 시도가 필요한 실정이다. 본 연구는 이러한 취지에서 감마선의 hormesis효과를 이용하고자 시도되었다. 저선량 감마선 조사가 고추의 역병 저항성을 유도하는지 여부를 밝히기 위해 광복과 다복 두 품종을 공시하였다. 저선량 감마선은 두 품종 모두 조사선량에 관계없이 발아율을 크게 제고시켰다. 병 저항성 증대에 관한 분석시 품종간에 차이가 있어 감수성 품종인 다복에서 뚜렷한 증대효과가 확인되었으며, 그 효과는 조사선량에 따라 차이가 있었다. 1,4 Gy조사구가 무조사구에 비해 뚜렷하게 저항성이 증가되었으며 특히 4 Gy조사시 병 저항성이 가장 높게 유도되었다. 이러한 현상은 모든 실험에서 일관된 경향을 나타내었고, 통계 분석시에도 유의차가 인정되었다. 반면에 저항성 품종인 광복에서는 무조사에 비해 감마선 조사에 따른 저항성의 증가를 확인할 수 없었다.