최근 기후변화 및 국제교역량, 여행객, 외국 이주민 증가 등으로 국내 농작물에 큰 피해를 입힐 수 있는 고위험 식물병의 유입이 꾸준히 증가하고 있다. 검역 대상인 병원체의 수가 증가함에 따라 검역기관 및 연구원의 업무량이 증가하고 있다. 본 연구에서는 지역별 주요 수출대상 과수인 포도, 단감, 감귤의 국내 미기록 병과 원인병원체에 대한 예찰조사를 수행하였다. 이를 위해 전국을 경기-강원, 충청, 전북, 전남, 경북, 경남 그리고 제주 등 7개 권역으로 나누고 각 권역 소재 대학에서 예찰조사를 수행하여 예찰네트워크를 구축하고자 하였다. 포도 대상 병은 모두 4종으로, Pierce’s disease (Xylella fastidiosa), brown rot (Monilinia fructigena), anthracnose (Greeneria uvicola), 그리고 esca (Phaeomoniella chlamydospora)을 조사하였고 경기-강원, 충청도, 전라북도, 그리고 경상북도 권역을 중심으로 각 권역당 3개 지역 그리고 지역당 3개 지점을 두고 조사하였다. 단감은 모두 3종으로, brown spot (Fusicladium levieri), black leaf spot (Adisciso kaki), 그리고 black spot (Phoma kakivora)을 조사하였고 국내 단감 주생산지인 경상남도와 전라남도 권역을 중심으로 각 권역당 3개 지역 그리고 지역당 3개 지점을 두고 조사하였다. 감귤 대상 병은 모두 2종으로, citrus scab (Elsinoë australis), Septoria spot (Septoria citri)을 조사하였고 감귤 주생산지인 제주권역을 중심으로 조사하였다. 모두 9종에 대한 예찰조사는 2019년 4월부터 10월까지 2주간격으로 실시하였다. 예찰조사결과 주요 수출대상 과수인 포도, 단감, 감귤의 국내미기록병 9종에 대한 원인병원체는 발견되지 않았다. 이 연구를 통해 식물병을 조기에 탐지할 수 있는 전국적인 모니터링 시스템을 구축하였고, 국외 외래유입병들의 예찰조사를 위한 지역 거점을 확보하였다고 평가된다.

In March of 2015, severe sooty mold was observed on blueberries cultivated in a farmer’s greenhouses in Goseong-gun, Gyeongsangnam-do, South Korea. Typical symptoms included a black or dark brown, superficial fungal growth on the leaves, stems, and fruit of blueberry plants. The fungal colonies on PDA were flat and black. The conidia were dark green in color, globose to sub-globose in shape and 3-5×3-4 μm in size. The ramoconidia were cylindrical and 18-42×3 μm in size. The conidiophores were dark brown, cylindrical-oblong in shape and 42-138×3-4 μm in size. To confirm the identity of the fungus(F130), the 18S rDNA as well as actin and β-tubulin gene sequences were PCR-amplified and sequenced. The pathogenicity of the isolate was then explored on 2-month-old potted blueberry plants. Based on the mycological characteristics, molecular identification, and pathogenicity on host plants, this fungus was identified as Cladosporium sphaerospermum. This is the first report on sooty mold of blueberry caused by C. sphaerospermum in Korea.

Circular leaf spot(CLS) disease causes considerable economic damage to persimmon(Diospyros kaki) in South Korea. Mycosphaerella nawae ascospores are the primary inoculum for CLS epidemics. In this study, we investigated the seasonal fluctuation of spore release and its relationship to environmental factors, based on spore trapping. We evaluated the seasonal pattern of released M. nawae ascospores in South Korea. During three persimmon growing seasons(2010 to 2012), we recorded the release of ascospores in two regions, Jinju and Gimhae, which are major producing regions of sweet persimmon in South Korea. The release of CLS ascospores was from the first week of May to the end of July. The maximum release of spores was observed in late June. A computer model used accumulated degree days to simulate ascospore release. The overall mean accumulated degree days, from 01 May to 50% ascospore release for the observed data(1174℃ days), was not significantly different from the predicted value of 1144℃ days. The mean differences between predicted and observed release percentages for the sampling periods were not significantly different from zero.

Bacterial cells communicate with each other through their specific chemical languages, by which bacteria regulate a set of genes in a multicellular behavior, including antibiotics, biofilm, motility, and virulence. The twitter communication in Gram positive bacteria is mediated by diffusible signal molecules, N-acyl homoserine lactones (HSLs), that differ with respect to the length, saturation and substitutions of the side-chain. In Gram negative bacteria, diffusible peptides control the physiological phenotypes. In this presentation, some general examples of bacterial twitter communication, such as Vibrio fischeri, Burkholderia glumae, Agrobacterium tumefaciens, and Serratia marcescens will be presented. The contribution of bacterial communication to pathogenicity of Pantoea ananatis, our model bacterium causing bacterial rice sheath rot and onion center rot diseases, will mainly be discussed.

Postharvest apple rot causes severe economic losses and lowers apple quality, and is one of the most important limiting factors of apple exports. Apples with rot symptoms were sampled from Geochang, South Korea. Isolation of the causal fungus was performed by culturing small pieces of diseased tissues on potato dextrose agar. Two different rot genera, Fusarium and Alternaria, were identified according to their morphological characteristics. To confirm the identity of the causal fungus, we sequenced the DNA of the complete internal transcribed spacer(ITS) rDNA gene region and translation elongation factor 1-alpha(EF1-α) region. Koch’s postulates were supported by pathogenicity tests conducted on apple fruit. Based on mycological characteristics, molecular identification, and pathogenicity tests, the two fungi were identified as Fusarium tricinctum and Alternaria alternata. To the best of our knowledge, this is the first report of postharvest apple rot caused by F. tricinctum and A. alternata in South Korea.

Bacterial fruit blotch(BFB) of cucurbits caused by Acidovorax citrulli(Acc) continues to diminish fruit yields. The aim of this study was to address whether two genetically distinct populations of Acc are present in watermelon-growing fields in Korea. For this purpose, we used the enterobacterial repetitive intergenic consensus polymerase chain reaction(ERIC-PCR) profiling and substrate-utilization profiles. According to the results of ERIC-PCR, group I and II strains showed clearly differentiated PCR-based fingerprinting profiles. Differences between group I and II strains included amplification of unique, group-specific DNA fragments such as the 1.3-, 0.28-, and 0.25-kb fragments in ERIC-PCR. Acc stains belonging to group I did not use L-leucine, whereas group II strains did use the substrate. Our results support the genetic differentiation of Acc strains into two groups and demonstrate that Acc strains from both groups are previously existed in watermelon-growing fields in Korea. Information about the genetic diversity of Acc under the present study will help scientists and managers form strategies to control BFB.

Streptomyces padanus IA70-5 has been shown to be a promising biological control agent for the suppression of pepper anthracnose. In this study, we assessed the potential use of strain IA70-5 as a biological control agent for Phytophthora blight caused by Phytophthora capsici. Strain S. padanus IA70-5 was found to inhibit the mycelial growth and zoosporangium formation of P. capsici causing Phytophthora blight on pepper plants. In experiments with hot pepper fruit, IA70-5 suppressed the progression of Phytophthora rot by over 90% in pre-inoculated treatments with culture suspension. In experiments with 60-day-old pepper plants, IA70-5 suppressed Phytophthora blight by over 90%. These results demonstrated the potential for S. padanus IA70-5 to provide a practical biological agent for the control of Phytophthora blight in the field.

Pseudomonas fluorescens B16 has been shown to be a promising biological control agent for the promotion of plant growth, root colonization, and suppression of bacterial wilt. This study investigated the dispersion of B16 from seed to radicle, and to the whole root system, and illustrated population changes within cucumber seeds and radicles using scanning electron microscopy (SEM), fluorescence microscopy (FM) and immunofluorescence microscopy (IFM). When cucumber seeds were soaked in a bacterial suspension of B16, bacterial cells entered the seeds through the pore at the base, colonized the inner plane, and proliferated germination advanced. Population densities of B16 were gradually increased, and increased initial populations within newly growing roots. The root surface was covered by cylindrical rod-shaped bacterial cells, and junctions between epidermal cells were covered preferentially. Previous studies exploring root colonization of rhizobacteria have not focused on colonized populations inside seeds. Our microscopic observations confirmed the importance of bacterial cells colonized inside seed coats. Population densities of B16 were then naturally sustained up to harvesting time. The results obtained in this study provide about a novel insight into the commercial application of biological control agents within seeds.

We analyzed the viable population changes of Paenibacillus polymyxa E681, a plant growth-promoting rhizobacterium, on seeds and roots after bioformulation at varying time intervals during the storage. The viable population of E681 on tested crop seeds sustained log 4-5 cfu/seed after 300 days of seed treatment. The ability of root colonization and inhibition of fungal mycellial growth was not influenced even after 300 days of seed treatment. The seed-soaking treatment returned better results than powder formulation, in increasing the initial population of E681 on plant roots. Collectively, it was found that E681 is a durable and stable biological control agent for application to crop seeds.

고추에 큰 피해를 일으키는 탄저병에 대한 강한 길항력이 있는 세균을 선발하기 위해 선행연구에서 식물뿌리 시료로부터 분리하여 보관중인 세균들을 대상으로 검정에 사용하였다. 총 457균주로부터 IA70-5균주를 최종 선발하였고, 16S rDNA 염기서열 분석을 통해 Streptomyces padanus로 동정하였다. S. padanus IA70-5는 색소를 분비하지 않고 운동성이 없으며 전형적인 Streptomyces속에 속하는 세균들처럼 나선형의 형태를 이루고 있었다. S. padanus IA70-5 균주는 in vitro에서 Colletotrichum acutaum의 균사생장, 포자발아, 그리고 부착기 형성을 효과적으로 억제하였다. 실내 고추 과실에 대하여 병원균 접종 전 IA70-5 배양액 처리 시 약 90%의 탄저병 억제효과를 나타내었다. 본 연구결과를 통하여 길항방선균 S. padanus IA70-5는 고추 탄저병을 억제하는 효과가 있음을 확인하였다.