Young-Kee Lee

Review of Disease Incidences of Major Crops of the South Korea in 2005

In 2004, average temperature was higher, and rainfall was less than those of previous year, The diseases of rice, barley, pepper, chinese melon, apple and oriental pear were surveyed. Seedling diseases, leaf blast, sheath blight and bacterial blight of rice, phytophthova blight, virus diseases and anthracnose of pepper, and sudden wilt syndrome and powdery mildew of chinese melon grown in plastic greenhouse were severe. Especially, sheath blight and bacterial blight of rice occurred two times higher than those of previous year, Panicle blight of rice decreased about 4 times, compared with the previous year, presumed that the lower rainy days, rainfall and RH suppressed spread of the fungal pathogens to panicles of rice. Lower rainfall during mid- and late Aug caused three-times less occurrence of phytophtora blight of red-pepper than that of the previous year, Another diseases surveyed occurred similar or less than those of the previous year.

Diversity and Pathogenicity of Fusarium Species Associated with Head Blight of Job`s Tears

율무(Coix lacryma-jobi)는 동아시아에 자생하는 작물로, 종실은 주로 건강식품이나 의약용으로 사용되고 있다. 2006년부터 2008년까지 국내 율무 재배 지역에서 이삭마름 증상이 관찰되었다. 병징은 겉껍질이 변색되고, 내부의 속씨는 마르고 쭉정이가 되는 것이다. 159개의 Fusarium균을 분리하였고, 분리 빈도별로 F. graminearum(34%), F. proliferatum(14.5%), F. verticillioides(10.1%), F. equiseti(6.9%), F. fujikuroi(6.3%) 순으로 분리되었고, 그 밖에 F. subglutinans, F. semitectum, F. poae, F. sporodochioides가 분리되었다. 분리균주의 elongation factor 1 alpha 유전자의 염기서열 분석을 통한 계통분석을 수행한 결과, NCBI GenBank에 등록된 균주와 동일한 것을 확인하였다. 분리균주의 병원성 검정을 수행한 결과, F. graminearum, F. proliferatum, F. verticillioides가 병원성이 강하였다. 이 연구는 Fusarium균에 의해 발생한 율무 이삭마름 증상에 대한 첫 번째 보고이다. 【Jobs tears (Coix lacryma-jobi) is native to East Asia, and grains of the plant are used as health food and medicinal material. Head blight symptoms of the plant were frequently observed during disease surveys in Korea from 2006 to 2008. The symptoms were characterized as discoloration of husks, and subsequently inside of mature grains were shriveled or emptied. One hundred fifty nine isolates of Fusarium species were obtained from the disease symptoms of the plant collected from several locations in the country. Out of the isolates, the most frequently isolated Fusarium species were F. graminearum (34%), F. proliferatum (14.5%), F. verticillioides (10.1%), F. equiseti (6.9%), and F. fujikuroi (6.3%). Other Fusarium species isolated were F. subglutinans, F. semitectum, F. poae, and F. sporodochioides. Elongation factor 1 alpha gene sequences of the isolates were used for phylogenetic analysis. Analyses of the sequences revealed that the isolates were confirmed to be identical with each reference species of NCBI GenBank. Pathogenicity tests showed that F. graminearum, F. proliferatum and F. verticillioides were strongly virulent to grains of Jobs tears. The present study is the first report of head blight of Jobs tears caused by Fusarium species in Korea.】

Bacterial Blight of Shallot, Caused by Pseudomonas syringae pv. porri, a New Disease in Korea

Shallots (Allium cepa var. ascalonicum L.) affected by bacterialblight disease received for diagnosis in March 2007 (Fig. 1A).Grower has estimated and we have confirmed that as much as two-third of the plant was affected by the disease in fields in the DaejungDistrict, Seokwipo of Jeju, Korea in April, 2007. The symptoms onleaves included yellowish and brownish leaf blight on leaf surface.Seriously infected plants shriveled and died in fields. Two isolates,BC2489 and BC2498 were recovered on trypticase soy agar (TSA)from symptomatic leaves of the plants. Pathogenicity was evaluatedon seven-week-old shallots by spot and spray inoculation. Bacteriawere grown on TSA for 48 h at 28

Occurrence of Stem Canker on Rape Caused by Leptosphaeria biglobosa in Korea

Stem canker symptoms were observed in a rape field in Muan, Korea during a disease survey in May 2006. A total of 15 isolates of Phoma sp. were obtained from the infected stems of the plant. All isolates were identified as Leptosphaeria biglobosa based on their morphological and cultural characteristics. The Korean isolates of L. biglobosa were assigned to `brassicae` among six subclades of L. biglobosa complex based on the entire ITS sequences of rDNA. Pathogenicity of the fungal isolates was confirmed on leaves and stems of rape by artificial inoculation. This is the first report that Leptosphaeria biglobosa causes stem canker of rape in Korea.

Characterization of Agrobacterium spp. Isolated from Roots of the Crown Gall-infected Grapevine in Chungbuk

The roots of grapevine in the field in which the crown gall was occurred severely in Chungbuk province were collected and Agrobacterium spp. were isolated from the roots using the selective media. The selected 13 isolates were identified as A. tumefaciens with fatty acid analysis using MIDI system, nucleotide sequence of 16S rDNA, biochemical characteristics, and PCR with the species-specific primers. A. vitis, a pathogen of crown gall disease of grapevine was not isolated from the roots. All of the isolates did not show pathogenicity on the tomato seedlings and the stem and root of grapevine. Eric-PCR showed that DNA band patterns of the root isolates were a little more similar to A. tumefaciens than A. vitis. However, overall similarity between the root isolates and the pathogenic strains of A. tumefaciens and A. vitis was low by rep-PCR. These results suggest that a pathogen causing crown gall in grapevine in Chungbuk province may transmitted through the seedlings rather than via soil or roots.

Occurrence of Goat's-Beard Powdery Mildew Caused by Podosphaera ferruginea in Korea

Powdery mildew symptoms were frequently on plants of goat`s-beard (Aruncus dioicus var. kamtschaticus) found cultivated in the island Ulleungdo in June 2008. The symptoms appeared as powdery mycelial colonies and dark brown cleistothecia on leaves, petioles, stems and budding flowers of the plant. Incidence of the disease was as high as 50-80% in the goat`s-beard fields. Specimens of the diseased plants were collected and examined for morphological characteristics of the causal fungus. On the basis of morphological characteristics of the conidial stage and the teleomorph, the fungus was identified as Podosphaera ferruginea. This is the first report of goat`s-beard powdery mildew caused by Podosphaera ferruginea in Korea.

Development of an Improved Loop-Mediated Isothermal Amplification Assay for On-Site Diagnosis of Fire Blight in Apple and Pear

Fast and accurate diagnosis is needed to eradicate and manage economically important and invasive diseases like fire blight. Loop-mediated isothermal amplification (LAMP) is known as the best on-site diagnostic, because it is fast, highly specific to a target, and less sensitive to inhibitors in samples. In this study, LAMP assay that gives more consistent results for on-site diagnosis of fire blight than the previous developed LAMP assays was developed. Primers for new LAMP assay (named as DS-LAMP) were designed from a histidine-tRNA ligase gene (EAMY_RS32025) of E. amylovora CFBP1430 genome. The DS-LAMP amplified DNA (positive detection) only from genomic DNA of E. amylovora strains, not from either E. pyrifoliae (causing black shoot blight) or from Pseudomonas syringae pv. syringae (causing shoot blight on apple trees). The detection limit of DS-LAMP was 10 cells per LAMP reaction, equivalent to 104 cells per ml of the sample extract. DS-LAMP successfully diagnosed the pathogens on four fire-blight infected apple and pear orchards. In addition, it could distinguish black shoot blight from fire blight. The Bühlmann-LAMP, developed previously for on-site diagnosis of fire blight, did not give consistent results for specificity to E. amylovora and on-site diagnosis; it gave positive reactions to three strains of E. pyrifoliae and two strains of P. syringae pv. syringae. It also, gave positive reactions to some healthy sample extracts. DS-LAMP, developed in this study, would give more accurate on-site diagnosis of fire blight, especially in the Republic of Korea, where fire blight and black shoot blight coexist.

On-Site Diagnosis of Fire Blight with Antibody-Based Diagnostic Strips

Gwang-Il Heo, Doo-San Shin, Soo-Hyeong Son, Chang-Sik Oh, Duck Hwan Park, Young-Kee Lee, and Jae-Soon Cha* Major in Plant Medicine, School of Applied Plant Science & Biotechnology, Chungbuk National University, Cheongju 28644, Korea Department of Horticultural Biotechnology, Kyung Hee University, Yongin 17104, Korea Applied Biology Program, Division of Bioresource Sciences, Kangwon National University, Chuncheon 24341, Korea Department of Agro-food Safety and Crop Protection, National Institute of Agriculture Sciences, Rural Development Administration, Wanju 55365, Korea

Crown Gall of Weeping Fig Caused by Agrobacterium larrymoorei and A. tumefaciens

Crown gall on lower stem of weeping fig(Ficus benjamina Roxb.) was first observed at Daejon in 2003. Tumors were about 15 cm in size and semi-round with rough surface texture of dark brown color. Two virulent isolates among ten bacteria isolated from the tumor tissues were characterized. Their colonies were convex, glistening, circular with an entire edge, and white or tannish cream in color on potato dextrose agar supplemented with 0.5% . They were rod shape with peritrichous flagellae, gram-negative, aerobic growth, oxidase-positive, and grew on D1M agar. The isolates were identified as Agrobacterium larrymoorei and A. tumefaciens based on biochemical and physiological characteristics, fatty acid profiles and substrate utilization patterns. Seedlings of some host plants excepting grapevine produced typical galls two to three weeks after inoculation with cell suspensions of the virulent strains. This is the first report on crown gall of weeping fig in Korea.

Crown Gall of Chrosanthemum Caused by Agrobacterium rubi and A. tumefaciens

Crown gall on lower stem and root of chrysanthemum(Dendranthema grandiflorum Kitamura) was observed at Hwasung and Gumi in 2001 and 2004, respectively. Tumors were semi-round with rough surface texture of dark brown color. Nine isolates inducing gall formation on lower stem of chrysanthemum among twenty isolates from the tumor tissues were characterized. Their colonies were convex, glistening, circular with an entire edge and whitish or tannish cream in color on potato dextrose agar supplemented with 0.5% . The virulent isolates were rod-shaped with peritrichous flagellae, gram negative, aerobic and growing on D1M agar. Among nine virulent isolates, one isolate was identified as Agrobacterium rubi and eight isolates were A. tumefaciens based on biochemical and physiological characteristics, fatty acid profiles and substrate utilization patterns. A. tumefaciens had strong pathogenicity and broad host range compared with A. rubi. This is the first report on crown gall of chrysanthemum in Korea. To our knowledge, crown gall of chrysanthemum caused by A. rubi is first report in this study worldwide.