• Asian Journal of Turfgrass Science
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• v.24 no.2
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• pp.165-169
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• 2010

Fusarium circinatum is the causal agent of the pine disease commonly referred to as pitch canker. In this study, F. circinatum was isolated from the diseased Pinus rigida in the golf courses, Korea. The morphological characteristics and the molecular features of the isolates were investigated to identify the pathogen. Histone H3 gene and IGS rDNA region was analyzed and consequently the isolates identified as F. circinatum. All of them have the same sequences and the mating type was determined as MAT1-1. The inhibitory effect of the methanol extracts from the disease resistant pine species, Pinus koraiensis and Pinus densiflora and a susceptible species, P. rigida were evaluated against the isolate, F. circinatum. As a result, the extracts of P. koraiensis and P. densiflora showed higher antifungal activity than that of the susceptible, P. rigida.

• The Plant Pathology Journal
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• v.35 no.3
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• pp.234-242
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• 2019

Thirty-four strains of bacteria were isolated from Phellodendron amurense. Using Nectria haematococca as an indicator strain, the best strain, B18, was obtained by the growth rate method. The morphological, physiological and biochemical characteristics of strain B18 and its 16S DNA gene sequence were identified, and the biocontrol effect of strain B18 was assessed in pot and field tests, as well as in a field-control test. Drilling methods were used to determine the antibacterial activity of metabolites from strain B18 and their effects on the growth of pathogen mycelia and spores. The best bacteriostatic rate was 85.4%. B18 can hydrolyse starch and oxidize glucose but does not produce gas; a positive result was obtained in a gelatine liquefaction test. According to 16S DNA gene sequencing, strain B18 is Bacillus methylotrophicus (GenBank accession number: MG457759). The results of pot and field-control trials showed 98% disease control when inoculating $10^8cfu/ml$ of the strain. The disease control effect of the B18 culture liquid (concentrations of $10^8$, $2{\times}10^6$, $10^6$, $5{\times}10^5$ and $2.5{\times}10^5cfu/ml$) in the field-control test was higher than 80%, and the cure rate of the original delivery solution was 96%. Therefore, in the practical forestry production, a $2.5{\times}10^5cfu/ml$ culture liquidshould be applied in advance to achieve good control effects.

• Research in Plant Disease
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• v.22 no.4
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• pp.276-283
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• 2016

Bacterial canker caused by Pseudomonas syringae pv. actinidiae (Psa) occurred at 202 kiwifruit orchards for the survey period of 2013-2016, of which Psa biovar 2 (Psa2) and Psa biovar 3 (Psa3) were detected at 73 and 129 kiwifruit orchards, respectively. The number of kiwifruit orchards infected by Psa3 in 2016 increased nearly two times compared to 2015. Psa3 was detected from all the kiwifruit cultivars except some kiwiberry cultivars growing in Korea. Yellow-fleshed cultivars Hort16A and Jecy-gold and red-fleshed cultivar Hongyang were highly susceptible to Psa3. Our epidemiological and random amplification of polymorphic DNA analyses indicated that the first Psa3 incidence on Hongyang orchard in Sacheon, Gyoungnam might result from an introduction of Psa3-contaminated pollens from China for artificial pollination in 2014 and recent outbreaks of Psa3 in Sacheon and Goseong, Gyoungnam in 2016 might be due to rapid spread of bacterial canker by secondary infection of Psa3 from Hongyang orchard to neighboring Jecy-gold and Hayward orchards.

• Proceedings of the Korea Contents Association Conference
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• 2018.05a
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• pp.459-460
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• 2018

In this paper, we present a data augmentation method that generates synthetic plant disease images using Generative Adversarial Networks (GANs). We propose a training scheme that first uses classical data augmentation techniques to enlarge the training set and then further enlarges the data size and its diversity by applying GAN techniques for synthetic data augmentation. Our method is demonstrated on a limited dataset of 2789 images of tomato plant diseases (Gray mold, Canker, Leaf mold, Plague, Leaf miner, Whitefly etc.).

• Proceedings of the Korean Society of Plant Pathology Conference
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• 2003.10a
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• pp.69.2-70
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• 2003

For the selection and breeding of chestnut varieties resistant to the chestnut blight fungus Cryphonectria parasitica, disease resistance and susceptibility of 28 varieties widely planted and growing in Korea were evaluated by artificial inoculation of a pathogenic fungus. For this experiment, a typical virulent strain (KCPC-19) was selected. Artificial inoculation was conducted into all varieties by using two different materials and methods, i.e., bark and wood tissue sections in the laboratory and living trees in the field. In the bark and wood tissue section method, the size of necrotic area and canker development on chestnut varieties were examined and compared 4 days after inoculation. There were wide variations of chestnut varieties in disease resistance and susceptibility against chestnut blight fungus, but 3 varieties, Daebo！, Ishizuchi, and Sandae, were shown to be relatively resistant to the disease with the necrotic area of 0.95-1.03 cm2, while Arima was the most susceptible with the size of 2.0 cm2. In the living tree inoculation examined 5 weeks after inoculation, 3 varieties, Daebo, Ishizuchi, and Riheiguri, showed the higher resistance, but Tono 2 did the highest susceptibility among tested varieties.

• Research in Plant Disease
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• v.17 no.2
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• pp.177-183
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• 2011

Four-year-old seedlings of Pinus thunbergii, Pinus densiflora and Pinus rigida were inoculated with Fusarium circinatum isolate (FT-7), the pitch canker fungus, from P. thunbergii, to evaluate the effects of the pathogen on disease development and gas exchange rate. Needle dehydration was evident on 2 of 10 seedlings of P. thunbergii and P. rigida at 18 and 21 days after inoculation, respectively, while no symptoms were observed in P. densiflora seedlings throughout the experiment. Gas exchange stopped completely in 4 of 5 measured seedlings of P. thunbergii and 2 of 5 measured seedlings of P. rigida at 25 days after inoculation, and in the remaining 3 seedlings of P. rigida at 39 days after inoculation. Disease development in P. thunbergii seedlings was faster than that in P. rigida seedlings. By the time, the experiment was ended at 78 days after inoculation, 9 of 10 seedlings of P. rigida and 8 of 10 seedlings of P. thunbergii seedlings treated with FT-7 was almost dead, but all seedlings of P. densiflora were still healthy. We suggest that P. densiflora is resistant to F. circinatum in the current study, and gas exchange rate of the species after inoculation does not differ significantly compared to that of untreated control.

• Research in Plant Disease
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• v.6 no.1
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• pp.36-38
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• 2000

A disease of Kalopanax pictus was found in Taebaec of Kang-won province. Korea, 1998. Typical symptoms were dark green to brown lesions appeared on the leaf and the stem canker. Many spores appeared on the lesions under humid conditions. A Botrytis species was consistently isolated from the infected plants. Conidia were obvoid to ellipsoid, 1-celled, hyaline or pale brown. The conidia were about 6-12${\times}$4-8$\mu\textrm{m}$ under scanning electron microscope, many micro-projections appeared on the surface of conidia. the isolated fungus infected heathy Kalopanax pictus. symptoms in inoculated plants were similar to those of originally diseased plants. The causal agent was identified as Botrytis cinerea. Gray mold of Kalopanax pictus was proposed to name this disease.

• International Journal of Industrial Entomology and Biomaterials
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• v.7 no.2
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• pp.93-106
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• 2003

Soilborne diseases pose a serious problem for mulberry cultivation during nursery plantation and established gardens, which cause severe loss in revenue generation of mulberry growers as compared to foliar diseases. Various soilborne diseases affect mulberry. Among them, root knot and root rot affect the established plantation resulting in severe loss in leaf yield apart from deterioration in leaf quality, which is a pre-requisite in successful sericulture to get the good quality of cocoons. Besides, stem-canker, cutting rot, collar rot and die-back, affect the initial establishment and survivability of mulberry plantation in nursery. The problem is difficult to handle, due to the complex nature of the diseases and also involvement of various biotic and abiotic factors. This is compounded by the occurrence of disease complex (especially nematode ＋ soilborne pathogenic microbes) in established mulberry gardens, which facilitates quick spread of the disease and enhance the plant mortality, resulting substantial loss in leaf yield. Therefore, prevention and timely control measures need to be taken up to protect the mulberry plants from different soilborne plant pathogens. In this review article, symptomatology, epidemiology, disease cycle and control measures of soilborne diseases of mulberry are discussed.

• Journal of Life Science
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• v.30 no.1
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• pp.1-9
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• 2020

Pseudomonas syringae pv. actinidiae, the causal agent of a bacterial canker disease in kiwifruit, is subdivided into five genetically distinct populations, namely biovars 1, 2, 3, 5, and 6. Of these, strains belonging to biovar 3 are responsible for a pandemic bacterial canker of kiwifruits since 2008. This study aimed to characterize the structure of the biovar 3 population and investigate the origin of biovar 3 strains isolated in Korea. The genetic variability of fifteen biovar 3 strains, thirteen Korean and two Chinese, were evaluated through random amplified polymorphic DNA (RAPD)-PCR. The RAPD results revealed the presence of eight lineages, designated as subgroups I-VIII, across the biovar 3 strains used in this study. As the strains in subgroups II and III from China were not found in the Korean examples, we concluded that six genetically different biovar 3 subgroups (I, IV, V, VI, VII, and VIII) are present in Korea. In PCR analysis using primers specific to the strains of New Zealand and Europe, Korean strains in subgroups V and VI amplified the relevant DNA bands, suggesting that these were introduced from these two origins, respectively. PCR primers specific to subgroup VIII were developed to monitor the spread of the first biovar 3 strain in Korea, and investigations revealed that this strain was not found in Korea after its first occurrence.

• The Plant Pathology Journal
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• v.28 no.2
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• pp.207-211
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• 2012

It has been known that streptomycin resistance in bacteria can occur as a results of chromosomal mutation or through gene acquisition or both. Chromosomal mutations for resistances are point mutations in the rpsL gene, which alter ribosomal protein S12. Acquired resistance has occurred when an $Sm^R$ plasmid carrying transposon Tn5393 with tandem strA-strB gene is transferred by conjugation. A total of 686 isolates of Xanthomonas smithii subsp. citri causal agent of citrus canker disease were collected from 26 citrus orchards in Jeju Island in 2003 and 2004 seasons. Forty-nine of 111 isolates from streptomycin non-sprayed orchards in 2003 season were resistant to streptomycin. Of 107 isolates from orchards sprayed one time with streptomycin, 58 isolates were resistant, and 166 of 221 isolates from orchards sprayed two times with streptomycin were resistant. In 12 orchards sprayed three or more times with streptomycin, 219 of 247 isolates were resistant to streptomycin. Twenty-five isolates of X. smithii subsp. citri were surveyed to identify the mechanisms of streptomycin resistance in this study. Twenty-one of these 25 isolates were resistant to streptomycin, and it was proven by PCR assay that 18 of the 21 streptomycin resistant isolates have the strB gene. In sixteen of the 21 streptomycin resistant isolates, it was occurred a point mutation altered codon lysine (AAG)-41 of rpsL gene to arginine (AGG). The streptomycin-sensitive isolates easily acquired the resistance by mixed culture with resistant isolates. The strB gene was amplified from the isolates that acquired the resistance by mixed culture, and one isolate of them was also point-mutated in codon 41 of rpsL gene to be resistant. In this study, most of the streptomycin-resistant isolates of X. smithii sub sp. citri in Jeju island expressed the resistance by both chromosomal point mutation and gene acquisition, and the resistance was easily acquired through conjugation by culture mixed with streptomycin resistant and sensitive strains.