• The Plant Pathology Journal
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• v.26 no.4
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• pp.421-423
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• 2010

New sources of barley (Hordeum vulgare L.) resistant to spot blotch, caused by Cochliobolus sativus, are needed to provide effective resistance because of the rapid change pathotype patterns of C. sativus in fields. The purposes of our study were to develop a method to screen barley for resistance to spot blotch disease and then use this methodology to screen barley genotypes for resistance to the major virulent pathotype Pt4 in barley populations in Syria. A transparent tape method, in which a conidial suspension of C. sativus was dropped onto transparent tape and placed, treated-side down, on the second leaf surface of barley plants. Disease symptoms of fungus were easily detected on the leaves covered by the transparent tape after 48h of inoculation. The transparent tape method was repeatable and the disease scores obtained were correlated (r = 0.91, P = 0.001) with those obtained by the seedling assay. This method may be beneficial in various plant pathology breeding programs.

• Korean journal of applied entomology
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• v.18 no.2 s.39
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• pp.77-84
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• 1979

Ten isolates of Xanthomonas oryzae were inoculated to three rice varieties; 'Milyang 23' in Kinmaze group, 'Yushin' in Kogyoku group and 'Tongil' in Rantai-emas group, at the seedling stage, early-tillering stage, Maximum-tillering stage and flag-leaf stage. Much fluctuation was existed in virulence pattern of isolates at each growth stage. Especially, the isolates of pathotype II showed much more variation in virulence. This suggests that there would be more sub-divided pathotypes involved in pathotype II. Isolate G 7716 of pathotype II showed its virulence to 'Yushin' variety only after booting stage. On the result of the analysis of variance for the reaction of three rice varieties to three isolates at each growth stage; the isolates, varieties, growth stages were the main factors of variations of virulence, and the interaction of isolates with varieties was significant but other interactions were not.

• Korean Journal of Veterinary Research
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• v.46 no.4
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• pp.371-379
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• 2006

Newcastle disease virus (NDV) is a single-stranded negative sense RNA virus, which has been classified as a member of the Avulavirus genus of the Paramyxoviridae family. It is also one of the most important pathogens in the poultry industry. The glycoproteins, fusion (F) and hemagglutinin-neuraminidase (HN), determine the virulence of NDV, and the relevant molecular structures have already been determined. NDV isolates differ in terms of virulence, and at least 2 of 9 genotypes (I-IX) have been shown to co-circulate. Therefore, it is clearly important to differentiate between vaccine strains and field isolates. In vivo pathogenicity tests have been the standard protocol for some time, but molecular methods appear preferable in terms of the rapidity of diagnosis, as well as animal welfare concerns. In this study, we have designed primer sets from HN gene for phylogenetic analysis and restriction enzyme analysis, and from F gene for pathotype-specific RT-PCR. Via the combination of 2 methods, 106 Korean NDV isolates obtained from 1980 to 2005 were differentiated into vaccine strains, and virulent genotypes VI and VII. The genotype VI viruses were only rarely isolated after 1999, and genotype VII, after it was initially isolated from poultry in 1995, recurred in 2000, and then became the main NDV constituting a threat to the Korean poultry industry.

• The Plant Pathology Journal
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• v.32 no.5
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• pp.423-430
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• 2016

Clubroot disease caused by Plasmodiophora brassicae is one of the most serious diseases in Brassica crops worldwide. In this study, the pathotypes of 12 Korean P. brassicae field isolates were determined using various Chinese cabbage including 22 commercial cultivars from Korea, China, and Japan, and 15 inbred lines. All P. brassicae isolates exhibited the typical clubroot disease on non-clubroot resistant cultivar, indicating that the isolates were highly pathogenic. According to the reactions on the Williams' hosts, the 12 field isolates were initially classified into five races. However, when these isolates were inoculated onto clubroot-resistant (CR) cultivars of Chinese cabbage, several isolates led to different disease responses even though the isolates have been assigned to the same race by the Williams' host responses. Based on the pathogenicity results, the 12 field isolates were reclassified into four different groups: pathotype 1 (GN1, GN2, GS, JS, and HS), 2 (DJ and KS), 3 (HN1, PC, and YC), and 4 (HN2 and SS). In addition, the CR cultivars from Korea, China, and Japan exhibited distinguishable disease responses to the P. brassicae isolates, suggesting that the 22 cultivars used in this study, including the non-CR cultivars, are classified into four different host groups based on their disease resistance. Combining these findings, the four differential hosts of Chinese cabbage and four pathotype groups of P. brassicae might provide an efficient screening system for resistant cultivars and a new foundation of breeding strategies for CR Chinese cabbage.

• Journal of Microbiology and Biotechnology
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• v.13 no.1
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• pp.110-118
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• 2003

Pseudomonas syringae pv. actinidiae strains, which cause canker disease in kiwifruit, were collected from kiwifruit orchards in Korea and identified using biochemical and physiological tests. The nucleotide sequences of the 16s rDNA and 16s-23s internally transcribed spacer of the isolates were found to be Identical to those of' the pathotype strain, Kwl 1, of P syringae pv. actinidiae. Remarkably, no coding sequence for phaseolotoxin biosynthesis or phaseolotoxin- resistant ornithine carbamoyltransferase was found by PCR amplification in any of the new Korean isolates of pseudomonas syringae pv. actinidiae, although this was clearly identified in the control pathotype Kwl 1 reference strain. In contrast, three primer sets derived from the coronatine biosynthetic gene cluster and DNA from the Korean strains yielded amplified DNA fragments of the expected size. A sequence analysis of the PCR products revealed that P. syringae pv. actinidiae and the Korean strains of pv. actinidiae contain coronafncate ligase genes (cfl)with identical sequences, whereas their. corR genes exhibited 91% sequence similarity. The production of coronatine, instead of phaseolotoxin, by the Korean strains of P. syringae pv. actinidiae was confirmed by a bioassay using reference pathovars known to produce coronatine and phaseolotoxin. The genes for coronatine biosynthesis in the Korean strains of P. syringae pv. actinidiae were found to be present on plasmids.

• Korean Journal of Microbiology
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• v.13 no.4
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• pp.143-156
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• 1975

A rotting bacterium was isolated from decayed root of ginseng (Panax ginseng Meyer), cultured purely, and its pathogenicity was confirmed by reinoculation test. The strain causing ginseng root rot was identified as Pseudomonas fluoresens biotype II. The strain was somewhat different from P.marginalis and P.talaasii, considering the number of flagella, pathotype and ability of indole production. The strain did not exhibit pathogenicity to other plants tested, such as red kidney bean(Phasolus vulgaris L.), soy bean (Glycine max Merr.), cucumber (Cucumis sativus L.) lettuce (Lactuca sativa L.) and cowpea bean (Vigna sinensis Savi.).

• Korean journal of applied entomology
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• v.18 no.2 s.39
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• pp.73-76
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• 1979

Two different isolates of Xanthomonas oryzae, KB 7785 of pathotype I and JN 7721 of pathotype III, that had been the most virulent isolates in the previous inoculation test, were reisolated from cultivar 'Milyang 23' and serially transferred to 10 times. They were inoculated to the 3 cultivars; 'Milyang 23' in Kinmaze group, 'Yushin' in Kogyoku group and 'Tongil' in Rantai-emas group cultivars. It was observed that the virulence of the isolate JN 7721 was more attenuated by the serial transfer on the Wakimoto's agar than the isolate KB 7785. The attenuation of virulence of the isolate JN 7721 was more significant at the cultivar 'Milyang23' than at the other cultivars. This suggests that the host-pathogen interactions and differences of the pathogenicity-maintenance ability among the pathogenic strains may be involved.

• Korean Journal Plant Pathology
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• v.2 no.2
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• pp.82-88
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• 1986

Five antifungal substances were isolated from the long-term storaged extract of common purslane, and identified as isobutyric, butyric, isovaleric, valerie and caproic acids belonging to short-chain fatty acids (C4­C6). Each of these fatty acids showed more or less antifungal potency against spore germination and mycelial growth of Alternaria alternata Japanese pear pathotype in vitro. Antifungal potency of each fatty acid against spore germination was greater than that against the mycelial growth. No one of these fatty acids completely inhibited the mycelial growth at concentration lower than 200 ppm, while 50 ppm of caproic acid and 200 ppm of valerie acid completely inhibited the spore germination. The results of bioassay also suggested that chain-length of the fatty acids might be related with the antifungal potency, since fatty acids with longer chain showed higher antifungal potency.

• The Plant Pathology Journal
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• v.28 no.3
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• pp.295-298
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• 2012

Genetic diversity among Pseudomonas syringae pv. morsprunorum isolates from Prunus mume in Korea and Japan was investigated by comparative sequence analysis of the 16S rRNA gene. The strains included 24 field isolates recovered from P. mume in Korea along with seven Japanese strains. Two strains isolated from P. salicina in Japan, one strain from P. avium in the United Kingdom, and the pathotype strain were also used for comparison with their 16S rRNA gene sequences. Nearly complete 16S rRNA gene sequences were sequenced in all 35 strains, and three sequence types, designated types I, II and III, were identified. Eleven strains consisting of five Korean isolates, five Japanese strains, and one strain from the United Kingdom belonged to type I, whereas the pathotype strain and another 19 Korean isolates belonged to type III. Another four Japanese strains belonged to type II. Type I showed 98.9% sequence homology with type III. Type I and II had only two heterogeneous bases. The 16S rRNA sequence types were correlated with the races of P. syringae pv. morsprunorum. Type I and II strains belonged to race 1, whereas type III isolates were included in race 2. Sequence analyses of the 16S rRNA gene from P. syringae pv. morsprunorum were useful in identifying the races and can further be used for epidemiological surveillance of this pathogen.

• Research in Plant Disease
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• v.7 no.2
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• pp.93-101
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• 2001

Occurrence of Fusarium wilt was surveyed in fields of cruciferous vegetable crops in Korea from 1996 to 1998. The disease severely occurred up to 40% in fields of Chinese cabbage and radish but slightly in Fields of cabbage. A total of 123 isolates was obtained from roots of the diseased plants and identified as Fusarium oxysporum based on the morphological and cultural characteristics. Pathogenicity of nine isolates selected from the isolates was tested by artificial inoculation to the hosts. All the isolates had similar virulence on Chinese cabbage and cabbage, although there were some differences in virulence on cultivars tested among the isolates. The isolates from radish were more virulent to radish than those from Chinese cabbage and cabbage. All isolates from the crucifers were not virulent to eight species of vegetable crops except the crucifers. The results of pathogenicity tests showed that the pathotype of Chinese cabbage-infecting isolates was identical to that of cabbage-infecting isolates, but somewhat different from that of radish-infecting isolates.