• Korean Journal of Plant Resources
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• v.32 no.4
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• pp.296-302
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• 2019

This study was accomplished to select breeding materials among the pear germplasm 6 species 43 accessions and check out the expression of scab incidence of inter specific hybrids of 5 crosses 609 seedlings for scab resistance breeding. Fruitlets scab incidence of P. pyrifolia, P. bretschneideri and P. ussuriensis were 59.5, 73.4 and 63.0% respectively, and also fruitlets scab incidence of interspecific hybrid cultivars between P. pyrifolia and P. bretschneideri were 77.7%. However, fruitlets scab incidence of P. communis and interspecific hybrid accessions between P. pyrifolia and P. communis were significantly less than 15%. As a result of the Duncan test, scab resistance of pear accessions were classified into two groups: P. communis and their hybrid were resistance and P. bretschneideri, P. pyrifolia, P. ussuriensis, and among their hybrid were susceptible. Also, it showed the same trend in the seedlings. Scab incidence of 'Seolwon' ${\times}$ 'Chuwhangbae' and 'Supergold' ${\times}$ 'Mantienhong' in P. pyrifolia seedlings showed more than 80%, while that of interspecific hybrid between P. pyrifolia and P. communis showed about 2%. It showed scab resistance of P. communis transferred to hybrid seedlings and expressed to be dominant in their seedlings. Namely, P. communis was good breeding materials for scab resistance.

• Research in Plant Disease
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• v.27 no.4
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• pp.164-171
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• 2021

In August 2020, 377 anthracnose strains were isolated from anthracnose-infected peppers collected from 25 farms in Sunchang-gun, Jeollabuk-do. Inhibition rate of mycelial growth of 11 pepper anthracnose fungicides registered in Korea was investigated for 62 strains selected by region and the degree of susceptibility to each fungicide was investigated. As a result of the fungicide susceptibility test of anthracnose to the fungicide, no resistant strains were observed in fluazinam, prochloraz manganese, and benomyl, but resistant strains appeared in at least three areas for other fungicides, and all strains in all regions were resistant to dithianon. Through this, it was confirmed that the fungicide resistance was expressed in the strain group due to the continuous treatment of the fungicide in some areas. By region, resistant strains to seven pesticides appeared in Sunchang-eup and Paldeok-myeon, and resistant strains to six pesticides appeared in Geumgwa-myeon, Bokheung-myeon, Ssangchi-myeon, Yudeung-myeon, and Pungsan-myeon. There was no significant correlation between fungicide registration time and emergence of resistant strains.

• The Korean Chronic Disease News
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• no.151
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• pp.9-9
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• 1993

• Research in Plant Disease
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• v.22 no.1
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• pp.18-24
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• 2016

This study was conducted to elucidate the cultural and pathogenic characteristics of Cladosporium cucumerinum PT1 and resistance of 81 commercial cucumbers (Cucumis sativus). Cucumber leaves and fruits appeared as scab were collected from a plastic film house located in Pyeongtaek, Gyeonggi-province, Korea in late March, 2015. A casual fungus was isolated from the diseased fruits on potato dextrose agar and it was identified as C. cucumerinum PT1 based on the morphological characteristics. To find out the effect of wounding and fruit size on the development of cucumber scab, small (<10 cm long), medium (10 to 20 cm long), and large (>20 cm long, commercially mature fruit) size cucumber fruits were harvested, C. cucumerinum PT1 pathogens were inoculated with a single droplet of suspension ($1{\times}10^5$ spores/ml) on wounded or unwounded cucumber fruits. Small fruits were completely damaged with showing severe water-soaking symptoms and fast pathogen growth regardless of wounded or unwounded. Meanwhile slight water-soaking symptoms on medium and large size fruits occurred and disease development into plant tissues was observed only on wounded fruits. Disease resistance of 81 commercial cucumber cultivars was evaluated on third-stage seedlings and small fruits by inoculating suspension ($1{\times}10^5$ spores/ml) of C. cucumerinum PT1. As a result, mini and pickling cultivar groups were resistant, 'Cheoeumcheoreom' cultivar was symptomless and the other cultivars were resistant to medium resistant. On the other hand, most of cucumber cultivars belonging to the other groups were susceptible. Disease resistance of cucumber against cucumber scab was significantly different among cultivars and a few cucumber cultivars showed different disease resistant responses to two bioassay methods using seedlings and small fruits. Therefore, to screen scab resistance in cucumber, a test using both fruits and seedlings is advisable. We think that the selected resistant cultivars can be used to control cucumber scab effectively under the farmhouse condition.

• Horticultural Science & Technology
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• v.35 no.2
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• pp.210-219
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• 2017

This study was conducted to establish an efficient screening method for radish (Raphanus sativus) cultivars that are resistant to black spot, which is caused by Alternaria brassicicola. Seven A. brassicicola isolates were selected and investigated for their ability to produce spores and pathogenicity. Of these isolates, A. brassicicola KACC 40036 and 43923 produced abundant spores in V-8 juice agar medium and showed pathogenicity and strong virulence on radish seedlings. We examined the resistance of 61 commercial cultivars of radish to A. brassicicola KACC40036, and found that there are no highly resistant radish cultivars; however, some cultivars, such as 'Geumbong' and 'Searom', showed weak resistance to A. brassicicola. For further study, we selected four radish cultivars that showed different disease responses to A. brassicicola KACC40036. According to the growth stage of the radish seedlings, inoculum concentration, and incubation temperature of radish, development of black spot on four cultivars has been investigated. The results showed that younger seedlings were more sensitive to A. brassicicola than older seedlings, and the disease severity depended on the concentration of the spore suspension. The disease severity of plants incubated in humidity chamber at $25^{\circ}C$ was greater than that of plants grown at $20^{\circ}C$ or $30^{\circ}C$. Taken together, we suggest the following method for screening for radish plants that are resistant to A. brassicicola: 1) inoculate 16-day-old radish seedlings with an A. brassicicola spore suspension ($2.0{\times}10^5spores{\cdot}mL^{-1}$) using the spray method, 2) incubate the inoculated plants in a humidity chamber at $25^{\circ}C$ for 24 h and then transfer the plants to a growth chamber at $25^{\circ}C$ with 80% relative humidity under a 12 h light/dark cycle, and 3) assess the disease severity of the plants two days after inoculation.

• Research in Plant Disease
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• v.26 no.3
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• pp.159-169
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• 2020

Pectobacterium carotovorum subsp. carotovorum (Pcc) causes bacterial soft rot on a wide range of crops worldwide, especially in countries with warm and humid climates. This study was conducted to establish an efficient screening method for resistant cultivars of Chinese cabbage to bacterial soft rot. Resistance degrees of 65 commercial Chinese cabbage cultivars to the Pcc KACC 10225 isolate were investigated. For further study, three Chinse cabbage cultivars (Taebong, Hadaejangkun, CR Alchan) showing different level of resistance to the bacterium were selected. The development of bacterial soft rot on the cultivars was tested according to several conditions such as growth stage of Chinse cabbage seedling, inoculum concentration, and incubation temperature after inoculation. On the basis of the results, we suggest that an efficient screening method for resistant Chinses cabbage to Pcc is to inoculate twenty one-day-old seedlings with a bacterial suspension of Pcc at a concentration of 1×10⁷ cfu/ml, and to incubate the plants in a dew chamber at 25℃ for 24 hr and then to cultivate in a growth room at 25℃ and 80% relative humidity with 12-hr light per day.

• Research in Plant Disease
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• v.24 no.3
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• pp.193-201
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• 2018

Pectobacterium carotovorum subsp. carotovorum (Pcc) causes bacterial soft rot on a wide range of crops worldwide, especially in countries with warm and humid climates. This study was conducted to establish an efficient screening method for resistant cultivars of radish (Raphanus sativus) to bacterial soft rot. Resistance degrees of 60 commercial radish cultivars to the Pcc KACC 10421 isolate were investigated. For further study, six radish cultivars (Awooriwoldong, YR Championyeolmu, Jeonmuhumu, Bitgoeunyeolmu, Sunbongaltari, Housecheongok) showing different level of resistance to the bacterium were selected. The development of bacterial soft rot on the cultivars was tested according to several conditions such as incubation temperature, seedling stage of radish, inoculum concentration to develop the disease. On the basis of the results, we suggest that an efficient screening method for resistant radish to Pcc is to inoculate twenty-day-old seedlings with a bacterial suspension of Pcc at a concentration of $8{\times}10^5cfu/ml$ and then to cultivate the plants in a growth room at $25^{\circ}C$ and 80% RH with 12-hour light per day.

• Horticultural Science & Technology
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• v.32 no.2
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• pp.217-226
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• 2014

Root-knot symptoms were found on a commercial tomato cultivar carrying Mi, a resistance gene to root-knot nematodes including Meloidogyne incognita, M. arenaria, and M. javanica in 2012 at Buyeo, Chungnam Province in Korea. The isolate was identified as M. incognita based on molecular analyses using two species-specific primer sets. Pathogenicity of the isolate on one susceptible and three resistant tomato cultivars to the root-knot nematodes was tested. The nematode isolate showed strong pathogenicity on all the tested cultivars at all tested incubation temperatures. In addition, resistance degree of 33 commercial tomato cultivars, 8 susceptible and 25 resistant cultivars to root-knot nematodes, was also tested. Plants were determined as resistant when they suppressed the nematode reproduction. All the cultivars demonstrated strong susceptibility to the nematode regardless of resistance of the tomato cultivars. To our knowledge, this is the first report on the occurrence of Mi infecting M. incognita isolate in Korea. On the other hand, to construct an efficient screening method for selecting resistant breeding source to the nematode isolate, root-knot development of M. incognita on four tomato cultivars according to several conditions such as inoculum concentration, plant growth stage, and incubation period after transplant was investigated. Reproduction of the nematode on all the tested cultivars according to inoculum concentration increased in a dose-dependent manner. Except for inoculum concentration, there was no significant difference in reproduction level of the cultivars according to the other tested conditions. On the basis of the results, we suggest an efficient screening method for new resistant tomato to the nematode isolate.

• Research in Plant Disease
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• v.16 no.3
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• pp.312-315
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• 2010

Pectobacterium carotovorum subsp. carotovorum (Pcc) causes soft rot disease in various plants. Although many studies about Pcc have been going on, little is known yet about the defense genes from plants. To identify defense associated genes in response to Pcc, we screened about 20 thousand Arabidopsis T-DNA knock out lines by inoculation with Pcc. We obtained a line (Atspt1) showing more susceptible symptom compared to WT (Col-0) on 1 day after the inoculation of Pcc on leaves of Arabidopsis with toothpicks. In this study, we optimized the system to select resistant and susceptible lines to Pcc from T-DNA inserted pool of Arabidopsis and expect the system and Atspt1 might be used for molecular breeding to produce resistant vegetables against Pcc.

• Research in Plant Disease
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• v.25 no.3
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• pp.108-113
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• 2019

Almost 30% of arable lands of North Korea are covered with paddy rice. In rice cultivation of North Korea, rice blast disease is the most important fungal disease and bacterial leaf blight is the most important bacterial disease. Seven North Korean rice cultivars had been tested for the disease resistance against rice blast pathogen, Magnaporthe oryzae and bacterial leaf blight pathogen, Xanthomonas oryzae pv. oryzae. The responses of seven cultivars against 17 different M. oryzae races from South Korea had been quite different. Among seven cultivars, Giljoo1ho was very resistant to all 18 different M. oryzae isolates from South Korea, nevertheless KI or KJ. Pyungdo5ho was very susceptible, it showed susceptible responses to 8 out of 10 KI races and 7 out of 8 KJ races of M. oryzae isolated in South Korea. However, the response to bacterial leaf blight was different from the response to rice blast pathogen. Gijoo1ho, Wonsan69ho, Onpo1ho, and Pyungdo15ho were susceptible to KXO42 (K1) and KXO90 (K2), respectively. Pyungdo5ho was resistant to KXO85 (K1) and KXO19 (K3), and Pyungyang21ho was resistant to K1 races. Based on these results, Giljoo1ho can be a good resource for the breeding of resistant rice cultivar against M. oryzae isolates from South Korea.