• Research in Plant Disease
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• v.25 no.2
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• pp.49-61
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• 2019

Plant viruses are among the important pathogens that cause severe crop losses. The most efficient method to control viral diseases is currently to use virus resistant crops. In order to develop the virus resistant crops, a detailed understanding of the molecular interactions between viral and host proteins is necessary. Recessive resistance to a pathogen can be conferred when plant genes essential in the life cycle of a pathogens are deficient, while dominant resistance is mediated by host resistance (R) genes specifically interacting with effector proteins of pathogens. Thus, recessive resistance usually works more stably and broadly than dominant resistance. While most of the recessive resistance genes have so far been identified by forward genetic approaches, recent advances in genome editing technologies including CRISPR/Cas9 have increased interest in using these technologies as reverse genetic tools to engineer plant genes to confer recessive resistance. This review summarizes currently identified recessive resistance genes and introduces reverse genetic approaches to identify host interacting partner proteins of viral proteins and to evaluate the identified genes as genetic resources of recessive resistance. We further discuss recent advances in various precise genome editing technologies and how to apply these technologies to engineer plant immunity.

• Research in Plant Disease
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• v.11 no.2
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• pp.98-105
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• 2005

All viruses have few genes relative to their hosts. Viruses, thus, utilize many host factors for efficient viral replication in host cell. Virus-host interactions are crucial determinations of host range, replication, and pathology. Host factors participate in most steps of positive-strand RNA virus infection, including entry, viral gene expression, virion assembly, and release. Recent data show that host factors play important roles in assembling the viral RNA replication complex, selecting and recruiting viral RNA replication templates, activating the viral complex for RNA synthesis, and the other steps. These virus-host interactions may contribute to the host specificity and/or pathology. Positive-strand RNA viruses encompass over two-thirds of all virus genera and include numerous pathogens. This review focuses on the importance of host factors involved in positive strand plant RNA virus genome replication.

• Korean journal of applied entomology
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• v.55 no.4
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• pp.389-403
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• 2016

Sugar beet nematode (Heterodera schachtii Schmidt) was first detected in 2011, in Chinese cabbage grown in the highland areas of Korea. Chemical control of the nematode by nematicides is not feasible due to its cyst-forming characteristics; therefore, the cultivation of non-host crops is a preferable alternative to utilize nematode-infected fields. In this study, a total of 276 plant cultivars belonging to 18 different families were screened to evaluate their resistance to the nematode. Based on the number of cysts formed following nematode inoculation, the tested crops were classified into 3 levels: susceptible, moderately susceptible, and resistant/immune. Among the 276 cultivars tested, 106 cultivars were susceptible, 40 cultivars were moderately susceptible, and 130 cultivars were resistant/immune. Among the resistant/immune cultivars, cyst formation was not observed on eggplant, tomato, lettuce, perilla, carrot, celery, watermelon, oriental melon, cucumber, pumpkin, chives, onion, welsh onion, balloon flower roots, deodeok (Codonopsis lanceolata), Jandae (Adenophora triphylla), and bean. Therefore, these plants are regarded as immune to the cyst nematode. However, many crops belonging to Solanaceae, Asteraceae, Chenopodiaceae, and Poaceae families showed moderate susceptibility or immunity, depending on the crop or cultivar. This study provides a basis for alternative crop recommendations for sugar beet nematode cyst-infected farms in Chinese cabbage production areas.

• Korean journal of applied entomology
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• v.28 no.1
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• pp.16-22
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• 1989

A series of experiments was undertaken to learn bionomics and gowt plant resistance of the seedcorn maggot, Delia platura(Meigen), under controlled(24$\pm$$2^{\circ}C$, RH70$\pm$5%, and LD 16:8h)and field conditions. The preoviposition period for the flies was 9 days. The females survived for an average of 50(3-77) and the males for 24(1-59) days. A greater proportion of flies emerged between 6:00 A.M. and 9:00 A.M., soon after the sun rise. After the over-wintering, adults started to emerge in mid-April from pupae located near the soil surface, and peaked in late April by others located deeper. The sex ratio was about 1:1 with total samples of 1,609 females and 1,641 males. Weight of pupae reared from onion was heavier than those from other diets in the laboratory, however its size was samller than that of natural flies. Considerably more eggs were laid near pea seeds than other hosts tested. Among beans, Bapmitkong with blue seed-coat and a cowpea bean strain were preferred for oviposition. 'Namcheon` cultivar was found to be susceptible to attack by the larvae in the laboratory.

• The Korean Journal of Mycology
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• v.38 no.2
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• pp.89-94
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• 2010

Plant pathogenic fungi are the most diverse and drastic causal agents of crop diseases threatening stable food production all over the world. Plant have evolved efficient innate immune system to scout and counterattack fungal invasion and pathogenic fungi also developed virulence system to nullify plant resistance machinery or signaling pathways and to propagate and dominate within their niche. A growing body of evidences suggests that post translational modifications (PTMs) and selective/nonselective degradations of proteins involved in virulence expression of plant pathogenic fungi and plant defense machinery should play pivotal roles during the compatible and incompatible interactions. This review elucidates recent investigations about the effects of PTMs and protein degradations on host defense and fungal pathogens' invasions.

• Research in Plant Disease
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• v.27 no.4
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• pp.137-148
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• 2021

Plant RNA viruses are one of the most destructive pathogens that cause a significant loss in crop production worldwide. They have evolved with high genetic diversity and adaptability due to the short replication cycle and high mutation rate during genome replication, which are characteristics of RNA viruses. Plant RNA viruses exist as quasispecies with high genetic diversity; thereby, a rapid population transition with new fitness can occur due to selective pressure resulting from environmental changes. Plant resistance can act as selective pressure and affect the fitness of the virus, which may lead to the emergence of resistance-breaking variants. In this paper, we introduced the evolutionary perspectives of plant RNA viruses and the driving forces in their evolution. Based on this, we discussed the mechanism of the emergence of variant viruses that overcome plant resistance. In addition, strategies for deploying plant resistance to viral diseases and improving resistance durability were discussed.

• Research in Plant Disease
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• v.21 no.2
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• pp.99-102
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• 2015

Cucumber mosaic virus (CMV) is one of the most destructive viruses in chilli pepper. An isolate of CMV was obtained from the chilli pepper cv. Chungyang showing top necrosis symptom in 2013 and designated as CMV-GTN. CMV-GTN was compared with the well-characterized isolate, CMV-Ca-P1, by investigating their amino acid sequences of the coat protein (CP) and biological reactions in several host plants. The CP of CMV-Ca-P1 composed of 217 amino acids but that of CMV-GTN composed of 218 amino acids by including additional valine in the $57^{th}$ amino acid position. Amino acid sequence similarity of the CP gene among CMV-GTN and other CMV isolates recorded in the GeneBank database ranged from 96% to 99%. CMV-GTN was selected as a representative isolate to screen the resistance pepper cultivars to CMV because it was highly pathogenic to tomatoes and peppers upon biological assays. The virulence of CMV-GTN was tested on 135 pepper cultivars which has been bred in Korea and compared with that of CMV-Ca-P1. Only the cv. Premium was resistant and three cvs. Hot star, Kaiser, and Good choice were moderately resistant to CMV-GTN, whereas two cvs. Baerotta and Kaiser were resistant to CMV-Ca-P1.

• Research in Plant Disease
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• v.24 no.2
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• pp.87-98
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• 2018

The fungal species contain diverse transposable elements and repetitive sequences up to ~10% of their genome. It has been reported that distribution of transposable elements tends to correlate with the host range of the pathogen. Moreover, transposable elements cause the loss of an avirulence gene in the pathogen, which resulted in disease on a resistance cultivar. Thus, the transposable elements in the fungal pathogens may be one of the key factors driving the plant-fungus interactive evolution. In this article, we reviewed classification and biological functions of transposable elements in Magnaporthe species.

• Research in Plant Disease
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• v.25 no.1
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• pp.1-7
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• 2019

The rice blast fungus, Magnaporthe oryzae, is one of the most economically important crop diseases. In addition, rice-M. oryzae interaction is a classical gene-for-gene host-pathogen system. Race variation in pathogen groups was proposed as the main mechanism for rapid break-down of resistance in newly introduced rice cultivars. These new pathogen race variations may be caused by changes in an avirulence gene, such as (i) point mutations, (ii) insertion of transposons, and (iii) frame shifts. The avirulence gene AVR-Pita1 is representative avirulence gene in which all of these mutations are reported. In this review, we present a useful information for avirulence gene AVR-Pita1 and its homologous genes AVR-Pita2 and AVR-Pita3. We also review examples that cause mutations in these evolutionarily significant genes.

• The Korean Journal of Pesticide Science
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• v.5 no.3
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• pp.18-25
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• 2001

Ethanol extracts from 46 plants were tested for their fungicidal activity against six plant diseases consisting of Maynaporthe grisea, Rhizoctonia solani, Botrytis cinerea, Phytophthora infestans, Puccinia recondita, and Erysiphe graminis in the greenhouse studies. Strong activity at 5 and 10 mg/pot was produced from the extracts of Helianthus annuus flowers and Zea mays leaves against P. grisea. In a test with B. cineara, extracts of H. annuus leaves, H. annuus flowers, Chrysanthmum coronarium var. spatiosum, Cucurbita moschata seeds, Lycopersicon esculentum, Z. mays, and Z. mays leaves had strong activities at 5 mg/pot. In a test with P. recondita, strong activity was obtained from the extracts of Capsicum frutescens, C. moschata seeds, H. annuus seeds, L. esculentum, and Malva veticillata at 5 mg/pot. Against E. graminis, extracts of Cucumis sativus, H. annuus seeds, Salanum tuberosum, Z. mays, and Z. mays leaves produced strong activities at 10 mg/pot. All the extracts were ineffective against P. infestans and R. solani. Among seven extracts tested, the extracts of H. annuus leaves and flowers were highly effective against all the strains of B. cinerea resistant to carbendazim, procymidone, and diethofencarb. Furthermore, potent fungicidal activity was produced from the extracts of C. coronarium var. spatiosum and C. moschata seeds against the SSR, SRR, and RSR strains of B. cinerea, and Z. mays and Z. mays leaves against SSR and RSR. Extract of L. esculentum showed very strong activity only against RRS of B. cinerea.