• KOREAN JOURNAL OF CROP SCIENCE
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• v.35 no.1
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• pp.97-107
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• 1990

The epidemiology of plant disease deals with the dynamic processes of host-pathogen interactions, which determine the prevalence and severity of the disease. Epidemic processes for most foliar diseases of plants follow a series of steps: arrival of pathogens on plant surfaces, initial infection, incubation period, latent period, sporulation, dissemination of secondary inoculum, and infectious period. These complex biological processes are influenced by the environment-Man also often interfers with these processes by altering the host and pathogen populations and the environment. Slowing or halting any of the epidemic processes can delay the development of the epidemic, so that serious losses in yield due to disease do not occur. It is generally recognized that the most effective and efficient method of minimizing disease damage is through the use of resistant cultivars, particularly when other methods such as fungicide applications are not economically feasible-Populations of plant pathogens are not genetically uniform nor are they necessarily stable. Cultivars bred for resistance to current populations of a pathogen may not be resistant in the future due to selection pressures placed on the pathogen populations. Understanding population development and genetic variability in the pathogen, and knowledge of the genetics of resistance in the plant should help in developing breeding strategies that wi1l provide effective and stable disease control through genetic resistance. In the United States, soybeans have ranked first in value of crops sold off the farm in recent years. Soybeans have been the leading U. S.

• The Plant Pathology Journal
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• v.28 no.1
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• pp.107-113
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• 2012

Trichomes are specialized epidermal structure having the functions of physical and chemical block against biotic and abiotic stresses. Several studies on $Capsicum$ species revealed that virus and herbivore resistance is associated with trichome-formation. However, there is no research on the structural characterization of trichomes developed on the epidermis of $Capsicum$ spp. Thus, this study attempts to charaterize the trichome morphologies in 5 species of $Capsicum$ using a Field Emission Scanning Electron Microscopy (FESEM). Six main trichome types were identified by their morphology under FESEM. Both glandular and non-glandular types of trichomes were developed on the epidermal tissues of $Capsicum$ spp. The glandular trichome were further classified into type I, IV and VII according to their base, stalk length, and stalk. Non-glandular trichomes were also classified into type II, III, and V based on stalk cell number and norphology. Almost all the species in $C.$ $chinense$ and $C.$ $pubescens$ had glandular trichomes. To our knowledge, this is the first study on classification of trichomes in the genus $Capsicum$ and, our results could provide basic informations for understanding the structure and function of trichomes on the epidermal differentiation and association with biotic stress tolerance.

• Korean Journal of Breeding Science
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• v.43 no.1
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• pp.81-91
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• 2011

Rice wild relatives have been recognized as reservoirs of genetic reinforcements to improve cultivating rice against biotic and abiotic stresses. A wild relative, Oryza. minuta(BBCC; Acc. 101141), was hybridized with a Korean Japonica cultivar, 'Hwaseong'(AA), followed by ovule culture and several times of back crossings to overcome high level of sterility. During evaluation of the introgression lines, breeding line exhibited resistance to bacterial blight with reasonable agronomic performances, and nominated as an elite breeding line, the 'Suweon497'. A mapping population, to dissect genetic basis of the resistance, was constructed by using $F_2$ progenies of the 'Suweon497' ${\times}$ 'Milyang23'. Association analysis between SSR marker genotypes and pathogenisity levels of each $F_2$ progeny revealed the end terminal region of rice chromosome 11 as the nesting place for the wild rice derived bacterial blight resistance gene, where at least four other genes, Xa3, Xa4, Xa26 and Xa31, have been reported.

• Horticultural Science & Technology
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• v.32 no.1
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• pp.129-132
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• 2014

A new resistant cabbage variety 'CT-171' to Fusarium wilt was bred by crossing $A337MSBC_5$ with resistance to the disease and 397-$G_6$ with good density and color. 'CT-171' was selected after combining ability, seed gathering and regional adaptability test in 2008. For breeding of resistant varieties, we investigated the development of Fusarium wilt on cabbage seedlings inoculated with Fusariumoxysporum f. sp. conglutinans by root dipping inoculation method. As a result, 'CT-171' showed higher resistance to Fusarium wilt than 'Asiaball' used as control. The maturity of new variety was 58 days and was faster than control and well suited for autumn cultivation because of cold resistance. The anthocyanin pigment of plant was not revealed. The weight, height and width of head were 1.5 kg, 14 cm and 15 cm, respectively and the core size was 5.7 cm and stable in various cultivation environments. 'CT-171' which showed good agricultural character and resistance to Fusarium wilt filed for variety protect right in Korea Seed & Variety Service on February 2013. The new variety will be appropriate for export and domestic consumption.

• Korean Journal of Plant Resources
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• v.29 no.6
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• pp.658-669
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• 2016

Rice blast, caused by a fungus Magnaporthe oryzae, is one of the most devastating diseases of rice worldwide. Analyzing the valuable genetic resources is important in making progress towards blast resistance. Molecular screening of major rice blast resistance (R) genes was determined in 2,509 accessions of rice germplasm from different geographic regions of Asia and Europe using PCR based markers which showed linkage to twelve major blast R genes, Pik-p, Pi39, Pit, Pik-m, Pi-d(t)2, Pii, Pib, Pik, Pita, Pita/Pita-2, Pi5, and Piz-t. Out of 2,509 accessions, only two accessions had maximum nine blast resistance genes followed by eighteen accessions each with eight R genes. The polygenic combination of three genes was possessed by maximum number of accessions (824), while among others 48 accessions possessed seven genes, 119 accessions had six genes, 267 accessions had five genes, 487 accessions had four genes, 646 accessions had two genes, and 98 accessions had single R gene. The Pik-p gene appeared to be omnipresent and was detected in all germplasm. Furthermore, principal component analysis (PCA) indicated that Pita, Pita/Pita-2, Pi-d(t)2, Pib and Pit were the major genes responsible for resistance in the germplasm. The present investigation revealed that a set of 68 elite germplasm accessions would have a competitive edge over the current resistance donors being utilized in the breeding programs. Overall, these results might be useful to identify and incorporate the resistance genes from germplasm into elite cultivars through marker assisted selection in rice breeding.

• Current Research on Agriculture and Life Sciences
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• v.28
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• pp.39-46
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• 2010

Selection procedures for breeding lines resistant to both bacterial wilt caused by Ralstonia solanacearum and Phytophthora blight caused by P. capsici were executed to generations from $F_2$ and $BC_1F_1$ to $F_4$ and $BC_1F_3$ of crosses between a Phytophthora resistant breed, 'Chilbok No. 1' and bacterial wilt resistant accessions introduced from Vietnam during 2009 and 2010. The breeding populations or lines were tested for resistance to P. capsici and resistant plants were selected. The resistant selections were inoculated with R. solanacearum to discard susceptible plants. Resistance to P. capsici was conspicuously improved by selection from $F_2$ and $BC_1F_1$ and the final selections showed a similar level of resistance to P. capsici as a commercial Phytophthora resistant cultivar, Muhanjilju. A few $BC_1F_2$ selections were crossed to a cytoplasmic male sterile line, Chilbok-A, to identify their nuclear genotype interacting with male sterile cytoplasm. Majority of them was fixed to maintainer (Nrfrf) and only two resulted segregating into male sterile and male fertile plants indicating that the pollen parents were heterozygous in the fertility-restoring gene.

• Horticultural Science & Technology
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• v.19 no.1
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• pp.54-59
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• 2001

The objective of this research was to develop a screening system for selection of grape downy mildew (Plasmopara viticola)-resistant grape cultivars or seedlings under greenhouse condition. Inoculum concentrations ranging from $10^4$ to $10^5spores/mL$ for screening of resistance were evaluated and $5{\times}10^4spores/mL$ was optimum. Of the tested 14 grape cultivars, Campbell Early and Niagara were resistant to grape downy mildew, Sheridan and Cheongsoo were moderate resistant, while Kaiji, Red Queen and Ruby Okuyama were susceptible under both greenhouse and field conditions. Vitis vinifera grape cultivars were more susceptible to grape downy mildew than V. vinifera-labrusca hybrids and V. vinifera-labrusca-aestivalis hybrids. In V. vinifera-labrusca hybrids, tetraploid grape cultivars were more susceptible than diploid culivars. The evaluated results of grape downy mildew resistance under greenhouse condition were in accordance with those of field condition. Results of this study indicated that both greenhouse and field procedures could be used to screen grape cultivars and seedlings for downy mildew resistance.

• The Plant Pathology Journal
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• v.38 no.6
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• pp.572-582
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• 2022

Sheath blight disease caused by the necrotrophic, soilborne pathogen Rhizoctonia solani Kuhn, is the global threat to rice production. Lack of reliable stable resistance sources in rice germplasm pool for sheath blight has made resistance breeding a very difficult task. In the current study, 101 rice landraces were screened against R. solani under artificial epiphytotics and identified six moderately resistant landraces, Jigguvaratiga, Honasu, Jeer Sali, Jeeraga-2, BiliKagga, and Medini Sannabatta with relative lesion height (RLH) range of 21-30%. Landrace Jigguvaratiga with consistent and better level of resistance (21% RLH) than resistant check Tetep (RLH 28%) was used to develop mapping population. DNA markers associated with ShB resistance were identified in F₂ mapping population developed from Jigguvaratiga × BPT5204 (susceptible variety) using bulk segregant analysis. Among 56 parental polymorphic markers, RM5556, RM6208, and RM7 were polymorphic between the bulks. Single marker analysis indicated the significant association of ShB with RM5556 and RM6208 with phenotypic variance (R²) of 28.29 and 20.06%, respectively. Co-segregation analysis confirmed the strong association of RM5556 and RM6208 located on chromosome 8 for ShB trait. This is the first report on association of RM6208 marker for ShB resistance. In silico analysis revealed that RM6208 loci resides the stearoyl ACP desaturases protein, which is involved in defense mechanism against plant pathogens. RM5556 loci resides a protein, with unknown function. The putative candidate genes or quantitative trait locus harbouring at the marker interval of RM5556 and RM6208 can be further used to develop ShB resistant varieties using molecular breeding approaches.

• The Plant Pathology Journal
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• v.35 no.4
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• pp.372-380
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• 2019

Pseudomonas syringae pv. actinidiae (Psa) is by far the most important pathogen of kiwifruit. Sustainable expansion of the kiwifruit industry requires the use of Psa-tolerant or resistant genotypes for the breeding of tolerant cultivars. However, the resistance of most existing kiwifruit cultivars and wild genotypes is poorly understood, and suitable evaluation methods of Psa resistance in Actinidia have not been established. A unique in vitro method to evaluate Psa resistance has been developed with 18 selected Actinidia genotypes. The assay involved debarking and measuring the lesions of cane pieces inoculated with the bacterium in combination with the observation of symptoms such as callus formation, sprouting of buds, and the extent to which Psa invaded xylem. Relative Psa resistance or tolerance was divided into four categories. The division results were consistent with field observations. This is the first report of an in vitro assay capable of large-scale screening of Psa-resistance in Actinidia germplasm with high accuracy and reproducibility. The assay would considerably facilitate the breeding of Psa-resistant cultivars and provide a valuable reference and inspiration for the resistance evaluation of other plants to different pathogens.

• Journal of Plant Biotechnology
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• v.31 no.1
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• pp.7-11
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• 2004

This study was carried out to establish a new breeding scheme which is connected with conventional breeding method and anther culture method. To develop a herbicide resistant and direct seeding rice, $F_1$ plants were subjected to anther culture and regenerated plants from 5 crosses were studied to confirm the introduction of bar gene. After PCR analysis, we selected 227 plants which were carrying herbicide resistance gene (bar) out of 1,508 regenerated plants from anther culture. Among 169 $A_2$ lines carrying herbicide resistant gene from 5 crosses including YR23235 (Dongjin Ds3(Ba $r^{R}$)/ Milyang165), 42 lines that had superior agronomic characters were selected for further research. Among them, YR23235Acp79 which showed herbicide resistance, direct seeding adaptability and superiority in major agronomic characters was named Milyang 204. This breeding scheme proved that the anther culture of $F_1$ plants crossed between transformant and cultivar or transform ant alone could be utilized in breeding programs for a rapid progeny fixation and development of a variety.y.