Search

To diagnose lily fasciation, lily bulbs showing fasciation were collected from several greenhouses in Jeju Island, South Korea. Bacteria were isolated from the lily bulbs and amplified with both primers for fasA in plasmid and for putative glycosyltransferase epsH gene in chromosome of Rhodococcus fascians. Three bacterial isolates were detected with the P450 primer set and identified as R. fascians by NCBI blast analysis. Twelve bacterial isolates were identified as R. fascians using RS02785 primer set, including the three bacterial isolates identified as the same pathogen using the P450 primer set. Pathogenicity of these bacterial strains identified as R. fascians was demonstrated. Apparent symptoms were observed on wounded lily leaves after inoculation with each bacterial suspension whereas no symptom was found on lily leaves treated with H2O. Furthermore, bacteria re-isolated from wounded sites were identified as R. fascians. Based on the results, these two sets of primers are recommended for quarantine of R. fascians..

Citrus mandarin is major industry in Jeju island where citrus mandarin had broadly grown. However, citrus fruits were damaged by crucial citrus diseases as melanose, scab and canker which caused finally yield loss of production. To prevent the loss of fruit harvest, a lot of synthetic fungicides have been used recklessly in some farms. Eventually, excessive usage of synthetic fungicides could lead the serious problems in environment. Therefore, eco-friendly disease managements have been required in recent researches to protect not only environments from synthetic fungicides residues but also to avoid crop loss by citrus diseases. In this current review, environment friendly disease management were introduced in citrus mandarin cultivation in Jeju. Eventually, the goal of this review is to improve Jeju citrus industry and environment by supporting scientific results to local farms.

Foliicolous lichens grow on the surface of living leaves in tropical and subtropical forests. Compared to a large number of species of foliicolous lichens reported from other regions in tropical and subtropical Asia, only six species of the otherwise abundant genus Strigula have been registered from South Korea so far. Three of these, morphologically identified as S. concreta, S. macrocarpa, and S. smaragdula, had previously been shown to share near-identical ITS sequences, casting doubt about the usefulness of this marker for species delimitation in the genus Strigula. To shed light on this conundrum, we surveyed the diversity of the genus Strigula in the Gotjawal forest area on Jeju Island south of mainland Korea, where the climate and vegetation are suitable for foliicolous lichens. As the result of a combined analysis of phenotype and molecular data of the ITS fungal barcoding marker, we found that material morphologically similar to known species formed two strongly supported clades, representing two species new to science, S. depressa Woo, Lücking & Hur sp. nov. and S. multiformis Woo, Lücking & Hur sp. nov., which are described herein. Strigula multiformis included the four previously sequenced specimens identified as S. concreta, S. macrocarpa, and S. smaragdula. A detailed analysis of morphological and anatomical characters revealed that all specimens of S. multiformis were anatomically uniform but varied in thallus morphology, mostly resembling S. smaragdula but with some forms similar to S. concreta and S. macrocarpa, explaining the previous misidentifications. This variation was found to be driven by leaf characters of the phorophyte species, as these apparently influence the morphology of the subcuticular thalli.

Melanose, caused by Diaporthe citri, is one of severe diseases in citrus, a major economic resource in Jeju island. To reduce the usage amount of organic synthetic fungicide, bio-sulfur was tested as an alternative chemical to control citrus melanose in the present study. Direct antifungal activity of bio-sulfur against D. citri was determined through in vitro experiment using artificial nutrient media. Disease severity of melanose on bio-sulfur pretreated citrus leaves was lower than that on untreated ones. To illustrate the mechanism of disease suppression by bio-sulfur, infection structures were observed with a fluorescent microscope and a scanning electron microscope. In fluorescent microscopic observation, most conidia rarely germinated. In addition, hyphal growth on leaves pretreated with bio-sulfur was inhibited compared to that on untreated ones. In scanning electron microscope images of bio-sulfur pretreated leaves, surfaces of most conidia were shrunk while hyphae were morphologically changed and frequently branched. Such microscopic observations were also found for leaves pretreated with a commercial fungicide Dithianon. These results suggest that bio-sulfur may be used to control citrus melanose as an environment friendly alternative to organic synthetic fungicides.

Bio-sulfur can be produced in the process of desulfurization from a landfill and collected by some microorganism such as Thiobacillus sp. as a sulfur element. In order to investigate practical use of bio-sulfur as an agent for controlling plant disease, in vitro antifungal activity of bio-sulfur was tested against Colletotrichum orbiculare known to cause cucumber anthracnose. Efficacy of bio-sulfur for suppressing anthracnose disease was also evaluated in vivo using cucumber leaves. Mycelial growth of C. orbiculare on medium containing bio-sulfur was inhibited. Disease severity of cucumber leaves pre-treated with bio-sulfur was significantly decreased compared to that of untreated ones. To illustrate how bio-sulfur could suppress anthracnose disease, structures of cucumber leaves infected with C. orbiculare were observed under a fluorescent microscope and a scanning electron microscope (SEM). Cucumber leaves pre-treated with bio-sulfur showed a low rate of appressorium formation whereas untreated ones showed abundant appressoria. Shrunk fungal hyphae were mostly observed on bio-sulfur-pretreated leaves by SEM. Similar results were observed on leaves pre-treated with a commercial fungicide Benomyl®. These results suggest that inhibition of appressorium formation of C. orbiculare by bio-sulfur may contribute to its suppression of cucumber anthracnose.

Chlorella, one single-cell green algae organism that lives autotrophically by photosynthesis, can directly suppress some plant diseases. The objective of this study was to determine whether pre-spraying with Chlorella fusca suspension could induce systemic acquired resistance (SAR) in cucumber plants against anthracnose caused by Colletotrichum orbiculare. In order to illustrate SAR induced by algae, infection structures in host cells were observed under a transmission electron microscope (TEM). Cytological changes as defense responses of host mesophyll cells such as accumulation of vesicles, formation of sheath around penetration hyphae, and thickness of cell wells adjoining with intracellular hyphae were demonstrated in cucumber leaves. Similar defense responses were also found in the plant pre-treated with DL-3-aminobutyric acid, another SAR priming agent. Images showed that defense response of host cells was scarcely observed in untreated leaf tissues. These cytological observations suggest that C. fusca could induce SAR against anthracnose in cucumber plants by activating defense responses of host cells.

Chlorella is one of the microorganisms which can live autotrophically by their own photosynthesis. It was previously revealed that pre-treatment of Chlorella fusca caused a suppression of appressorium formation on the cucumber leaves after inoculation with Colletothrichum orbiculare. In this study, the ultrastructures of C. orbiculare on the cucumber leaves pretreated with C. fusca were observed using both scanning electron microscope (SEM) and transmission electron microscope (TEM). The SEM images revealed that most fungal conidia and hyphae were attached with lots of C. fusca cells. Also, the conidia could germinate but not form appressorium, which is necessary to penetrate into host tissue. These observations suggested that C. fusca adjoined to the fungus may play a role in suppression of the appressorium formation. On the other hand, the observations of TEM showed no remarkable cytological differences on the ultrastructures of the intracellular hyphae between in the pre-treated and untreated leaves. It seemed that the fungus could grow in the pre-treated plant tissues as in the untreated one. Based on these observations, it is suggested that the suppression of appressorium on the leaf surfaces by the C. fusca cells may be a main cause of the reduction of the anthracnose disease.

Received September 8, 2015 Revised December 10, 2015 Accepted January 2, 2016 Elsinoe fawcettii causing citrus scab was suppressed by rhizobacterial strains such as Burkholderia gladioli MRL408-3, TRH423-3 and Pseudomonas fluorescens THJ609-3, TRH415-2 having antifungal activity. The leaf surface of Satsuma mandarin, which was pre-treated with the rhizobacterial strains, was observed by a scanning electron microscope (SEM) after inoculation with E. fawcettii. The number of lesions was reduced on the leaves pre-treated with the rhizobacterial strains compared to those of untreated leaves. Especially, the lesions numbers was apparently reduced on the leaves pre-treated with B. gladioli MRL408-3. The observation by SEM revealed that not only the germination rate but also the length of germ tube of the pathogen were decreased on the rhizobacterial strains pre-treated leaves. These inhibition of the fungal growth was more strongly expressed on the leaves pre-treated with commercial fungicide imibenconazole, by which the lesions was rarely found on the leaves. Based on these results, it was suggested that rhizobacterial strains may inhibit the germination and growth of the E. fawcettii on the surface of citrus leaves, resulting in decrease of disease severity.

Citrus canker caused by Xanthomonas citri subsp. citri (Xcc) is one of the most important bacterial diseases of citrus. Because citrus canker is not found in many countries including European Union and Australia, Xcc is strictly regulated in order to prevent its spread. In this study, the effects of X-irradiation on Xcc growth either in the suspension or on the surface of citrus fruits were investigated. The suspension containing 1×10(7) cfu/ml of Xcc was irradiated with different absorbed doses of X-irradiation ranging from 50 to 400 Gy. The results showed that Xcc was fully dead at 400 Gy of X-irradiation. To determine the effect of X-irradiation on quarantine, the Xcc-inoculated citrus fruits were irradiated with different X-ray doses at which Xcc was completely inhibited by an irradiation dose of 250 Gy. The D10 value for Xcc on citrus fruits was found to be 97 Gy, indicating the possibility of direct application on citrus quarantine without any side sterilizer. Beside, presence of Xcc on the surface of asymptomatic citrus fruits obtained from citrus canker-infected orchards was noted. It indicated that the exporting citrus fruits need any treatment so that Xcc on the citrus fruits should be completely eliminated. Based on these results, ionizing radiation can be considered as an alternative method of eradicating Xcc for export of citrus fruits.

Anthracnose caused by Colletotrichum gloeosporioides has been destructive during pepper fruit production in outdoor fields in Korea. In vitro antifungal activities of 15 different plant essential oils or its components were evaluated during conidial germination and mycelial growth of C. gloeosporioides. In vitro conidial germination was most drastically inhibited by vapour treatments with carvacrol, cinnamon oil, trans-cinnamaldehyde, citral, p-cymene and linalool. Inhibition of the mycelial growth by indirect vapour treatment with essential oils was also demonstrated compared with untreated control. Carvacrol, cinnamon oil, trans-cinnamaldehyde, citral and eugenol were among the most inhibitory plant essential oils by the indirect antifungal efficacies. Plant protection efficacies of the plant essential oils were demonstrated by reduced lesion diameter on the C. gloeosporioides-inoculated immature green pepper fruits compared to the inoculated control fruits without any plant essential oil treatment. In planta test showed that all plant essential oils tested in this study demonstrated plant protection efficacies against pepper fruit anthracnose with similar levels. Thus, application of different plant essential oils can be used for eco-friendly disease management of anthracnose during pepper fruit production.

Chlorella, one single-cell green algae organism that lives autotrophically by photosynthesis, can directly suppress some plant diseases. The objective of this study was to determine whether pre-spraying with Chlorella fusca suspension could induce systemic acquired resistance (SAR) in cucumber plants against anthracnose caused by Colletotrichum orbiculare. In order to illustrate SAR induced by algae, infection structures in host cells were observed under a transmission electron microscope (TEM). Cytological changes as defense responses of host mesophyll cells such as accumulation of vesicles, formation of sheath around penetration hyphae, and thickness of cell wells adjoining with intracellular hyphae were demonstrated in cucumber leaves. Similar defense responses were also found in the plant pre-treated with DL-3-aminobutyric acid, another SAR priming agent. Images showed that defense response of host cells was scarcely observed in untreated leaf tissues. These cytological observations suggest that C. fusca could induce SAR against anthracnose in cucumber plants by activating defense responses of host cells.

Olive flounder (Paralichthys olivaceus) is an important aquaculture fish species in Jeju Island, South Korea. Due to the intensification of flounder fish farming, huge amounts of chemical antibiotics are used against several fish diseases. This has many harmful side effects on fish, as well as human consumers. Hence, an alternative to chemical antibiotic agents is needed for disease control. In this study, three strains of rhizobacteria (BRH433-2, TRH415-2, and THJ609-3) were isolated from the rhizosphere of plants. Assays of their antibacterial activity against fish pathogens, such as S. iniae, S. parauberis, V. anguillarum, and E. tarda, were performed with untreated broth culture (without cell separation), supernatant, and precipitated pellets separated by centrifugation. Among these, the cell suspension prepared from the precipitated pellet showed significant antimicrobial activity when compared with that of the untreated broth culture and centrifugal supernatant. These results indicate that the three isolated rhizobacterial strains exhibit antibacterial activity. Analysis of the 16S rDNA sequences of the BRH-433-2, THJ609-3, and TRH415-2 strains showed the highest similarity to Burkholderia gladioli (99.5%), Pseudomonas baetica (97.7%), and P. koreensis and P. baetica (98.4%), respectively. We suggest that the strains hold promise in disease management of fish.

This study was conducted to survey the diversity and distribution of mushrooms growing spontaneously on Jeju Island in the last eight years. Approximately 2,000 specimens of mushrooms were collected in Gotjawal, Hallasan Natural Park, and Oreum, the habitats where a rich diversity of mushrooms was expected, from 2006 to 2013. They were identified as 74 families, 213 genera and 511 species. Thus, including 69 families, 99 genera and 561 species from the previous study conducted in 2005, a total of 83 families, 257 genera and 740 species of wild mushrooms have been recorded. This study would support new information for fungal flora in Korea and preliminary data for further studies on mushroom diversity.

Citrus canker caused by Xanthomonas citri subsp. citri (Xcc) is one of the most important diseases on citrus. Although Satsuma mandarin cultivating mostly in Korea is moderately resistance to canker, occurrence of the disease were more frequently reported since last decade. Like other diseases in citrus, citrus canker was mainly protected by chemical fungicide in the field. Due to the side effect of the chemicals, alternative method of disease control is recently required. In this study four rhizobacterial strains TRH423-3, MRL408-3, THJ609-3 and TRH415-2 are selected by testing its antifungal activity against Xcc. Pre-inoculation with the selected rhizobacterial strains caused disease suppression on the citrus leaves after inoculation with the citrus canker pathogen. Similarly, in the field test symptoms of citrus canker were less developed in the citrus trees applied several times with the selected rhizobacterial strains compared with those of untreated trees. Therefore, it is suggested that the selected rhizobacterial strains may be valuable as an alternative method in the environmentfriendly citrus farm.

Phospholipases hydrolyze phospholipids into fatty acids and other lipophilic substances. Phospholipid signaling is crucial for diverse cellular processes in plants. However, the precise role of phospholipases in plant cell death and defense signaling is not fully understood. Here, we identified a pepper (Capsicum annuum) patatin-like phospholipase (CaPLP1) gene that is transcriptionally induced in pepper leaves by avirulent Xanthomonas campestris pv. vesicatoria (Xcv) infection. CaPLP1 containing an N-terminal signal peptide localized to the cytoplasm and plasma membrane, leading to the secretion into the apoplastic regions. Silencing of CaPLP1 in pepper conferred enhanced susceptibility to Xcv infection. Defense responses to Xcv, including the generation of reactive oxygen species (ROS), hypersensitive cell death and the expression of the salicylic acid (SA)-dependent marker gene CaPR1, were compromised in the CaPLP1-silenced pepper plants. Transient expression of CaPLP1 in pepper leaves induced the accumulation of fluorescent phenolics, expression of the defense marker genes CaPR1 and CaSAR82A, and generation of ROS, ultimately leading to the hypersensitive cell death response. Overexpression (OX) of CaPLP1 in Arabidopsis also conferred enhanced resistance to Pseudomonas syringae pv. tomato (Pst) and Hyaloperonospora arabidopsidis infection. CaPLP1-OX leaves showed reduced Pst growth, enhanced ROS burst and electrolyte leakage, induction of the defense response genes AtPR1, AtRbohD and AtGST, as well as constitutive activation of both the SA-dependent gene AtPR1 and the JA-dependent gene AtPDF1.2. Together, these results suggest that CaPLP1 is involved in plant defense and cell death signaling in response to microbial pathogens.

In higher plants, glutamate decarboxylase (GAD, EC 4.1.1.15) is known as a key enzyme in the synthesis of γ-aminobutyric acid (GABA), which is not only a valuable food component for animals, but is also a signaling molecule in plants. Although the completion of the soybean genome sequencing has made it possible for the identification of GAD gene families, the systematic analysis of GAD genes in soybean has not yet been reported. Based on the recently released soybean whole-genome sequences, in this study, we identified five GAD genes that contain conserved residues and calmodulin (CaM)-binding domain in the C-terminal region. This indicates that the putative soybean GADs (GmGADs) are Ca2+/CaM-binding proteins. An abundance of GmGAD4 and 5 transcripts have been observed in cotyledons, whereas GmGAD1 and 3 were expressed in hypocotyls and roots of 7-day-old soybean sprouts. In addition, we have determined a positive correlation between the expression of GmGAD genes and GABA accumulation during the germination process. Furthermore, the induction of GmGAD1, 4, and 5 transcripts following infection of hypocotyls with Phytophthora sojae suggests that GABA may play a role in the resistance mechanism. Taken together, our comparative genomic analysis of GAD genes and encoded proteins in soybean is the first step toward the functional dissection of this family, and we present information that will assist future studies on GABA metabolism and signaling research.

Traditional knowledge on wild mushrooms in Gyeongnam province near of Hallyeo-Haesang National Park was investigated. It was interviewed from 145 of people in age of 50th`s to 90th`s living in 53 villages. Total 19 mushrooms were used for food in which Ramaria botrytis was the most frequently used and followed Macrolepiota procera and Lentinula edodes. L. edodes was uniquely both medicinal and edible. Chlorophyllum neomastoidea, poisonous mushroom, was used as an insect repellent. The most various mushrooms were found in Irun, Geoje where 10 species of mushrooms were used and followed Jingyo, Hadong where 8 species were used. Among the interviewed people, the number of female was more than double compared to that of male and most of the interviewed people were 70th`s and 80th`s in age.

Four species such as Amanita gemmata, Tricholoma aurantiipes, Panellus violaceofulvus, and Leucopaxillus septentrionalis which were found in Jeju Island, are first reported in Korea. Four species were identified with macro- and microscopic descriptions and distinctive characters are presented for each species. A. gemmata and T. aurantiipes were collected in evergreen broadleaf forest of Gwaneumsa and the former also founded in Manjanggul. P. violaceofulvus was collected in subalpine plants including Abies koreana and Carpinus laxiflora of Halla Mountain. And L. septentrionalis recorded in deciduous broadleaf forest of Tamla valley.

The knowledge of native wild mushrooms traditionally using in Jeju Island, that have specific native environment and various biodiversity, was investigated. From Jeju and Seogwipo cities including 7 provinces 4 locals, so total 50 villages, data was collected in the entire area and voice of the 93 elderly people between the age of fifty and ninety were recorded. As a result, total 23 native wild mushrooms were used in which 2 species were poisonous mushrooms, 7 species were medicinal mushrooms, 2 species was used for folk religion, 2 species were not used for living but for attention and 12 species were edible mushrooms. Also, a total of 267 cases of traditional knowledge was collected, in which 197 cases were about edible mushrooms for 12 species, 43 cases were about poisonous mushrooms for 2 species, 16 cases were about medicinal mushrooms for 7 species. Interestingly, the fortune for agriculture was told depending on spore mass release of Cyathus stercoreus which grows in animal feces and compost. It is considered as the distinctive traditional knowledge of Jeju Island.

The efficacy of resistance in tomato plants, induced by rhizobacteria isolated from Jeju Island in Korea, against late blight disease caused by Phytophthora infestans was tested. Among the bacterial isolates tested, pre-inoculation with four isolates induced an effective defense against late blight. The four isolates, TRH423-3, TRH427-2, KRJ502-1 and KRY505-3, were identified as Burkholderia gladioli, Miamiensis avidus, Acinetobacter quenomosp and Bacillus cereus, respectively, by sequencing the ribosomal intergenic spacer region. They also promoted the growth of tomato seedlings. To illustrate resistance mechanisms, the infection process by P. infestans was examined using a fluorescence microscope. There were no noticeable differences in the rate of germination and appressorium formation between the untreated and pre-inoculated plants. However, callose was more frequently formed at the penetration sites on the leaves of pre-inoculated plants than the untreated plants, suggesting that these rhizobacterial isolates induce defense responses against P. infestans.

To understand fungal species in evergreen broadleaf forest, occurrence and habitate of wild mushrooms spontaneously growing at the Dongbaekdongsan of Seonheulgot in Jeju Island were investigated. Fungal samples were collected from an area of 500 m 2 size consisting of four designated plots from in June 2007 to December 2008. Wild mushrooms were identified 69 genera and 178 species within the sampling places. Among 178 species, twenty-eight genera and fifty species were first reported in Jeju Island. Especially, Amanita pseudogemmata was first recorded in Korea. The mushroom species were divided into six groups on the basis of fungal habitats in which 44 species were on dead tree, 29 species on fallen leaf, 99 species on soil surface, 2 species on animal feces, 2 species on insect or mushroom, and 2 species on moss.

Suppression effect of the 12 bacterial isolates from plant rhizosphere against late blight caused by Phytophthora citrophthora were investigated on citrus fruits. Among the bacterial isolates, THJ609-3, TRH423-3, BRH433-2, Lyso-chit and KRY505-3 presented disease suppression after wound inoculation with the fungal pathogen in vivo. The anti-fungal activity was evaluated by measuring the length of inhibition zone of the mycelium P. citrophthora adjacent to the effective bacterial isolates in which all of the 5 bacterial isolates showed antagonistic effects. However, there was no positive correlations between the efficacy of disease suppression and the antagonistic effect. On the other hand, Lyso-chit and KRY505-3 were identified as Bacillus cereus, BRH433-2 as B. circulans and TRH423-3 as Burkholderia gladioli, respectively, by analysis of rDNA sequence on the internal transcript spaces. It is suggested that the effective bacterial isolates may be useful for finding biological control agents against late blight especially on environment-friendly farm where the application of fungicide is limited.

This research was conducted to develop a sequential screening procedure for bacteria antagonistic against Phytophthora capsici, and to evaluate control efficacy by candidate antagonistic bacteria selected by this procedure against Phytophthora blight of pepper in the field. A total of 231 bacterial strains were isolated from soils and roots of cucumber, pepper, and tomato plants grown in fields at 12 locations in Korea in 2000 and 2001. From these, 88 strains were pre-selected using a radicle assay. These strains were then screened in a seedling assay with 2-week-old pepper seedlings inoculated with 1000 zoospores of P. capsici g−1 potting mixture, a concentration which caused complete death of the seedlings. Based on the results of this screen, 15 potentially antagonistic strains with at least 50% control efficacy of seedling infection by P. capsici were selected and further tested in 5-week-old pepper plants. In the in planta trials, four bacterial strains, KJ1R5, KJ2C12, KJ9C8, and 11S16, consistently showed significant (P=0.05) disease suppression against P. capsici infection and were examined as candidate biocontrol agents for their antagonistic effects in the field by artificial inoculation in 2001 and 2002. Plants treated with the bacterial strains KJ1R5, KJ2C12, and KJ9C8 had significantly (P=0.05) lower disease severity and incidence than untreated controls in at least one test. These field test results have demonstrated that the radicle and seedling assays are very effective as part of the screening procedure to select candidate antagonistic bacteria against P. capsici on pepper. Therefore, effective biocontrol agents for Phytophthora blight of pepper could be selected through the sequential screening procedure developed in this study.

The infection behaviour of Colletotrichum orbiculare was observed using a transmission electron microscope (TEM) in the leaves of cucumber plants preinoculated with plant growth-promoting rhizobacteria (PGPR) Serratia marcescens (90-166) or Pseudomonas fluorescens (89B61) after inoculation with the anthracnose pathogen. Moreover, the structural defence mechanisms mediated by pretreating DL-3-amino butyric acid or amino salicylic acid was compared with those mediated by these two PGPR. In untreated plants broadly spread intercellular/intracellular hyphae were found in leaf tissues. The cytoplasm of fungal hyphae appeared intact and the electron densities of intercellular and intracellular hyphae were not high even at 5 days after fungal inoculation, indicating lack of defence responses. However, in the leaves of plants preinoculated with both PGPR active defence responses were observed, i.e. sheath formation at penetration sites, and accumulations of endoplasmic reticula or of numerous vesicles around intracellular hyphae. Furthermore, the electron densities of most intracellular and intercellular hyphae were higher than those of untreated control plants. In the leaves of plants pretreated with both chemicals, the hyphae of the pathogen were rarely observed at 5 days after challenge inoculation. Similar to the case of PGPR-pretreated plants, the most intercellular and intracellular hyphae in plant tissues were electron dense. However, no active defence responses were observed in leaf tissues. Moreover, in some cases, hyphal growth was restricted to the epidermal cell layer, and in particular, was not observed to develop in mesophyll cells of the plants. These results suggest that the mechanisms of systemic-ally induced resistance are differently expressed by preinoculating with PGPR or by pretreating with chemicals.

In this study, among the wild mushrooms collected on Jeju Island for the recently 9 years, 5 species are newly reported to Korea. They are identified as Ramariopsis subtilis, Coltriciella pusilla, Lactifluus ochrogalactus, Microstoma insititium and Morchella semilibera based on macromorphological and microscopic observation. In addition, Lactifluus ochrogalactus and Microstoma insititia were re-identified by analysis of internal transcribed spacer of ribosomal DNA.

Resistance inductions on the leaves of cucumber plant by an arbuscular mycorrhiza Glomus intraradices were investigated. In addition, the infection structures were observed at the penetration sites on the leaves of plant inoculated with Colletotrichum orbiculare using a fluorescence microscope. The severity of anthracnose disease caused by Colletotrichum orbiculare was significantly decreased on the leaves of cucumber plant colonized with G intraradices compared with those of non-treated control plants. As a positive control, pre-treatment with DL-3-aminobutyric acid (BABA) caused a remarkable reduction of the disease severity on the pathogen-inoculated leaves. There were no significant differences in the frequency of either germination or appressorium formation of the plant pathogen between mycorrhiza colonized and non-treated plants. It was also the same on the BABA pre-treated plants. However, the frequency of callose formation was significantly high on the leaves of G intraradices colonized plants compared to those of non-treated control plants at 5 days after challenge inoculation. On the leaves of BABA treated plants callose formation was not significantly high than those of non-treated, although the disease severity was more strongly suppressed. It was suggested that the resistance induced by colonization with G. intraradices might be related to the enhancement of callose formation at the penetrate sites on the leaves invaded by the pathogen, whereas resistance by BABA did not.

Bacterial isolates TRL2-3 and TRK2-2 showing anti-fungal activity in vitro test against some plant pathogens were identified as Pseudomonas putida and Micrococcus luteus, respectively. Pre-treatment with both bacterial isolates at the concentration 1.0 and cfu/ml in the rhizosphere could trigger induced systemic resistance in the aerial part of cucumber plants against anthracnose caused by Colletotrichum orbiculare. However, the pre-treatment with the higher concentration at 1.0 cfu/ml of both isolates could not induce resistance after challenge inoculation with C. orbiculare. As a positive control, the treatment with DL-3 amino butyric acid caused a remarkable reduction of disease severity whereas the lesions on the leaves of untreated plants developed apparently after the fungal inoculation. From these results, it was recomended that disease control using both bacterial isolates inducing systemic resistance in the field where chemical application is forbid.

Jeju native sorghums were grown with six different planting densities () from April 3 to September 6 in 2000 in Jeju island to determine the influence to growth, yield and feed value by the planting densities. Days to heading were delayed from 66 days to 69 days as increasing of plant density. Plant height was 195.1cm at plot, whereas that was 216.5cm at plot, indicating that the plant was higher by the decrease of the planting density. As plant density increased, the number of leaves and steam diameter were decreased. Fresh forage yield increased from 25.4 to 61.3 MT/ha, dry matter (DM) yield from 5.8 to 16.5 MT/ha, crude protein (CP) yield from 0.4 to 1.5 MT/ha and total digestible nutrients (TDN) yield from 2.7 to 8.8 MT/ha as planting density from plot. Crude protein content increased from 7.0 to , ether extract content from 1.7 to , nitrogen free extract content from 36.9 to and TDN content from 46.1 to as planting density was decreased. whereas crude fiber content decreased from 43.9 to and crude ash content from 8.4 to .

In order to identify the growth characteristics, the yield and chemical composition of Jeju native sorghum(Sorghum bicolor L.) based on seeding date in Jeju region. Seeding carried out the 10-day intervals from March 27 to May 27 in 2000, respectively. Plant height was 222.9 cm, Showing the highest on seeding date, April 7 among that of any other seeding date. On the other hand, those of early and late seeding gradually decreased. The results of stem diameter, number of leaves were similar to those of the plant height. The yield of fresh, dry matter forage, crude protein and TDN found the highest on April 7 seeding, 48.0 MT/ha, 12.0 MT/ha, 1.0 MT/ha, 5.3 MT/ha, respectively. In early and late seeding, the yield was gradually decreased. According to delaying the seeding date, March 27 to May 27, the contents of crude protein (from 7.8 to ) ether extract(from 1.7 to ), nitrogen free extract(from 34.1 to ) and TDN(from 42.9 to ) were gradually increased, respectively. On the other hand, those of crude fiber (from 40.6 to ) and crude ash (from 10.3 to ) were decreased. These results showed that April 7 was the optimum seeding date with the sole object of feed production of Jeju native sorghum.

Citrus melanose is one of the most important diseases in orchards cultivating citrus in the world. Although the disease does not cause yield loss, the profitability of the infected fruits is often reduced in the fresh-market, resulting in economic loss. In this study, disease reduction was proven by pre-treatment with Pseudomonas putida strain THJ609-3. In order to illustrate mechanism of the disease reduction by the bacterial strain, the infection behaviors of Diaporthe citri and necrosis deposit of plant tissue were observed using a fluorescence microscope. On the leaves pre-treated with the strain THJ609-3, germination rates of D. citri conidia were significantly decreased compared to those of the untreated control. Scanning electron microscopical observations showed that bacterial cells were attached to the surface of fungal hyphae. Furthermore, morphological change of germ tubes of the conidia was detected. These results suggest that the disease reduction may be caused by the direct antifungal activity of the bacterial strain on the leaf surfaces.

Induced systemic resistance (ISR) can be activated by biotic agents, including root-associated beneficial bacteria to inhibit pathogen infection. We investigated priming-mediated ISR in cucumber induced by Pseudomonas azotoformans GC-B19 and Paenibacillus elgii MM-B22 against Colletotrichum orbiculare (causal fungus of anthracnose). In addition, we examined whether this ISR expression was bacterial density-dependent by assessing peroxidase activity in the presence and absence of the pathogen. As a result, root treatment with the ISR-eliciting strains GC-B19 and MM-B22 or the chemical inducer DL-β-amino-n-butyric acid (positive control) significantly inhibited fungal infection process (conidial germination and appressorium formation) and disease severity compared with the non-ISR-eliciting strain, Pseudomonas aeruginosa PK-B09 (negative control), and MgSO4 solution (untreated control). These treatments effectively induced rapid elicitation of hypersensitive reaction-like cell death with H2O2 generations, and accumulation of defense-related enzymes (β-1,3-glucanase, chitinase, and peroxidase) in cucumber leaves in the “primed” state against C. orbiculare. In addition, ISR expression was dependent on the bacterial cell density in the rhizosphere. This ISR expression was derived from the presence of sustained bacterial populations ranging from 104 to 106 cells/g of potting mix over a period of time after introduction of bacteria (106 to 1010 cells/g of potting mix) into the rhizosphere. Taken together, these results suggest that priming-mediated ISR against C. orbiculare in cucumber can be induced in a bacterial density-dependent manner by Pseudomonas azotoformans GC-B19 and Paenibacillus elgii MM-B22.

Defense mechanisms against anthracnose disease caused by Colletotrichum orbiculare on the leaf surface of cucumber plants after pre-treatment with plant growth promoting rhizobacteria (PGPR), amino...

Importing citrus fruits infected by Asiatic citrus canker caused by Xanthomonas citri pv. citri (Xcc) can act as an inoculum source for the disease epidemic in citrus canker-free countries. In this study, the pathogenicity of the causal agent of Asiatic citrus canker surviving on infected Satsuma mandarin fruits was evaluated. The washing solution of infected Satsuma mandarin fruits did not cause lesion formation on the citrus leaves. However, a typical citrus canker lesion was formed on the leaves after inoculation with higher concentrations of the inoculum from the washing solution (washing solution II). It indicated that the pathogenicity of the citrus canker surviving on the symptomatic Satsuma mandarin fruits was not changed. Scanning electron microscopic observation showed that the numbers of bacterial cells on the leaves of Satsuma mandarin which inoculated with the washing solution directly (washing solution I) was less compared to those of leaves inoculated with the washing solution II. This result spports that the pathogenicity of Xcc surviving on Satsuma mandarin fruits may not be changed but that the sucessful infection of citrus caker may depend on the concentration of the inoculum.

The relationship between age-related resistance of peper plants to Phytophthora capsici and contents of carbohydrates, amino acids, phenolics and mineral nutrients in pepper stems was studied using two pepper cultivars, Hanbyul (susceptible) and Kingkun (resistant). With increasing age of pepper plants, the two cultivars, which differ in their susceptibility to Phytophthora blight, became gradually resistant to the disease. The cultivar Kingkun distinctly showed the age-related resistance to Phytophthora blight at the second branch stage. The weight of dry matter in healthy stems of pepper plants at the second branch stage was twice that at the six leaf stage. The resistant cultivar Kingkun contained lower levels of fructose, glucose and sucrose in stems than the susceptible cultivar Hanbyul at the different developmental stages. No consistent differences between the developmental stages of the plants were recognized with regard to their glucose content. However, the contents of fructose and sucrose in the cultivar Hanbyul greatly increased at the second branch stage. The levels of inositol reduced in both pepper cultivars during plant development. In view of the fact that there were only slight changes in the amount of total amino acids, it seems unlikely that there is a relationship between the amino acid metabolism and the retardation of Phytophthora infection during plant development. The amounts of total phenolic compounds in pepper stems were relatively low at the later growth stages of the plants and also in the resistant cultivar Kingkun. The contents of macroelemental nutrients such as nitrogen, phosphorus, potassium, calcium and magnesium were drastically reduced in pepper stems at the later plant growth stage. No significant differences between the cultivars or the plant growth stages were found in the silicon and microelemental nutrients such as sodium, iron, zinc and manganese. These results suggest that the expression of age-related resistance of pepper plants may be due to the morphological and nutritional changes in tissues of pepper stems during ageing, i.e. the pronounced increase in weight of dry matter, the significant decrease in amounts of mineral nutrients such as nitrogen, phosphorus, potassium, calcium and magnesium, and the tow contents of fructose, glucose and sucrose in the stem tissues. Zusammenfassung Untersucht wurde der Zusammenhang zwischen der altersabhangigen Resistenz von Paprikapflanzen gegenuber Phytophthora capsici und den Kohienhydrat-, Aminosauren-, Phenol- und Mineralnahrstoffgehalten in Paprikastengeln bei den zwei Sorten Hanbyul (anfallig) und Kingkun (resistent). Mit zunehmendem Pflanzenalter zeigten die zwei Sorten, die unterschiedliche Phytophthora-Faule-Anfalligkeit aufweisen, steigende Krankheitsresistenz. Die Sorte Kingkun zeigte deutlich die altersabhangige Resistenz gegen die Phytophthora-Faule im Wachstumstadium mit zwei Zweigen. Das Trockengewicht von gesunden Paprikastengeln bei Pflanzen im Wachstumstadium mit zwei Zweigen betrug das doppelte von Pflanzen im 6-Blattstadium. In den Stengeln der resistenten Sorte Kingkun wurden in verschiedenen Wachstumstadien niedrigere Fruktose-, Glukose- und Sucrosegehalte als in der anfalligen Sorte Hanbyul ermittelt. Es konnten keine konsequenten Unterschiede im Glukosegehalt verschiedener Wachstumstadien festgestellt werden. Bei der Sorte Hanbyul wurden jedoch wesentlich hohere Fruktose- und Sucrosegehalte im Zweizweigenstadium festgestellt. Der Gehalt an Inositol verkleinerte sich mit zunehmendem Wachstum in beiden Paprikasorten. Da es nur geringfugige Anderungen im gesamten Aminosauregehalt gab, ist es unwahrscheinlich, das ein Zusammenhang zwischen Aminosauremetabolismus imd einer Verlangsamung eine Phytophthora-Iniektion wahrend der Pflanzenentwicklung besteht. In spateren Stadien war der Gehalt an phenolischen Verbindungen verhaltnismasig klein wie auch bei der resistenten Sorte Kingkun. Eine signifikante Reduzierung der Makromineralnahrstoffe wie Stickstoff, Phosphor, Kalium, Kalzium und Magnesium wurde in alteren Paprikastengeln ermittelt. Bei den Mikromineralnahrstoffen wie Natrium, Eisen, Zink und Mangan sowie Silikon konnten jedoch keine signifikanten Sorten- oder Wachstumstadiumunterschiede festgestellt werden. Diese Ergebnisse deuten darauf hin, das der Ausdruck einer altersabhangigen Resistenz bei Paprikapflanzen mit morphologischen und Nahrstoffgehaltveranderungen des Stengelgewebes, d. h. der signifikanten Trockengewichtzunahme, der signifikanten Abnahme von Mineralnahrstoffen wie Stickstoff, Phosphor, Kalium, Kalzium und Magnesium sowie der niedrigen Fruktose-, Glukose- und Sucrosegehalte des Stengelgewebes, zusammenhangen konnte.

The colonization of an arbuscular mycorrhizal fungus Glomus intraradices BEG110 in the soil caused a decrease in disease severity in cucumber plants after fungal inoculation with Colletotrichum orbiculare. In order to illustrate the resistance mechanism mediated by G. intraradices BEG110, infection patterns caused by C. orbiculare in the leaves of cucumber plants and the host cellular responses were characterized. These properties were characterized using transmission electron microscopy on the leaves of cucumber plants grown in soil colonized with G. intraradices BEG110. In the untreated plants, inter- and intra-cellular fungal hyphae were observed throughout the leaf tissues during both the biotrophic and necrotrophic phases of infection. The cytoplasm of fungal hyphae appeared intact during the biotrophic phase, suggesting no defense response against the fungus. However, several typical resistance responses were observed in the plants when treated with G. intraradices BEG110 including the formation of sheaths around the intracellular hyphae or a thickening of host cell walls. These observations suggest that the resistance mediated by G. intraradices BEG110 most often occurs in the symplast of the host cells rather than in the apoplast. In addition, this resistance is similar to those mediated by biotic inducers such as plant growth promoting rhizobacteria.

Efficacy of resistance induction by the bacterial isolates Pseudomonas putida (TRL2-3), Micrococcus luteus (TRK2-2) and Flexibacteraceae bacterium (MRL412), which were isolated from the rhizosphere of plants growing in Jeju Mountain, were tested in a greenhouse. The disease severity caused by Phytophthora infestans was effectively reduced in the potato plants pre-inoculated with bacterial isolates compared with those of the untreated control plants growing in a greenhouse. In order to estimate the level of protection by the bacterial isolates, Mancozeb WP (Diesen M®, Kyong nong) and DL-3-amino butyric acid (BABA) were pre-treated, whereas Dimethomorph WP (Forum®, Kyong nong) and phosphonic acid (H3PO3) were post-treated the challenge inoculation with the pathogen. Disease severities of chemical pre-treated as well as post-treated plants were reduced compare to those of the untreated. The disease reduction in the plants pre-treated with Mancozeb WP was the highest, whereas that of post-treated with Dimethomorph WP was the lowest. The yields of plants pre-inoculated with three bacterial isolates were greatly increased than those of control plants. These results suggest that biological control by bacterial isolates might be an alternative strategy against late blight disease in potato plants growing in greenhouse.

Infection structures were observed at the penetration sites on the leaves of cucumber plants inoculated with Colletotrichum orbiculare using a fluorescence microscope. The cucumber plants were previously drenched with suspension of bacterial strains Pseudomonas putida or Micrococcus luteus. The plants pre-inoculated with both bacterial strains were resistant against anthracnose after inoculation with C. orbiculare. To investigate the resistance mechanism by both bacterial strains, the surface of infected leaves was observed at the different time after challenge inoculation. At 3 days after inoculation there were no differences in the germination and appressorium formation of conidia of C. orbiculare as well as in the callose formation of the plants between both bacteria pre-inoculated and non-treated. At 5 days, the germination and appressorium formation of the fungal conidia were, however, significantly decreased on the leaves of plants pre-inoculated with M. luteus at the concentration with 1.0 × 10(7) cfu/ml. Furthermore, callose formation of plants cells at the penetration sites was apparently increased. In contrast, there were no defense reactions of the plants at the concentration with 1.0 × 10(6) cfu/ml of M. luteus. Similarly, inoculation P. putida caused no plant resistance at the low concentration, whereas increase of callose formation was observed at the higher concentration. The results of this study suggest that the resistant mechanisms might be differently expressed by the concentration of pre-treatment with bacterial suspension.

To select active bacterial strains to control plant diseases, 57 bacterial strains were isolated from the rhizosphere of the plants growing in various areas such as coast, middle and top of Halla M...