A total of 24 isolates of Phytophthora infestans were tested and analyzed for their resistance to metalaxyl fungicides. Sensitivity to metalaxyl was determined by growing isolates on 20% V8 medium amended with 0, 5, and 100 microg/ml metalaxyl. Four isolates among the 24 tested were resistant to metalaxyl. Eleven isolates were intermediate and nine isolates were sensitive. Amplified fragment length polymorphism (AFLP) assay was used to identify the amplification products of resistant isolates. As a result, selected fragments were cloned, sequences and primer pairs were developed which linked to metalaxyl insensitivity in P. infestans using competitive PCR.
Clone Cells ; DNA* ; Genetic Markers* ; Phytophthora infestans* ; Phytophthora* ; Polymerase Chain Reaction

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(R), Kyong nong) and DL-3-amino butyric acid (BABA) were pre-treated, whereas Dimethomorph WP (Forum(R), 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.
Butyric Acid ; Cytophagaceae ; Micrococcus luteus ; Phytophthora infestans* ; Phytophthora* ; Pseudomonas putida ; Rhizosphere ; Solanum tuberosum*

Genetic diversity of 21 Korean Phytophthora capsici isolates was analyzed by using several molecular markers such as random amplified polymorphic DNA(RAPD), M-13, microsatellite and random amplified microsatellite sequences(RAMS). The overall average similarity coefficient among the isolates was 86% based on the combined data obtained by the molecular markers. No molecular markers were found to be associated with hosts or geographic regions. In addition to RAPD, analysis based on repeated sequences such as (GTG)5, M-13 and RAMS could be used to assess population structure of P. capsici.
Genetic Variation* ; Microsatellite Repeats ; Phytophthora*

A total of 187 endophytic fungi were isolated from 11 plant species, which were collected from 11 locations in Korea. Their antifungal activities were screened in vivo by antifungal bioassays after they were cultured in potato dextrose broth and rice solid media. Antifungal activity against plant pathogenic fungi such as Magnaporthe grisea (rice blast), Corticium sasaki (rice sheath blight), Botrytis cinerea (tomato gray mold), Phytophthora infestans (tomato late blight), Puccinia recondita (wheat leaf rust), and Blumeria graminis f. sp. hordei (barley powdery mildew) was determined in vivo by observing the inhibition of plant disease development. Twenty (11.7%) endophytic fungi fermentation broths were able to control, by more than 90%, at least one of the six plant diseases tested. Among 187 liquid broths, the F0010 strain isolated from Abies holophylla had the most potent disease control activity; it showed control values of more than 90% against five plant diseases, except for tomato late blight. On the other hand, fourteen (7.5%) solid culture extracts exhibited potent disease control values of more than 90% against one of six plant diseases. The screening results of this study strongly suggested that metabolites of plant endophytic fungi could be good potential sources for screening programs of bioactive natural products.
Abies ; Biological Assay ; Biological Products ; Botrytis ; Fermentation ; Fungi* ; Glucose ; Hand ; Korea ; Lycopersicon esculentum ; Magnaporthe ; Mass Screening* ; Phytophthora infestans ; Plant Diseases ; Plants* ; Solanum tuberosum

In order to investigate biodiversity and establish identification system for Phytophthora spp. in Korea, a variety of band pattern was produced by using the URP (universal rice primer). The fingerprint patterns of Phytophthora spp. showed many common and variable fragments according to their isolates in distinct genotypes. In particular, P. drechsleri was classified into four distinct types (I to IV). P. drechsleri (KACC 40498 and KACC 40499) and P. cryptogea (KACC 40413) appeared to have almost equal bands despite their being different species. Ninety isolates of Phytophthora spp. were clustered into 13 groups based on UPGMA (unweighted pair group method with arithmetic means) analysis. These DNA fingerprinting data would be helpful for inter- and intra-species identification of Phytophthora species.
Biodiversity ; Dermatoglyphics ; DNA Fingerprinting* ; DNA* ; Genotype ; Korea* ; Phytophthora*

Phytophthora diseases have become a major impediment in the citrus production in Thailand. In this study, an isolate of Phytophthora denominated as PHY02 was proven to be causal pathogen of root rot of Pomelo (Citrus maxima) in Thailand. The isolate PHY02 was morphologically characterized and identified as Phytophthora palmivora based on molecular analysis of an internal transcribed spacer rDNA sequence. This work also presents in vitro evaluations of the capacities of Chaetomium spp. to control the P. palmivora PHY02. As antagonists, Chaetomium globosum CG05, Chaetomium cupreum CC3003, Chaetomium lucknowense CL01 inhibited 50~61% mycelial growth, degraded mycelia and reduced 92~99% sporangial production of P. palmivora PHY02 in bi-culture test after 30 days. Fungal metabolites from Chaetomium spp. were tested against PHY02. Results showed that, methanol extract of C. globosum CG05 expressed strongest inhibitory effects on mycelial growth and sporangium formation of P. palmivora PHY02 with effective dose ED50 values of 26.5 microg/mL and 2.3 microg/mL, respectively. It is interesting that C. lucknowense is reported for the first time as an effective antagonist against a species of Phytophthora.
Chaetomium* ; Citrus ; DNA, Ribosomal ; Methanol ; Phytophthora* ; Sporangia ; Thailand

Sequence characterized amplified region (SCAR) markers are one of the most effective and accurate tools for microbial identification. In this study, we applied SCAR markers for the rapid and accurate detection of Phytophthora katsurae, the casual agent of chestnut ink disease in Korea. In this study, we developed seven SCAR markers specific to P. katsurae using random amplified polymorphic DNA (RAPD), and assessed the potential of the SCAR markers to serve as tools for identifying P. katsurae. Seven primer pairs (SOPC 1F/SOPC 1R, SOPC 1-1F/SOPC 1-1R, SOPC 3F/SOPC 3R, SOPC 4F/SOPC 4R, SOPC 4F/SOPC 4-1R, SOPD 9F/SOPD 9R, and SOPD 10F/SOPD 10R) from a sequence derived from RAPD fragments were designed for the analysis of the SCAR markers. To evaluate the specificity and sensitivity of the SCAR markers, the genomic DNA of P. katsurae was serially diluted 10-fold to final concentrations from 1 mg/mL to 1 pg/mL. The limit of detection using the SCAR markers ranged from 100 microg/mL to 100 ng/mL. To identify the limit for detecting P. katsurae zoospores, each suspension of zoospores was serially diluted 10-fold to final concentrations from 10 x 10(5) to 10 x 10(1) zoospores/mL, and then extracted. The limit of detection by SCAR markers was approximately 10 x 10(1) zoospores/mL. PCR detection with SCAR markers was specific for P. katsurae, and did not produce any P. katsurae-specific PCR amplicons from 16 other Phytophthora species used as controls. This study shows that SCAR markers are a useful tool for the rapid and effective detection of P. katsurae.
Cicatrix ; DNA ; Ink ; Korea ; Limit of Detection ; Phosphatidylcholines ; Phytophthora ; Polymerase Chain Reaction ; Sensitivity and Specificity

A rapid radicle assay for prescreening antagonistic bacteria to Phytophthora capsici, causal agent of Phytophthora blight of pepper was developed. Sixty-four bacterial strains with in vitro antifungal activity selected out of 1,400 strains isolated from soils of Ansung, Chunan, Koyang, and Paju, Korea in 1998 were used for development of the bioassay. Uniformly germinated pepper seeds dipped in bacterial cells for 3 hours were placed near the edges of growing mycelia of P. capsici on water agar containing 0.02% glucose. Five-week-old pepper plants (cv. Nockwang) were inoculated to compare with results of the radicle assay developed in this study. For plant inoculation, pepper seeds were sown in potting mixtures incorporated with the bacterial strains, then transplanted into steam-sterilized soils 3 weeks later. Plants were hole-inoculated with zoospores of P. capsici 2 weeks after transplanting. Disease incidence and severity were determined in radicle and plant assessments, respectively. In radicle assay, six strains, GK-B15, GK-B25, OA-B26, OA-B36, PK-B09, and VK-B14 consistently showed the significant (P=0.05) disease reduction against radicle infection by the fungus, four of which also did in plant assessments. Strains OA-B36 and GK-B15 consistently reduced the fungal infection in both the radicle assay and the plant assessment. Therefore, prescreening strains using the radicle assay developed in this study followed by plant assay could reduce time and labor, and improved the possibility of selecting antagonistic bacteria for control of Phytophthora blight of peppers.
Agar ; Bacteria* ; Biological Assay ; Chungcheongnam-do ; Fungi ; Glucose ; Gyeonggi-do ; Incidence ; Korea ; Phytophthora* ; Plants ; Soil ; Water

The activities of enzymes responsible for lignification in pepper, pre-inoculation with arbuscular mycorrhizal (AM) fungus of Glomus intraradices and/or infection with pathogenic strain of Phytophthora capsici, and the biological control effect of G. intraradices on Phytophthora blight in pepper were investigated. The experiment was carried out with four treatments: (1) plants pre-inoculated with G. intraradices (Gi), (2) plants pre-inoculated with G. intraradices and then infected with P. capsici (Gi+Pc), (3) plants infected with P. capsici (Pc), and (4) plants without any of the two microorganisms (C). Mycorrhizal colonization rate was reduced by about 10% in pathogen challenged plants. Root mortality caused by infection of P. capsici was completely eliminated by pre-inoculation with antagonistic G. intraradices. On the ninth day after pathogen infection, Peroxidase (POD) activity increased by 116.9% in Pc-treated roots but by only 21.2% in Gi+Pc-treated roots, compared with the control, respectively. Polyphenol oxidase (PPO) and Phenylalanine ammonia-lyase (PAL) activities gradually increased during the first 3 d and dramatically decreased in Pc-treated roots but slightly decreased in Gi+Pc-treated roots, respectively. On the ninth day after pathogen infection, PPO and PAL decreased by 62.8% and 73.9% in Pc-treated roots but by only 19.8% and 19.5% in Gi+Pc-treated roots, compared with the control, respectively. Three major POD isozymes (45,000, 53,000 and 114,000) were present in Pc-treated roots, while two major bands (53,000 and 114,000) and one minor band (45,000) were present in spectra of Gi+Pc-treated roots, the 45,000 POD isozyme was significantly suppressed by G. intraradices, suggesting that the 45,000 POD isozyme was induced by the pathogen infection but not induced by the antagonistic G. intraradices. A 60,000 PPO isozyme was induced in Pc-treated roots but not induced in Gi+Pc-treated roots. All these results showed the inoculation of antagonistic G. intraradices alleviates root mortality, activates changes of lignification-related enzymes and induces some of the isozymes in pepper plants infected by P. capsici. The results suggested that G. intraradices is a potentially effective protection agent against P. capsici.
Capsicum ; cytology ; enzymology ; microbiology ; Lignin ; metabolism ; Pest Control, Biological ; methods ; Phyllachorales ; cytology ; physiology ; Phytophthora ; cytology ; physiology ; Plant Proteins ; metabolism

Dual biocontrol of both insects and plant pathogens has been reported for certain fungal entomopathogens, including Beauveria bassiana and Lecanicillum spp. In this study, we demonstrate, for the first time, the dual biocontrol potential of two fungal isolates identified by morphological and phylogenetic analyses as Isaria javanica. Both these isolates caused mortality in the greater wax moth, and hence can be considered entomopathogens. Spores of the isolates were also pathogenic to nymphs of the green peach aphid (Myzus persicae), with an LC₅₀ value of 10⁷ spores/mL 4 days after inoculation and an LT₅₀ of 4.2 days with a dose of 10⁸ spores/mL. In vitro antifungal assays also demonstrated a strong inhibitory effect on the growth of two fungi that are pathogenic to peppers, Colletotrichum gloeosporioides and Phytophthora capsici. These results indicate that I. javanica isolates could be used as novel biocontrol agents for the simultaneous control of aphids and fungal diseases, such as anthracnose and Phytophthora blight, in an integrated pest management framework for red pepper.
Aphids* ; Beauveria ; Capsicum ; Colletotrichum ; Fungi* ; Hemiptera ; In Vitro Techniques ; Insects ; Mortality ; Moths ; Nymph ; Pest Control ; Phytophthora ; Plants* ; Prunus persica ; Spores