• The Plant Pathology Journal
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• v.16 no.1
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• pp.29-35
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• 2000

The internal transcribed spacer regions (ITS I, 5.8S and ITS II) of the ribosomal DNAs were amplified from Korean isolates of Phytophthora spp. and sequenced to characterize them. Sequences from 33 isolates previously identified as P. boehmeriae, P. cactprum, P. cambivora, P. capsici, P. cinnamomi, P. erythroseptica, P. infestans, P. megasperma, P. melonis, P. nicotianae, P. palmivora and P. sojae were compared with published sequences, and a phylogenetic tree was produced. All isolates belonging to 10 species, P. cactorum, P. cambivora, P. capsici, P. cinnamomi P. citricola, P. infestans, P. nicotianae, P. palmivora and P. sojae were clearly clustered into published isolates of each species above 97% bootstrap value. Cucurbits isolates of Phytophthora previously identified as either P. melonis or P. drechsleri showed distinct evolutionary lineages from the P. megasperma was closely related to isolates of P. cryptogea-P. drechsleri showed distinct evolutionary lineages from the P. cryptogea-P. drechsleri complex group, indicating that P. melonis is a valid species. A Korean isolate of P. megasperma was closely related to isolates of P. erythroseptica showed distant genetic relationship with published isolates of P. erythroseptica (CBS 956.87). It is probable that the two Korean isolates could be genetically different from foreign isolates or misidentified. A grouping of species according to ITS sequence divergence matched, to some degree, the broad classification based on type of papilla. However, a separation of semi-papillate species and papillate species was not wvident in this study.

• The Plant Pathology Journal
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• v.17 no.4
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• pp.227-230
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• 2001

Bioassay techniques using young leaves and roots were developed to screen resistance of Atractylis spp. against Phytophthora drechsleri. Among 638 plants collected from various regions of Korea from 1994 to 1996, 67 were pre-screened in fields naturally infested with P. drechsleri, which is the causal pathogen of rhizome rot of Atractylis. Among the pre-screened sources, 18 (ca. 26.8%) were highly resistant to the pathogen in leaf inoculation. In the root inoculation test, abundant sporangia were formed in susceptible plant roots, while only a few or no sporangia were produced on the roots which were found resistant in the leaf inoculation test. Among the selected resistant plants, A. japonica 96066 and 96104 were used to cross with another species, A. macrocephala 96362 that showed high yield with good quality of rhizome but susceptible to the pathogen. The F$_1$hybrids designated as HA03 turned out to be resistant to the pathogen, indicating that resistant gene(s) was inherited. Among intra-species hybrids of A. japonica, HA07 and HA09 were resistant to the pathogen in leaf inoculation and moderate in root inoculation. However, HA08 was susceptible in both inoculation tests. This result suggests that the parent material might be genetically heterogeneous. Further genetic study should be carried out to verify this phenomenon.

• Korean Journal of Medicinal Crop Science
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• v.9 no.3
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• pp.211-219
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• 2001

The disease incidence rates of Phytophthora root rot of A. macrocephala caused by P. drechsleri were dramatically increased in two distinctive periods at experimental fields of National Crop Experiment Station(NCES), Suwon, in 1999 and in 2000 ; one was in the period of 30 to 45 days old seedling stage in spring and the other was just after heavy rainy season in late summer or in early fall. The disease was occurred at seedling stage under the conditions of ${{\geq}15^{\circ}C}$ of average temperature with ${{\geq}100mm}$ rainfalls for 20 days and the tendencies were similar in both year. By the disease, rhizome propagated field was more damaged(18.6%) than seed propagated field(56.0%). Comparing the disease incidence rates at five different fields in Suwon, Youngju and Andong, the damages at soil improving fields and non-mulching fields were less severe than those at continuous cropping fields without soil improvement and mulching fields and occurrence. Expansion of the disease were seemed to be highly related with the populations of P. drechsleri in soils depend on the cultivation method and field conditions. Although the populations of the pathogen in soils collected from Andong and Youngju, in which rhizome were continuously propagated for two and three years respectively, were comparably less than that from Suwon, in which rhizome were propagated for one year, however, the damages by the disease were more severe in Andong and Youngju. So, two or more years of cultivation at the same field may not be useful for Atractylodes plants..

• The Plant Pathology Journal
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• v.17 no.3
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• pp.154-158
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• 2001

A severe root rot of kiwifruit caused by a species of Phytophthora occurred in 1-to 5-year-old vines at the south coast region of Korea in 1997. Infected vines exhibited leaf chlorosis, scorch and defoliation, root and stem rot, and eventual death. The disease was relatively severe in poorly drained lowlands, of which 19 out of 23 fields were damaged by the disease. Meanwhile, only one among 58 upland fields was infected by the disease. Incidence of infected vines reached over 80% in heavily damaged fields and a species of Phytophthora was isolated from inner tissues of roots, stems, and rhizosphere soils of the plants. The causal pathogen was identified as P. drechsleri based on its mycological characteristics. Pathogenicity of the fungus was confirmed by artificial inoculation to seedlings of kiwifruit 'Hayward'. The pathogen was re-isolated from the inoculated plants showing symptoms similar to those observed in the fields. Root rot of kiwifruit caused by P. drechsleri has not been reported previously in Korea.

• The Plant Pathology Journal
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• v.15 no.4
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• pp.228-235
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• 1999

Genetic diversity of ninety-five Korean isolates of Phytophthora was investigated on the basis of PCR-RFLP of ribosomal DNA. The isolates were previously identified as following fifteen species by mycological and cultural characteristics; P. boehmeriae, P. cactorum, P. cambivora, P. capsici, P. cinnamoni, P. citricola, P. citrophthora, P. cryptogea, P. drechsleri, P. erythroseptica, P. infestans, P. megasperma, P. nicotianae, P. palmivora and P. sojae. The regions of small subunit (SSU) and internal transcribed spacer (ITS) of rDNA were amplified with primer pair, NS1 and ITS4, by polymerase chain reaction (PCR) and digested with nine restriction enzymes. P. boehmeriae, P. cactorum, P. cambivora, P. capsici, P. cinnamomi, P. citricola, P. citrphthora, P. infestans, P. nicotianae and P. palmivora showed specific band patterns for each species. However, P. sojae and P. erythroseptica presented identical band patterns and P. cryptogea, P. drechsleri and P. megasperma were divided into six groups, which were not compatible with delineation of the species. A group originated from cucurbits showed distinct band patterns from other groups, but the other five groups were closely related within 96.0% similarity, forming one complex group. Consequently, Korean isolates of Phytophthora were divided into thirteen genetic groups and each group was readily differentiated by comparing digestion patterns of AvaII, HaeIII, MboI, HhaI and MspI. Therefore, PCR-RFLP of rDNA using the five enzymes can be used to differentiate or identify the Phytophthora species reported in Korea so far.

• Korean Journal Plant Pathology
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• v.14 no.4
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• pp.299-302
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• 1998

V8 juice agar (V8A) has been the most popular and commonly used medium for growth and reproduction of Phytophthora. However, frequently V8 vegetable juice is not available or difficult to obtain in Korea. We therefore developed widely accessible medium to substitute for V8A using domestically available five juices; two carrot (KCJA), two tomato (KTJA) and a vegetable-mix (KVMA). To prepare 10% juice medium, each vegetable juice 100 ml, DW 900 ml, agar 17 g and Ca CO3 0.5∼1.0g were supplemented to adjust pH ca. 6.0 Mycelial growth of P. cactorum and P. capsici on KTJA and KVMA was equally effective as V8A for the growth of P. cactorum, P. capsici, P. drechsleri and P. nicotianae under light. Sporangial production of P cactorum, P. capsici and P. nicotianae on KTJA and KVMA was as good as V8A and slightly better than CKJA, but the difference was insignificant by P. cactorum and P. nicotianae. The four fungi successfully formed oospores on all the media although the numbers were varied among species and media. While KTJA was the best for P. cactorum and P. capsici, V8A was the best for P. capsici and P. drechsleri. However, KCJA stimulated highest number of oopspores of P. nicotianae. Overall results showed that domestically available vegetable juices were highly effective on growth and reproduction of Phytophthora and comparable to V8 juice. Therefore, the domestic juice medium can be successfully replaced V8A in Phytophthora study.

• Mycobiology
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• v.31 no.4
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• pp.235-247
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• 2003

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.

• The Plant Pathology Journal
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• v.22 no.4
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• pp.309-313
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• 2006

Phytophthora blight(PB), caused by Phytophthora drechsleri f. sp. cajani is the third potentially important disease of pigeonpea in the Deccan Plateau(DP) of India after wilt and sterility mosaic. In the rainy-season of 2005, an outbreak of PB was seen throughout DP. To quantify the incidence and spread of the disease, a systematic survey was conducted in the major pigeonpea growing regions of DP during the crop season 2005. Attempts were made to determine the effect of cropping systems on the PB development and identify resistant cultivars, if any, grown by farmers and on research farms. Widespread incidence of PB was recorded on improved, and or local cultivars grown in different intercropping systems. Majority of improved cultivars grown at research farms were found susceptible to PB(>10% disease incidence). Pigeonpea intercropped with groundnut, black gram and coriander had less disease incidence(${\leq}10%$). Three wilt and SM resistant pigeonpea cultivars KPL 96053, ICPL 99044, and ICPL 93179 were found resistant(<10%) to PB as well. However, their resistance to PB needs confirmation under optimum disease development environments.

• The Plant Pathology Journal
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• v.32 no.1
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• pp.16-24
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• 2016

In this study, antifungal activity of essential oils of Cymbopogon citratus and Ocimum basilicum and two fungicides Mancozeb and Metalaxyl-Mancozeb in six different concentrations were investigated for controlling three species of Phytophthora, including P. capsici, P. drechsleri and P. melonis on pepper, cucumber and melon under in vitro and greenhouse conditions, respectively. Under the in vitro condition, the median effective concen- tration ($EC_{50}$) values (ppm) of plant essential oils and fungicides were measured. In greenhouse, soil infested with Phytophthora species was treated by adding 50 ml of essential oils and fungicides (100 ppm). Disease severity was determined after 28 days. Among two tested plant essential oils, C. citratus had the lowest $EC_{50}$ values for inhibition of the mycelial growth of P. capsici (31.473), P. melonis (33.097) and P. drechsleri (69.112), respectively. The mean $EC_{50}$ values for Metalaxyl-Mancozeb on these pathogens were 20.87, 20.06 and 17.70, respectively. Chemical analysis of plant essential oils by GC-MS showed that, among 42 compounds identified from C. citratus, two compounds ${\beta}$-geranial (${\alpha}$-citral) (39.16%) and z-citral (30.95%) were the most abundant. Under the greenhouse condition, Metalaxyl-Mancozeb caused the greatest reduction in disease severity, 84.2%, 86.8% and 92.1% on melon, cucumber, and pepper, respectively. The C. citratus essential oil reduced disease severity from 47.4% to 60.5% compared to the untreated control ($p{\leq}0.05$). Essential oils of O. basilicum had the lowest effects on the pathogens under in vitro and greenhouse conditions. These results show that essential oils may contribute to the development of new antifungal agents to protect the crops from Phytophthora diseases.

• The Plant Pathology Journal
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• v.28 no.1
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• pp.1-9
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• 2012

In this study, 200 isolates of fluorescent pseudomonads were isolated from different fields of East and West Azarbaijan and Ardebil provinces of Iran. These bacterial isolates were screened on the basis of a dual culture assay, the presence of known antibiotic genes, and their ability to successfully colonize roots and to promote plant growth. Twelve isolates exhibited 30% or more inhibition of mycelia growth of $P.$ $drechsleri$. Genes encoding production of the antibiotics 2,4-diacetylphloroglucinol, phenazine-1-carboxylic acid, and pyoluteorin were detected in some strains but none of the strains possessed the coding gene for production of antibiotic pyrrolnitrin. In an $in$ $vitro$ test for root colonization, the population density on roots of plants treated with most of the above strains was more than 6 $\log_{10}$ CFU $g^{-1}$ roots, with a maximum of 7.99 $\log_{10}$ CFU $g^{-1}$ roots for strain 58A. Most of the strains promoted significant plant growth in comparison to non-treated controls. In green house studies, the percentage of healthy plants in pots treated with strains 58A and 8B was 90.8% and 88.7%, respectively. The difference between these treatments and treatment with the fungicide metalaxyl was not significant.