• 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.

• Korean Journal Plant Pathology
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• v.14 no.2
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• pp.115-119
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• 1998

Root rot of carnation caused by isolates of Phytophthora was found at Kongju, 1996. Infected plants appeared symptoms of wilting, brown discoloration on collar area and consequently led to death. The causal pathogen was identified as Phytophthora nicotianae based on morphological, cultural and physiological characteristics. Mycelium was grown to rosette colony pattern on corn meal agar and the growth was 10.2 mm/day on 10% clarified V8 medium at $25^{\circ}C$. Swelling with radiating hyphae was formed in water and on agar within 7 days. Chlamydospores were abundantly produced on agar within 7 days. Sporangium was prominent papillate, 2~3 apex, 1.2 : 1 l/b ratio, lateral attacment on sporangiospore and was rarely produced on solid media but produced in water. The shape of sporangium was spherical or ovoid, and the size was 34~73$\times$32~60 (av. 33$\times$66.5) ${\mu}{\textrm}{m}$ in dimension. The isolates were heterothallic, and mating type A2. Oogonium was spherical, ovoid, 26~36 (av. 36 ${\mu}{\textrm}{m}$) in diameter, and antheridium was amphygynious to oogonia. The fungus was able to grow 10~35$^{\circ}C$, and optimal temperature was 27$^{\circ}C$.

• Korean Journal Plant Pathology
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• v.14 no.5
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• pp.452-457
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• 1998

Thirty-eight isolates of Phytophthora sp. caused rots on roots and basal stems were collected from five flowering plants from 1992 to 1997 at eight cultivation areas in Korea. All the isolates were identified as P. nicotianae based on following characteristics. The fungus produced markedly papillate, not caducous and ovoid to spherical sporangia, abundant chlamydospores, and small oospores with amphigynous antheridia only when paired with either A1 or A2 mating type. All isolates grew well at 35$^{\circ}C$ and showed distinct arachnoid colony patterns on CMA and PDA. Sizes of sporangia and chlamydospores of five representative isolates from each plant averaged 43-52$\times$30-38 ${\mu}{\textrm}{m}$ and 28 ~34 ${\mu}{\textrm}{m}$. Mating type of the isolates was either A1 or A2, and oogonia and oospores were measured as 28~31 ${\mu}{\textrm}{m}$ and 21~25 ${\mu}{\textrm}{m}$. PCR-RFLP analysis of rDNA of the five isolates resulted that restriction band patterns of the small subunit and ITS regions were identical to a perilla isolate of P. nicotianae, but distinct from P. cactorum and P. capsici. Cross inoculation tests showed that the five isolates had pathogenicity to lily, christmas cactus, anthurium, baby's breath and carnation with different degrees. However, each isolate showed stronger pathogenicity to its corresponding original host than others. Among five lily cultivars Georgia and Quririna were more susceptible than Napoli and others. This is first report of Phytophthora root and stem rot of lily, Christmas cactus, anthurium, baby's breath and monochoria in Korea.

• Mycobiology
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• v.43 no.3
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• pp.288-296
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• 2015

Thailand is one of the largest citrus producers in Southeast Asia. Pathogenic infection by Phytophthora, however, has become one of major impediments to production. This study identified a pathogenic oomycete isolated from rotted roots of pomelo (Citrus maxima) in Thailand as Phytophthora nicotianae by the internal transcribed spacer ribosomal DNA sequence analysis. Then, we examined the in vitro and in vivo effects of Chaetomium globosum, Chaetomium lucknowense, Chaetomium cupreum and their crude extracts as biological control agents in controlling this P. nicotianae strain. Represent as antagonists in biculture test, the tested Chaetomium species inhibited mycelial growth by 50~56% and parasitized the hyphae, resulting in degradation of P. nicotianae mycelia after 30 days. The crude extracts of these Chaetomium species exhibited antifungal activities against mycelial growth of P. nicotianae, with effective doses of $2.6{\sim}101.4{\mu}g/mL$. Under greenhouse conditions, application of spores and methanol extracts of these Chaetomium species to pomelo seedlings inoculated with P. nicotianae reduced root rot by 66~71% and increased plant weight by 72~85% compared to that in the control. The method of application of antagonistic spores to control the disease was simple and economical, and it may thus be applicable for large-scale, highly effective biological control of this pathogen.

• Korean Journal of Soil Science and Fertilizer
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• v.51 no.1
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• pp.28-34
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• 2018

Yuzu (Citrus junos) gummosis disease, caused by Phytophthora nicotianae, was first reported in 1997. As known in citrus, Phytophthora is the most fastidious soil-borne pathogen to control. In order to minimize its damage to Citrus spp., integrated pest management (IPM) approach, including fungicide chemicals and resistant cultivars, is necessary. Therefore, in this study we tried to evaluate tolerance of yuzu cultivars and its related species against yuzu Phytophthora. Trifoliate orange was evaluated as a susceptible host to yuzu Phytophthora by both mycelial growth onto extract media and immature fruit inoculation. However, in zoospores spray-inoculation on 2-year-old cuttings tree, trifoliate orange appeared to have a resistant property as showing less than 6% diseased leaf rate. Among yuzu cultivars only 'Namhae No. 1' appeared resistant property against both P. nicotianae and P. citrophthora. The 'Namhae No. 1' showed 5.7% and 10.6% diseased leaf ratio by P. nicotianae and P. citrophthora, respectively. Clearly, in order to reduce damages caused by two yuzu Phytophthora, we suggest that growers may utilize a trifoliate orange as a rootstock and 'Namhae No. 1' as a scion for fruit production.

• The Plant Pathology Journal
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• v.20 no.4
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• pp.235-239
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• 2004

Phytophthora rot on sword bean, Canavalia gladiata, which has not been reported yet in Korea, occurred in some fields of Jinju in 2003. The disease develops on the basal stem of the plant, but is also often observed on leaves and pods. Rot lesions begin with small dark brown spots and as these are water-soaked, they enlarge rapidly. The magnitude of at the field reached 40%. Abundant sporangia of Phytophthora were formed on the surface of diseased pods and were mummied later. The causal fungus was identified as P. nicotianae with the following mycological characteristics: Sporangium-readily formed in water, papillate, noncaducous, ovoid to spherical, 24-58 (L) ${\times}$ 22-35 (W) in size; Oogonium-spherical, smooth walled, and 22-30; Oospore- aplerotic, spherical, and 18-24; Antheridium- amphigynous, unicellula, and spherical; Chlamydospore- abundant, spherical, and 25-35; Sexuality- heterothallic, and A1 or A2; Optimum growth temperature- about 28$^{\circ}C.$ The fungus showed strong pathogenicity to sword bean. Symptoms similar to those observed in the fields appeared 2 days and 4 days after inoculation with and without wound on pods. This is the first report of Phytophthora rot of sword bean in Korea.

• Korean Journal Plant Pathology
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• v.14 no.4
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• pp.294-298
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• 1998

Since 1995, boxthorn bight caused by Phytophthora spp. has occurred at Chongyang areas in Chungnam province. Infected plants showed yellows and wilt at early stage, but the symptom rapidly progressed into blight due to the decay of roots and basal stem tissues. The disease was relatively severe in poorly drained lowlands and incidence reached ca. 20% in some fields. Two species of Phytophthora were constantly isolated from freshly infected roots and asal stems. Among 39 isolates collected, 26 were identified as P. nicotianae and 13 as P. drechsleri based on their mycological characteristics. Both fungi showed strong pathogenicity to boxthorn cv. Chongyang No. 1. However, the former expressed stronger pathogenicity than the latter. Phytophthora blight of boxthorn caused by the fungi has not been reported n Korea previously.

• Research in Plant Disease
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• v.7 no.1
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• pp.8-10
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• 2001

A stem and root rot disease of kalanchoe (Kalanchoe sp.) which is a succulent plant that provides consumers with a durable flowering pot was found in Koyang, Kyounggi province, Korea in May 1998. We found that stems and roots of potted kalanchoe had dark brown spots at the soil level. The causal organism was identified as Pjytophtora nicotianae on the basis of mycological characteristics. The fungus produced markedly papillate, ovoid to spherical sporangia, and abundant chlamydospores. Sporangia were 20∼48$\times$24∼64㎛(avg. 35.0$\times$47.3㎛) in size, and optimum temperature for the mycelial growth of the isolate was 30$\^{C}$. The fungus showed relatively different pathogenicity to 14 kalanchoe cultivars including K. blossfelana cv. Florus. cultivars florsu, calypso, Maya, and Redsing were susceptible to thedisease in root dip inoculation. This is the first report demonstrating the stem rot on kalanchoe caused by P. nicotianae in Korea.

• Korean Journal of Agricultural Science
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• v.15 no.1
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• pp.76-81
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• 1988

This study was done to find out the antifungal activity of two antibacterial antibiotics, Chlorampenicol and Streptomycin sulfate, against Phytophthora n. var. Parasitica, the causal agent of Phytophthora blight of sesame, growing on artificial media. On PDA medium, Chlorampenicol at 10 ppm, Streptomycin sulfate at 25ppm highly inhibited mycerial growth and completely inhibited zoosporangial formation of Phytophthora n. var. parasitica, and Chlorampenicol at 5 ppm, Streptomycin sulfate at 10 ppm slightly inhibited the mycerial growth and zoosporangial formation of the fungus. These antibiotics showed considerably increased inhibitory effect on the fungal growth when they were mixed with other chemical. Protein content in myceria of the fungus was decreased and abnormal growth of mycerial apex was observed by treatment of these antibiotics. Phytotoxicity on sesame seedlings was not observed by application of them.

• The Plant Pathology Journal
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• v.35 no.2
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• pp.172-177
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• 2019

A duplex PCR method was developed for simultaneous detection and identification of tobacco root rot pathogens Phytophthora nicotianae and Thielaviopsis basicola. The specific primers for P. nicotianae were developed based on its internal transcribed spacer (ITS) regions of ribosomal gene, ras gene and hgd gene, while the specific primers for T. basicola were designed based on its ITS regions and ${\beta}$-tubulin gene. The specificity of the primers was determined using isolates of P. nicotianae, T. basicola and control samples. The results showed that the target pathogens could be detected from diseased tobacco plants by a combination of the specific primers. The sensitivity limitation was $100fg/{\mu}l$ of pure genomic DNA of the pathogens. This new assay can be applied to screen out target pathogens rapidly and reliably in one PCR and will be an important tool for the identification and precise early prediction of these two destructive diseases of tobacco.