• Korean Journal Plant Pathology
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• v.13 no.2
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• pp.129-131
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• 1997

Occurrence of brown rot was observed on imported orange fruits, and irregular brown spots were appeared as an intial symptom. White colored mycelia were developed rapidly on the surface of the fruits under the humid condition and resulted in rotting of the fruits. The causal organism of brown rot of orange was identified as Phytophthora citrophthora. Most sporangia were nondeciduous, papillate, ovoid, and measured 25.5~51.5$\times$17.9~34.7 ${\mu}{\textrm}{m}$ in size. P. citrophtora was pathogenic on Satsuma mandarin as well as orange. Symptoms were produced 3~7 days after artificial inoculation of sporangia and mycelia mixture on the fruits of orange and Satsuma mandarin, which were similar to those on the naturally infected fruits.

• Research in Plant Disease
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• v.16 no.1
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• pp.35-40
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• 2010

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.

• 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.

• Research in Plant Disease
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• v.10 no.2
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• pp.94-99
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• 2004

'Shiranuhi' citrus cultivar bred by crossing 'Kiyomi' tangor and 'Nakano No.3' ponkan is cultivated in polyethylene film house, and the number of cultivating farmers is rapidly increasing in recent years. Recently, some diseases are taking place on 'Shiranuhi' fruit in some orchards, and were to be big problem in some case. It was surveyed that six diseases were mainly taken place in 'Shiranuhi' cultivating orchards in Jeju Island. They were Phytophthora citrophthora, Alternaria sp., Penicillium digitatum, Botrytis cinerea, Diaporthe citri and Xanthomonas axonopodis pv. citri.

• The Plant Pathology Journal
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• v.17 no.3
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• pp.184-188
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• 2001

Phytophthora-induced diseases on citrus in Jeju island have been considered of minor importance because of the use as root stock of trifoliate orange, which is immune to Phytophthora. However, brown rot on fruit, which severely occurred in 1998 and 1999, has become a great threat to citrus production in the island. About one-half of the surveyed orchards were infected in 1998 and 4 out of 19 infected fields showed over 20% fruit infection rate. The disease was less severe in 1999, with an estimated infected area and total fruit reduction of 3,155 ha and 15,300 tons, respectively. Typical gummosis was also occasionally observed on cv. Shiranugi, which is mostly cultivated under plastic film houses. Two types of Phytophthora were consistently isolated from various plant parts, identified as P. citrophthora and P. nicotianae. The former was isolated from the aerial parts of the fruit, young leaf, and shoot in the fields. Meanwhile, the latter was only isolated from the basal stem showing gummosis in plastic film houses.

• 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.5
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• pp.402-407
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• 1998

Phytophthora rot on jujube fruit has occurred at several cultivation areas in Kyung-buk and Kyung-nam provinces. Symptoms consisted of brownish to reddish rot on fruits resulting in early drop or mummification. The causal fungus isolated from infected fruits and adjacent leaf stalks was identified as Phytophthora citricola, which has never been reported in Korea. Sporangia were semi-papillate, noncaducous and highly variable in shapes. Plerotic oospores with paragynous antheridia were abundant is single cultures. Sporangia of two isolates were measured as 38-76$\times$20-40 ${\mu}{\textrm}{m}$ and averaged 51.4$\times$27.0 and 55.6$\times$36.0 ${\mu}{\textrm}{m}$. Oogonia were ranged from 26 to 36 ${\mu}{\textrm}{m}$ and averaged 31.3 and 32.0 ${\mu}{\textrm}{m}$. Colony pattern was slightly radiated with sparse aerial mycelia on common media. Minium, optimum and maximum temperatures for mycelial growth were recorded at 7, 25, and 32$^{\circ}C$, respectively. Among tested media, 10% V8A was the best and $25^{\circ}C$ was better than 15$^{\circ}C$ for oospore formation of the fungus. The jujube isolates of P. citricola were readily differentiated from other closely related species in the genus, namely; P. nicotianae, P. citrophthora, P. cactorum, P. capsici, and P. plalmivora on the basis of PCR-RFLP of r-DNA. The fungus showed strong pathogenicty to jujube, apple, pear, orange, persimmon and eggplant, and relatively weak to citron, tomato, pepper and cucumber. In this study, P. citrocola is firstly identified and jujube fruit rot caused by the fungus is recorded as a new disease in Korea.