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Phytophthora Rot on Sword Bean Caused by Phytophthora nicotianae
Jee, Hyeong-Jin,Shen, Shun-Shan,Park, Chang-Seuk,Kwon, Jin-Hyeuk The Korean Society of Plant Pathology 2004 Plant Pathology Journal Vol.20 No.4
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.
Occurrence of Stem and Fruit Rot of Paprika Caused by Nectria haematococca
Jee, Hyeong-Jin,Ryu, Kyung-Yeol,Shim, Chang-Ki,Nam, Ki-Woong The Korean Society of Plant Pathology 2005 Plant Pathology Journal Vol.21 No.4
Since 2000 severe rots on aerial and underground parts of paprika (Capsicum annum L.) has occurred in most surveyed glasshouses throughout the country. A total of 56 isolates of a fungus were consistently isolated from various plant parts such as fruit, stem, branch, and root collected from 16 farms in five provinces. Anamorph stage of the fungus was identified as Fusarium solani based on its morphological characteristics. However, the fungus readily produced a sexual structure of perithecia on infected plant tissues and on agar media. Since the fungus formed abundant perithecium by a single isolate, it was considered as a homothallic strain of Nectria haematococca, the teleomorph of F. solani. Irregularly globose perithecia with orange to red color formed sparsely to gregariously on dead tissues of fruits and basal stems at the late infection stage, which is a diagnostic sign for the disease. Perithecia ranged from 125 to 220 ${\mu}m$ in diameter varied among isolates. Asci enveloping eight ascospores were cylindrical and measured 60-80x8-12 ${\mu}m$. Ellipsoid to obovate ascospores are two-celled and measured 11-18x4-7 ${\mu}m$. Ascospores were hyaline, slightly constricted at the central septum, and revealed longitudinal striations that is characteristic of the species. This fungus that has never been reported in Korea has previously become a threat to paprika cultivation because of its strong pathogenicity and nationwide distribution.
Outbreak of Phytophthora Rot on Pear Under Environmental Conditions Favorable to the Disease
Jee, Hyeong-Jin,Cho, Weon-Dae,Nam, Ki-Woong,Park, Young-Seob The Korean Society of Plant Pathology 2001 Plant Pathology Journal Vol.17 No.4
From April to May 1998, Phytophthora rot on pear, which has not been reported in Korea before, became an epidemic in the southeast part of the country under abnormally higher temperature and prolonged rainy days. Average temperature was about $3^{\circ}$ higher than in normal years, and 29 days were rainy during the 2 months in the areas surveyed. Over 1,000 orchards estimated at about 270 ha in 19 cultivation areas were infected by the disease, which occurred on all parts of the tree such as leaves, shoots, branches, stems, and flower clusters. Among 43 isolates collected from various locations and plant parts, 41 were identified as Phytophthora cactorum while 2 were identified as P. cambivora based on their mycological characteristics. The representative isolates revealed strong pathogenicity not only to pear but also to apple and peach. Among 23 pear cultivars tested, 7 were estimated as susceptible, 4 were moderate, and 11 were resistant to the pathogen. Results suggest that Phytophthora disease on pear is a potential threat to pear cultivation when environmental factors are favorable to disease development.
Control of Powdery and Downy Mildews of Cucumber by Using Cooking Oils and Yolk Mixture
Jee, Hyeong-Jin,Shim, Chang-Ki,Ryu, Kyung-Yul,Park, Jong-Ho,Lee, Byung-Mo,Choi, Du-Hoe,Ryu, Gab-Hee The Korean Society of Plant Pathology 2009 Plant Pathology Journal Vol.25 No.3
Powdery and downy mildews caused by Sphaerotheca fusca and Pseudoperonospora cubensis are the most common and serious diseases of cucumber worldwide. In spite of the introduction of highly effective systemic fungicides, control of these diseases remains elusive. Hence, this study aimed to develop an alternative method to chemicals in controlling the diseases by using different types of cooking oil. Egg yolk, which contains a natural emulsifier, lecithin, was selected as a surfactant to emulsify the oils. Among the different cooking oils used, soybean, canola (rape seed), safflower, sunflower, olive, and corn oils showed over 95% control values against powdery mildew of cucumber in a greenhouse test. In particular, 0.3% canola oil emulsified with 0.08% yolk (1 yolk and 60 ml canola in 20 l spray) was found to be the most effective. The treatment resulted in 98.9% and 96.3% control efficacies on powdery and downy mildews, respectively, of cucumber in the field. Canola oil exhibited direct and systemic effect, wherein powdery mildew of cucumber was suppressed only on treated leaves but not on non-treated leaves in a plant, while mycelia and conidia of the pathogen were severely distorted or destroyed by the treatment. The prospect of using the canola oil and yolk mixture as a natural fungicide is highly promising because of its effectiveness, availability, low cost, simple preparation, and safety to humans and the environment. The use of the canola oil and yolk mixture is expected to be an effective fungicide for use in organic farming and home gardening.
Severe Root Rot on Hydroponically-Grown Lettuce Caused by Phytophthora drechsleri
Jee, Hyeong-Jin,Nam, Ki-Woong,Cho, Weon-Dae The Korean Society of Plant Pathology 2001 Plant Pathology Journal Vol.17 No.5
Phytophthora root rot of lettuce, which has not been reported in Korea before, occurred severely in liquid hydroponic culture. The disease occurred in all seasons and was most severe in summer from June to August, showing over 90% infection rate in some farms. A total of 51 isolates collected from various farms were all identified as Phytophthora drechsleri. The fungus showed strong pathogenicity to lettuce and Chinese cabbage, moderate pathogenicity to cucurbits and tomato, and weak pathogenicity to pepper. However, the fungus was not pathogenic to other leafy vegetables namely: chicory, kale, endive, garland chrysanthemum, spinach beet, and perilla. Among 10 species of Phytophtora inoculated to lettuce, only P. drechsleri and P. cryptogea were found pathogenic.
Phytophthora Root Rot of Chinese Cabbage and Spinach Caused by P. drechsleri in Korea
Jee, Hyeong-Jin,Kim, Wan-Gyn,Cho, Weon-Dae The Korean Society of Plant Pathology 1999 Plant Pathology Journal Vol.15 No.1
Phytophthora root rot of Chniese cabbage and spinach is reported for the first time in Korea. The diseases ocurred at Yangju, Seosan and Yeocheon in Korea from 1995 through 1998, mainly in lowland and submerged areas. Symptoms consisted of stunt, yellows, wilt and eventual death due to root rot. Fourteen isolates collected from naturally infected plants were all identified as P. drechsleri based on mycological characteristics. PCR-RFLP analysis of rDNA of the isolates confirmed the above result, since the restriction band patterns of the small subunit and internal transcribed spacers were identical to P. drechsleri and P. cryptogea, but distinct from closely related species of P. erythroseptica, P. cambivora, P. sojae and P. megasperma. The pathogen showed strong pathogenicity to Chinese cabbage, moderate to spinach, radish, cabbage and tomato, and weak or none to brown mustard, kale, chicory and pepper in pathogenicity tests.