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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.
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.
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.
Jin-Hyeuk Kwon,Hyeong-Jin Jee,Jinwoo Kim 경상대학교 농업생명과학연구원 2015 농업생명과학연구 Vol.49 No.5
From August to October of both 2012 and 2013, powdery mildew was observed on white-fruited creeping cucumber(Melothria japonica [Thunb.] Maxim.) at Jinju, Korea. White mycelial colonies were observed on leaves and petioles. Lesions of severe infections were discolored or brown. In the present study, the morphological features of the anamorphic and teleomorphic reproductive stages of the fungus were studied. To complete the fungal identification, the sequence of the internal transcribed spacer region of a ribosomal RNA(ITS rRNA) gene was determined. Based on morphological characteristics and analysis of the ITS rRNA gene, the fungus causing the powdery mildew symptoms was identified as Podosphaera fusca. Although the host range of powdery mildew caused by P. fusca has been previously described, no full description and illustration of the infection, including symptoms and signs on white-fruited creeping cucumber, has yet appeared. To the best of our knowledge, this is the first full description of powdery mildew on white-fruited creeping cucumber, featuring molecular identification, symptoms, and signs.
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.
Effect of Potassium Phosphonate on the Control of Phytophthora Root Rot of Lettuce in Hydroponics
Jee, Hyeong-Jin,Cho, Weon-Dae,Kim, Choong-Hoe The Korean Society of Plant Pathology 2002 Plant Pathology Journal Vol.18 No.3
The effect of potassium phosphonate ($KH_2PO_3 or $K_2 HPO_3$) on the control of Phytophthora root rot of lettuce was evaluated in a liquid hydroponic culture. Phosphonate 100 ppm strongly inhibited mycelial growth of Phytophthora species in vitro but did not affect normal growth of lettuce in a greenhouse test. Application of the chemical before infection showed over 94% control value, while it was less than 35% when applied after infection. In a field trial, phosphonate 100 ppm, which was directly supplemented into the nutrient solution, satisfactorily controlled the disease as it did not develop until 28 days after transplanting and remained at less than 2% infection rate at the end of cultivation. Meanwhile, in the control plot, the disease initiated at 7 days after transplanting and developed rapidly reaching over 70% infection rate at 28 days. Population density of the causal pathogen, R drechsleri, in a heavily infested farm was 22.0-25.0 cfu/100 ml of nutrient solution. However, it decreased to 1.3-2.0 cfu/100 ml at 7 days after treatment with phosphonate 200 ppm.
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.