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Streptobacillus sp.가 생산하는 pullulanase에 관한 연구
오두환,지희숙,최형택,신원철,유주현 연세대학교 산업기술연구소 1986 논문집 Vol.18 No.2
A bacterium with the highest pullulanase activity was isolated from the soil and identified as Streptobacillus sp. Y-716. The optimum culture condition of Streptobacillus sp. for the production of pullulanase was as follows; 1.2%(w/v)soluble starch, 0.7%(w/v) CH₃COONH₄, 0.05%(w/v) MgSO₄7 H₂O, 0.01%(w/v)FeSO₄7H₂O, at 30℃, for 48 hrs. The pullulanase from the culture broth of Streptobacillus sp. Y-716 was purified about 46 fold by ammonium sulfate precipitation, dialysis. DEAE-cellulose and Sephadex G-200 column chromatography. The purified enzyme was stable between pH 5.0 and pH 7.5. It was inactivated rapidly above 35℃. The Km value and Vmax of the purified enzyme were 0.0137mg/m/ and 0.666μm/min. on pullulan, respectively.
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.
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.
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.