• The Plant Pathology Journal
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• v.24 no.1
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• pp.67-73
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• 2008

Seedling damping-off and bottom rot caused by Rhizoctonia solani are yield limiting diseases of crisphead lettuce. To provide biocontrol measure in the management of the diseases, biocontrol strain Pseudomonas aeruginosa LY-11 was isolated from lettuce rhizosphere and introduced into crisphead lettuce rhizosphere by the seed coating delivery method. Alginate was used as a coating material to generate beads containing $10^6-10^{6.5}$ colony-forming units (CFUs) of viable bacterial cells of LY-11. When seeds germinated from the alginate beads containing the strain LY-11, the bacteria established mostly in plant rhizosphere to maintain at least $10^4$ CFU per gram of plant tissues. Crisphead lettuce seedlings germinated from the entrapped seeds were less affected from damping-off and bottom rot with disease control values of 70.4% and 85.4% respectively. Although P. aeruginosa LY-11 colonized plant rhizosphere and not phyllosphere, the result indicated that bottom rot caused by the foliar inoculation of R. solani was effectively reduced by the rhizobacteria. All data suggested that immobilized rhizobacterial application in seeds by alginate coating could control damping-off and induce induced systemic resistance of crisphead lettuce to reduce bottom rot.

• Korean Journal of Food Science and Technology
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• v.27 no.4
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• pp.546-554
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• 1995

Vacuum cooling of crisphead lettuce by pilot-scale vacuum cooling apparatus, transportation under the conventional and cold-chain systems and distribution were carried out for its freshness prolongation and application of cold-chain system for fresh fruits and vegetables. Changes in temperatures of crisphead lettuce were also measured during transportation. $Q_{10}$ value for respiration rate of crisphead lettuce was $1.7{\sim}2.4$ and its initial freezing point was $-0.2^{\circ}C$. Cooling the vegetable to $0^{\circ}C$ was possible in less than 30 minutes by vacuum cooling. The shelf-life was extended by more than 90% by the combination of vacuum cooling and low temperature distribution.

• Research in Plant Disease
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• v.10 no.4
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• pp.324-330
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• 2004

This studies were investigated the occurrence of sclerotinia rot at the crisphead lettuce field in Uiryeong-Gun, Gyeongsangnam-Do from January to May in 2003. Average incidence rates of sclerotinia rot on crisphead lettuce was up to 21.9% at the five plastic houses. A total of 140 isolates of Sclerotinia sp. were obtained from diseased leaves of crisphead lettuce. Among them, the fungi YR-1 was isolated, which showed highly virulent on the whole plant. the YR-1 was identified as Sclerotinia sclerotiorum based on the formation, color, shape and size of sclerotium and apothecium. For the pathogenicity test, the most suitable inoculum quantity of YR-1 strain was selected as the triturated mycelial suspension of $A_{550}$=0.8, 40 ml showing disease incidence of 94%, and the symptom showed as same as at the fields, the leaves and stem had rotten and developed white downy mycelial at the diseased lesion on the leaves and stems, and produced black and irregular sclerotinia. This is the first report on the pathogenicity test using by triturated mycelial suspension-inoculum of the pathogen for the sclerotinia rot of crisphead lettuce.

• Journal of Bio-Environment Control
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• v.7 no.1
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• pp.35-41
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• 1998

This experiment was conducted to find out the effect of artificial light sources(high-pressure sodium lamp, metal halide lamp and fluorescent lamp) on growth of crisphead lettuce(Lactuca sativa L.) in a plant factory. No significant differences in leaf fresh and dry weight were presented among them. Lettuce plants grown under fluorescent lamp showed the lowest growth. Considering the growth of lettuce and efficiency of lamps, it is worth using HPS(high-pressure sodium) lamp in plant factories. The leaves of lettuce plants grown under artificial light sources showed tipburn symptoms at 14th day after transplanting. The beginning of tipburn symptom have been seen on the ninth to tenth leaves from the cotyledons. It is estimated that the occurrence of tipburn was related to rapid growth and K uptake of the lettuce Plants. The Ca, Mg. Cu and Zn elements tended to be accumulated in the nutrient solutions but the T-N, P, Fe and Mn elements keep in balance in them.

• Journal of Life Science
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• v.14 no.4
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• pp.689-695
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• 2004

This study was investigate the occurrence of bottom rot caused by Rhizoctonia solani at the crisphead lettuce fields in Uiryeong-gun, Gyeongsangnam-do from November to December in 2003. Incidence of bottom rot on crisphead lettuce was up to 5.3% at the six plastic houses. A total of 30 isolates of R. solani were obtained from diseased leaves of plants and were tested by artificial inoculation to the host. Among them, PY-1 isolate was selected showing highly virulent on the whole plant and was identified as R. solani AG1 (IB) based on the anastomosis test, morphological and cultural characteristics. Symptoms of bottom rot by PY-1 isolate produced small dark brown, depressed and elliptical spots on the lower part of leaves in the early stage as same as at the fields, were enlarged onto the upper part of leaves later, and the infected plant wilted and ultimately died in the end. For the pathogenicity test, triturated mycelia-inoculum (A$_{550}$=1.0) of PY-1 isolate was selected the most effective inoculum showing disease incidence of 51.1% for the mycelial inoculation at pot assay. Otherwise, WSRP media-inoculum (wheat brane ： sawdust ： rice brane ： PDB media=30 g ： 10 g ： 10 g ： 100 ml, w/w/w/v) of PY-1 isolate was effectual inoculum showing disease incidence of 61.6% for soil inoculation at the plastic house. Also, in selection of density and amount of inoculum, most suitable density of triturated mycelia-inoculum and amount of WSRP media- inoculum were determined as $A_{550}$=1.0 and 40 ml, respectively. This is the first report on the pathogenicity test using by WSRP media-inoculum of R. solani PY-1 isolate for the bottom rot of crisphead lettuce.

• Research in Plant Disease
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• v.11 no.2
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• pp.152-157
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• 2005

In a course of searching for biofungicide to control crisphead lettuce bottom rot caused by Rhizoctonia solani, we have isolated an antagonistic bacterium from lettuce rhisophere soil. A total of 702 bacterial isolates were isolated and tested for in vitro growth inhibition of R. solani. Seven strains appeared to have strong antagonistic effect against R. solani in in vitro growth inhibition assay. In the pot experiments, a strain BW-13 showed the most potent disease control effect on the both lettuce seedlings and adults plants. Therefore, the BW-13 was selected as a biocotrol candidate against crisphead lettuce bottom rot. Based on its morphology, physiological characteristics, and 165 rRNA gene analysis, the BW-13 was finally identified as Stenotrophomonas maltophilia. This study indicated that S. maltophilia BW-13 could be used as a biocontrol agent to control crisphead lettuce bottom rot.

• Journal of Crop Science and Biotechnology
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• v.10 no.1
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• pp.27-32
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• 2007

RAPD, Inter-SSR, and AFLP markers were used to assess the genetic diversity of lettuce cultivars and the phylogenetic relationships in Lactuca spp. A total of 216 polymorphic bands from seven RAPD primers, four Inter-SSR primers, and five AFLP primer combinations were used to elucidate the genetic similarity among lettuce cultivars. Forty-four lettuce accessions were subdivided into discrete branches according to plant type: crisphead, butterhead, and stem type, with some exceptions. The leafy- and cos-type accessions were intermingled in other groups with no discrete branch indicating that these are more diverse than others. Three accessions, including the Korean cultivar 'Cheongchima', the Korean local landrace 'Jinjam', and the German cultivar 'Lolla Rossa' were classified as the most diverse accessions. Twenty bands were unique in specific cultivars. Among these, three were specific in a plant type; one in Korean leafy type, one in crisphead type, and one in cos type lettuce. In the phylogenetic analysis among Lactuca species, L. saligna, L. serriola, and L. georgica clustered in a sister branch of the L. sativa complex. Two L. virosa accessions show the highest intra-specific relationships. L. perennis outlied from all the other Lactuca species at a genetic similarity of 0.53 and clustered with two Cichorium species, C. intybus and C. endivia, with genetic similarity of 0.67. The phylogenetic tree was supported by data from polymorphism of chloroplast genome which was revealed by PCR-RFLP.

• The Plant Pathology Journal
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• v.27 no.1
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• pp.59-67
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• 2011

A bacterial strain CH-67 which exhibits antagonism towards several plant pathogenic fungi such as Botrytis cinerea, Fulvia fulva, Rhizoctonia solani, Sclerotinia sclerotiorum, Colletotrichum sp. and Phytophthora sp. was isolated from forest soil by a chitin-baiting method. This strain was identified as Burkholderia cepacia complex (Bcc) and belonging to genomovar IX (Burkholderia pyrrocinia) by colony morphology, biochemical traits and molecular method like 16S rRNA and recA gene analysis. This strain was used to develop a bio-fungicide for the control of tomato leaf mold caused by Fulvia fulva. Various formulations of B. pyrrocinia CH-67 were prepared using fermentation cultures of the bacterium in rice oil medium. The result of pot experiments led to selection of the wettable powder formulation CH67-C containing modified starch as the best formulation for the control of tomato leaf mold. CH67-C, at 100-fold dilution, showed a control value of 85% against tomato leaf mold. Its disease control efficacy was not significantly different from that of the chemical fungicide triflumidazole. B. pyrrocinia CH-67 was also effective in controlling damping-off caused by Rhizoctonia solani PY-1 in crisphead lettuce and tomato plants. CH67-C formulation was recognized as a cell-free formulation since B. pyrrocinia CH-67 was all lethal during formulation process. This study provides an effective biocontrol formulation of biofungicide using B. pyrrocinia CH-67 to control tomato leaf mold and damping-off crisphead lettuce and tomato.

• Magazine of the Korean Society of Agricultural Engineers
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• v.30 no.4
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• pp.23-44
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• 1988

The evaportranspiration of upland crops was measured by four types of lysimeter and water consumption characteristics together with the optimum irrigation point by the crops was defind. Among the evapotranspiration estimation formulas, the constant of wind function in the modified Penman equation was corrected to agree with the meteorological conditions of Korea. The evapotranspiration of the crops in the project standard year was estimated according to the cropping system of the project area in Chungju, and from the estimated evapotras - spiration, net duty of water per one time and irrigation in tervals were investigated. The results obtained are summarized as follows: 1. The evapotranspiration of the same crop measured at the same plot was slightly different by the lysimetric methods, and among the four types of lysimeter, the accuracy of the floating lysimeter was the highest. 2. The yields among the watering treatments showed the significance of 5% in the expe- riment with red cabbage and Chinese cabbage, and significance of 1% in the crisphead lettuce, and the optimum irrigation point for the tested crops was defined ad pF 2.0 by the least squre difference test. 3. The evapotranspiration of the crops in the mid-season stage showed maximum among the growing stages, and the average daily evapotranspiration by the crops over the growing seasons of cabbage, crisphead lettuce, Chinese cabbage, summer cucumber, tornato, salary and autumn cucumber was 4.18mm, 4.77mm, 3.9qrnm, 5.68mnn, joonim, 4.26mm and 3.3qrnn, respectively. 4. From the investigated soil moisture extration pattern(SMEP) of the crisphead lettuce, cucumber and tomato, the proportion of the first layer in the initial stage showed over so%, and the SMEP of the lowest fourth layer during the late-season stage in the experiment cabbage and Chinese cabbage was 15.8% and 16.9, respectively, with showed that the root elongated th the lowest soil layer. 5. The total available moisture(TAM) of clay loam was 21.2-23.3mm and that of sandy loam was 16.1 - 19.0mm under the optimum irrigation point of pF. 2.0, and the total readily available moisture( TRAM) of the crops cultivated in the clay loam soil was larger than that cultivated in the sandy loam soil, and the TRAM during the mid-and late-season were larger than that of the inital and crop development stage. 6. The estimated evapotranspration by the corrected Pennam equation, whkh corrected the constant of the wind function in the modified Penman equation, was nearly agreed with the actually measured evaporanspiration of grass. 7. Among the several evaportranspiration estimation methods, the evapotranspiration es- timated by the corrected Pennam equation was closed to the actual evapotranspiration of reference crop (grass) evapotranspiration, therefore it is suggested to use the corrected Penman equation to determine the duty of water of corps. 8. The average crop coefficient (Kc) of cabbage by the corrected Penman equation was 0.94 and that of crisphead lettuce, summer cucumber, tomato, salary, Chinese cabbage and autumn cucumber was 1.07, 1.22, 1.02, 1.01, 1.35, 1.09, respectively 9. The estimated total evapotranspiration of cabbage in the project area( Chungju) by the corrected Penman equation was 223.9mm and that of crisphead lettuce, Chinese cabbage, summer cucumber, tomato, salary and auturun cucumber was 215.7mm, 205.9mm, 359.Omrn, 300.9mm, 332.lmm and 202.7mm, respectively. 10. The net duty of water per one time of the crops cultivated in the sandy loam soil, and the net duty of water per one time in the mid-season & late-season showed larger than that of the initial stage. 11. The shortest irrigation interval of cabbage in the project area was 4.2 days, and that of crisphead lettuce, Chinese cabbage, cucumber, tomato and salary was 1.2days, 2.3days, 1.8days, 2.2days and 2.7days, respectively.

• Applied Biological Chemistry
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• v.38 no.3
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• pp.239-247
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• 1995

The improvement of distribution system and freshness prolongation of crisphead lettuce were carried out through vacuum cooling and distribution under the low temperature. Lettuce that vacuum-cooled and transported by cold storage car was shown better freshness than that distributed by conventional method when they arrived at cunsuming area. And it took $10{\sim}17$ hours until their temperatures arrived at same temperatures when they were stored at $0{\sim}15^{\circ}C$ cold storage room. It was cooled to $1^{\circ}C$ after 27 minutes with vacuum cooling apparatus. The weight loss of lettuce that vacuum cooled and transported by cold storage car was below 5% after 30 days cold storage. And ascorbic acid and chlorophyll retentions were 86% and 52%, respectively. The shelf-life of crisphead lettuce, distributed by vacuum cooling and cold storage car transportation, was 5 days at $15^{\circ}C$ and over 40 days at $0^{\circ}C$, respectively. However, when it was distributed by conventional method, it was only 3 days at $15^{\circ}C$ and 20 days at $0^{\circ}C$, respectively.