• 한국균학회지
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• 제48권4호
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• pp.519-521
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• 2020

Damping-off symptoms were frequently observed on young plants of Indian lettuce (Lactuca indica) grown in a farmer's vinyl greenhouse located in Goseong, Gangwon province of Korea during a disease survey in June 2019. The incidence of diseased plants in the vinyl greenhouse investigated was 30-50%. Four isolates of Rhizoctonia sp. were obtained from the diseased plants and identified as Rhizoctonia solani AG-4 based on the morphological characteristics and anastomosis test. Three isolates of R. solani AG-4 were tested for pathogenicity on Indian lettuce by artificial inoculation. All the tested isolates induced damping-off symptoms on the inoculated plants. The symptoms were similar to those observed in plants from the farmer's vinyl greenhouse investigated. This is the first report of R. solani AG-4 causing damping-off in Indian lettuce.

• 한국식품위생안전성학회지
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• 제23권2호
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• pp.129-136
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• 2008

Three benzimidazole pesticides commonly used in korean lettuce were subjected to a field residue trial to ensure safety of terminal residue in the harvest. The residual patterns of three benzimidazole pesticides, which were carbendazim, benomyl and thiophanate-methyl were examined after applying with the recommended dose in two types of korean lettuce (Chima and Chuckmeon) and their DT50 were calculated. In Chima lettuce, biological half-lives of carbendazim, benomyl and thiophanate-methyl were 2.56, 1.37 and 2.54 days, respectively and their required time under MRL(5.0 mg/kg as carbendazim) were 4.5, 2.2 and 1.0days. In Chuckmeon lettuce, biological half-lives of them were 3.41, 1.70 and 4.20 days, respectively and their required time under MRL were 5.4, 1.9 and 0.5days.

• 한국작물학회:학술대회논문집
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• 한국작물학회 2017년도 9th Asian Crop Science Association conference
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• pp.114-114
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• 2017

The aim of this research is to improve Korean lettuce varieties in terms of Fusarium wilt, bolting under hot weather and nutritional function applying genomics approaches. To find related gene/molecular markers, we selected 96 lettuce varieties which are popular in domestic fresh vegetable markets. To construct frame works of the genomic approaches, we exploited GBS(Genotyping by Sequencing) and found total 61,407 SNPs from lettuce whole genomes (MAF>0.02). We observed that Three SNPs array per 100kb of lettuce genome. Average LD decay is expected to expand up to 3.9M(million)bp. Thus, we concluded that about 104 SNPs exist within a LD, which is sufficient to use GWAS(Genome-wide Association Study) to explore the useful gene/molecular markers. In addition, we optimized mass screening method to evaluate disease resistance levels against Fusarium wilt and are testing the bolting sensitivity during summer growing season for those lettuce allele mining set.

• Preventive Nutrition and Food Science
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• 제9권2호
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• pp.121-125
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• 2004

Effects of chemical treatment with a citric acid solution or ozonated water on microbiological changes in lettuce and cabbage during storage were studied. Fresh lettuce and cabbage samples were cut into small pieces and treated by soaking in either ozonated water or a citric acid solution. After treatment, populations of total bacteria, yeast and mold, and E. coli were determined. Numbers of microorganisms increased during storage, but ozonated water and citric acid treatments retarded the increase in microbial growth. Among treatments, 1 % citric acid treatment was the most effective in terms of microbiological change and inhibition of polyphenoloxidase (PPO). For lettuce, citric acid treatment decreased the microbial growth overall by 1.5 log CFU/g and inhibited the PPO activity by 80%. These results indicate that chemical-treated lettuce and cabbage retained a better quality than those of the control during storage.

• 한국환경농학회지
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• 제20권5호
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• pp.340-345
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• 2001

High rates of nitrogen fertilization dangerously increase the nitrate content of vegetable crops, and the accumulation of nitrate in edible crops is undesirable because of potential risks to human health. Micronutrient solution containing Cu, Mn, Mo, Zn was tested for the suppression of nitrate accumulation in lettuce grown in pots treated with Mg fertilizer under a greenhouse condition. The micronutrient solution was sprayed on leaves at 3 and 4 weeks after transplanting of 20-day old seedlings. Plants were harvested after 5-week growth, and yield, contents of chlorophyll, sugar, micronutrient and nitrate, and also nitrate reductase activity were measured. Fresh weight of lettuce was significantly increased by the application of Mg and micronutrients, and the effect was the most significant in the Mg+micronutrient treatment. Also contents of chlorophyll and micronutrients were higher in the plants of micronutrient treatments. Contents of nitrate were reduced by about 14-18% in lettuce with Mg and/or micronutrient applications. Compared to the plants of control treatment, nitrate reductase activity was also higher in those plants treated with micronutrients, and in the treatment of Mg+micronutrients the enzyme activity was six times as high as that of control treatment. Although the effect of mineral nutrients on the suppression of nitrate accumulation in lettuce was relatively small in this study, an appropriate supply of mineral nutrients could be one of the solutions for the nitrate accumulation in vegetables.

• Journal of Applied Biological Chemistry
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• 제50권4호
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• pp.239-243
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• 2007

Effects of aqueous chlorine dioxide ($ClO_2$) treatment on the microbial growth and the quality of iceberg lettuce during storage were examined. Lettuce samples were treated with 0, 5, 10, and 50 ppm of $ClO_2$ solution and stored at $4^{\circ}C$. Aqueous $ClO_2$ treatment significantly decreased the populations of total aerobic bacteria, yeasts and molds, and coliforms on the shredded lettuce. Fifty ppm $ClO_2$ treatment reduced the initial populations of total aerobic bacteria, yeasts and molds, and coliforms by 1.77, 1.34, 1.10 log CFU/g, respectively. Aqueous $ClO_2$ treatment caused negligible changes in the Hunter color L, a, and b values during storage. Sensory evaluations exhibited that there were no significant changes among treatments. These results indicate that the aqueous $ClO_2$ treatment can be useful in improving the microbial safety of the iceberg lettuce during storage and extending the shelf life.

• 한국토양비료학회지
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• 제46권1호
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• pp.32-39
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• 2013

The relationship between relative water contents of lettuce leaves and biochemical activities in lettuce was examined in this study to explore an adaptation response of lettuce to water stress from soils. Soil water contents and relative water contents of leaves were positively related to show $R^2$=0.8728. Hydrogen peroxide contents of leaves rapidly increased with reduction of soil water content, whereas soluble protein contents and dry matters rapidly decreased. And chlorophyll a and b contents of leaves decreased with increase in carotenoid content. Furthermore, the activities of ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR), and dehydroascorbate reductase (DHAR) increased dramatically, and mRNA transcript levels of APX, MDHAR and DHAR also increased. Relationship of relative water content of lettuce leaves to hydrogen peroxide, to ascorbate peroxidase activity, to dehydroascorbate reductase activity, and to monodehydroascorbate reductase activity was shown to be positively correlated. It is highly plausible from this study that these enzyme activities could be developed as an indicator of water states in soils.

• 한국토양비료학회지
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• 제43권4호
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• pp.498-505
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• 2010

AMF 접종원 처리가 원예작물의 생육에 미치는 효과를 구명하기 위하여 상추 (Lactuca sativa L.)에 파종단계와 이식단계에서 수단그라스를 기주식물로 증식한 g 당 30개의 포자와 AMF가 감염된 뿌리, 균사 및 토양이 혼합된 접종원을 처리한 후 이식 전후에 걸쳐 작물의 생장반응과 수량성을 비교 검토하였으며, AMF 포자밀도와 감염률 및 감염양상을 조사하였고, 작물의 무기양분의 흡수양태를 분석하였다. 상추의 파종단계에서 AMF 접종원을 처리한 후 생육반응을 조사한 결과, 파종 후 3주가 경과한 초기에서 AMF 접종원 처리구의 상추는 대조구보다 엽수는 9%, 엽의 생체중은 59%, 엽면적은 58% 및 엽장과 엽폭은 21-22%가 증가하였으며 엽록소함량은 2%가 향상되었다. 파종 후 9주가 경과하여서는 파종단계와 이식단계에서의 AMF 접종원 처리구는 대조구에 비해 엽수는 21%와 18%, 엽의 생체중은 51%와 41%, 근체중은 56%와 47%가 각각 증가하였으며 엽록소함량은 18%와 19%가 향상된 것으로 조사되었다. 상추 엽의 P 함량을 분석한 결과 이식단계에서 AMF 접종원 처리구가 대조구보다 217%가 증가된 P 함량을 보임으로서 P의 흡수이용이 증진되었고 상추의 생육에 영향을 미친 것으로 판단된다. 상추 근권토양의 AMF 포자밀도는 상추의 생육초기에 AMF 접종원 처리구가 대조구의 3배를 상회하는 높은 수준으로 나타났고, 9주가 경과하였을 때는 276-295%가 증가된 것으로 조사되었다. AMF 감염률 또한 대조구에 비해 크게 향상된 것으로 조사되었고 생육 후기에는 낭상체와 균사가 치밀하게 발달됨으로서 AMF 의존도가 높음을 확인하였다.

• 한국식품과학회지
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• 제23권2호
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• pp.133-140
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• 1991

잎상추(Lactuca sativa L.) 저장 중 재배적요인(품종 및 재배시기) 및 저장요인(저온 및 high-density polyethylene film 포장)이 저장수명 및 품질에 미치는 영향을 구명하기 위하여 생체중량 감소, 외관품위, 황화, 클로로필 및 카로티노이드 함량, 비타민 C 및 nitrate 함량을 조사하였다. 생체중량 감소 및 외관품위의 열화는 포장처리에 의해, 그리고 $4{\sim}5^{\circ}C$ 보다는 $0{\sim}1^{\circ}C$가 더 억제 되었다. 품종간 비교에서는 "적축면" 보다는 "청치마"에서, 그리고 재배시기별 비교에서는 가을재배 보다는 겨울재배에서 이들의 변화가 다소 지연되었다. 저장 중 잎상추의 황화현상은 카로티노이드 함량변화 보다는 주로 클로로필의 파괴 때문이었다. Vitamin C의 저장 전 함량은 "적축면" 보다는 "청치마"에서, 그리고 가을재배 보다는 겨울재배 시 많은 양을 함유하고 있었다. 저장 중 비타민 C는 저장 초기부터 전처리구에서 급격히 감소하였으나, $4{\sim}5^{\circ}C$에 비해 $0{\sim}1^{\circ}C$에서 감소가 다소 지연되었다. Nitrate의 경우는 저장 전 함량은 "적축면"은 3812.6 ppm을 함유하고 있었고, "청치마"는 2856.6 ppm을 함유하고 있었다. 저장 중 nitrate 함량변화는 $4{\sim}5^{\circ}C$에 비해 $0{\sim}1^{\circ}C$에서 다소 억제되었다.

• The Plant Pathology Journal
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• 제24권1호
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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.