This study was to evaluate the growth potential of E. coli O157:H7 in lettuce leaf extracts and on lettuce leaf surface at various temperatures. The pathogen can survive and multiply in the extracts and leaf surface of lettuce. The population of E. coli O157:H7 in the lettuce extracts reached to 4.79 log CFU/mL at 37℃. The multiplication of pathogen in lettuce extracts initiated within 10 hours of inoculation over 15℃ conditions. And it can survive in the lettuce leaf extracts at 4℃ for 100 hours at least. And this pathogen can multiply on lettuce leaf surface and the population of pathogen on the lettuce leaf surface increased to 1.82 log CFU/g at 25℃. At 37℃, the pathogen density increased to 1.53 CFU/g within 3 days after inoculation. At all temperature, irrespective of the inoculation level, similar trends in growth of E. coli O157:H7 were observed. These results emphasize the growth potential of E. coli O157:H7 in lettuce leaf extract and on lettuce leaf surface. To reduce the risk of outbreak, it is important to maintain the cold chain system during storage before the consumption.

Produce, including leafy vegetables, has been implicated in several outbreaks of food illness. To evaluate microbiological safety of lettuce and it’s cultivation area, a total of 147 samples were collected from lettuce farms and post harvest facility at Icheon, Gyeonggi province. The collected samples were assessed for presence of sanitary indicator microorganisms (Aerobic plate count, coliform count, Escherichia coli) and foodborne pathogens (Escherichia coli O157:H7, Salmonella spp., Staphylococcus aureus, Listeria monocytogenes, Bacillus cereus). The population of APC was over 4.0 log CFU from most of the samples. While the numbers of APC, and coliform of lettuce at 62 days after transplanting were 4.18 log CFU/g, and 1.00 log CFU/g, respectively, those of 10 days after transplanting were 5.37 log CFU/g, and 2.87 log CFU/g, respectively. B. cereus was highly detected from soil and balance which were contaminated with 3.5 log CFU/g, and 2.6 log CFU/100 cm2, respectively. The number of E. coli recovered from gloves was 3.5 log CFU/hand. However, E. coli O157:H7, Salmonella spp., and L. monocytogenes were not detected. These data suggested that risk management system should be introduced to lettuce farms to enhance safety of lettuce.

This study was conducted to develop an organic control method of two spotted spider mite (Tetranychus urticae) by using cooking oil and yolk mixture (COY) through evaluating its acaricidal activity in laboratory and green house. In laboratory, there is no significant difference in acaricidal activity against T. urticae within the COY including soybean, canola (rape seed), sunflower and olive oil. The acaricidal activity against T. urticae. increased from 17.6% to 94.1% as the COY became concentrated between 0.1% to 1%. The COY acricidal activity was effected by the quantity of treatment according to application methods. The COY dealt with T. urticae eggs presented 95% of the ovicidal activity. In rose greenhouse damaged by T. urticae, the COY (0.3%) was sprayed three times and resulted in the high control value of mites between 69.0% to 89.6%.

Insecticidal activity of 20 plant species against adults of Myzus persicae, female adults of Tetranychus urticae, and 2<SUP>nd</SUP> or 3<SUP>rd</SUP> instar larvae of Plutella xylostella was evaluated in this study. Thirteen plant extracts showed over 80% acaricidal activity to T. urticae at the concentration of 1%, while Capsicum annuum (hot-pepper seed), Inula helenium, and Acorus calamus revealed 82.8-86.2% acaricidal activities at 0.5%. Insecticidal activities of the plant extracts to M. persicae and P. xylostella were relatively low compare to the mite. Among the plant extracts, C. anuum and Brassica juncea revealed 48.6% and 42.9% respectively insecticidal activities to the aphid at the concentration of 0.5%. Extracts of C. anuum and Jeffersonia dubia provided 55% and 50% insecticidal activity against P. xylostella at 1%. And, the highest antifeeding activity of the insect was observed in the J. dubia extract as 79.4%. Results indicated that some plant extracts including hot pepper seed could be used as potential botanical pesticides for organic farming.

Among various food base baiting materials, beer and macerated cucumber were the most effective to induce slug that is a troublesome pest on leafy vegetables, especially on lettuce. However, the baits attracted only but did not kill the pest. When the baits were combined with various insecticidal organic materials, a few combinations such as beer and cigarette mixture successfully induced and killed the slug in the field test. The most effective combination of beer 50 ㎖ and a cigarette contained in a small plastic box killed 25 slugs per night. While macerated cucumber 50 ㎖ and a cigarette mixture killed only 4.3 slugs. The bait of beer and cigarette mixture revealed 68.4% control value against slug damage when treated for 3 consecutive days in a lettuce cultivation greenhouse. The bait also effectively reduced the slug damage in a lettuce nursery showing 58.3% control value. The method seemed highly useful for the control of slug in the organic farming system in which application of pesticides are strictly prohibited.

Background : Garlic is one of the important vegetables and a source of natural anti-oxidants. This study was carried out to investigate the antioxidant activities including 2,2-diphenyl-1-picr yl-hydrazil (DPPH), 2,2'-azino-bis-3-ethylbenzothiazoline-6-sulphonic acid (ABTS), ferric reducing antioxidant power (FRAP), reducing power (RP) and total polyphenol content (TPC) of A. ampel oprasum L. Methods and Results : DPPH, ABTS, FRAP, TPC, and RP were analyzed the extract of aerial plant part in 22 accessions of A. ampeloprasum by spectrophotometry mathod. A. tuberosum Rottler ex Spreng. was used as a control. DPPH was ranged from 0.35 to 3.06 ㎍ ASC ㎎-1 dw. ABTS and FRAP showed wide variation from 4.37 to 29.30 ㎍ Trolox ㎎-1 dw and 3.18 to 10.8 ㎍ ASC ㎎-1 dw, respectively. RP and TPC were ranged from 3.43 to 9.51 ㎍ GAE ㎎-1 dw, and 0.8 to 18.63 ㎍ ASC ㎎-1 dw, respectively. Cluster analysis of A. ampeloprasum germplasm was divided into two major groups. Group Ⅰ (7 accessions) characterized as higher antioxidant activities than the group Ⅱ (15 accessions) and had similar antioxidant activities with A. tuberosum as a control. FRAP value showed a significant strong positive correlation with DPPH (r = 0.868*) and ABTS activity (r = 0.826*). Principal component analysis showed that the first two principal components (PC1 and PC2) cumulatively explained 85.64 % of total variation. Conclusion : From the above results, we may suggest that A. ampeloprasum aerial parts might have useful as a new material for functional food.

To verify the multiplication of microorganisms on the surface of strawberries, the fate of E. coli DH5α::gfp at different temperatures, times and strawberry extract concentrations were measured. The population of E. coli DH5 α::gfp rapidly increased by 7.36~7.78 log CFU/g at 25~30℃ for 24 hr and slowly increased by 6.49~8.49 log CFU/g at 10~20℃ for 48 hr. However, E. coli DH5α::gfp did not grow at 10~15℃ on the surface of the strawberries, regardless of the contact times with the bacterial suspension. E. coli DH5α::gfp reached 1.52~3.26 log CFU/g at 20℃ as the contact frequency increased from two to six times. The contact frequencies did not significantly differ. In the case of the six-time contact on the surface of the strawberry at 25 and 30℃, the E. coli DH5α::gfp increased by 5.17 and 5.01 log CFU/g. The effects of the strawberry extracts on the growth of E. coli DH5α::gfp showed that sterilization and non-sterilization do not affect the growth of microorganisms for 96 hr. In the minimal broth, the growth of E. coli DH5α::gfp increased by 1 log CFU/g for 96 hr. In less than 50 percent of the strawberry extracts, the growth rate of E. coli DH5α::gfp was higher than in the control and increased by 4 and 5 log CFU/g at 50 and 25 percent of strawberry extracts, respectively. Therefore, E. coli DH5α::gfp can multiply and survive on the surface of strawberries when it comes into contact with the fruit extract.

This work was carried out to evaluate the resistance of potato germplasm against late blight in Korea. Seven races ofPhytophthora infestans were detected from the main potato growing areas. Three races of pathogen were isolated from mono-crop-ping areas a

광전역이 수도엽신의 광합성에 미치는 영향을 구명코져 일반형 2품종(추청벼, 화진벼)과 통일형 2품종(삼강벼, 칠성벼)에 대하여 분얼기에서 출수기에 이르는 기간동안 무처리, 30%, 70% 차광처리하여 분얼기와 출수기에 고저 광도 조건하에서 광합성 특성 및 이와 관련한 생리, 생태적 특성을 검토한 결과를 요약하면 다음과 같다. 1. 차광처리에 의한 건물중의 감소는 70% 차광처리구에서 많았으며, 분얼기보다 출수기가 현저하였고, LAR 및 SLA도 출수기에 높았다. 2. 분얼기 저광도(5Klux)하의 개체의 광합성 능력은 낮은 편이며, 무처리<30%<70% 차광처리의 순이었고, 고광도(33Klux)하에서는 무처리구 보다 30% 차광처리구가 가장 높았다. 3. 출수기에 단엽의 광합성 능력은 무처리에 비하여 70%차광처리구가 오히려 높았다. 4. 광합성에 대한 호흡비율(Respiration/Photosynthesis×100)은 무처리구에 비하여 차광처리구에서 전반적으로 낮았다. 5. CGR, RGR, NAR은 무처리구에 비하여 차광정도가 높을수록 감소하였다. 6. 차광처리는 수량 구성요소중 특히 1수 영화수를 감소시켜 정조수량이 감소되고, 따라서 수확지수도 저하되었다.

우리나라에서 육성 보급하고 있는 대표품종으로 Japonica Japonica 교잡인 일반형 품종 2품종(추청벼, 화진벼)과 Indica Japonica 교잡인 통일형 품종 2품종(삼강벼, 칠성벼)을 공시하여 생육시기별로 6회에 걸쳐 광합성 및 호흡 특성과 아울러 광합성의 일중변화와 이와 관련한 특성등을 구명코자 실험한 결과를 요약하면 다음과 같다. 1. 분얼기 동화부위의 배분(엽신중비율)이 일반형 품종에 비하여 통일형품종에서 높은 특성을 보였다. 2. 생육시기별 광합성 능력은 출수기 이전인 8월 1일에서 가장 높았고 호흡에 대한 광합성 효율(Respiration/Photosynthesis)은 7월 25일에서 가장 높았으며 삼강벼와 추청에서 특이하였다. 3. 1일중의 광합성 곡선은 출수기에는 오전 11~12시(1991.8.12~14)에 peak를 보이는 정규곡선을 나타냈으며 출수 2주일 후(9.2~3)에는 동화량의 peak가 13~14시에 있었으며 통일형품종이 일반형 품종에 비하여 높았다. 4. 광합성과 호흡작용의 일중 전환시각은 전품종 공히 표준 일출시각보다 30~60분 늦은 시간에 CO2 고정이 시작되고 오후에는 표준일몰 시각보다 50~60분 빠른 시점에서 광합성에서 호흡작용으로 전환되는 양상을 보여 주었다. 5. 광합성과 엽록소함량 및 근의 생리적 활력과는대체로 정의 상관이 인정되나 엽의 암호흡은 일정한 경향이 없었다. 6. 통일형인 칠성벼와 삼강벼는 Japonica형인 추청벼나 화진벼에 비하여 수확지수가 현저히 높았다.

우리나라에 육성보급하고 있는 대표적인 벼품종으로 Japonica Japonica 교잡인 일반형품종 2품종(추청, 화진)과 Indica Japonica 원연교잡으로 육성한 통일형품종 2품종(삼강, 칠성)을 공시 하여 광합성 및 물질생산특성과 이와 관련된 주요 생리적특성을 구명코져 온도와 광도 조건을 달리하여 생육특기별로 실험한 결과 그 개요를 들어보면 다음과 같다. 2. 유묘기에 있어서도 통일형 품종은 일반형품종에 비하여 저온에서 광합성능력이 저하되나 상온에서는 오히려 높았다. 3. 저온에 의한 호흡율의 저하는 유묘기, 분얼기 모두 품종간 차이는 적으나 유묘기보다 분얼기에 저하정도가 큰 특징을 보였다. 4. 생육단계별 specific leaf area는 품종간에 큰 차이없이 분얼기가 가장 높고 유수변화기에서 출수기에 갈수록 높아지는 특성을 보였다. 5. 출수기의 광합성능력은 7KLx의 저광도에서는 일반형품종이 통일형품종 보다 조해도가 낮으나 60KLx의 광도하에서는 통일성품종이 높았으며 특히 2위엽에서 높은 특성을 보였다. 6. 출수기의 엽위별 광합성에 호흡율(R/P 100)은 3위엽에서 현저히 높았고 품종간에도 그경향은 일정하였다. 7. CGR는 전반적으로 통일형품종이 일반형품종에 비하여 높았고 RGR는 품종간에 대차가 없었으나 NAR는 통일형인 삼강에서 현저히 높았다. 8. 통일형품종이 일반형품종에 비하여 1수영화수 및 주당 정조중도 많았고 수확지수도 높은 특성을 보여 주었다.