전 세계적으로 농업해충의 약제 저항성 발달에 따른 방제 효율 저하는 농약의 과다 사용을 초래하여 농업의 생산성 저하 및 환경 파괴 문제 등을 야기하고 있다. 뿐만 아니라 위생해충의 경우에도 약제 저항성 발달이 심각한 수준으로 나타남에 따라 인류 보건에 큰 위협이 되고 있다. 해충의 약제 저항성은 자연계에 존재하는 극히 낮은 빈도의 저항성 형질이 반복적인 약제 사용에 따라 선발되는 과정을 통해 발달 되는데, 해충 약제 저항성의 효과적 관리를 위해서는 저항성 발달 기작의 규명과 신속·정확한 진단법의 확립이 필수적이다. 현재까지의 저항성 관리 는 저항성 발달 후 대응적(reactive)으로 이루어져 왔으나, 미래에는 보다 다양한 분자 마커를 활용하여 저항성 형질 빈도를 관리 가능한 수준에서 유지하는 선제적(proactive) 저항성 관리도 가능할 것으로 예상하고 있다. 본 발표에서는 해충 약제 저항성 연구의 현재 상황과 미래 전망에 대해 소개하고자 한다.

The two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae), is one of the most important pest species, because it devastates many horticultural and ornamental crops and fruit trees. The resistance ratios calculated for the LC50 value in acequinocyl- and pyridaben-resistant strain was 4,237- and 5,555-fold higher than that of the susceptible strain, respectively. The objective of this study was to evaluate the cross-resistance to several acaricides and to identify the mechanisms associated with acequinocyl- and pyridaben-resistant strain of T. urticae.

A residual contact vial plus water (RCVpW) bioassay method was established to monitor insectiside resistance in field populations of the melon thrips, Thrips palmi. Resistance level against six major insecticides were evalutated in five regions to test applicability of RCVpW as an on-site resistance monitoring tool. Reduced mortality in response to six test insecticides were exhibited compared to the RDA susceptable strain showing 100 % mortality, indicating different degree of resistance. An apparently reduced mortality to emamectin benzoate and chlofenapyr was observed in some field populations, suggesting uneven distribution of resistance to these insecticides in field populations. In addition, spinosad resistance was high and widely distributed in the test regions. Synergistic bioassay revealed that cytochrome P450-mediated metabolic factor is involved in spinosad resistance in the Korean population.

Enterohemorrhagic Escherichia coli (EHEC) O157:H7 is a food-borne bacterial pathogen that causes various diseases in both humans and animals such as hemorrhagic colitis and hemolytic uremic syndrome. Because cattle are the main reservoir of this microorganism, undercooked meat and meat byproducts contaminated with EHEC O157:H7 are most commonly associated with epidemic disease outbreaks. As an enteric pathogen, EHEC O157:H7 enters the body via a fecal-oral route and must survive passage through the gastric stomach at pH 1.5 to 3.5 to establish an infection within the gastrointestinal tracts. Therefore, the ability to resist such acidic environments is important to the pathogenesis of EHEC O157:H7 during a host infection. In this review, we will discuss on the acid resistance (AR) mechanisms induced by EHEC O157:H7 when E. coli encounters acidic environments.

Phosphine (PH3) resistance in the stored-products insect pests has been reported throughout the world in various insect species, including Rhyzopertha dominica, Tribolium castaneum, and Cryptolestes ferrugineus, leading farmers and fumigators to identify new fumigation tools to control PH3-resistant insect pests in storage facilities. Understanding PH3-resistance mechanisms in insects might contribute to providing clues for the development of new chemicals, including fumigants, to control various PH3-resistant insects. A proteomic study has shown 15 decreased proteins in the PH3-resistant R. dominica (CRD343 strain) in comparison to the PH3-susceptible R. dominica, and among those 15 proteins, dihydrolipoamide dehydrogenase (DLD), a protein involved in the Krebs cycle, was identified (Park et al., 2008). The DLD polymorphisms responsible for genetic resistance have disulfide active sites for PH3 binding and are highly sensitive to arsenic exposure after mutagenesis in insects (R. dominica and T. castaneum) and Caenorhabditis elegans (Schlipalius et al., 2012). Here, two PH3- resistant S. oryzae strains were used to understand the development of PH3 resistance in these insects. Acute toxicity test by PH3 on the two PH3-resistant strains was undertaken followed by ethyl formate inhibition study on cytochrome c oxidase activity. The Lineweaver-Burk plots after inhibition studies showed there were significantly difference in inhibition mode between the resistant strains and the control. The RT-qPCR analysis and the next-generation sequencing of the mitochondrial DNA revealed significant changes in metabolism and energy production. Taken together, the PH3 resistance in S. oryzae was definitely acquired by the overall transformation of biochemical reactions to overcome PH3 toxicity.

The diamondback moth (DBM), Plutella xylostella, is a globally distributed and important economic pest. Chemical control is the primary approach to regulate populations of this pest. Chlorantraniliprole is the first commercial insecticide that belongs to the new chemical class of diamide insecticides. In this study, the resistant strain was observed 1578-fold resistance to chlorantraniliprole. Point mutation (G4946E) in ryanodine receptor (RyR) showed a high frequency. Enzyme assays indicated that glutathione S-transferase (GST) activity in the resistant strain was 2.4 times higher compared with the susceptible strain, whereas no difference was seen for P450 and esterase. In addition, the expression of two GSTs genes was up-regulated. These findings pave the way for the complete understanding of the mechanisms of diamide insecticides resistance in insects.

Repetitive applications of drugs to tumor tissues and animals induced resistance and/or tolerances which caused severe problem in agriculture and medicine. However, we still do not clearly understand the molecular and cellular mechanisms underlying development of resistance and tolerance to chemicals. Drosophila is one of the most widely used model for studying fundamental phenomena in sciences using its available genetic and genomic resources. To investigate unknown molecular and cellular basis of drug resistance development, we applied Drosophila with two different concentrations of a chemical after treating them with Ethyl methanesulfonate mutatgenesis. We found that flies treating with two different concentration of chemicals showed different susceptibility to a chemical. We have established two different lines showing different susceptibility to a chemical. We will use these lines to compare any differences in mRNA expression profiling and enzyme activities. (This work was supported by project title: Investigation on cross drug resistance mechanisms using Drosophila as a model (PJ010821032016) from Rural Development Administration).

The cotton aphid, Aphis gossypii (Glover) (Hemiptera:Aphididae), is a highly polyphagous pest that directly or indirectly damages cultivated plants. Six field-collected populations of cotton aphid, A. gossypii (BY-A, BY-B, YJ-A, YJ-B, CJ-A, and CJ-B) were tested for susceptibility to 14 different insecticides. Most population exhibited high to very high levels of resistance to neonicotinoid. Among them, a strain showing resistance to imidacloprid were selected and showed 1,543-fold in resistance as compared with susceptible strain. Piperonyl butoxide (PBO), diethyl maleate (DEM), and S,S,S tributyl-phosphorothiolate (DEF) failed to synergize imidacloprid in this resistant population. In addition, the activity of detoxification enzymes (P450, EST, GST) were no differences between susceptibility and imidalcoprid resistance strain. However, by analyzing the nicotinic acetylcholine receptor β1 subunit loop D, R81T point mutation was detected in BY-A, BY-B, YJ-A, and YJ-B strain.

The green peach aphid, Myzus persicae (Sulzer), is one of the most serious pest in cabbage cultivation. Field survey was carried out to know the insecticide resistance levels in five main cabbage cultivation regions (Pyeong-chang, Hong-cheon, Bong-wha, Mu-ju and Je-ju) in 2009~2011. The green peach aphid can resist a wide range of insecticides in five surveyed local populations. Among the nine tested insecticides, four chemicals (methomyl, bifenthrin, pymetrozine and flonicarmid) showed less than 60% mortality in the recommended concentration in most years of local populations. Multi resistant (MR) strain was selected from these populations and modified AChE (MACE: StoF mutation), MtoL mutation in para-type sodium channel, esterase over-expression were observed in almost of all populations including MR strain. Especially, StoF and MtoL mutations were highly correlated with resistance ratio and population based quantitative sequencing results. Therefore, these results suggested that molecular-biology based resistance monitoring can applied resistance management in M. persicae.

The green peach aphid, Myzus persicae (Sulzer), is one of the most serious pest in cabbage cultivation. Field survey was carried out to know the insecticide resistance levels in five main cabbage cultivation regions (Pyeong-chang, Hong-cheon, Bong-wha, Mu-ju and Je-ju) in 2009. The green peach aphid can resist a wide range of insecticides in five surveyed local populations. Among the nine tested insecticides, four chemicals (methomyl, bifenthrin, pymetrozine and flonicarmid) showed less than 50% mortality in the recommended concentration in all populations. Multi resistant (MR) strain was selected from these populations and esterase over-expression, modified AChE (MACE) and mutation(s) in para-type sodium channel were analysed using native IEF and quantitative sequencing with five local populations. Esterase over-expression and MACE (StoF mutation) were observed in all populations including MR strain. LtoF mutation is well known as a kdr mutation in para-type sodium channel. However, even though LC50 values of MR strain noted over 2,000 times higher than that of susceptible strain against bifenthrin, any mutation was not detected in para type sodium channel and also local populations. These results suggested that unusual case could be existed in pyrethroid resistance mechanism in green peach aphid.

The TSSM is one of the most destructive pests on various orchard trees and garden plants. Abamectin resistance mechanisms in two resistant TSSM strains (PTF, ca. 155-fold; AbaR, ca. 3700-fold) were investigated with an emphasis on target site insensitivity mechanism. Detoxification enzyme assays revealed that metabolic factors contributed by EST and/or P450are involved in abamectin resistance. Synergistic assays showed that enhanced detoxification enzyme activity is not enough to account for the high level of abamectin resistance, further suggestive of the involvement of additional resistance mechanism, most likely target site insensitivity. As a putative target site for abamectin, we cloned the cDNA fragments of glutamate-gated chloride channel (Tuglucl) and determined its full length nucleotide sequences. Amino acid sequence comparison among the four strains showed that the Gly323Asp mutation located in the third transmembrane domainis only found in the AbaR strain, suggesting it is likely associated with the target site insensitivity conferring a high level of abamectin resistance.

Imidacloprid에 저항성을 보이는 복숭아혹진딧물에 대해 몇가지 저항성 기작을 조사하였다. 복숭아혹진딧물에 약제를 처리한 후의 체벽잔류량은 처리 후 시간이 지남에 따라 서서히 감소되었으나 감수성계통과 저항성계통 간에 체벽침투력의 유의성은 없었다. 체내잔류량은 양 계통에서 시간이 지남에 따라 점차 증가되었으며 감수성에서 많았다. 배설량은 저항성계통이 감수성계통보다 많아 약제 대시가 빠르게 나타났다. Imidacloprid 저항성계통의 acetylcholine-sterase (AChE) 활성은 감수성계통 보다 약 1.4배 높았으며, imidacloprid는 AChE를 저해하지 않았다. 저항성계통에 대해 산화효소 저해제인 PBO(piperonyl butoxide)와 esterase 저해제인 IBP (iprobenfos)를 혼합하여 사용한 결과 Imidacloprid : PBO의 비율은 1 : 1과 1 : 5에서 각각 69.4, 250배의 독성을 보였으며, IBP와 혼합사용(1 : 1과 1 : 5)에서는 각각 227, 80.6배의 독성을 보였다. 감수성계통에 PBO와 IBP를 imidacloprid와 같은 비율로 혼합처리 하였을 경우 단독처리와 독성차이가 보이지 않았다. -naphtyl butyrate와 -naphtyl acetate 기질을 사용하여 비특이적 esterase의 활성을 측정한 결과 저항성계통의 감수성 계통보다 esteraseghkf성이 높게 나타났다. 따라서 imidacloprid 저항성 복숭아혹진딧물의 저항성 기작에는 산화효소와 esterase가 관여되고 있음을 알 수 있었다.

수산시설용 그물감 재료로 많이 사용되고 있는 PE 및 나일론과 신소재섬유로 구성된 Hi-PE 그물실의 내후성 기구를 파악하기 위하여 그물실에 인공광원을 조사한 후 시간의 경과에 따른 그물실 표면의 형태적 변화와 밀도 및 광각X선 회절 측정을 실시하였으며, 이들 결과를 인장시험에 의한 기계적 물성 특성과 비교「고찰하였다. 실험의 결과를 요약하면 다음과 같다. 1. 그물실 표면의 형태적 변화는 염색 처리된 PE와 나일론 그물실의 경우에는 표면에 안료가 석출되었을 뿐 균열은 나타나지 않았으나, 미처리된 Hi-PE 그물실의 경우 자외선 etching에 따른 균열의 현저한 증가를 확인할 수 있었다. 2. 그물실의 분자 충진 밀도의 경우, 염색된 PE 및 나일론 그물실의 경우에는 노출시간이 증가함에 따라 큰 변화는 없었으나, Hi-PE 그물실의 경우에는 분자사슬의 재배열과 chain scission 등의 영향에 의해 밀도가 증가하였다. 3. 세 그물실 모두 회절 피크의 2θ에는 큰 변화가 없는 것으로 보아 결정구조의 근본적인 변화는 없다고 생각할 수 있다. 4. 잔여 강도는 염색처리된 PE 및 나일론 그물실에서 각각 90.8%와 75.3%로 높게 나타났으나, 미처리된 Hi-PE 그물실에서는 68.3%로 가장 작았으며, 이는 전자현미경에 의해 촬영된 그물실 표면의 형태적 변화와도 잘 일치하고 있다.

당근뿌리혹선충(Meloidogyne hapla)에 대한 저항성품종을 선발하고자 175개 고추품종을 대상으로 조사하였다. 그 결과 재래종 15품종(IT 102794, 104806, 105516 등)과 도입종 2품종이 저항성이었고 재배품종 중에서는 홍탑고추, 강산고추, 홍실고추와 부강고추가 중도저항성이었다. 저항성반응을 보인 품종에서는 감수성인것에 비하여 선충의 침입수도 적었고 발육도 부진하였다. 또 에스테라제와 퍼옥시다제의 활력에서 저항성 고추품종의 뿌리는 감수성인 것에 비하여 현저히 높았다.