복숭아혹진딧물(Myzus persicae)은 다식성으로 담배, 감자, 고추, 배추, 복숭아 등에 심각한 피해를 입히는 대표적인 농업해충이다. 본 연구에 서는 국내 복숭아혹진딧물 야외개체군의 λ-cyhalothrin, imidacloprid 및 flupyradifurone에 대한 약제 저항성 발달 수준과 점 돌연변이(R81T, L1014F, M918L)의 발생 여부를 확인하였다. 또한, qRT-PCR을 통해 사이토크롬 P450 유전자인 CYP6CY3 발현량을 확인하였다. 그 결과, λ -cyhalothrin은 저항성비(Resistance Ratio, RR)가 12개 모든 지역이 > 200으로 높은 저항성을 보였다. Imidacloprid와 flupyradifurone은 YS, UR, HY, 그리고 WJ 개체군에서 > 200의 저항성비로 높은 저항성을 나타냈다. R81T는 12개 집단 중 약 50%, L1014F는 약 33.3%, M918L은 100%에서 발현하였다. 또한 qRT-PCR을 통해 imidacloprid 저항성 개체에서 subunit CYP6CY3의 발현량이 높게 나타난 것을 확인하였다. 이러 한 결과는 M918L 점 돌연변이는 λ-cyhalothrin 저항성 진단마커로, R81T와 CYP6CY3의 높은 발현은 imidacloprid 저항성 진단마커로 활용이 가능하다는 것을 시사한다.

살충제 저항성 벼멸구의 벼멸구 저항성 벼 품종에 대한 생육 차이를 조사하기 위하여, 2015년 채집한 벼멸구를갖지고 Imidacloprid 약제도태를 실시하여 저항성 벼멸구 계통을 수립하였다. 도태 벼멸구 계통의 추천농도에서의살충력은 살충활성을 감수성 계통(100% 살충력) 비하여 현저히 낮았으며(2.7%), 저항성비는 17.76이었다. Imidacloprid저항성 벼멸구 계통의 9종 살충제에 대한 살충활성을 비교하여 dinotefuran을 제외한 네오니코티노이드계 살충제(acetamiprid, clothianidin, thiamethoxam, thiacloprid)에서는 교차저항성을 확인하였고, 카바메이트계, 피레스로이드계,설폭사민계에는 저항성이 없음을 확인할 수 있었다. Imidacloprid 저항성 벼멸구 계통의 벼멸구 저항성 벼품종인친농(bph2유전자)과 감수성 벼품종인 추청벼에서의 생육의 차이를 조사한 결과 도태계통을 저항성 벼품종에서사육한 처리구에서 기타 처리구에 비하여 1령약충기가 1일정도 빨랐으며, 산란수, 순증가율(R0), 내적자연증강율(rm),배수기간(Dt)에서 유의하게 차이를 보여주었다.

Colony collapse disorder (CCD), a phenomenon of honeybees disappearance, has been reported since 2006. Chronic exposure to neonicotinoid insecticides, particularly imidacloprid, has been suggested to impair forager’s ability for foraging and be a main cause of CCD. Recently, it has been reported that imidacloprid induces insulin resistance in animal cell line by blocking glucose uptake. Similarly to human insulin, insulin-like peptide (ILP) of insects is involved in maintaining blood glucose contents in hemolymph by regulating the concentration of trehalose and glycogen. Therefore, we have hypothesized that sublethal concentration of neonicotinoid may affect the metabolic pathway of honey bees as well. We investigated the transcription levels of the genes involved in the insulin/insulin-like signaling (IIS) pathway, such as AmILP and AmInR, following an acute or a chronic dietary exposure of sublethal concentrations of imidacloprid to foragers. In both experiments, honeybees showed increased expression levels of ILP and InR in a dose-dependent manner. Our results suggest that sublethal dose of imidacloprid likely upregulates IIS pathway, thereby rendering honey bees to become resistant to insulin.

The melon and cotton aphid Aphis gossypii Glover (Hemiptera; Aphididae) is one of the most serious pests worldwide. We surveyed insecticide susceptibility in A. gossypii field populations to 12 insecticides to examine resistance ratios. The levels of insecticide resistance were extremely high, especially to neonicotinoids. One point mutation was found in the beta1 subunit loop D region of the nicotinic acetylcholine receptor (nAChR) of the imidacloprid-resistant strain. Feeding behavior analysis using an electrical penetration graph showed that sublethal doses of imidacloprid had significant effects on the duration of phloem ingestion. In addition, higher doses of imidacloprid induced contact toxicity rather than inhibition of feeding behavior. Temperature and insecticide are two important factors that affect survival, reproduction and other physiological processes of insects. To determine interactions of temperature and insecticide treatment on susceptible and imidacloprid-resistant strains of A. gossypii, adults were exposed to three temperatures (17, 22, and 28℃) or combinations of three temperatures and imidacloprid (LC20), and the expression of several genes (heat shock protein 70, cuticle protein, cytochrome P450, and elongation factor) were analyzed. Additionally, the effect of electron beam irradiation on development, reproduction, and several gene expression of imidacloprid-resistant and -susceptible A. gossypii were compared.

Temperature and insecticide are two important factors that affect survival, reproduction and other physiological processes of insects. To determine interactions of temperature and insecticide treatment on susceptible (S) and imidacloprid-resistant strains (IMI-R) of Aphis gossypii, adults were exposed to three temperatures (17, 22, and 28℃) or combinations of three temperatures (17, 22 and 28℃) and imidacloprid (LC20), and the expression of several genes (heat shock protein 70, cuticle protein, cytochrome P450, and elongation factor) were analyzed. The expression level at 17℃ of heat shock protein 70, cuticle protein, and elongation factor in S strain were up-regulated with increased time and higher than those of IMI-R strain. However, expression of cytochrome P450 was not affected by elevated temperature both S and IMI-R strain. Combined treatment of elevated temperature and imidacloprid were significantly up-regulated only cuticle protein in S strain and higher than those of IMI-R strain.

The cotton aphid, Aphis gossypii (Glover), is one of the main pests in various vegetable crops due to insecticide resistance in Korea. Some insect pests noticed neonicotinoid insecticide resistance such as Nilaparvata lugens, Bemisia tabaci and Myzus persicae etc. and the major player which contributed for developing the resistance was over-expression of P450, particularly CPY6 family. However, A. gossypii was a unique case that they developed non-P450 dependent resistant mechanism. Previously we reported that two point mutations (RtoT in nicotinic acetylcholine receptor, nAChR, beta 1 subunit and RtoT with LtoS in a transcript variant) contribute to develop the imidacolprid resistance in A. gossypii. Moreover we surveyed the mutation(s) in various local field populations. Based on the 3D modeling, we hypothesize that RtoT mutation can reduce the imidacloprid sensitivity. A stretch of 33 amino acid was deleted in the N-terminal region of original transcript of nAChR beta 1 subunit that contained RtoT with LtoS mutations in resistant strain. Among the two transcripts, only original transcript differently expressed between imidacloprid susceptible and resistant strain (resistant ratio = 3,800). Six alpha subunit (1∼5, 7) transcript levels were not significantly different between two strains. Therefore mutation and down-regulation of nAChR beta 1 subunit is also associated with imidacloprid resistance in the A. gossypii.

The effect of electron beam irradiation on development and reproduction of susceptible strain (S) and imidacloprid-resistance strain (IMI-R) of Aphis gossypii were compared. Nymphs and adults of S and IMI-R strain were irradiated at target doses of 50, 100, 150, and 200 Gy. When nymphs were irradiated, emergence rate was not affected at all target dose, but number of F1 nymphs was perfectly inhibited at 150 Gy in both strains when irradiated to the adults, longevity slightly decrease at 150 Gy and above. Fecundity was strongly decreased at 100 Gy, but was not completely inhibited even at 200 Gy. Emergence rate of F1 nymph was decreased at 100 Gy and completely inhibited at 200 Gy. However, there was no significant differences on development and reproduction of S and IMI-R strain. We also conducted the comet assay immediately after irradiation and over the following 7 day periods. In addition, we performed quantitative real-time PCR on several genes.

The melon and cotton aphid Aphis gossypii Glover (Hemiptera; Aphididae) is one of the most serious pests worldwide. We surveyed insecticide susceptibility in A. gossypii field populations to 12 insecticides (6 neonicotinoids, 3 pyrethroids and 3 others) to examine resistance ratios. The levels of insecticide resistance were extremely high, especially to neonicotinoids, such as acetamiprid, clothianidin, thiacloprid and imidacloprid. To identify the neonicotinoid resistance mechanisms, we used an imidacloprid-resistant (IMI-R) strain as a model strain. IMI-R showed an extremely high resistance ratio and also cross-resistance to all the test neonicotinoids. However, there was little or no cross-resistance to the other insecticides, including sulfoxaflor. Synergist tests and enzyme activity assays suggested the absence of resistance mechanisms based on enhanced detoxification enzymes, such as cytochrome P450, esterase and glutathione S-transferase. One point mutation was found in the beta1 subunit loop D region of the nicotinic acetylcholine receptor (nAChR) of the IMI-R strain. This R81T point mutation was also found in field populations collected from 5 regions. Therefore, the R81T point mutation was identified as an important mechanism of imidacloprid resistance in A. gossypii.

The effect of electron beam irradiation on development and reproduction of imidacloprid-resistant (R strain) and -susceptible (S strain) Aphis gossypii were compared. Nymphs and adults of R and S strain were irradiated at target doses of 50, 100, 150, and 200 Gy. When nymphs were irradiated, emergence was not affected at all target dose, but number of F1 nymph was perfectly inhibited at 150 Gy in both strains. When irradiated to the adults, longevity slightly decrease at 150 Gy and above. Fecundity was strongly decreased at 100 Gy, but was not completely inhibited even at 200 Gy. Emergence of F1 nymph was decreased at 100 Gy and completely inhibited at 200 Gy. However, there were no significant differences on development and reproduction of R and S strain. We also conducted the comet assay immediately after irradiation and over the following 10 day period. Severe DNA fragmentation in A. gossypii cells was observed just after irradiation and the damage was repaired during the post-irradiation period in a time-dependent manner. These results suggest that electron beam irradiation induced abnormal development, reproduction, and DNA damage in A. gossypii, but there were no significant differences between R and S strain.

The cotton aphid, Aphis gossypii (Glover), is one of the most serious pests in various vegetable crops. In Korea, some field populations of A. gossypii especially in greenhouse showed high resistance against neonicotinoids. The imidaclopridresistant strain (IR) selected from one of the greenhouse strains was found to be about 3,800 folds more resistant to imidacloprid, compared to the susceptible strain (S), as judged by LC50 values. To identify differentially expressed genes in IR, an isogenic strain, reverse susceptible strain (IRS) was generated from IR and comparative transcriptome analyses based on GS-FLX were conducted using total RNAs extracted from both IR and IRS. Also we confirmed protein expression patterns by 2DE and detoxification enzyme over-expression by synergist test. However there was no significant variation among IR, IRS and S. Comparison of the nucleotide sequence of seven nicotinic acetylcholine receptor (nAChR) subunit (alpha 1-5,7 and beta 1) genes from S and IR strain revealed a point mutation causing an arginine to threonine substitution (R81T) in the loop D region of the nAChR beta 1 subunit of the IR. These mechanisms were also reported in M. persicae and this amino acid change confers a vertebrate-like character to the insect nAChR and results in reduced sensitivity to neonicotinoids. Moreover an extra point mutation, L80S (leucine to serine substitution) was also detected nearby R81T mutation in nAChR beta 1 subunit variant. These mutations can be an additive factor in imidacloprid resistance in A. gossypii. This is the first report of imidacloprid resistance mechanism in A.gossypii. Further, this would be helpful in managing A. gossypii resistant populations in field.

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 cotton aphid, Aphis gossypii Glover is an important sap-sucking pest of many pant, including cucumber and pepper. The objective of the present study was to determine the effects of sublethal concentrations of two insecticides (imidacloprid and flonicamid) and the action mechanisms on the feeding behavior of A. gossypii. The median lethal concentrations (LC50) of imidacloprid and flonicamid for adult A. gossypii were 2.01 and 1.92 ppm, respectively. The sublethal concentrations of imidacloprid were 0.22 ppm (LC10) and 0.82 ppm (LC30), and those of flonicamid were 0.094 ppm (LC10) and 0.56 ppm (LC30). The developmental period of A. gossypii nymphs at LC30 was 3.6 days for both insecticide which shorter than controls (4.2 days). Adult longevities at LC10 and LC30 of imidacloprid were 15.2 and 13.6 days, respectively. Adult longevity at LC10 and LC30 of flonicamid was 11.1 and 9.9 days, respectively. Control adult longevity was 15.5 days. Total fecundity was decreased at both sublethal concentration of two insecticides. Feeding behavior analysis using an electrical penetration graph showed that sublethal doses of imidacloprid and flonicamid had significant effects on the duration of phloem ingestion. However, higher doses of flonicamid induced starvation by inhibition of phloem ingestion and higher doses of imidacloprid induced contact toxicity rather than inhibition of feeding behavior.

The cotton aphid, Aphis gossypii (Glover), is one of the most serious pest in seed potato and various vegetable cultivation. The imidacloprid-resistant strain (IR) was over 300-fold more resistant to imidacloprid compared to a susceptible strain (S) as judged by LC50 values. A highly imidacloprid-resistant local field population (L) was collected from cucumber at Gangwha island in 4th August 2011. Even though neonicotinoid insecticides especially imidacloprid were sprayed six times during June and July, aphid density was too high to be counted. To identify differentially expressed genes in IR or L, comparative transcriptome analyses based on GS-FLX were conducted using total RNAs extracted from IR, L and S strains. Futhermore, to search the resistance associated proteins in IR or L, comparative proteome analyses based on 2DE were conducted using total proteins extracted from IR, L and S strains. Few common candidate genes detected among IR and L such as ABC genes. Comparison of the nucleotide sequence of six nicotinic acetylcholine receptor (nAChR) subunit (alpha 1-5, beta 1) genes from IR, L and S strain revealed a point mutation in the loop D region of the nAChR beta 1 subunit of the IR, causing an arginine to threonine substitution (R81T). These mechanisms also reported in Myzus persicae and this amino acid change confers a vertebrate-like character to the insect nAChR and results in reduced sensitivity to neonicotinoids.