RNAi 기법은 예쁜꼬마선충을 비롯하여 초파리, 생쥐, 인체및 식물들을 포함한 다양한 생물종에서 작용기작이 잘 알려져 있고, 특정 유전자들의 발현을 제어하기 위해 사용되어 왔다.본 논문은 RNAi 기법을 통해 구축된 뿌리혹선충 저항성 형질전환식물체들의 개발현황, 발전 및 응용 가능성에 대해 고찰하고자 하였다. 지난 10여년에 걸쳐 진행된 연구들을 통해 다양한 분화단계의 뿌리혹선충으로부터 분석된 79,978개의 EST가 GenBank에등록되었고, 고구마뿌리혹선충(M. incognita)과 당근뿌리혹선충(M. hapla)의 전체 게놈 염기서열이 해독됨으로써 뿌리혹선충의 기생에 관련된 단백질들 및 식물세포벽 분해 관련 효소들에 대한 정보를 이용할 수 있게 되었다. RNAi의 기본 기작은 모든 진핵생물종에서 잘 보존되어 있고, 최근 식물기생선충들에서 RNAi 효과에 대한 연구결과들이 많이 발표되었다. 서로 다른 뿌리혹선충들에서 현재까지 22종 이상의 RNAi를위한 목표 유전자들이 보고되었다. 제2령 식물기생선충(second-stage juvenile of plant parasitic nematodes)에게dsRNA의 섭취를 유도하는 octopamine, resorcinol, serotonin등의 화합물들이 발견되었고, 이를 이용하여 선충 유전자의 발현제어를 쉽게 판별할 수 있는 새로운 기술의 활용이 가능하게 되었다. 최근에 RNAi 기술의 응용 및 발전을 통해 형질전환식물체에서 발현된 dsRNA에 의한 식물기생선충 유전자들의 발현제어가 증명되었고, 이를 위한 핵심 요소들로서 적절한 선충 표적 유전자의 선택, 식물체 내 높은 함량의 dsRNA의 발현 및선충이 섭취할 수 있는 충분한 양의 dsRNA의 운반 등이 중요하다는 것이 밝혀졌다. 특히, 비표적 유전자서열(off-target gene sequence)의 발현제어를 피하기 위해 다음과 같은 사항들이 고려되어야 한다. 1)비표적 유전자서열을 확인할 수 있는 소프트웨어의 개발 및 이를 통한 비표적 유전자서열을 제거한 RNAi 벡터를 제작하여야 한다. 2)식물과 동물에서 상동성이 높은 표적 유전자의 발현을 피해야 한다. 3)전사해석틀(open reading frames)의 염기서열들 보다 상동성이 낮은 5' 혹은 3'-비해석부위(untranslated regions)로부터 표적 유전자를설계하여야 한다.

Spatial association of entomopathogenic and free-living nematode populations were analyzed at the landscape scale. Free-living nematodes were classified into functional guilds based on their trophic level (i.e. bacterivores, carnivores, fungivores, and omnivores) and life history characteristics (i.e. r-selected colonizing versus K-selected persisting species) in the soil ecosystem. Differences in life history traits were hypothesized to result in different spatial associations of populations. Spatial aggregation indices were calculated for each nematode group. Spatial associations were analyzed and compared for entomopathogenic nematodes (EPN) and each trophic/life history group of free-living nematodes based on spatial analysis of distance indices (SADIE). Spatial aggregation indices (Ia) revealed that taxa with more K-selected persisting life history were less aggregated in their habitat, whereas more r-selected colonizer life history types showed more aggregation. Spatial aggregation index of EPN populations was similar to that of relatively r-selected colonizer type free-living nematodes, which share several life history traits including high reproductive rates and insect phoresy. There were substantial spatial associations between EPN and r-selected colonizer life history free-living nematode taxa.

 ,  , Surveys were conducted on the occurrence of nematodes in the root systems of 1-3-year old Cymbidium hybida Swartz cultivated for export in Korea. The most frequently detected plant-parasitic nematode was Ditylenchus sp. with 4.7, 43.7, and 49.7/200 cc growth medium in 1, 2, and 3 year-old cymbidiums, respectively. And the densities of non-parasitic nematodes, dorylaimids, were 35.3, 70.5, and 155.8/200 cc growth medium in 1, 2, and 3-year-old cymbidiums, respectively. Three-year-old cymbidiums collected from Siheung, Ansan, and Gimpo had low densities of Aphelenchus sp. and Aphelenchoides sp. with under 40 individuals/pot, and the dorylaimid densities were 56-824/pot. To evaluate the effects of nematicides on Ditylenchus sp. in cymbidium, Emamectin benzoate EC, Fosthiazate SL, and Cadusafos CS were tested at two farms in Ansan and Gimpo. Emamectin benzoate EC showed control effects of 75.7 and 89.5%, whereas Fosthiazate SL and Cadusafos CS showed 27.2 and 65.3% and 30.1 and 90.5%

본 연구는 누에의 식엽성 곤충을 대체할 실험곤충으로서의 유용성과 자외선이 한국산 곤충병원성선충 (Heterorhabditis sp. 202 strain, Heterorhabditis sp. Gyeongsan strain, Steinernema sp. 223 strain, S. carpocapsae Pocheon strain, S. glaseri Dongrae strain, S. longicaudum Nonsan strain) 의 병원성과 생존에 미치는 영향을 알아보기 위하여 수행하였다. 누에에 대한 곤충병원성선충의 병원성을 조사한 결과 누에의 령기나 곤충병원성선충의 계통이나 종에 따라 상이한 병원성을 나타내었는데 5령충에 대해서는 Steinernematidae선충의 병원성이 높았고, 1령충에 대해서는 Heterorhabditidae선충의 병원성이 높았다. UV-C는 곤충병원성선충에 유해하여 노출 60분후에는 모든 선충이 치사되었다. UV-C 조사는 곤충병원성선충의 병원성에도 영향을 미쳐 노출 10분 후에도 누에나방 3령충에 대하여 6.7% 이하의 보정사충율을 나타내었다. 야외 뽕나무밭(UV량: 2.3mW/㎠)에서 곤충병원성선충, S. carpocapsae Pocheon strain을 엽면 살포 4시간 후 채취한 뽕나무 잎을 급상한 누에는 치사되지 않았다. 뽕잎에서 4.0mW/㎠의 UV 1시간 노출은 곤충병원성선충, S. carpocapsae Pocheon strain의 누에에 대한 병원성에 차이를 보이지 않았다.

본 연구는 10년 이상 과채류를 재배하여 뿌리혹선충 피해가 많이 발생되었던 시설재배 토양에서 친환경적인 뿌리혹선충방제를 위하여 밀기울 토양환원처리 효과를 구명하였다. 토양소독처리후 뿌리혹선충의 밀도를 조사한 결과 시험전과 비교하여 모든 처리구에서 뿌리혹선충밀도가 감소하는 경향을 보였지만 특히 밀기울처리구에서는 높은 방제효과를 보였다. 처리후 90일경에도 밀기울처리구가 매우 낮게 유지되었으며 멜론의 생육도 가장 양호하였다. 수확기 멜론의 고사율을 조사한 결과 무처리구 65%인데 비해 밀기울처리구, 3%로 현저히 낮았으며 과실의 크기와 품질도 밀기울처리구가 우수하였다. 따라서 밀기울 토양환원처리는 뿌리혹선충 발생포장에 농약을 사용하지 않고 멜론을 1작기 동안 안전하게 재배할 수 있는 유망한 소독방법일 뿐만 아니라 멜론의 품질을 개선하는데 매우 효과적인 방법으로 생각되었다.

Since pine wilt disease was first reported in Busan in 1988, this disease has become a serious threat to pine forests in Korea. A general survey for Bursaphelenchus xylophilus group (B. xylophilus, B. mucronatus) nematodes were carried out to determine their geographic range, host tree species and insect vectors, Monochamus species. Based on the survey results, B. xylophilus were found over 57 cities or district and a similar nematode, B. mucronatus also has been isolated over 30 cities or district including Jeju and Pocheon. The Asian type of B. mucronatus was founded from Pinus thunbergii and P. densiflora, generally associated with M. alternatus as its insect vector. The European type of B. mucronatus which was limited distribution to the central areas, such as Yeongwol, Bonghwa, Yeongdeok, was also found on P. koraiensis and P. desiflora associated with M. saltuarius. Both Monochamus species transmitted both Bursaphelenchus species and co-existed in Muju and Yeongdeok predicted as their range margin. Their range margins shifted northwards compared to 2006, seemingly as a result of climate change. Recently, the European type of B. mucronatus has been identified in other several areas since it was first reported in Pocheon in 2008. Several reports indicate the potential pathogenicity of European type of B. mucronatus and other species, B. sexdentati and B. lenoni in Europe. Therefore, sustainable survey and the study for the newly invading Bursaphelenchus species as well as the member of B. xylophilus group should be performed to protect Korean forests.

Effect of four nematicidal herbal extracts (Daphne genkwa, Eugenia caryophyllata, Quisqualis indica and Zingiber officinale) and 3 acricidal herbal extracts (Pharbitis nil, Xanthium strumarium, and Desmodium caudatum) on entomopathobenic nematodes [Steinernema carpocapsae Pocheon strain (ScP) and Heterorhabditis sp. Gyeongsan strain (HG)], silkworm (Bombyx mori), and ground beetles (Synuchus sp.) were investigated in the laboratory and field. D. genkwa was highly toxic to ScP and HG (100% mortality) at the concentration of 5,000 ppm in X-plate. All the infective juveniles of HG were dead after 3 days by E. caryophyllata and Q. indica. The mortality of ScP and HG was below 10% by D. genkwa, D. caudatum, E. caryophyllata, Q. indica and Z. officinale at the concentration of 1,000 ppm two days after treatment while mortality of HG was 62.8% by D. genkwa at the concentration of 1,000 ppm in X-plate. However, 1,000 ppm had not effect on nematode survival and pathogenicity of ScP in sand column. On the contrary, E. caryophyllata had effect on pathogenicity of HG. Mean number of dead Galleria mellonella larva of HG was 0.5 in E. caryophyllata treatment. Q. indica did not effect silkworm reared on mulberry leaves at the treatment of 1,000 ppm in 10 days after treatment. However, there were 20.0 and 100% mortalities in the treatment of D. genkwa 3 and 10 days after treatment, respectively. The weight of silkworm was low in D. genkwa and did not pupate. The weight of pupa and cocoon were not different in E. caryophyllata, P. nil, Q. indica, X. strumarium and Z. officinale. D. genkwa, E. caryophyllata, P. nil, Q. indica and Z. officinale had no effect on ground beetles, Synuchus sp. in forest soil.

Five effective strains against tobacco cutworm, Spodoptera litura (Lepidoptera: Noctuidae), Steinernema carpocapsae (GSN1), Steinernema sp. (GSNUS-10), Steinernema sp. (GSNUS-14), Heterorhabditis bacteriophora Hamyang (HbH), and Heterorhabditis sp. (GSNUH-1) were selected among 14 isolates of Korean entomopathogenic nematode in laboratory tests. LC₅₀ values of above five strains against tobacco cutworm were various by different nematode strains and developmental stages of tobacco cutworm. LC₅₀ value of S. carpocapsae (GSN1) was the lowest by 4.0~8.3 infective juveniles (Ijs) and 2nd instars of tobacco cutworm was most susceptible. Pathogenicity of five effective strains against tobacco cutworm depends on nematode strain, concentration, and application times. The most effective strain was determined as S. carpocapsae (GSN1). Two or three times of applications were effective regardless of nematode strain, or concentration. Efficacy of S. carpocapsae (GSN1), Steinernema (GSNUS-10), Steinernema (GSNUS-14), and Heterorhabditis (GSNUH-1) was variable depending on nematode strain, concentration, application times, and host variety. S. carpocapsae (GSN1) was the most effective and inoculation of 100,000 infective juveniles per ㎡ (720,000 Ijs/7.2 ㎡=1×10⁹ Ijs/㏊) resulted in higher efficacy. Three times of application of nematodes led to higher control efficacy than one or two applications. Efficacy of nematodes was higher on Chinese cabbage than cabbage or kale.

This study was conducted to investigate occurrence and biodiversity of phytoparasitic nematodes in kiwifruit orchards in Korea. Soil samples were collected from 11 locations of Gosung, Goheung, Namhae, Bosung, Sacheon, Suncheon, Wando, Jangheung, Jeju, Jindo, Haenam from April to August, 2008. Phytoparasitic nematodes were found in 115 among 178 soil samples. The major genera of phytoparasitic nematodes on kiwifruit were Meloidogyne spp.(52.2%), Tylenchinae (42.1%), Tylenchus spp. (9.0%), Helicotylenchus spp. (9.0%) and Tylenchorhynchus spp. (6.7%). Ditylenchus spp., Hirschmaniella spp., Trichodorus spp. and Psilenchus spp. were also detected, even though their frequencies were very low. According to the cultivation period, the phytoparasitic nematodes were found as follows; 16.9% of soils under 5 years of kiwifruit cultivation, 10.7% 6~10 years, 23.0% 11~15 years, 3.9% 16~20 years and 5.6% over 21 years respectively. The frequency of phytoparasitic nematodes is higher in the open field (50.0%) than that in plastic houses (13.5%). The frequency of phytoparasitic nematodes was 36.5% in the field where vegetables were previously cultivated and 12.9% in the field where rice was previously cultivated.

The study was conducted to gather basic information on the occurrence of phytophagous nematodes for the establishment of nematode management strategy in major highland crop production such as chinese cabbage, carrot and potato. Soil samples were collected from five areas in 48 fields in the highland and sub-highland (425m to 1136m asl) areas in 2006. Majority (88%) of the soil samples contained the root-knot nematodes, Meloidogyne hapla. The average density of the root-knot nematodes in chinese cabbage, carrot and potato fields were 8.3, 18.0 and 25.9 nematodes/100g soil, respectively. Helicotylenchus sp., Pratylenchus sp. and Dorylaimida sp. were also detected but in low densities.Root-knot nematode damage was not detected in potato growth and harvest at 0, 2, 12, 23 nematodes/100g soil densities.

Laboratory tests were conducted to determine the susceptibility of the alfalfa weevil, Hypera postica to Korean entomopathogenic nematodes, Steinernema carpocapsae GSN1 strain (ScG), S. glaseri Dongrae strain (SgD), Heterorhabditis bacteriophora Hamyang strain (HbH), and Heterorhabditis sp. Gyeongsan strain (HeG) at the petri dish assay. The larval mortality of H. postica was significantly different depending on nematode species and treatment concentration. SgD and HeG strain were more effective against H. postica larva than ScG and HbH strain. When SgD and HeG strain were treated with the rate of ＞20 infective juveniles (ijs) per alfalfa weevil larva, mortality was ca. 77.5-100% at the late instars of H. postica in 3 days. The number of established nematode was significantly different depending on nematode species, whereas number of progeny was not significantly different. The mean number of established ijs of SgD strain in a host was the highest at 80 ijs by 30.2. The highest progeny number of HeG strain was 2,671.5 with 80 ijs. All nematode strains were not parasitic entirely to H. postica adults. These results show that alfalfa weevil late larva is highly susceptible to Korean entomopathogenic nematodes in the laboratory.

A survey was conducted to find out the major plant parasitic nematode in Chrysanthemum morifolium fields in Korea from May to June in 2005. A genus of Pratylenchus was determined as the most important plant parasitic nematode based on analysis of total 50 samples from 8 cities of chrysanthemum field. Pratylenchus showed 86% occurrence rate and average numbered 1,095 per 200㏄ soils and Ig root. Five Pratylenchus isolates, "Muan", "Masan", "Tean", "Gumi", "Jeongup", were selected for the molecular identification of the species of Pratylenchus, and ITS and D3-28S ribosomal DNA were amplified by PCR. For the ITS, only" Muan" isolate was differentiated by total 1 kb PCR amplification, which was 200 bp larger than all the other isolates. There was no size variation in amplified D3-28S rDNA and all isolate represented approximately 320 bp of PCR product. Sequence data of D3-28S rDNA were analysed by MegAlign program in DNASTAR software and phylogenetic tree was constructed. Sequence homology was 100% between "Gumi" isolate and "Tean" isolate and "Jeongup" isolate was also close to these isolates by 99.7% sequence homology. "Gumi", "Tean" group and "Jeongup" isolate were determined to be closely related to Pratylenchus vulnus by 96.7% and 96.3% similarity in respectively. D3 sequence of "Masan" isolate was 100% identical to P. penetrans, and "Muari" isolate showed 99.7% similarity to P. brachyurus. This result was congruent with the branch divergence pattern shown in phylogenetic tree.

Total of 36 sweet potato field soils were sampled to survey the occurrence of the root-knot nematodes (RKN). The 61% of sweet potato fields in Haenam, 40% in Iksan and 31% in Yeju were infested with RKN, respectively. Average population density of RKN was 324 juveniles per 300 g soil. The resistance screening of sweet potato cultivars against RKN was carried out by using clay pots in a greenhouse. Average temperature under ground 10 ㎝ in pot was 21.5℃ during the test. There was no difference in number of egg sacs among different inoculation methods, however the egg-inoculation method was easy for treatment and had stable for results. The multiplication ratio of Melioidogyne incognita differed from 6.3 times (Jeungmi) to 63.2 times (Yulmi) by sweet potato cultivars. There were no cultivars showing resistance to M. incognita, but Jinmi, Jeungmi and Borami had resistance to M. arenaria, M. hapla and M. javanica.

Five strains of Korean entomopathogenic nematodes (EPN), steinernematids and heter-orhabditids were evaluated and tried in laboratory, pot, and vegetable greenhouses for environmentally friendly control of diamondback moth (DBM), Plutella xylostella, from 2002 to 2005. LC₅₀ values of five EPN strains against DBM were different depending on nematode strain and DBM instar. LC₅₀ value of Steinernema carpocapsae GSN1 (GSN1) was the lowest representing 2.6~3.9 infective juveniles (Ijs, 3rd stage) to 2nd to 4th instars of DBM. Pathogenicity of five effective strains against DBM was different depending on nematode strain, concentration, application times, and vegetable in pot. The most effective nematode was GSN1. Steinernema spp. was more effective than Heterorhabditis spp. against DBM. Two or three times of applications of EPN were effective regardless of nematode strain and concentration in pot. Efficacy of EPN was different depending on vegetable species. Efficacy was higher on Chinese cabbage, red mustard, and Ssamchoo than that on cabbage, kale, and leaf broccoli. Efficacy of GSN1, Steinernema GSNUS-10, Steinernema GSNUS-14, and Heterorhabditis GSNUH-l was variable depending on nematode strain, concentration, application times, and vegetable in greenhouse experiments. GSN1 was the most effective and 100,000 infective juveniles per ㎡ (=1 × 10⁹ Ijs/ha) resulted in higher efficacy. Three times of application of nematodes led to higher control efficacy than one or two applications. Efficacy of nematodes was higher on Chinese cabbage than cabbage or kale in greenhouse.

This study was conducted to get basic information on the occurrence of plant-parasitic nematodes for the establishment of nematode management strategy in major potato production areas in Korea. Nationwide soil collection was done in 11 areas of Cheju, Yesan, Gimchun, Goryoung, Hong chun, Pyungchang, Gimjae, Milyang, Namwon, Gangnung, and Inje in 2004-2005. Root-knot nematode juveniles(J2) were detected in 30 samples among the 50 samples. The average density was 12-69 J2/100㏄ soil. Pratylenchus sp., Helicotylenchus sp., Ditylenchus sp., Tylenchus sp., and Tylenchorh-ynchus sp. were also detected in various locations, however, their densities were very low. Root-knot nematode females were collected from tomato roots inoculated with the potato field soils for PCR-RFLP identification. The females from Cheju, Milyang, and Goryung showed PCR products of 500 bp. And the Dra I restriction enzyme digestions showing 290 bp and 230 bp fragments confirmed their identity as Meloidogyne hapla.

Korean entomopathogenic nematodes were introduced into cultural management of turfgrasses to enhance white grub control in golf courses for saving labour and expenses and contribution to giving safe playing and working places for golfers and superintendents by environmentally friendly control strategy. The turfgrass height influenced efficacy of entomopathogenic nematodes. Efficacy was higher at short turfgrass both in pot using Galleria mellonella larvae and in golf courses using 2nd instar of Exomala orientalis and Ectinohoplia rufipes as baits. Aeration increased the efficacy of entomopathogenic nematodes which were lower virulent. Pre-aeration was more effective than post-aeration. Exomala orientalis larval population was reduced 80.4 and 66.0% in the pre-aeration and post-aeration with entomopathogenic nematode, Steinernema carpocapsae Pocheon strain compared to 35.4% in the no aeration treatment.

우리나라 더덕의 주 재배지인 전라남북도, 경상북도, 경기도, 강원도, 제주도, 울릉도 등 15지역 116개 재배포장을 대상으로 한 식물기생선충의 분포와 피해를 조사하였다. 분포가 확인된 9속의 선충 중 Ditylenchus citri, Meloidogyne hapla, M. incognita, Pratylenchus neglectus, Tylenchorynchus claytoni 등 5종이 동정되었다. 이들 중 M. hapla의 포장검출률이 61.9%로 가장 높았고, Tylenchu spp. 16.1%, Pratylenchus neglecrus 7.8%, Ditylenchus citri 5.1%, Helicotylenchus sp. 5.1%순이었다. 더덕 2년생을 대상으로 한 지역별 당근뿌리혹선충에 의한 피해는 포장감염률과 감염주율이 각각 67.0%, 60.2%였으며 평균 감수율은 10%였다. 전북지역 더덕 재배지에서 당근뿌리혹선충에 의한 피해는 재배년수가 길어질수록 많았고, 평야지가 산간지나 중산간지보다 많은 경향이었다.

골프장의 문제해충들 중 녹색콩풍뎅이(Popillia quadriguttata) 성충의 방제를 위하여 세 종의 한국산 곤충병원성선충 Steinernema carpocapsae KCTC 0981BP 계통 (ScK), S. glaseri Dongrae 계통(SgD), Heterorhabditis sp. KCTC 0991BP 계통 (HsK)을 이용하여 실험을 수행하였다. 3일 후, 녹색콩풍뎅이 성충 한 마리당 900마리의 선충을 처리하였을 때, 치사율은 ScK가 , HsK가 , SgD가 를 각각 나타냄으로써 이용한 선충 모두가 높은 병원력을 나타내었다. 성충 한 마리 당 900마리의 선충을 처리한 3일 후의 치사율은 ScK는 , HsK는 , SgD는 였다. 선충의 녹색콩풍뎅이 성충 표면부착율과 침입율은 접종 선충의 종과 밀도에 따라 차이가 있었다. 즉, 성충한 마리당 900마리의 선충을 처리하였을 때 녹색콩풍뎅이 성충의 표면에서 검출된 HsK의 비율은 였으며, SgD는 , ScK는 였다. 녹색콩풍뎅이 성충 내에 침입한 선충의 검출여부에 따른 선충의 침입율은 성충 한 마리 당 900마리의 선충을 처리한 3일 후 ScK는 , HsK와 SgD는 각각 를 보였다. 반면, 성충 한 마리 당 90마리의 선충을 처리한 3일 후의 ScK 검출율은 , SgD는 였으나 HsK는 발견되지 않았다.