有效防治蛴螬的昆虫病原线虫鉴定及其生物学特性

为筛选出对华北地区蛴螬具有较强致病力的昆虫病原线虫,从河北省采集的30份土样中分离线虫,通过形态学和分子生物学方法进行鉴定,分析其生物学特性,并测定线虫对该地区3种蛴螬的致病力。结果表明,经鉴定所分离的昆虫病原线虫为樱桃异小杆线虫Heterorhabditis beicherriana的1个品系,将其命名为LF品系;该线虫具有较强的耐高温能力,38℃水浴12 h后存活率达28.4%;具有较好的耐干燥能力,相对湿度50.5%处理9 h后存活率可达80.0%,在此条件下仍然具有较强的侵染能力,可使大蜡螟Galleria mellonella在72 h内全部死亡;具有较强的水平运动能力,30℃处理24 h后有42.2%的个体迁移到3.6 cm外培养皿圆孔处。该线虫对蛴螬具有较强的致病力,室内试验中,在200 IJs/头剂量下对华北大黑鳃金龟Holotrichia oblita、暗黑鳃金龟Holotrichia parallela和铜绿丽金龟Anomala corpulenta幼虫处理7 d后,3种幼虫1龄末期幼虫死亡率均可达70.0%以上;室外盆栽试验中,5 000 IJs/盆剂量下处理7 d后,3种幼虫2龄中期幼虫死亡率均达到了80.0%以上。表明樱桃异小杆线虫LF品系对华北地区蛴螬类地下害虫生防潜能巨大。     

小杆线虫Oscheius tipulae JL1的鉴定及生物学特性

利用大蜡螟Galleria mellonella L.诱集法,从采自吉林省的土样中分离到小杆类昆虫病原线虫1种。经形态学、ITS及28S rDNA序列分析鉴定,明确了该线虫为Oscheius tipulae JL1。室内生物测定结果表明:24 h时,线虫JL1浓度为120 IJs/larva及以上时,大蜡螟的死亡率达90%以上;48 h时,浓度40 IJs/larva时,大蜡螟死亡率达93%以上;60 h时,浓度高于20 IJs/larva时,大蜡螟死亡率100%。耐热性方面,在38℃下处理8 h,线虫死亡率快速增加,35℃处理16 h,线虫死亡率开始快速增加。线虫JL1在35和38℃条件下,分别至少可耐16和8h的高温,死亡率分别在3.2%和15.3%以下。结果表明该线虫具有较好的耐热力、侵染力和致死力,未来有望用于害虫防治。     

昆虫病原线虫对腰果云翅斑螟的室内致病力

研究了小卷蛾斯氏线虫Steinernema carpocapsae All品系、Biosys品系,格氏斯氏线虫S.glaseri NC52品系,长尾斯氏线虫S.longicaudum X-7品系,嗜菌异小杆线虫Heterorhabditis bacteriophora H06品系和印度异小杆线虫H.indica LN2品系6个昆虫病原线虫品系在室内对腰果云翅斑螟Nephopteryxsp.幼虫的致病力。结果表明,除了嗜菌异小杆线虫,其他参试线虫对腰果云翅斑螟3龄幼虫均具有较高的致病力,致死率80.0%~95.0%,各处理差异不显著。嗜菌异小杆线虫对腰果云翅斑螟幼虫控制效果最差,显著低于其他参试线虫。选择小卷蛾斯氏线虫All品系进一步研究其对腰果云翅斑螟的致病效果,结果发现,其对腰果云翅斑螟3龄幼虫处理24h后的LC50为22.94IJs/头。处理24h,小卷蛾斯氏线虫All品系对1~3龄幼虫的致死率(72.5%~84.7%)显著高于4~5龄幼虫(15.0%~30.0%);处理120h,对蛹的致死率仅为20.0%。研究表明,小卷蛾斯氏线虫All品系对腰果云翅斑螟低龄幼虫在室内具有一定控制潜力。     

对铜绿丽金龟具有高致病力的昆虫病原线虫的筛选

为筛选对铜绿丽金龟Anomala corpulenta幼虫具有生防潜力的昆虫病原线虫品系, 测定了9个昆虫病原线虫品系对铜绿丽金龟1 龄幼虫的致病力, 以及不同施用剂量、环境温度及土壤相对湿度条件对线虫致病力的影响。生测结果表明, 樱桃异小杆线虫品系Heterorhabditis beicherriana D26-6对铜绿丽金龟幼虫致病力最高, 处理11 d后的校正死亡率达到了98.3%;对线虫D26-6致病力的单因子测定发现, 侵染铜绿丽金龟幼虫的最佳剂量为150 IJs/头、最佳温度范围为20~30℃、最佳土壤湿度为18%, 有较好的开发应用潜力。     

昆虫病原线虫JLSY 003的鉴定及其生物学特性测定

经28S rDNA和ITS序列分析,从吉林省松原市土样中分离到的昆虫病原线虫JLSY 003为Oscheius myriophila品系.本研究以大蜡螟末龄幼虫为寄主,测定该线虫的生物学特性.结果表明,JLSY 003浓度为80IJs/larva时具有较高的侵染力,致死中时间LT50为15.409 h,侵染24、48h...     

不同种昆虫病原线虫对同一寄主个体的竞争及对线虫繁殖的影响

采用注射侵染和自然侵染法，测试了长尾斯氏线虫X-7品系、小卷蛾斯氏线虫All品系和嗜菌异小杆线虫H06品系对同一寄主大蜡螟幼虫的相互作用，及其对线虫繁殖的影响。结果表明，无论是注射侵染还是自然侵染法，对大蜡螟幼虫个体的致死竞争能力最强的是长尾斯氏线虫，其次是小卷蛾斯氏线虫，嗜菌异小杆线虫的致死能力最弱。在同一大蜡螟幼虫体内时。异小杆线虫的繁殖受斯氏线虫的不利影响较大，而两种斯氏线虫的繁殖受异小杆线虫的不利影响较小。两种斯氏线虫对各自的繁殖影响不大。     

嗜菌异小杆线虫沧州品系对暗黑鳃金龟幼虫的致病力

室内测定了嗜菌异小杆线虫沧州品系在不同侵染剂量、不同环境温度及不同土壤湿度条件下对暗黑鳃金龟幼虫的致病力。结果表明,幼虫的死亡率随线虫施用剂量和处理时间的增长而升高,其中侵染期线虫剂量为400、250、200条/mL时,幼虫死亡率分别在处理后72、96 h和120 h达到100%;30℃和25℃是该线虫侵染的最佳温度,幼虫死亡率分别在处理后48 h和96 h达到100%;土壤湿度为14%和17%时,幼虫死亡率分别在96 h和120 h达到100%。     

哈尔滨两种斯氏线虫及其共生菌的分离鉴定和低温侵染力分析

从哈尔滨当地土壤中分离出2个斯氏线虫品系。并通过分子生物学技术对这2种斯氏线虫的内转录间隔区(ITS)进行PCR扩增和序列分析,明确这2种哈尔滨斯氏线虫分别是海滨斯氏线虫Steinernema litorale和拟双角斯氏线虫Steinernema ceratophorum,其扩增的DNA片段长度分别为913和1000 bp。关于海滨斯氏线虫的共生菌研究目前尚未见报道,进而对其共生菌进行了分离鉴定,通过扩增核糖体16S rDNA片段,确定海滨斯氏线虫携带的共生菌为伯氏杆菌Xenorhabdus bovienii,其扩增片段大小为1388 bp;拟双角斯氏线虫携带的共生菌为Xenorhabdus budapestensis,其扩增片段大小为1517 bp。为了验证海滨斯氏线虫及拟双角斯氏线虫在高寒地区的活力,在低温条件下对大蜡螟的侵染力进行了测定。结果表明,5℃条件下侵染144 h,4种线虫处理的大蜡螟幼虫均未死亡;10℃条件下,海滨斯氏线虫表现出明显较高的侵染力,在处理96 h大蜡螟幼虫的校正死亡率为85.83%,其他3个处理校正死亡率都为0;15℃条件下,拟双角斯氏线虫表现出明显较高的侵染力,在处理72 h大蜡螟的校正死亡率为89.17%,海滨斯氏线虫在处理72 h大蜡螟未出现死亡,处理96 h开始出现死亡,且校正死亡率为87.5%,而拟双角斯氏线虫在处理96 h后校正死亡率为96.67%,拟双角斯氏线虫表现出较高的侵染力显著高于其他2种处理,但与海滨斯氏线虫相比,二者无显著差异。     

影响昆虫病原线虫共生菌发酵液杀虫活性相关因子研究

应用生物测定法,研究了甘肃省3种土著昆虫病原线虫的4个优良品系共生菌的杀虫活性,及日光和紫外照射、温度对杀虫活性的影响。结果表明,不同线虫及品系共生菌对大蜡螟的胃毒活性存在显著差异,异小杆线虫共生菌HMP0627对大蜡螟的胃毒活性最高,校正死亡率和体重抑制率分别为22.20%和36.02%,斯氏线虫共生菌SAX0664对大蜡螟也有较高的致死作用。4个线虫品系共生菌对日光和紫外光照射都有较强的适应性,1.999 mmol/(m2·s)日光下照射1 h和18 W紫外灯照射30 min仍具有胃毒毒力。不同共生菌对温度的适应性存在显著差异,随着温度的升高,共生菌的胃毒毒力显著下降。到50 ℃时,异小杆线虫共生菌HMP0627仍有较高的致死率和体重抑制率,斯氏线虫共生菌SKX0657仍有较高的体重抑制率。     

海南槟榔园昆虫病原线虫对红脉穗螟的致病力

红脉穗螟Tirathaba rufivena Walker是槟榔上的重要害虫。本研究采用大蜡螟诱捕法,对海南省主要槟榔产区槟榔园中采集到的土样进行昆虫病原线虫的诱捕,并评估了目标线虫对红脉穗螟的致病力。在采集的150份土样中共有12个土样经检测发现含有昆虫病原线虫,检出率为8%。其中,屯昌、定安和万宁三个市县采集的土样中检出的带线虫比率相对较高,分别为12.90%、11.76%和10.00%,而海口和保亭土样中未检出昆虫病原线虫。在室内以大蜡螟为试虫测试线虫的致病力,结果表明诱捕的12个线虫种群均对大蜡螟幼虫具有一定的致病力,但致病力的大小存在较大差异（120 h校正死亡率21.11%～72.22%）。选取致病力较高的Tc05、Wn01和Wn09样本测试对红脉穗螟3龄幼虫的致病作用,结果显示在600 IJs/mL线虫液处理后24 h,Wn01种群对寄主的校正死亡率达到86.67%,半致死浓度LC₅₀为283.70 IJs/mL;Tc05和Wn09对红脉穗螟的致病力相近,校正死亡率分别为61.67%和65.00%,LC₅₀分别为504.75 IJs/mL和502.70 IJs/mL。研究表明,Wn01,Tc05和Wn09线虫种群对红脉穗螟幼虫具有一定的控制潜力。     

昆虫病原线虫异小杆属新种Heterorhabditis beicherriana共生菌的分离及致病性

昆虫病原线虫共生菌在农业及医药领域已成为一种重要的生物活性资源。本研究通过致死的昆虫血腔和侵染期线虫直接分离线虫Heterorhabditis beicherriana的共生细菌,根据形态学特征、生理生化特性及16S rDNA序列初步鉴定为Photorhabdus luminescens,系统发育分析显示为发光杆菌属新亚种菌株。采用共生菌细菌体稀释液注射接种进行致病性测定,结果显示,每头大蜡螟幼虫接种菌量为600 cfu/mL,72 h时死亡率达到100%;24 h时LC₅₀为213.13 cfu/mL,48 h时LC₅₀为46.87 cfu/mL。这为研究该线虫H.beicherriana的致病机制奠定基础,以期发掘新的具有重要价值的活性资源。     

不同品系昆虫病原线虫抗逆性分析

昆虫病原线虫作为一种高效的生物防治因子,具有广泛的应用前景.但昆虫病原线虫的生物活性受自然环境影响较大,筛选抗逆优良品系对于更好地推广和应用昆虫病原线虫具有十分重要的意义.为了评价昆虫病原线虫的抗逆性差异及生防潜力,在室内条件下测试了17个采自不同地区的昆虫病原线虫品系对高温、低温及干燥环境的抗性.结果显示:Stein...     

Comparative efficacy of indigenous heterorhabditid nematodes from north western Himalaya and Heterorhabditis indica (Poinar,Karunakar & David) against the larvae of Helicoverpa armigera (Hubner)

The efficacy of three Heterorhabditis spp of entomopathogenic nematodes (EPNs) from north western Himalaya, India was studied against the larvae of pod borer, Helicoverpa armigera (Hubner) (Lepidoptera: Noctuidae), under the laboratory conditions. The larvae were exposed to 10, 20, 30 and 40 infective juveniles (IJs) of each nematode species for different time periods and they were found to be susceptible to all the EPNs tested. However, the susceptibility of larvae to nematode infection varied according to the concentrations of IJs and their exposure periods. The efficacy of these indigenous entomopathogenic nematodes was also compared against commercially available entomopathogenic nematode, H. indica. Appreciably good performance was achieved by H. bacteriophora (HRJ), which showed 73.3% mortality of insect larvae in 96 h exposure time against third instar larvae, while H. indica produced 80.0% mortality. However it was noticed that with the advancement of larval stage its mortality rate reduced and vice versa with the exposure period. All tested EPNs were also found to reproduce within the host and maximum production of IJs was recorded in H. bacteriophora (26.0 ± 3.76 × 10³ IJs/larva) at the concentration of 40 IJs/larva.     

Desiccation survival of entomopathogenic nematodes of the genusHeterorhabditis

The present study aims at determining the desiccation tolerance of entomopathogenic nematodes from the genusHeterorhabditis recently isolated in Israel. We first verified the most suitable desiccation conditions that lead to induction of the anhydrobiotic state usingHeterorhabditis bacteriophora HP88. After direct exposure of infective juveniles (IJs) to 97% and 93% r.h. for 96 h, the survival rate was > 70%. By contrast, exposing HP88 IJs to 88% and 85% r.h. resulted in poor survival (< 10%) or complete mortality. Following exposure to 97% and 93% r.h. for 24, 48, 72 or 96 h, survival ranged from 68% to 79% with no significant differences between the exposure periods. Stepwise reduction of r.h. conditions (97% > 93% > 88% > 85% r.h.) at a 24-h or 72-h interval resulted in enhanced survival (30% survival) of IJs at the final r.h. level compared with IJs which were either directly exposed to 85% r.h. (0% survival) or were preconditioned at the higher r.h. levels prior to exposure to 85% r.h. (15% survival).H. bacteriophora HP88 IJs were able to survive for at least 18 days after preconditioning. At 97% r.h. nematode viability remained stable at 70–85% and at 93% r.h. survival ranged between 37% and 60%. The data indicate that survival is influenced by rate of water removal from the nematode’s body and a minimal relative humidity level (>93%). Substantial differences in survival ability were observed among IJs of 12 new heterorhabditid populations, isolated from different climatic regions in Israel, which were preconditioned at 97% r.h. for 72 h following by an additional 72 h at 93% r.h. Maximum survival was recorded with HIS-19 (64%), moderate (40–55%) survival was observed with seven isolates, includingH. bacteriophora HP88, and five isolates displayed poor (<25%) desiccation tolerance. Contribution from the Agricultural Research Organization, Bet Dagan, Israel, No. 502-99, 1999 series.     

Genetic improvement of the desiccation tolerance and host-seeking ability of the entomopathogenic nematode <Emphasis Type="Italic">Steinernema feltiae</Emphasis>

Entomopathogenic nematodes (EPNs) from the genus Steinernema (Steinernematidae) are used for biological control of insect pests. The infective stages of these nematodes are intolerant of extreme environmental conditions. Genetic improvement has been suggested as an approach for improving their ability to overcome these limitations. In this study, we bred a heterogeneous population of the EPN Steinernema feltiae Filipjev for desiccation tolerance (both rapid and slow) and enhanced host-seeking ability. We selected for tolerance of rapid desiccation by exposing infective juveniles (IJs) to ambient conditions (22–25°C; 50–65% r.h.) for 100 min. A survival rate of 80–90% was reached after ten selection cycles. To select for tolerance of slow desiccation, we exposed IJs to 97% r.h. for 72 h, followed by further exposure to 85% r.h. for an additional 72 h. A high survival rate (>85%) was obtained after 20 selection cycles. We selected for enhanced downward dispersal by forcing IJs to move through a sand column to reach larvae of last-instar Galleria mellonella placed at the bottom of the column. After 25 selection cycles, the majority (>75%) of these nematodes were found at the layer close to the insects. No reduction in fitness was detected in the selected populations. Nevertheless, the nematode population selected for enhanced downward dispersal displayed significantly higher infectivity than the foundation population. The population selected for slow desiccation was more tolerant of heat stress than the foundation population. These findings establish the basis for improvement of this nematode for use as a biological control agent under field conditions.     

昆虫病原线虫与黑色粘板配合使用对韭菜迟眼蕈蚊的防治

为探索昆虫病原线虫与色板配合使用对韭菜迟眼蕈蚊的综合防治技术,采用培养皿滤纸法比较7品系昆虫病原线虫对韭蛆3龄幼虫的致病力,盆栽法研究斯氏线虫属3品系线虫的保苗和防治效果;并通过温室和田间试验比较10种颜色粘板和3个粘板高度对迟眼蕈蚊成虫的诱集效果,研究线虫与黑色粘板配合使用对韭菜迟眼蕈蚊的防治效果。结果表明:SF-SN品系线虫对韭菜迟眼蕈蚊3龄幼虫致病力最高,LD50为60.0条/头,施用线虫剂量为200、400条/头时,其保苗和防治效果高低依次为SF-SN、All、NC116,其中施用SF-SN品系5 d,保苗效果达62.74%,防治效果达60.26%;黑色粘板诱集效果极显著高于其它色板,且下部(色板下缘离地面1 cm处)诱集成虫量最多,与中部(15 cm)、上部(30 cm)之间差异极显著。研究表明,SF-SN品系线虫主要用于防治幼虫,黑色粘板主要诱杀成虫,二者配合使用防治效果可达97.60%,能够极大地降低虫口基数。     

昆虫病原线虫对甘薯蚁象的致病力测定

昆虫病原线虫是隐蔽性害虫的有效生物防治因子,对8种斯氏线虫和3种异小杆线虫进行筛选证实夜蛾斯氏线虫Steinernema feltiae对甘薯蚁象Cylas formicarius的致病力最强;在此基础上进一步研究了11个不同地理来源的S.feltiae品系对甘薯蚁象末龄幼虫的致病力,获得强致病力的品系S.feltiae JY-17并测定了不同因素对该线虫品系致病力的影响。研究结果表明：在25℃条件下,甘薯蚁象不同发育阶段对S.feltiae JY-17的敏感性依次为末龄幼虫〉低龄幼虫〉蛹〉预蛹期〉成虫;在不同测试温度条件下,sfeltiae JY-17致病力由高到低顺序为25℃〉20℃〉30℃〉15℃〉10℃〉35℃;在25℃条件下,当寄主密度为196．6头·m^-2时,线虫对蚁象末龄幼虫的LD50=5．532条·头^-1,LD90=28．049条·头^-1;当线虫与寄主比例为5：1时,LT50=44．306h。本研究为利用昆虫病原线虫防治甘薯蚁象提供了理论依据。