亚洲玉米螟雌蛾产卵偏好寄主植物的筛选及对葎草挥发性化学成分的电生理反应

【目的】鉴定亚洲玉米螟Ostrinia furnacalis雌蛾在寻找产卵寄主时起重要作用的植物挥发性化学物质,以探索亚洲玉米螟和寄主之间的化学通讯机制。【方法】首先利用田间产卵和风洞行为试验,从酸模叶蓼Polygonum lapathifolium、苘麻Abutilon theophrasti、葎草Humulus scandens、玉米Zea mays和稗草Echinochloa crusgalli 5种寄主植物中筛选出亚洲玉米螟雌蛾的产卵偏好寄主;并结合顶空吸附采样法,收集该寄主植物挥发性化学物质;再应用全二维气相色谱与飞行时间质谱联用系统(GC×GC-TOFMS)鉴定植物挥发性物质的化学成分及含量;最后利用气相色谱-触角电位联用仪(GC-EAD)测定亚洲玉米螟雌蛾对提取物中化学成分的触角电位反应。【结果】田间产卵试验结果表明,亚洲玉米螟雌蛾在不同寄主植物上的落卵量依次为玉米酸模叶蓼葎草稗草苘麻。风洞行为试验结果表明,亚洲玉米螟雌蛾对葎草的产卵趋性显著高于其他寄主植物。GC×GCTOFMS结果表明,葎草的植物挥发性化学物质主要成分有45种,其中,萜烯类相对含量高达86.29%,醛类、酮类和酯类相对含量合计仅占15.83%。GC-EAD结果显示,芳樟醇、α-葎草烯、桧烯、月桂烯、2-正戊基呋喃、壬醛、α-法呢烯、反式-罗勒烯和苯甲醛等9种挥发性物质能引起亚洲玉米螟雌蛾明显的电生理反应。【结论】亚洲玉米螟雌蛾对不同产卵寄主的选择具有显著差异性,寄主植物的理化因素是造成选择差异性的主要因素,葎草的植物挥发性化学物质对亚洲玉米螟有较强的吸引作用;芳樟醇、α-葎草烯、桧烯、月桂烯、2-正戊基呋喃、壬醛、α-法呢烯、反式-罗勒烯和苯甲醛9种挥发性化学物质对亚洲玉米螟产卵寄主的选择有重要作用。     

星天牛不同为害状态下山核桃挥发物成分的GC-EAD和行为反应

【目的】为了挖掘对星天牛Anoplophora chinensis有行为反应的山核桃Juglans mandshurica挥发物。【方法】采用动态顶空套袋吸附法收集不同为害状态[健康(CK)、天牛取食、产卵和钻蛀后]山核桃释放的挥发物,并运用气相色谱-质谱联用仪(GC-MS)、气相色谱-触角电位测量系统(GC-EAD)及"Y"型嗅觉仪技术分析鉴定出对星天牛产生电生理及行为反应的挥发物。【结果】GC-EAD反应结果表明:星天牛成虫对不同为害状态下山核桃释放的挥发物中的蒎烯、罗勒烯、对二乙苯、萜品烯、壬醛、α-萜品醇、五甲基苯、丙烯酸-2-乙基己酯、2,6-二甲基萘以及正十六烷10种挥发物产生显著的触角电位反应,对其他挥发物无反应,其中蒎烯和罗勒烯的反应较强。嗅觉反应结果表明:蒎烯仅对星天牛雄虫产生显著的引诱作用(P≤0.05),罗勒烯对星天牛雌雄虫产生极显著的引诱作用(P≤0.01);丙烯酸-2-乙基己酯对星天牛雌虫产生显著的驱避作用(P≤0.05),对二乙苯仅对星天牛雄虫产生显极著的驱避作用(P≤0.01),壬醛对星天牛雄虫产生显著的驱避作用(P≤0.05)。【结论】本研究结果表明,罗勒烯对星天牛雌成虫产生较强的引诱作用,而丙烯酸-2-乙基己酯对其雌成虫产生较好的驱避作用;蒎烯和罗勒烯对星天牛雄成虫产生较强的引诱作用,而对二乙苯和壬醛则对其雄成虫产生较好的驱避作用。     

横坑切梢小蠹对植物挥发物的电生理和行为反应

为筛选出适宜配制横坑切梢小蠹(Tomicus minor Hartig)引诱剂的有效化合物,测定了横坑切梢小蠹雌、雄成虫对寄主云南松主要挥发性化合物的触角电位(EAG)和行为反应。结果表明:与对照相比,在10 g·L-1浓度刺激下所测试的9种植物挥发物都能引起横坑切梢小蠹雌、雄虫触角的EAG反应,且触角对不同挥发物的EAG反应差异显著(P0.05),其中雌、雄虫对(+)-α-蒎烯、(+)-柠檬烯、(+)-3-蒈烯、β-蒎烯和异松油烯的EAG反应较强;在剂量反应试验中,雌、雄虫的EAG反应都随着(+)-α-蒎烯、(+)-柠檬烯、(+)-3-蒈烯和β-蒎烯浓度的增加而增强,当浓度增加到10 g·L-1时,EAG反应最强;而雌、雄虫对异松油烯的EAG反应在1 g·L-1最强;除(+)-柠檬烯没有明显的定向作用外,(+)-α-蒎烯、β-蒎烯、(+)-3-蒈烯和异松油烯对横坑切梢小蠹均表现出了明显的引诱作用;行为反应多重比较表明,(+)-α-蒎烯在10 g·L-1浓度下对雌雄虫的引诱作用最大。该研究结果可为开发横坑切梢小蠹林间引诱剂提供参考。     

两近缘种夜蛾对低浓度烟草挥发物的触角电位反应

寡食性的烟夜蛾Helicoverpa assulta (Guenée)和广食性的棉铃虫Helicoverpa armigera (Hübner)是实夜蛾属的2近缘种昆虫,在它们的寄主植物中,只有烟草为其共同寄主,为明确它们对烟草挥发物嗅觉感受能力的差异,测定了这2种夜蛾的处女雌蛾、交配雌蛾及雄蛾对20种低浓度(1.0×10-5 mol · L-1)烟草挥发物的触角电位反应,并对其中6种化合物进行了剂量反应测定,结果表明,(1) 2种夜蛾对测试化合物均可产生EAG反应且反应趋势相似:对植物中普遍存在的绿叶气味、脂肪族和芳香族化合物的反应显著高于具有烟草"种"特异性的单萜类、倍半萜类和杂环化合物,表明2种夜蛾远距离定向时,对植物"种"的辨识能力均较差.(2) 2种夜蛾对脂肪族C6_化合物的EAG反应最强,碳链延长或缩短都会导致反应强度的降低.(3) 烟夜蛾对大多数化合物的EAG反应大于棉铃虫,表明在远距离寄主定向时其嗅觉感受器对寄主挥发物的感受能力强于棉铃虫.(4) 烟夜蛾交配雌蛾对β-水芹烯和桧烯的EAG反应高于其处女雌蛾和雄蛾,除此之外2种夜蛾的EAG反应未见显著的性别差异,推测β-水芹烯和桧烯可能是烟夜蛾在烟草上产卵的"信号"物质.(5) 剂量反应曲线表明,在测试的浓度范围内,2种夜蛾对6种类型化合物的EAG反应强度与其浓度呈正相关,且均未达到饱和.由此可知,与棉铃虫相比,烟夜蛾嗅觉神经系统在其寄主定向行为中所起的作用更重要、也更专化.     

小菜蛾对合成植物挥发物的活性反应

在室内检验了小菜蛾已交配和未交配雌、雄成虫对3种合成植物挥发物乙酸顺-3-己烯酯（Z-3-hexenyl acetate,ACTE）、异硫氰酸丙烯酯（allyl isothiocyanate,NCS）和顺-3-己烯醇（Z-3-hexen-1-ol,OH）的触角电位(EAG)反应。不同浓度（0.008 μg/μL、0.08 μg/μL、0.2 μg/μL、0.8 μg/μL、8 μg/μL、20 μg/μL和40 μg/μL）实验表明,随着刺激化合物浓度的提高,小菜蛾反应活性增强。但小菜蛾的性别及其交配状态可能影响其对3种化合物的反应强度：不同性别及交配状态的小菜蛾对ACTE的反应差异不大;未交配雌、雄虫对OH的反应强于已交配雌、雄虫;未交配雌虫对低浓度的NCS反应较强,NCS超过一定浓度时已交配雌虫的反应强于未交配雌虫,雄虫对NCS反应较小且与交配状态无关。以小菜蛾性信息素作为对照,在湖北长阳和越南河内试验了这3种植物挥发物诱芯（6 μL/诱芯）对小菜蛾的引诱作用。结果表明,在湖北,第1天时 ACTE、NCS对雄虫具有很强的引诱作用,引诱量显著大于性诱剂的引诱量,但随着诱芯放置时间延长,NCS引诱作用迅速下降,第2天时引诱作用已经很小;ACTE的引诱作用下降缓慢,第4天的诱蛾量才显著小于性信息素的诱蛾量,OH的引诱力较弱。在河内,ACTE、NCS、OH第1天对小菜蛾引诱作用很强,引诱量大于性信息素,但差异不显著;随着诱芯放置时间延长,3种挥发物对小菜蛾的引诱量均下降很快,第4天的引诱力就很弱。3种植物挥发物的混合物(体积比1∶1∶1)对小菜蛾的引诱作用与性信息素相似,且诱蛾活性持效期相对较长。无论在越南或湖北,植物挥发物或其混合物均很少引诱到雌虫。     

云斑天牛对10种植物挥发物的EAG和行为反应

【目的】为了探明对云斑天牛Batocera lineolata Chevrolat成虫具有行为导向的寄主植物挥发物对成虫行为反应的影响。【方法】采用触角电位(EAG)和"Y"型嗅觉仪技术,测定云斑天牛成虫(未交配雌虫、未交配雄虫、已交配雌虫)对10种寄主植物挥发物的电生理和行为反应。【结果】所选化合物在特定浓度下,均能引起云斑天牛成虫较为明显的EAG反应,浓度为100μg/μL时,云斑天牛成虫对所测试的植物挥发物的EAG反应最强,其中未交配雌、雄及已交配雌虫对(Z)-3-己烯-1-醇的EAG反应相对值均为最大,分别达2.35、2.31和2.22。行为反应生测中,(Z)-3-己烯-1-醇对未交配雌、雄虫可产生明显的引诱作用,芳樟醇则对两者具有明显的趋避作用,而已交配雌虫对所有化合物均无明显趋性。【结论】试验结果可为开发对其有效的林间引诱剂提供一定的理论依据。     

一种测定植物挥发物对棉铃虫引诱作用的无选择性风洞嗅觉仪(英文)

发展了一套测定棉铃虫Helicoverpaarmigera (H櫣ｂｎｅｒ)对植物挥发物的行为反应的生测系统。这套系统由嗅觉仪、风洞和风洞室组成。用这套系统测定了棉铃虫对萎蔫后的枫杨Pterocaryastenoptera叶、加拿大杨Populuscanadensis叶、香椿Toonasisnensis叶、新鲜的芹菜与胡萝卜花挥发物以及苯乙醛的行为反应。结果显示 ,萎蔫的枫杨叶、加拿大杨叶、香椿叶的挥发物均对棉铃虫处女雌蛾表现出显著的引诱作用 ,而对已交配过的雌蛾和雄蛾无明显的引诱作用 ;新鲜的芹菜与胡萝卜花挥发物对棉铃虫两性性成虫均不表现出显著的引诱作用 ;苯乙醛对棉铃虫处女雌、雄蛾有较强的引诱作用。讨论了杨树枝把引诱棉铃虫的原因。     

甘薯蚁象对不同甘薯品种植物挥发物的EAG和嗅觉反应

【目的】为筛选对甘薯蚁象Cylas formicarius(Fabricius)有引诱作用的植物挥发性物质。【方法】采用顶空气体采样法收集5个甘薯品种的植物挥发物,通过气相-质谱联用系统(GC-MS)进行物质鉴定及定量分析,测定甘薯蚁象成虫对候选挥发物的触角电位(EAG)反应和嗅觉趋向选择行为。利用Y型嗅觉仪测定甘薯蚁象成虫对5个甘薯品种茎叶的嗅觉反应。【结果】5种甘薯品种的植物挥发物种类和含量有所差异。7种候选挥发物(罗勒烯、柠檬烯、壬醛、β-石竹烯、葎草烯、法尼烯和乙酸-顺-3-己烯酯)均引起甘薯蚁象雌、雄成虫的EAG反应。其中,雌虫对柠檬烯、壬醛和β-石竹烯的反应相对值较大;而引起雄虫反应相对值较大的挥发物为罗勒烯、柠檬烯、葎草烯。在趋向行为反应中,柠檬烯和壬醛对甘薯蚁象雄虫的吸引作用高于对照,而雌虫对葎草烯、柠檬烯有极显著的趋向选择。甘薯蚁象成虫对5种茎叶的反应率为40.90%~65.21%,且5个甘薯品种的茎叶挥发物均没有显著的引诱作用(P0.05)。【结论】甘薯蚁象雌、雄成虫对甘薯植物挥发物具有不同的EAG及趋向行为反应,气味化合物柠檬烯与甘薯蚁象偏爱选择密切相关。     

华北大黑鳃金龟对桃树挥发物的电生理反应

【目的】华北大黑鳃金龟Holotrichia oblita是一种分布范围广,寄主种类多的农业害虫。本研究鉴定了桃树顶空挥发物中对华北大黑鳃金龟雌虫具有触角电生理活性的化合物,并探索桃树挥发物活性成分的剂量对华北大黑鳃金龟雌、雄虫触角电生理反应的影响。【方法】采用顶空吸附法收集桃树枝叶挥发物,用气相色谱 触角电位联用技术(GC-EAD)和气相色谱 质谱联用技术(GC-MS)鉴定有电生理活性的桃树挥发物成分,最后用触角电位(electroantennograph, EAG)技术测试这些挥发物在0.01,0.1, 1, 10和100 μg剂量下引起的华北大黑鳃金龟雌、雄成虫EAG反应。【结果】桃树挥发物中能引起华北大黑鳃金龟雌成虫触角电生理反应的成分有7种,包括Z-β-罗勒烯、顺-3-己烯乙酸酯、顺-3-己烯醇、壬醛、水杨酸甲酯以及2种未知化合物。所测试的对华北大黑鳃金龟雌成虫触角具有电生理活性的5种桃树挥发物成分在各剂量下都能引起雌、雄成虫明显的EAG反应。雌、雄虫对同种物质的EAG反应随着剂量的增加而有增大的趋势,并且雌虫的EAG反应显著高于雄虫。【结论】桃树挥发物中,罗勒烯、顺-3-己烯乙酸酯、顺-3-己烯醇、壬醛、水杨酸甲酯均能引起华北大黑鳃金龟雌、雄成虫的剂量依赖性的触角电生理反应,而且存在显著的性别差异。可利用这些化合物开展行为反应和田间诱集试验,进一步验证其对华北大黑鳃金龟的引诱活性。     

日龄和交配状态对亚洲玉米螟雄蛾内生殖器特征的影响

【目的】揭示日龄和交配对亚洲玉米螟Ostrinia furnacalis雄蛾内生殖器官的影响,以及亚洲玉米螟雄蛾的交配状态和性信息素诱捕之间的关系。【方法】采用行为学和生殖器解剖技术,研究不同日龄和交配状态亚洲玉米螟雄蛾内生殖器特征,并将其与田间性信息素诱捕雄蛾进行比较。【结果】除了精巢、输精管、储精囊、附腺、复射精管和单射精管外,亚洲玉米螟雄蛾内生殖系统还包含1对附腺囊,同时单射精管非角质化区分为5段(PS1-5),PS1又细分为5区(PS1Ⅰ-Ⅴ)。生殖器内含物可分为5级(0-4级),存在充满和未充满生殖器两种状态。1日龄雄蛾内生殖系统不同器官的内含物等级存在差异,但是日龄对雄蛾生殖系统内含物等级无明显影响。交配后0 h亚洲玉米螟雄蛾,除输精管、储精囊和附腺囊外,其余生殖器官内含物等级较未交配雄蛾的均发生显著变化。随着交配后时间的增加,雄蛾生殖器内含物等级逐渐恢复,各器官内含物等级恢复的速度存在差异,交配后60 h所有内含物等级均恢复到未交配状态。但是直到交配后228 h,交配雄蛾PS5内含物仍然表现出断裂等形态特征,和未交配雄蛾存在差异。性信息素引诱雄蛾中有60.9%的生殖系统表现出未交配雄蛾特征。【结论】利用PS5内含物的形态可以鉴别亚洲玉米螟雄蛾的交配状态,性信息素群集诱杀的亚洲玉米螟雄蛾大部分是未交配。本研究结果为亚洲玉米螟雄蛾交配状态的判定和蛾类害虫性信息素测报和防治的有效性提供了一定依据。     

Delaying corn rootworm resistance to Bt corn

Transgenic crops producing Bacillus thuringiensis (Bt) toxins for insect control have been successful, but their efficacy is reduced when pests evolve resistance. To delay pest resistance to Bt crops, the U.S. Environmental Protection Agency (EPA) has required refuges of host plants that do not produce Bt toxins to promote survival of susceptible pests. Such refuges are expected to be most effective if the Bt plants deliver a dose of toxin high enough to kill nearly all hybrid progeny produced by matings between resistant and susceptible pests. In 2003, the EPA first registered corn, Zea mays L., producing a Bt toxin (Cry3Bb1) that kills western corn rootworm, Diabrotica virgifera virgifera LeConte, one of the most economically important crop pests in the United States. The EPA requires minimum refuges of 20% for Cry3Bb1 corn and 5% for corn producing two Bt toxins active against corn rootworms. We conclude that the current refuge requirements are not adequate, because Bt corn hybrids active against corn rootworms do not meet the high-dose standard, and western corn rootworm has rapidly evolved resistance to Cry3Bb1 corn in the laboratory, greenhouse, and field. Accordingly, we recommend increasing the minimum refuge for Bt corn targeting corn rootworms to 50% for plants producing one toxin active against these pests and to 20% for plants producing two toxins active against these pests. Increasing the minimum refuge percentage can help to delay pest resistance, encourage integrated pest management, and promote more sustainable crop protection.     

Bt corn has a higher lignin content than non-Bt corn

Bt corn has been genetically modified to express the Cry1Ab protein of Bacillus thuringiensis to kill lepidopteran pests. Fluorescence microscopy and staining with toluidine blue indicated a higher content of lignin in the vascular bundle sheaths and in the sclerenchyma cells surrounding the vascular bundle in all ten Bt corn hybrids, representing three different transformation events, studied than of their respective non-Bt isolines. Chemical analysis confirmed that the lignin content of all hybrids of Bt corn, whether grown in a plant growth room or in the field, was significantly higher (33-97% higher) than that of their respective non-Bt isolines. As lignin is a major structural component of plant cells, modifications in lignin content may have ecological implications.     

Extruding foams from corn starch acetate and native corn starch

Because of the hydrophilic characteristics of native starch foams and the cost of modifying starch, the uses of starch and modified starch foams are hindered. To decrease hydrophilicity and cost of starch foams, native corn starch was blended with starch acetate and extruded. A twin-screw mixing extruder was used to produce the foams. Native starch content, screw speed, and barrel temperature had significant effects on molecular degradation of starches during extrusion. The melting temperature of extruded starch acetate/native starch foam was higher (216 degrees C) than that for starch acetate (193.4 degrees C). Strong peaks in the X-ray diffractograms of extruded starch acetate/native starch foam suggested new crystalline regions were formed. Optimum conditions for high radial expansion ratio, high compressibility, low specific mechanical energy requirement, and low water absorption index were 46.0% native starch content, 163 rpm screw speed, and 148 degrees C barrel temperature.     

Insecticidal proteins from Bacillus thuringiensis protect corn from corn rootworms.

Field tests of corn co-expressing two new delta-endotoxins from Bacillus thuringiensis (Bt) have demonstrated protection from root damage by western corn rootworm (Diabrotica virgifera virgifera LeConte). The level of protection exceeds that provided by chemical insecticides. In the bacterium, these proteins form crystals during the sporulation phase of the growth cycle, are encoded by a single operon, and have molecular masses of 14 kDa and 44 kDa. Corn rootworm larvae fed on corn roots expressing the proteins showed histopathological symptoms in the midgut epithelium.     

Management of corn leafhopper (Homoptera: Cicadellidae) and corn stunt disease in sweet corn using reflective mulch

Plastic reflective mulches significantly reduced populations of corn leafhopper, Dalbulus maidis (DeLong & Wolcott), adults and the incidence of corn stunt disease caused by Spiroplasma kunkelii (CSS) in late planted sweet corn (Zea mays L.). The reflective mulches were more effective than were either foliar or soil applied insecticides in managing both the leafhopper and the pathogen it transmits. Yields of marketable ears were 1.5 to 2 times greater in reflective mulch plots than from fallow plots. This was due to larger ears (individual ear weight and length) rather than an increase in the number of ears. The use of reflective mulches provides an alternative strategy to insecticides in the management of both D. maidis and corn stunt disease. Such a strategy may prove useful to growers in Latin America and to limited resource growers and organic growers in the United States who wish to grow corn without the use of insecticides.     

Incidence and levels of fumonisin contamination in Colombian corn and corn products

A survey was conducted to determine the levels of fumonisins B1 and B2 in corn and corn-based products available in Colombia for human and animal consumption. A total of 120 samples were analyzed by acetonitrile-water extraction, cleanup with a strong-anion-exchange column, and liquid chromatography with o-phthaldialdehyde-2-mercaptoethanol derivatization and fluorescence detection. The samples of corn and corn-based products for animal intake were taken at different feed manufacturing plants, whereas the samples used for human foods where purchased from local retail stores. The number of positive samples for fumonisin B1 was 20.0% higher in corn and corn-based products for animal intake (75.0%) than in corn and corn-based products for human consumption (55.0%). The levels of fumonisin B1 were also higher in corn and corn-based products for animal intake (mean = 694 μg/kg; range = 32–2964 μg/kg), than in corn and corn-based products for human intake (mean = 218 μg/kg; range = 24–2170 μg/ kg). The incidence and levels of fumonisin B2 were lower than those for fumonisin B1. Corn and corn-based products for animal consumption had an incidence of fumonisin B2 of 58.3%, with a mean value of 283 μg/kg, and a range of 44–987 μg/kg. The incidence of fumonisin B2 in corn-based products for human intake was 35.0%, with a mean value of 118 μg/kg and a range of 21–833 μg/kg. The highest incidence and levels of fumonisins were found in samples of hominy feed, with concentrations ranging from 86 to 2964 μg/kg fumonisin B1 and 57 to 987 μg/kg fumonisin B2.