钙肥对葡萄根瘤蚜生长发育和繁殖的影响

【目的】为明确葡萄所需的大量元素钙对葡萄根瘤蚜 Daktulosphaira vitifoliae(Fitch）生长发育和繁殖的影响。【方法】在温室中,设置不同 Ca⁽²⁺⁾浓度（0、2 和 4mmol·L(2+)浓度（0、2 和 4mmol·L^(-1)）的钙全营养液于葡萄全生育期浇灌葡萄,评价离体根段对葡萄根瘤蚜的存活率、若蚜、成蚜寿命和繁殖力的影响。【结果】随着钙离子浓度的增加,葡萄根瘤蚜在葡萄根上的 1 龄若蚜历期缩短 0.80 倍以上,成蚜历期增加超过 1.88倍,寿命显著延长超过 1.18 倍,产卵量提高 3.34 倍以上。与 0 mmol·L(-1)）的钙全营养液于葡萄全生育期浇灌葡萄,评价离体根段对葡萄根瘤蚜的存活率、若蚜、成蚜寿命和繁殖力的影响。【结果】随着钙离子浓度的增加,葡萄根瘤蚜在葡萄根上的 1 龄若蚜历期缩短 0.80 倍以上,成蚜历期增加超过 1.88倍,寿命显著延长超过 1.18 倍,产卵量提高 3.34 倍以上。与 0 mmol·L^(-1) Ca(-1) Ca⁽²⁺⁾和 2 mmol·L(2+)和 2 mmol·L^(-1) Ca(-1) Ca⁽²⁺⁾处理相比,葡萄根瘤蚜在 4 mmol·L(2+)处理相比,葡萄根瘤蚜在 4 mmol·L^(-1) Ca(-1) Ca⁽²⁺⁾处理下的葡萄根上,内禀增长率 r_m、周限增长率 λ 和净增殖率 R_0均最高,分别为（0.191 ± 0.003）、（1.210 ± 0.004）和（169.070 ± 11.897)(P < 0.05）,且世代发育历期显著缩短（P <0.05）。特定年龄龄期存活率 S_(xj)、种群特定年龄繁殖力 m_x和种群特定年龄繁殖值 l_xm_x在 4mmol·L(2+)处理下的葡萄根上,内禀增长率 r_m、周限增长率 λ 和净增殖率 R_0均最高,分别为（0.191 ± 0.003）、（1.210 ± 0.004）和（169.070 ± 11.897)(P < 0.05）,且世代发育历期显著缩短（P <0.05）。特定年龄龄期存活率 S_(xj)、种群特定年龄繁殖力 m_x和种群特定年龄繁殖值 l_xm_x在 4mmol·L^(-1)Ca(-1)Ca⁽²⁺⁾处理种群中保持较高水平,随着钙浓度降低,葡萄根瘤蚜的各生命参数明显降低。【结论】钙元素对葡萄根瘤蚜的生长发育和繁殖能力具有促进作用,葡萄根瘤蚜发生葡萄园更应合理使用钙肥。     

棉蚜人工饲料配方筛选及蔗糖浓度优化研究

【目的】棉蚜Aphis gossypii是一种重要的农业害虫,筛选并优化出适用于棉蚜饲养的人工饲料,有助于开展棉蚜生物学和生态学研究。【方法】在不同蚜虫人工饲料配方基础上,将饲料pH值和蔗糖浓度分别调整为7.6和25%,设计了以氨基酸、维生素、无机盐和蔗糖等为营养基础的5种人工饲料（配方Ⅰ、Ⅱ、Ⅲ、Ⅳ、Ⅴ）。通过比较棉蚜成蚜在这5种饲料上的存活率和繁殖力,筛选出适合棉蚜饲养的最佳饲料配方。将最佳饲料配方蔗糖浓度调整为30%（配方VI）,比较了棉蚜在蔗糖浓度25%和30%两个配方、棉花植株上的存活率、若蚜发育历期、产仔率、平均产蚜量和寿命,及不同棉蚜试验种群的生命表参数。【结果】取食配方Ⅴ饲料的棉蚜成蚜存活率和产蚜量最高。棉蚜在配方V与配方VI人工饲料上均能完成世代发育,成蚜产仔率可达到100%。人工饲料配方V、VI和棉花植株饲养的棉蚜寿命分别为15.39、13.52和20.29 d,平均产蚜量分别为16.99、16.85和26.73头,内禀增长率分别为0.24、0.23和0.29。【结论】综合所有参数比较及本着节约成本的原则,筛选的人工饲料配方Ⅴ（含25%蔗糖）更适用于棉蚜饲养。     

高CO_2浓度对两种色型豌豆蚜体内营养物质含量及消化酶活性的影响

【目的】明确红、绿两种色型豌豆蚜Acyrthosiphon pisum(Harris)对大气CO_2浓度升高响应的生理机制。【方法】通过CO_2人工气候箱,设置中等浓度(550±27μL/L)和高浓度(750±37μL/L)CO_2浓度,并以当前浓度(375±18μL/L)为对照。在设置以上CO_2浓度的人工气候箱种植蚕豆苗并接入6 h以内的豌豆蚜初产若蚜,记录各虫态的蜕皮和存活情况直至羽化。测定连续3代饲养在蚕豆上的红、绿两种色型豌豆蚜体内营养物质含量和消化酶活力,同时测定蚕豆叶片组织营养物质含量。【结果】大气CO_2浓度升高可显著增加蚕豆叶片内可溶性蛋白、可溶性糖、游离氨基酸和淀粉含量。中等CO_2浓度(550±27μL/L)条件下,F0代两种色型豌豆蚜体内营养物质含量较对照均无显著变化,F_2代蛋白质、总氨基酸、可溶性糖和糖原含量较对照均显著增加,总脂肪和游离脂肪酸含量较对照显著降低,且F_2代绿色型豌豆蚜体内可溶性糖含量显著高于红色型的。高CO_2浓度(750±37μL/L)条件下,3世代两种色型豌豆蚜体内蛋白质、总氨基酸、可溶性糖和糖原含量均显著高于对照,总脂肪和游离脂肪酸含量显著低于对照。其中,F1和F_2代绿色型豌豆蚜体内蛋白质、总氨基酸、可溶性糖和糖原含量显著高于红色型的。CO_2浓度(550±27和750±37μL/L)升高条件下,F0代两种色型豌豆蚜体内消化酶活力较对照无显著变化,F_2代胃蛋白酶和胰蛋白酶活力较对照显著降低,脂肪酶和淀粉酶活力显著升高,3世代两色型间消化酶活力均无显著差异。【结论】高CO_2浓度下,蚕豆叶片组织营养物质含量发生改变从而引起以之为食的豌豆蚜体内营养物质含量与消化酶活力的变化,且绿色型豌豆蚜体内蛋白质、总氨基酸、可溶性糖和糖原含量的变化大于红色型豌豆蚜的,这对未来大气CO_2浓度升高的环境下豆科植物主要害虫豌豆蚜的防治具有参考价值。     

光周期和温度对桃小食心虫越冬幼虫出土及病菌感染的影响

【目的】桃小食心虫Carposina sasakii Matsumura越冬代是田间防治的重点,明确光周期和温度对越冬幼虫出土的影响,对桃小食心虫预测预报和综合防治具有重要意义。【方法】在实验室条件下,设置不同光周期和温度组合,每天记录桃小食心虫越冬幼虫的出土数量、病菌感染率。【结果】桃小食心虫越冬幼虫出土时间差异很大,最短20 d,最长可达116 d,且出土时间分散。温度对桃小食心虫越冬幼虫的出土率有显著影响(2011,df=3,F=9.9,P<0.05;2012,df=3,F=5.519,P<0.05),试验光周期对其出土率无显著影响(2011,df=2,F=0.577,P>0.05;2012,df=2,F=9.9,P>0.05),桃小食心虫在不同温度下出土规律不同。桃小食心虫越冬幼虫白僵菌感染率随着温度升高而显著提高(2011,df=3,F=65.713,P<0.05;2012,df=3,F=29.198,P<0.05),细菌感染率随着温度升高而显著降低(2011,df=3,F=28.705,P<0.05;2012,df=3,F=38.97,P<0.05)。【结论】桃小食心虫越冬代幼虫出土持续时间长,出土时间分散,温度对其出土率及病菌感染率有显著影响。     

烟草钾营养对Q型烟粉虱发育、存活和寄主选择性的影响

【目的】明确烟草钾营养对Q型烟粉虱Q-biotype Bemisia tabaci(Gennadius)的寄主选择性、发育和存活的影响,旨在为通过调节寄主植物营养控制Q型烟粉虱种群数量提供理论依据。【方法】水培法培养经K1(0 mmol/L)、K2(3 mmol/L)、K3(6 mmol/L)、K4(9 mmol/L)及K5(12 mmol/L)5个不同钾浓度处理的烟草,研究Q型烟粉虱在不同处理烟草上的寄主选择性、发育历期和存活率。【结果】Q型烟粉虱在不同钾浓度处理烟草上的寄主选择性、发育历期和存活率均有显著差异,取食和产卵偏好性顺序为K2>K1>K3>K4>K5,卵到成虫羽化发育历期顺序为K5(22.54 d)>K4(2 1.96 d)>K1(20.92 d)>K2(20.32 d)>K3(20.23 d),卵到成虫羽化存活率顺序为K3(88.72%)>K2(85.05%)>K1(82.03%)>K4(77.02%)>K5(69.92%)。【结论】可以通过调节钾营养来控制Q型烟粉虱在烟草上的种群数量。     

正交实验优化小菜蛾室内种群的繁殖条件

【目的】明确小菜蛾Plutella xylostella室内种群扩繁时的寄主植物、成虫密度等因子的影响作用。【方法】采用=正交实验设计,分析了成虫接虫量、寄主植物和寄主叶龄等因素对小菜蛾子代扩繁倍数的影响。【结果】(1)接虫量、寄主对小菜蛾的繁殖量有极显著的影响(P<0.01)。寄主叶龄对小菜蛾的繁殖量有显著的影响(P<0.05)。根据各因素的F值大小,可确定对扩繁量的影响作用顺序为接虫量(F=24.11,P=0.001)>寄主(F=14.21,P=0.004)>生育期(F=7.40,P=0.019)。(2)各因素配对分析结果表明:1对/株的繁殖倍数与3对/株、4对/株的繁殖倍数存在极显著差异(P<0.01),与2对/株的繁殖倍数存在显著差异(P<0.05)。2对/株的繁殖倍数与3对/株、4对/株的繁殖倍数存在极显著差异(P<0.01)。甘蓝寄主上的繁殖倍数与白菜、菜心、花椰菜上的繁殖倍数均存在极显著差异(P<0.01),而白菜、菜心、花椰菜上的繁殖倍数三者间均无显著差异(P>0.05)。6叶龄时繁殖倍数与10叶期的繁殖倍数存在极显著差异(P<0.01),与4叶期、8叶期的繁殖倍数存在显著差异(P<0.05)。而10叶期、4叶期、8叶期的繁殖倍数3者间均无显著差异(P>0.05)。【结论】室内种群的最适合扩繁条件是接虫量1对/株,寄主植物为甘蓝,生育期为6叶龄。     

麦长管蚜对E-β-法尼烯的嗅觉行为反应

【目的】测定麦长管蚜Sitobion avenae Fabricius对E-β-法尼烯(E-β-farnesene,EβF)矿物油溶液反应的最低阈值浓度,为EβF的田间应用提供依据。【方法】观察麦长管蚜3龄若蚜对不同浓度EβF的逃逸行为和"Y"型管嗅觉行为反应。每天定时分5次(9:00,11:30,14:00,16:30和19:00)滴加10μL EβF于滤纸上,滤纸用牙签固定于麦苗盆中心,持续处理5 d。每盆麦苗处理前接1龄若蚜15头。记录成蚜翅型及2周后蚜虫总数量。【结果】随着EβF浓度升高,麦长管蚜3龄若蚜3 min内逃离数显著增加,有翅蚜比例显著增加,种群个体数量显著下降,驱避效果明显增强。EβF浓度为200 ng/μL和≥600 ng/μL使蚜虫逃离数显著增加(P0.05)。"Y"型管选择行为测试结果表明,EβF≥600 ng/μL对3龄若蚜具有极显著的驱避作用(P0.01)。与对照相比,EβF≥600 ng/μL处理极显著提高了有翅蚜比例(P0.01);EβF≥400 ng/μL极显著抑制蚜虫种群个体数量增长(P0.01),但与600 ng/μL处理差异不显著。【结论】600 ng/μL EβF矿物油溶液为麦长管蚜驱避剂的最低阈值浓度。     

链脲佐菌素诱导C57BL/6J小鼠2型糖尿病模型研究

目的建立与2型糖尿病(非胰岛素依赖型糠尿病、NIDDM)病人临床特征和发病过程相似的NIDDM动物模型.方法用高脂肪饲料喂养C57BL/6J雄性断乳小鼠3周,腹腔注射链脲佐菌素(STZ),继续喂养4周,测定给药前和给药后1、3、4周非空腹血糖、实验结束时非空腹胰岛素水平,观察胰腺形态学变化.结果喂养3周后(给药前)高脂饲料-STZ组及高脂饲料-柠檬酸组血糖浓度(7.0±0.39)mmol/L、( 6.8±0.45)mmol/L高于普通饲料-STZ组及普通饲料-柠檬酸组(5.3±0.40)mmol/L、(5. 4±0.39)mmol/L,P＜0.05;实验结束时,高脂饲料-STZ组血糖浓度(13 .1±2.01)mmo/L高于高脂饲料-柠檬酸(6.9±0.46)mmol/L、普通饲料-柠檬酸组(6.0± 0.46)mmol/L和普通饲料-STZ组(7.1±0.62)mmol/L(P＜0.05),各组间血浆胰岛素浓度、体重及饮水量差异无显著性,P＞0.05;实验过程中高脂饲料STZ组和柠檬酸组小鼠每天进食热量(64.49±9.2)kJ/只,(70.7±9.6)kJ/只, 显著高于普通饲料STZ组和柠檬酸组(52.7±7.9)kJ/只,(57.3±11.7)kJ/只;各组小鼠胰腺和胰岛细胞形态正常.结论高脂肪饲料和STZ是用C57BL/6J断乳幼鼠建立NIDDM模型所必须的,100mg/kg体重STZ对普通饲料小鼠血糖无影响;用高脂饲料和STZ 处理的小鼠血糖升高、胰岛素浓度正常,与NIDM病人临床特征和发病过程相似;C57BL/6J小鼠易得,建模方法简便,费用低,是在NIDDM实验研究中能广泛使用的较理想的非遗传性NID DM动物模型.     

不同寄主上桃粉大尾蚜的取食偏好及形态变异研究

【目的】桃粉大尾蚜Hyalopterus pruni Geoffroy是一种常见的农业害虫,分布广泛。本文对采自上海地区粘核毛桃Amygdalus persica L.var.scleropersica(Reich.)Yüet Lu、紫叶李Prunus cerasifera Ehrhar f.atropurpurea(Jacq.)Rehd.和芦苇Phragmites australis(Cav.)Trin.ex Steud.3种植物上桃粉大尾蚜的取食偏好和形态变异进行了研究。【方法】通过叶碟法观测桃粉大尾蚜对3种寄主叶片的取食偏好,同时测量体长、体宽、触角各节长、喙末端长和宽、各足节长等30个形态指标,基于对形态数据的统计分析,包括主成分分析、聚类分析和判别分析,研究不同寄主植物上桃粉大尾蚜的形态变异。【结果】饲以3种寄主植物叶片时,来自粘核毛桃和芦苇上的桃粉大尾蚜对各寄主叶片的总体喜食程度依次为芦苇>粘核毛桃>紫叶李,来源于紫叶李上的个体对3种叶片的喜食程度为芦苇>粘核毛桃=紫叶李;形态数据分析发现粘核毛桃和紫叶李上的桃粉大尾蚜各指标间均无显著差异(P>0.05),但二者与芦苇上的个体在触角节Ⅱ、触角末节鞭部长、喙末端长和中足胫节的长度间差异显著(P<0.05),紫叶李与芦苇上的个体前足跗节Ⅰ长这一指标差异显著(P<0.05),此外,主成分分析筛选的体长、头宽、触角各节和各足长度等特征构成的前四个主成分对总体方差的累计贡献率达到66.206%,其中贡献率较高的特征为触角和各足节长度,系统聚类和典型判别分析的结果显示采自芦苇上的桃粉大尾蚜区别于粘核毛桃和紫叶李上的,归为一类,同为蔷薇科植物的紫叶李和粘核毛桃上的桃粉大尾蚜克隆有小部分重叠。【结论】禾本科植物上的桃粉大尾蚜种群形态特征与蔷薇科植物上的相比,触角节Ⅱ和末节鞭部、喙末端长、中足胫节的长度存在一定的分化,初步推测造成桃粉大尾蚜形态分化的原因主要为寄主植物营养成分及其表面特征,其种内变异的具体机制仍需进一步探索。     

甲烷菌对厌氧真菌不同碳源代谢的影响

【目的】探讨碳源和甲烷菌对厌氧真菌碳代谢的影响。【方法】利用体外批次厌氧发酵法,比较厌氧真菌纯培养(Orpinomyces sp.和Neocallimastix sp.)及其与甲烷菌共培养(F1:Orpinomyces sp.+Methanobrevibacter sp.和N3:Neocallimastix sp.+Methanobrevibacter sp.)发酵不同类型碳水化合物代谢产物的差异。【结果】对厌氧真菌和甲烷菌共培养F1和N3的研究显示,F1发酵木薯粉[(26.44±0.22)mmol/L]的乳酸产量是发酵玉米芯[(1.31±0.04)mmol/L]的20.18倍,是N3发酵木薯粉[(1.59±0.03)mmol/L]的16.63倍,玉米芯[(0.79±0.08)mmol/L]的33.47倍。当F1和N3中的厌氧真菌纯培养时,各组乳酸产量均1.90 mmol/L。对F1进一步研究,结果显示发酵体系中木薯粉添加量在0.8%–2.0%之间时,乳酸产量随木薯粉添加量增加而增加。当含量在1.0%–2.4%之间时,随木薯粉添加量增加,甲烷和乙酸产量逐渐降低。比较F1发酵大米粉、木薯粉、玉米粉、小麦粉和土豆粉的发酵结果,发现乳酸产量与底物中支链淀粉的含量成正相关(R2=0.9554)。当F1发酵葡萄糖和麦芽糖时,乳酸产量5.00 mmol/L。当以麦芽糊精为底物时,乳酸产量高达(28.00±0.95)mmol/L。【结论】本文首次报道碳源和甲烷菌能够增强厌氧真菌的乳酸代谢途径并且这种增强存在种属特异性。     

Evaluation of artificial diets for rearing Aphis glycines (Hemiptera: Aphididae)

Artificial aphid diets have been previously developed for the pea aphid, Acyrthosiphon pisum (Harris), and the green peach aphid, Myzus persicae (Sulzer). The ability to rear aphids on an artificial diet allows for selectively adding or subtracting compounds from an aphid's food source to determine the effect on fecundity and longevity. Five diets previously developed for the green peach aphid and the pea aphid were tested for their suitability for rearing soybean aphid, Aphis glycines Matsumura. The best diet, originally developed for the green peach aphid and based on the amino acid profile of young potato plants, allowed 12 generations of soybean aphids to develop. For all diets tested, aphid fecundity, and longevity were greatly reduced in comparison with aphids reared on soybean, Glycine max (L.) Merr., plants or on detached soybean leaves. In addition, mean developmental time was significantly longer for aphids reared on artificial diets.     

A Dietary Test of Putative Deleterious Sterols for the Aphid Myzus persicae

The aphid Myzus persicae displays high mortality on tobacco plants bearing a transgene which results in the accumulation of the ketosteroids cholestan-3-one and cholest-4-en-3-one in the phloem sap. To test whether the ketosteroids are the basis of the plant resistance to the aphids, M. persicae were reared on chemically-defined diets with different steroid contents at 0.1–10 µg ml⁻¹. Relative to sterol-free diet and dietary supplements of the two ketosteroids and two phytosterols, dietary cholesterol significantly extended aphid lifespan and increased fecundity at one or more dietary concentrations tested. Median lifespan was 50% lower on the diet supplemented with cholest-4-en-3-one than on the cholesterol-supplemented diet. Aphid feeding rate did not vary significantly across the treatments, indicative of no anti-feedant effect of any sterol/steroid. Aphids reared on diets containing equal amounts of cholesterol and cholest-4-en-3-one showed fecundity equivalent to aphids on diets containing only cholesterol. Aphids were reared on diets that reproduced the relative steroid abundance in the phloem sap of the control and modified tobacco plants, and their performance on the two diet formulations was broadly equivalent. We conclude that, at the concentrations tested, plant ketosteroids support weaker aphid performance than cholesterol, but do not cause acute toxicity to the aphids. In plants, the ketosteroids may act synergistically with plant factors absent from artificial diets but are unlikely to be solely responsible for resistance of modified tobacco plants.     

褐带蚜小蜂产卵器刺入对寄主桃蚜存活、生长发育和繁殖力的影响

[目的]褐带蚜小蜂Aphelinus maculatus是2016年的中国新纪录种,是桃蚜Myzus persicae的重要寄生蜂之一.为科学评估褐带蚜小蜂对桃蚜的控制作用,研究了褐带蚜小蜂产卵器刺入对寄主桃蚜存活、生长发育和繁殖力的影响.[方法]培养皿中用油菜叶单头饲养、每天记录被褐带蚜小蜂产卵器刺入1次的桃蚜存活数...     

Antibiosis and antixenosis of six commonly produced potato cultivars to the green peach aphid, Myzus persicae Sulzer (Hemiptera: Aphididae)

The antibiotic and antixenotic resistance of six commonly produced potato cultivars in Iran including Aozonia, Agria, Cosima, Cosmos, Kondor and Savalan to the green peach aphid, Myzus persicae Sulzer, were investigated under laboratory conditions at 20 ± 2oC, 65 ± 5% RH and 16:8h (L:D) in 2009. Antibiosis experiments showed significant differences in the developmental time, nymphal survivorship, fecundity, adult longevity of the green peach aphid among the potato cultivars. Intrinsic rate of natural increase (r m) for apterous aphids varied significantly with the potato cultivars on which the aphids were reared. This value ranged from 0.225 to 0.293 females/female/day, which was lowest on Cosmos and highest on Aozonia. Additionally, the estimated net reproductive rate (R0) and finite rate of increase (λ) for apterous aphids were the lowest on Cosmos. For the antixenosis experiment, no significant difference was found in aphid's preference to the potato cultivars. However, Aozonia was preferred more than the other five cultivars by the apterous aphids. Therefore, our results demonstrated that among the investigated cultivars the Cosmos cultivar is moderately resistant to the green peach aphid.     

Performance of Myzus persicae (Hemiptera: Aphididae) clones on different host-plants and their host preference

The performance of eighteen clones of Myzus persicae (Sulzer) on pepper and tobacco plants at 20 degrees C and L16:D8 and the choice of young adult apterae between tobacco and pepper leaf-discs were examined. The clones were collected from weeds and peach in two tobacco-growing regions: Katerini, northern Greece and Karditsa, central Greece (only from weeds) and from Lehonia, central eastern Greece where tobacco is not cultivated. All clones did well on both hosts. However, the analysis of data revealed a significant effect of "region / host plant origin" on aphid performance. The mean values of adult weight, intrinsic rate of increase and fecundity of the clones collected in Lehonia and reared on tobacco were significantly lower than the observed values for clones from Katerini and Karditsa. Aphids from Lehonia had significantly higher mean values for developmental time on tobacco than clones from the other regions whereas the opposite was observed when aphids were reared on pepper. Aphids collected in Lehonia performed better on pepper than those originating from the tobacco-growing regions. A choice test revealed differences among the clones originating from different regions. Fifty three percent and 43% of aphids from weeds and peach from Lehonia, respectively, chose pepper. By comparison 41.5% and 40.0% of aphids from peach and weeds from Katerini, respectively and 49.5% of aphids from Karditsa preferred tobacco. The results are discussed in relation to host specialization in M. persicae.     

Life history traits of Aphis gossypii Glover (Hom., Aphididae) reared on four widely distributed weeds

Variation in the life history traits of cotton aphids, Aphis gossypii Glover, reared on four widely distributed weeds, Ageratum houstonianum Mill., Bidens pilosa L. var. radiata Sch. Bip., Solanum nigrum L. and Spermacoce latifolia Aubl., were investigated. Cotton aphids were reared in the laboratory at 25°C. Each host plant had a distinct effect on aphid life history traits. Cotton aphids reared on S. nigrum had a significantly shorter developmental period, and age-specific fecundity peaked early. In contrast, cotton aphids reared on S. latifolia had a long developmental period and low age-specific fecundity. Cotton aphids that fed on B. pilosa and A. houstonianum displayed intermediate rates of growth and age-specific fecundity. Because the curves of age-specific fecundity ( m_x ) and age-specific net maternity ( l_x  m _x ) on each host plant were close together, development time and the pattern of age-specific fecundity were the major factors determining the population growth potential of the cotton aphid on each weed. As a result, the intrinsic rate of population growth for aphids reared on S. nigrum was significantly higher ( r_m =0.527 ± 0.011) than it was for aphids reared on S. latifolia ( r_m =0.194 ± 0.012).     

Effect of a fungal lectin from Xerocomus chrysenteron (XCL) on the biological parameters of aphids

Aphids are important pests of crop plants in Europe. Increasing resistance of aphids to insecticides and their side effects on the environment and non target organism's including human's stimulated research on alterative methods of aphid control, including the use of entomotoxic proteins. Lectins are carbohydrate binding proteins that are widely distributed in nature; they have been isolated from microorganisms, fungi, plants and animals. Several of these proteins were tested for their potential biocide effect on plenty of pests. A fungal lectin, namely Xerocomus Chrysenteron lectin (XCL) was previously purified and was shown to be toxic for several pests including aphids. XCL was clearly the most toxic lectin against M. persicae. In this work, bioassays using artificial diets incorporating a broad range of XCL concentrations (from 10 microg x ml(-1) to 5000 microg x ml(-1)) were developed to assess the negative effects of XCL on the biological parameters (development duration, weight and fecundity) of M. persicae a polyphagous aphid found on more than 400 host plant species and transmitting more than 100 viral diseases. A significant mortality of aphids was observed, corresponding to the LC50 and LC90 of 0, 46 and 6, 02 mg/ml respectively after 24hrs. Significant differences of M. persicae weight, development duration and fecundity (P < 0.05) was observed between the tested XCL concentrations. Conavalia ensifomris lectin (ConA) was included as lectin reference on the bioassay experiments and was shown to be less toxic and induced lower negative changes in M. persicae biological parameters when compared with XCL.     

A reappraisal of sterol biosynthesis and metabolism in aphids

Aphids of Schizaphis graminum (Rondani) (biotype C) reared on its host-plant, Sorghum bicolor (L.) Moench, sequestered campesterol, stigmasterol and sitosterol. Aphids reared for 72 hr on holidic diets supplemented with [4-¹⁴C]-sitosterol contained both [¹⁴C]-sitosterol and [¹⁴C]-cholesterol, indicating that these aphids are capable of dealkylation at C-24. When aphids were reared on artificial diets containing [2-¹⁴C]-mevalonic acid, no detectable amounts of radioactively labelled desmethyl sterols, nor metabolic intermediates in sterol synthesis (i.e. squalene, 2,3-oxidosqualene, 4,4-dimethyl and 4-monomethyl sterols) were found to accumulate in their tissues. The relevance of these findings to previous research suggesting the ability of aphids, via their symbiotes, to synthesize sterols is discussed.     

Survival, growth, and reproduction of two aphid species on sucrose solutions containing host or non-host honeydews

Aphids, like most phloem-feeding insects, commonly exhibit a high degree of host specificity. Plant-specific chemical compounds are likely to serve as important host selection cues for monophagous aphids and such substances could be present in aphid honeydew. Apterous virginoparae ofMyzus persicae (Sulzer) andPhorodon humuli (Schrank) were reared on a buffered sucrose solution containing various aphid honeydews or a mixture of amino acids. In two separate experiments, the host-specificP. humuli (hop aphid) could grow and reproduce only on diets containing honeydew collected from hop (Humulus lupulus L.).M. persicae (the green peach aphid, GPA) did not perform well on diets containing hop honeydew, perhaps because hop is a poor GPA host. Honeydew collected from preferred GPA host plants rape,Brassica napus L., and jimsonweed,Datura stramonium L., allowed GPA growth and reproduction. Hop aphids, however, performed poorly on rape and jimsonweed honeydew diets. Bell pepper,Capsicum annuum L., honeydew supported neither the hop aphid nor GPA. The study of aphid honeydew components may contribute towards a more complete understanding of host preference and selection phenomena in aphids.     

A functional genomics approach identifies candidate effectors from the aphid species Myzus persicae (green peach aphid)

Aphids are amongst the most devastating sap-feeding insects of plants. Like most plant parasites, aphids require intimate associations with their host plants to gain access to nutrients. Aphid feeding induces responses such as clogging of phloem sieve elements and callose formation, which are suppressed by unknown molecules, probably proteins, in aphid saliva. Therefore, it is likely that aphids, like plant pathogens, deliver proteins (effectors) inside their hosts to modulate host cell processes, suppress plant defenses, and promote infestation. We exploited publicly available aphid salivary gland expressed sequence tags (ESTs) to apply a functional genomics approach for identification of candidate effectors from Myzus persicae (green peach aphid), based on common features of plant pathogen effectors. A total of 48 effector candidates were identified, cloned, and subjected to transient overexpression in Nicotiana benthamiana to assay for elicitation of a phenotype, suppression of the Pathogen-Associated Molecular Pattern (PAMP)-mediated oxidative burst, and effects on aphid reproductive performance. We identified one candidate effector, Mp10, which specifically induced chlorosis and local cell death in N. benthamiana and conferred avirulence to recombinant Potato virus X (PVX) expressing Mp10, PVX-Mp10, in N. tabacum, indicating that this protein may trigger plant defenses. The ubiquitin-ligase associated protein SGT1 was required for the Mp10-mediated chlorosis response in N. benthamiana. Mp10 also suppressed the oxidative burst induced by flg22, but not by chitin. Aphid fecundity assays revealed that in planta overexpression of Mp10 and Mp42 reduced aphid fecundity, whereas another effector candidate, MpC002, enhanced aphid fecundity. Thus, these results suggest that, although Mp10 suppresses flg22-triggered immunity, it triggers a defense response, resulting in an overall decrease in aphid performance in the fecundity assays. Overall, we identified aphid salivary proteins that share features with plant pathogen effectors and therefore may function as aphid effectors by perturbing host cellular processes.