ACOMPARATIVE STUDY ON THE ELECTROANTENOGRAM RESPONSES OF THREE APHID SPECIES TO PLANT VOLATILES

Abstract  Electroantennogram responses (EAGs) to 39 plant volatiles from Aphis glycines, A. gossypii and Myzus persicae were recorded. The olfactory system of these three aphid species differentially responded to green leaf, aromatic, mono-and sequiterpene chemicals. The EAG depolarizatin to green leaf chemicals and their isomers were more pronounced than to terpenes, alcohols and aldehydes, 6 carbon atom compounds being the most effective. It was shown that there was certain difference in the olfactory spectra of these three aphid species to plant volatiles. Higher responses in A. glycines and A. gossypii were elicited by the leaf aldehydes and esters than by the corresponding alcohols, which are in contrast with those in M. persicue . The activity of aphid olfactory system was related to molecular structures of the compounds. The responses to saturated alcohols and aldehydes were higher than those to unsaturated. The responses of spring emigrants of A. glycines to terpene derivatives (alcohols, aldehydes and esters) were higher than those of A. gossypii , but were lower to terpene hydrocarbons. The dissimilarity in olfactory spectra of the aphid species reflected the evolution of their host plant selection specificity. In the evolution, their chemosensory system adapted to perceive host plants. The shapes of the EAGs evoked by the various components were consistently different, with the slowest recovery for geraniol, 1-decanol and (±)-β-cit-ronellol, and ware related to number of carbon atoms in straight chain saturated alcohols.     

Alatae production and population increase of aphid vectors on virus-infected host plants

Summary Zucchini yellow mosaic virus (ZYMV) and Aphis gossypii Glover are two components of a recently identified plant-parasite system that provides an excellent opportunity to study interrelations between a virus and a vector that share the same host, but have no direct physiological interaction. In a field experiment we documented numbers of alate and apterous A. gossypii on healthy Cucurbita pepo and on plants inoculated with virus 0, 7, 14, and 21 days before aphid infestation. When plants were inoculated and infested simultaneously, more than twice as many alatae were produced after 20 days of colony growth than on any other treatment. This indicates that properties unique to the early stages of viral infection somehow stimulated wing formation. Because it is spread by the activities of alatae, virus dispersal would be greater as a result of these properties. Developmental rate, total numbers of aphids, and numbers of alatae and apterae decreased as the time between virus inoculation and aphid colonization increased.     

蓝光照射对黄瓜无翅瓜蚜驱避行为的影响

蓝光照射可以降低黄瓜Cucumis sativus上蚜虫的种群密度,但蓝光照射后无翅蚜虫是如何被驱离的尚未见报道。本文以盆栽黄瓜为供试材料,研究蓝光照射对黄瓜上无翅瓜蚜Aphis gossypii驱避行为的影响。结果表明,蓝光照射对设施黄瓜上的无翅蚜有较强的驱避作用,光照强度越大、照射时间越长,黄瓜上蚜虫的虫口减退率越大。蓝光照射后无翅蚜主要通过黄瓜主茎离开黄瓜向花盆的土下迁移,少部分蚜虫还可以顺着花盆向盆外迁移。光强越强,相同时间内迁离黄瓜的蚜虫越多。300 lux蓝光照射10 h后,蚜虫种群的校正虫口减退率达到64.03%。相同的蓝光光强和照射时间下,晚间蓝光照射处理后蚜虫的迁移数量多于白天。地面黄光环境对蓝光驱避黄瓜蚜虫具有较强的促进作用,盆外放置黄板,迁向盆外的蚜虫量增加。黄光点亮30 min后关闭,同时打开蓝光可以提高蓝光对蚜虫驱避作用。因此,蓝光照射可以驱离黄瓜上的无翅蚜,驱离的无翅蚜主要迁移到盆内土中,少量的可以迁出花盆。     

Quantifying spatial correlations in extinction risk for an aphid metapopulation

Metapopulation persistence depends on dispersal offsetting local extinction risks. The mitigating power of dispersal to offset local extinction risks is substantially reduced if extinction risks are highly spatially correlated. Extinction risks are likely to be spatially correlated when mechanisms driving local extinction act on large spatial scales, such as climatic events or far-ranging predators. In this paper I develop a method to quantify spatial correlations in local extinction risks within a region. I then show that colonies of the aphid Aphis lugentis within clusters of their host plant, Senecio bigelovii, do not have strong spatial correlations in extinction risks, even though the primary mechanism for colony extinction is over-predation by far-ranging predators (ladybugs and syrphid flies). Consequently, dispersal potentially plays an important role offsetting local extinction. Aphids did experience a weak, but significantly positive correlation in extinction risk in one of the two years of this study as well as increasing extinction risks across all plant clusters in both years. These observations point to important gaps in our understanding of how population synchrony affects metapopulation persistence.     

Temperature-dependent life attributes of an aphidophagous ladybird, Propylea dissecta

Reproductive attributes, age-specific fecundity and natality based life-tables of an aphidophagous ladybird, Propylea dissecta (Mulsant) were investigated at five temperatures, using aphid, Aphis gossypii as prey. Pre-oviposition period decreased significantly with increase in temperature up to 27°C and thereafter increased at a slower rate. Egg viability dropped significantly at temperature extremes. Females lived longer than males; however, longevity decreased significantly with increase in temperature. The predicted total fecundity and oviposition rate were 952.54 eggs and 35.15 eggs per day at 27°C predicted by a mathematical model compared to empirical estimates of 856.00±30.00 eggs and 39.7±2.26 eggs per day. Age-specific fecundity was triangular and temperature dependent. The peak in oviposition rate occurred earlier at higher temperatures. The highest values of net reproductive rate (R_o=431.1), intrinsic rate of increase (r_m=0.2134 day^-1) and finite rate of increase (λ=1.2379 day^-1) were recorded at 27°C, which suggests it is the optimum temperature for the mass rearing of P. dissecta.     

Above‐ and Belowground Trophic Interactions on Creeping Thistle (Cirsium arvense) in High‐ and Low‐Diversity Plant Communities: Potential for Biotic Resistance?

The capacity of local communities to control introduced plants is called biotic resistance. Biotic resistance has been almost exclusively tested for plant competition and above ground herbivores and pathogens, while neglecting root herbivores and soil pathogens. Here, we present biotic resistance by above- and below ground herbivores in concert, and relate the abundance of the plant enemies to the species diversity of the local plant communities. The study was carried out in a 7-year-old biodiversity field experiment. We used creeping thistle (Cirsium arvense) as a model, and quantified sap-sucking herbivores: above ground aphids, their antagonists, and root-feeding nematodes. As plant diversity treatments, we used field plots sown with high (15 plant species, HSD) or low (4 plant species, LSD) diverse seed mixtures in 1996 and that were not weeded. Creeping thistle became established spontaneously at the start of the experiment. In 2002, in HSD plots, 90 % of the plant community was made up by 11 species, compared to seven species in LSD plots. No differences were found for C. arvense abundance or biomass. Above ground, three aphid species were found on C. arvense-Uroleucon cirsii, Aphis fabae, and Macrosiphum euphorbiae, but the latter was found only in low densities. Significantly more aphid species were found on individual plants in HSD plots. Moreover, in HSD plots, on average 10 % of aphids were parasitized, while no parasitism was observed in LSD plots. In the root zone of C. arvense, significantly more nematodes were found in HSD than in LSD plots, and a significantly higher proportion of those nematodes were plant parasites. The dominant plant parasitic nematode in both treatments was Paratylenchus. We conclude that biotic resistance by natural enemies may be enhanced by plant species diversity, but that above- and below ground sap-sucking herbivores do not necessarily have to respond similarly to the diversity of the surrounding plant community.     

植物挥发性物质对蚜虫性信息素诱蚜效果的影响(英文)

本研究首先是在不同的寄主植物中利用蚜虫性信息素进行田间诱蚜实验。结果表明寄主植物影响性信息素田间诱蚜的种类和效果。在桃园 ,以蚜虫性信息素荆芥内酯和荆芥醇为性诱剂的水盆诱捕器 ,诱到 3种蚜虫的雄蚜 ,分别是桃蚜、桃粉大尾蚜和莲缢管蚜。其中 ,桃蚜占绝大多数 ,且还被性信息素的单一组分植物提取的荆芥内酯所吸引。麦田中诱到的雄蚜为麦二叉蚜。苹果园中诱到的雄蚜是绣线菊蚜和梨中华圆尾蚜 ,且性信息素诱捕器中的数目远多于对照诱捕器。据田间诱蚜实验结果推测 ,荆芥内酯和荆芥醇对桃粉大尾蚜有吸引作用 ,荆芥内酯可能是绣线菊蚜和梨中华圆尾蚜性信息素的一个组分。另外进行的田间实验表明寄主植物挥发性物质对蚜虫性信息素诱蚜效果有影响 ,当荆芥内酯诱捕器同时释放桃叶挥发物时 ,诱到的桃蚜雄蚜数量明显增加。触角电位记录实验也表明桃蚜雄蚜对桃叶挥发物和桃芽挥发物有反应。     

棉花型和瓜型棉蚜形态和生态适应力的分化

棉蚜由于长期在同种或同类植物上生活,形成了多种寄主专化型。本研究以室内长期用单一寄主培养的棉花型和瓜型棉蚜为材料,采用形态测定、生命表技术、对寄主的选择性试验,以及接触刺激等方法,研究了两寄主型棉蚜的形态分化和生态适应力的差异。结果表明,瓜型棉蚜的一些形态特征值（如体长）极显著地大于棉花型个体,但是头宽、口针和各腿节的长度与体长的比值却极显著的小于棉花型个体。采用7个形态指标与体长的比值,可将瓜型和棉花型棉蚜区分开来。在24℃和26℃下瓜型蚜的净增殖率（R₀）极显著地高于棉花型蚜。27℃和32℃显著缩短了瓜型蚜的平均世代长度,而对棉花型蚜无影响。棉花型蚜对接触刺激的反应比瓜型蚜敏感。两寄主型蚜对寄主的选择能力表现为瓜型蚜显著强于棉花型蚜。因此,两寄主型棉蚜存在明显的形态和生态适应力的分化。     

Bt毒蛋白在转Bt基因棉中的表达及其在害虫-天敌间的转移

以常规棉泗棉3号作为对照,采用酶联免疫生测法（ELISA）和室内生物测定法,研究了转Bt基因棉新棉33B和GK-12不同组织器官中Cry1Ac或Cry1Ab毒蛋白的表达及其向靶标害虫（棉铃虫）、非靶标害虫（棉蚜）以及天敌（龟纹瓢虫）的传递和影响。研究结果表明,新棉33B各组织器官中Bt毒蛋白的表达量较高,为79.7～1 390.0 ng/g鲜重,GK-012较低为165～2640 ng/g鲜重。在花盛期,新棉33B各组织器官中Bt毒蛋白的表达量依次为：柱头、花 >子房、花瓣>群尖;而5～7叶期的初展嫩叶、现蕾初期的幼蕾及花铃期的幼铃表达量相当,而且与花盛期群尖的表达量没有明显区别。同样处于花盛期的GK-12,其各组织器官中Bt毒蛋白的表达量依次为：花药>柱头>花瓣>群尖>子房;而5～7叶期的初展嫩叶、现蕾初期的幼蕾及花铃期的幼铃表达量相当,而且与花盛期群尖的表达量没有明显差异。常规对照棉的幼铃、花药、柱头以及子房中痕量Bt毒蛋白的存在可能与传粉昆虫等的活动有关。在转Bt基因棉田采集的棉蚜和棉铃虫老龄幼虫,其体内均可检测到Bt毒蛋白;在新棉33B棉田采集的龟纹瓢虫幼虫和成虫体内也可检测出Bt毒素。当以Bt棉田的棉蚜饲喂龟纹瓢虫时,龟纹瓢虫的生长发育、存活以及繁殖等基本没有受到影响。     

南京地区棉蚜的飞行活动节律及其飞行能力

昆虫的飞行活动规律及飞行能力是研究其能否迁飞的基础。通过采用春季到秋季20 m高空黄盆诱蚜、高空所诱蚜和春季木槿树上有翅蚜的卵巢解剖,以及春夏秋三季田间有翅蚜的吊飞试验等方法,研究了南京地区棉蚜Aphis gossypii的飞行活动节律和飞行能力。结果表明,有翅棉蚜的日羽化高峰出现在19:00～20:00。2001年南京地区棉蚜的春、秋两季迁飞高峰分别在5月8日和10月25日。5月份高空诱集的棉蚜中,95.7%个体的卵巢小管数在7条以下,而木槿上羽化后1天的有翅蚜中有35.2%个体的卵巢小管数在7条以上;高空诱蚜和木槿上蚜的平均卵巢小管数存在极显著差异,分别为3.94±1.65和5.88±1.92。8月中下旬棉田棉蚜存在低空飞行行为,并且出现飞行高峰时有翅蚜的卵巢小管数平均在6条以下,超过6条则停止飞行。羽化后1～2天有翅棉蚜吊飞个体的飞行比率和平均飞行距离表现为春、秋季显著大于夏季,三季的最长飞行距离分别为3.89 km、6.15 km和1.44 km。