Effects of an optical brightener on the development, body weight and sex ratio of Spodoptera frugiperda (Lepidoptera: Noctuidae)

The incorporation of stilbene-derived optical brighteners into baculovirus formulations can substantially enhance virus infectivity and persistence of inoculum in the field. We evaluated the effect of the optical brightener Tinopal UNPA-GX (Sigma Chemical Co.) on the weight, development time, adult emergence and sex ratio of the principal pest of maize in the Americas, Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae). Tinopal UNPA-GX was incorporated into semi-synthetic diet at a final concentration of 0.1 or 0.05% (w/v) and larvae of S. frugiperda were individually reared on the Tinopal-treated or an untreated control diet. In both Tinopal treatments, the weights of larvae and pupae were significantly reduced by up to 36 and 13%, respectively. The duration of larval development was increased by up to 30% compared to the controls. Adult emergence was high in all treatments (≈90%) and was not affected by the presence of Tinopal in the diet. Significant differences in the proportion of adult females were observed in the 0.05% Tinopal treatment but not in the control or 0.1% Tinopal treatments. By affecting the integrity of the peritrophic membrane and the rate of sloughing of intestinal epithelial cells, natural pest populations exposed to optical brightener residues from bioinsecticide applications are likely to suffer a reduction in growth rate and other correlates of insect fitness.     

Insect allelochemic effects of sesquiterpene lactones from Melampodium

The crude syrups of Melampodium americanum L. and Melampodium leucanthum Torr. and Gray and their principal sesquiterpene lactones, melampodin A and melampodinin A, significantly inhibit growth and deter feeding of the fall armyworm, Spodoptera frugiperda (J. E. Smith). Melampodin A and melampodinin A caused 2.3 × and 5.5 × greater S. frugiperda larval mortality, respectively, than glaucolide A, a sesquiterpene lactone with previously demonstrated insect allelochemic effects.     

Dietary mixtures of cysteine and serine proteinase inhibitors exhibit synergistic toxicity toward the red flour beetle,Tribolium castaneum

1. Combinations of a cysteine proteinase inhibitor (CPI) and serine proteinase inhibitors (SPI) in wheat germ diets were toxic to larvae of the red flour beetle, Tribolium castaneum, when tested at levels where individual inhibitors were nontoxic.2. Mixtures of 0.1% (w/w) CPI (E-64) plus 1% of either of three plant SPIs (soybean Kunitz trypsin inhibitor, soybean Bowman-Birk trypsin-chymotrypsin inhibitor, or lima bean trypsin inhibitor) inhibited T. castaneum growth, resulting in 82–97% reduction in larval weight gain 17 days after hatching and 40–60% mortality.3. Supplemention of diet containing 0.1% E-64 plus 1% soybean Kunitz trypsin inhibitor (STI) with a mixture of amino acids at 7% caused a partial reversal of the growth inhibition, with 91% of the larvae surviving.4. Diet containing 0.1% E-64 plus either 5 or 10% STI resulted in 100% mortality of the larvae during the first or second instar.5. Addition of a mixture ofamino acids at 20% to the 0.1% E-64 plus 10% STI diet allowed 89% of the larvae to develop into adults.6. The synergism between different classes of proteinase inhibitors in the insect's diet that enhances growth inhibition and toxicity demonstrates the potential for an insect pest management strategy involving the coordinated manipulation of two or more types of digestive enzyme inhibitor genes in plants.     

不同品种玉米对草地贪夜蛾生长发育及繁殖的影响

为评价新入侵害虫草地贪夜蛾对我国不同品种玉米的为害潜能,本文采用组建实验种群生命表的方法研究了草地贪夜蛾对3种甜质型玉米(穗甜1号、正甜68和华金甜1号)以及3种糯质型玉米(京科糯2000、广黑甜糯和广糯1号)的生存适合度,分析了草地贪夜蛾生物学指标与玉米叶片主要营养物质及粗纤维含量间的相关性。结果表明: 取食甜质型玉米的草地贪夜蛾的幼虫存活率、蛹重、雌成虫产卵量均显著高于取食糯质型玉米;取食甜质型玉米草地贪夜蛾的内禀增长率介于0.1566～0.1843,净生殖力介于187.97～353.35,也均高于取食糯质型玉米(内禀增长率介于0.0998～0.1465,净生殖力介于25.89～95.34),表明取食甜质型玉米的草地贪夜蛾具有更高的种群增长能力。甜质型玉米叶片中主要营养物质维生素C、淀粉、可溶性糖、蛋白质、脂肪、总氨基酸及粗纤维的含量普遍高于糯质型玉米,草地贪夜蛾的净生殖力与维生素C、淀粉、可溶性糖、蛋白质及粗纤维的含量均存在显著正相关关系。草地贪夜蛾在甜质型玉米上具有更高的生存适合度。     

Effects of soybean proteinase inhibitor on development, survival and reproductive potential of the sugarcane borer, Diatraea saccharalis

One approach that can be employed in integrated pest management is the use of proteins with antinutritional effects on insect metabolism and development. The antimetabolic properties of soybean proteinase inhibitor (SPI) on growth of neonate larvae of the sugarcane borer, Diatraea saccharalis (Fabricius, 1794) (Lepidoptera: Crambidae) have been evaluated. When incorporated into an artificial diet at 0.5% (w/w), SPI retarded growth rate and development of larvae when compared with larvae fed on artificial diet alone. However, larval survival was not significantly affected. The purpose of our research was to calculate demographic statistics for the sugarcane borer reared on diet either with or without semi-purified extract of SPI. Net reproductive rate (R ₀), instantaneous rate of increase (r _m), combined age-specific survivorship (l _x) and age specific fecundity (m _x) provide information about population growth potential. These parameters were measured in order to determine the effects of the proteinase inhibitor on the insect's population dynamics. The observed differences would potentially translate into large reductions in population growth, indicating a potential value of using SPI for protecting sugarcane plants against damage by the sugarcane borer.     

Lethal and sublethal effects of the naturally derived insecticide spinosad on parasitoids of Spodoptera frugiperda (Lepidoptera: Noctuidae)

Laboratory studies were performed on the lethal and sublethal effects of spinosad on three important species of parasitoids attacking Spodoptera frugiperda (J.E. Smith) in Mexico. Reproduction of the braconid Chelonus insularis (Cresson), on treated egg masses was completely eliminated at 200 parts per million (ppm) and reduced by ∼70% at 20 ppm compared to the controls. Adult C. insularis did not avoid contact with residues on maize (200 ppm), but suffered a 7-day reduction in longevity after contact with residues. Initial toxicity of spinosad applied to a natural host of S. frugiperda was concentration dependent and resulted in 23 to 100% mortality of the eulophid Euplectrus plathypenae Howard at 25 to 200 ppm, respectively. The survival of Eu. plathypenae was initially reduced, especially in males, following contact with field weathered residues on maize (200 ppm). However, survival of both sexes rapidly returned to control values on foliage sampled after rainfall. A similar effect was observed in the mortality response of female Eu. plathypenae exposed to residues on sorghum. The ichneumonid Eiphosoma vitticolle Cresson did not avoid reproduction in S. frugiperda larvae that were externally contaminated with 200 ppm spinosad, although all spinosad-treated hosts died before the parasitoid progeny could develop. We use these results to predict the impact of spinosad applications on the foraging and reproduction of these parasitoids in the field. Such predictions require validation by field studies.     

Egg limitation and the functional response of the parasitoid Campoletis grioti (Hym: Ichneumonidae)

The hypothesis that mature egg availability during a parasitoid's lifetime affects the functional response, as well as a parasitoid's handling time and searching efficiency, was tested. Campoletis grioti Blanchard (Hym: Ichneumonidae) female parasitoids and Spodoptera frugiperda Smith (Lep: Noctuidae) host larvae were used as an example. Each female of C. grioti was confined with different host densities (6, 10, 30, 50, 80, 120 and 160 larvae/day) of first and second S. frugiperda instars until the female died. We found that C. grioti showed a type II functional response, with a reduction in the number of parasitized hosts in relation to female ageing. Handling time and searching efficiency increased over time. When we standardized the data simulating unlimited egg supply, the functional response, handling time and searching efficiency became constant throughout the parasitoid's life. We discuss the relationship between egg availability and functional response and its associated parameters, and its consequence on biological control programs.     

土著昆虫素毒蛾在本地植物芦苇与入侵植物互花米草上的生活史

互花米草(Spartina alterniflora)入侵盐沼生态系统导致了土著广食性昆虫素毒蛾(Laelia coenosa)发生宿主转移。但是, 目前对素毒蛾在互花米草和芦苇(Phragmites australis)上的生活史规律的比较尚未见报道, 而此信息对评价素毒蛾能否持续利用互花米草具有重要的参考价值。为了明确素毒蛾在其原始宿主芦苇和外来新宿主互花米草上的生活史动态, 我们在上海崇明长江口盐沼湿地中, 对素毒蛾在芦苇和互花米草生境中的发生情况进行了系统调查。结果显示, 虽然素毒蛾在芦苇和互花米草上均一年发生3代, 并都以幼虫越冬, 但在互花米草生境中, 越冬代幼虫开始越冬的时间要比芦苇中晚20 d左右, 其他世代中的多个虫态在互花米草上持续出现的时间也比芦苇上延迟了约10 d。这些结果表明, 互花米草入侵后素毒蛾在外来植物上出现的持续时间虽然发生了延长, 但其年世代数未变化。我们推测素毒蛾在互花米草和芦苇上生长发育规律的差异可能受生境的资源可利用性及两种植物的营养与防御水平调控。     

Differential effects of sugar-mimic alkaloids in mulberry latex on sugar metabolism and disaccharidases of Eri and domesticated silkworms: enzymatic adaptation of Bombyx mori to mulberry defense

Mulberry leaves (Morus spp.) exude latex rich in sugar-mimic alkaloids, 1,4-dideoxy-1,4-imino-d-arabinitol (d-AB1) and 1-deoxynojirimycin (DNJ), as a defense against herbivorous insects. Sugar-mimic alkaloids are inhibitors of sugar-metabolizing enzymes, and are toxic to the Eri silkworm, Samia ricini, a generalist herbivore, but not at all to the domesticated silkworm, Bombyx mori, a mulberry specialist. To address the phenomena, we fed both larvae diets containing different sugar sources (sucrose, glucose or none) with or without sugar-mimic alkaloids from mulberry latex. In S. ricini, addition of sugar-mimic alkaloids to the sucrose (the major sugar in mulberry leaves) diet reduced both growth and the absorption ratio of sugar, but it reduced neither in B. mori. The midgut soluble sucrase activity of S. ricini was low and inhibited by very low concentrations of sugar-mimic alkaloids (IC₅₀=0.9–8.2 μM), but that of B. mori was high and not inhibited even by very high concentrations (IC₅₀>1000 μM) of sugar-mimic alkaloids. In S. ricini, the addition of sugar-mimic alkaloids to the glucose diet still had considerable negative effects on growth, although it did not reduce the absorption ratio of glucose. The hemolymph of S. ricini fed sugar-mimic alkaloids contained sugar-mimic alkaloids. The trehalose concentration in the hemolymph increased significantly in S. ricini fed sugar-mimic alkaloids, but not in B. mori. The trehalase activities of S. ricini were lower and inhibited by lower concentrations of sugar-mimic alkaloids than those of B. mori. These results suggest that sugar-mimic alkaloids in mulberry latex exert toxicity to S. ricini larvae first by inhibiting midgut sucrase and digestion of sucrose, and secondly, after being absorbed into hemolymph, by inhibiting trehalase and utilization of trehalose, the major blood sugar. Further, our results reveal that B. mori larvae evolved enzymatic adaptation to mulberry defense by developing sucrase and trehalase that are insensitive to sugar-mimic alkaloids.     

家蚕幼虫BmToll9基因对肽聚糖和金黄色葡萄球菌的响应表达

【目的】Toll信号通路是昆虫中重要的免疫信号通路,其中Toll受体在保持Toll通路的正常免疫应答、抵抗外源病原体中起到关键的作用。本研究旨在探究肽聚糖和金黄色葡萄球菌Staphylococcus aureus对家蚕Bombyx mori Toll受体基因BmToll9-1和BmToll9-2表达的影响。【方法】将革兰氏阳性菌细胞壁主要成分肽聚糖和革兰氏阳性菌金黄色葡萄球菌分别注射感染家蚕5龄第1天幼虫,诱导其发生免疫反应;采用实时荧光定量PCR分析注射后不同感染时间点BmToll9-2和BmToll9-1基因在家蚕幼虫中肠、表皮、脂肪体和丝腺中的相对表达水平。【结果】往家蚕5龄幼虫中注射肽聚糖或金黄色葡萄球菌后,BmToll9-2基因出现了时间和组织的差异性表达。注射肽聚糖和金黄色葡萄球菌均能诱导5龄幼虫中肠BmToll9-2基因的表达上调,注射肽聚糖和金黄色葡萄球菌分别在3和6 h时对基因表达的诱导效果最好,且注射金黄色葡萄球菌比注射肽聚糖对基因表达的诱导效果更好。注射金黄色葡萄球菌能引起5龄幼虫表皮、脂肪体和丝腺中BmToll9-2基因的表达上调,分别于注射后24, 6和24 h时诱导效果最好。注射金黄色葡萄球菌亦能诱导同源的BmToll9-1基因的上调表达。【结论】家蚕幼虫BmToll9基因在肽聚糖或金黄色葡萄球菌注射处理后均能在不同组织中发生上调表达,推测BmToll9基因参与了家蚕对肽聚糖和金黄色葡萄球菌的免疫反应。     

Physiological and genetic modifications of the expression of the yeast mitochondrial adenosine triphosphatase inhibitor

1. The oligomycin-sensitive ATPase activity of submitochondrial particles of the glycerol-grown “petite-negative” yeast: Schizosaccharomyces pombe is markedly stimulated by incubation at 40°C and by trypsin activations are treatment. Both increased in Triton-X 100 extracts of the submitochondrial particles.

2. A trypsin-sensitive inhibitory factor of mitochondrial ATPase with properties similar to that of beef heart has been extracted and purified from glycerolgrown and glucose-grown S. pombe wild type, from the nuclear pleiotropic respiratory-deficient mutant S. pombe M126 and from Saccharomyces cerevisiae.

3. ATPase activation by heat is more pronounced in submitochondrial particles isolated from glycerol-grown than from glucose-grown S. pombe. An activation of lower extent is observed in rat liver mitochondrial particles but is barely detectable in the “petite-positive” yeast: S. cerevisiae. No activation but inhibition by heat is observed in the pleitotropic respiratory-deficient nuclear mutant S. pombe M126.

4. The inhibition of S. pombe ATPase activity by low concentrations of dicyclohexylcarbodiimide dissapears at inhibitor concentrations above 25 μM. In Triton-extract of submitochondrial particles net stimulation of ATPase activity is observed at 100 μM dicyclohexylcarbodiimide. The pattern of stimulation of ATPase activity by dicyclohexylcarbodiimide in different genetic and physiological conditions parallels that produced by heat and trypsin. A similar mode of action is therefore proposed for the three agents: dissociation or inactivation of an ATPase inhibitory factor.

5. We conclude that “petite-positive” and “petite-negative” yeasts contain an ATPase inhibitor factor with properties similar to those of the bovine mitochondrial ATPase inhibitor. The expression of the ATPase inhibitor, measured by ATPase activation by heat, trypsin or high concentrations of dicyclohexylcarbodiimide, is sensitive to alterations of the hydrophobic membrane environment and dependent on both physiological state and genetic conditions of the yeast cells.     

Modes of reproduction of the hybridogenetic fish Squalius alburnoides in the Tejo and Guadiana rivers: an approach with microsatellites

The Squalius alburnoides complex was produced by hybridization between female S. pyrenaicus (PP genome) and an hypothetical paternal ancestor related with Anaecypris hispanica (AA genome). This study examined a diversity of mating types and found that there is the potential for considerable gene exchange among diploid, triploid and tetraploid hybrids. Using microsatellites, genomes were attributed to Squalius pyrenaicus (P) or reconstituted “nuclear non-hybrid” S. alburnoides (A), and subsequently confirmed in hybrids. Recombination of AA genomes in the “nuclear non-hybrid males” and recombination of the homogametic genomes (AA or PP) after exclusion of the heterogametic genome in triploid females (PAA) were observed by analysing parents and progeny of breeding experiments. Reproduction of tetraploids, generating a symmetric tetraploid genotype (PPAA) in the progeny, suggests a process that could potentially lead to the formation of a new bisexual species. Present results also support: (i) previously hypothesized pathways, in which PPA S. alburnoides females exclude the A genome, exhibit meiotic recombination between the P genomes and generate haploid eggs; (ii) reconstitution of the diploid maternal ancestor genome (PP) as well as of the unknown paternal ancestor (AA); (iii) the occurrence of the same genomic reproductive mechanisms when Anaecypris hispanica is involved; and (iv) the existence of an A. hispanica-like ancestor as the paternal ancestor of S. alburnoides.     

Regulation of primary carbon metabolism in Kluyveromyces lactis

In the recent past, through advances in development of genetic tools, the budding yeast Kluyveromyces lactis has become a model system for studies on molecular physiology of so-called “Nonconventional Yeasts.” The regulation of primary carbon metabolism in K. lactis differs markedly from Saccharomyces cerevisiae and reflects the dominance of respiration over fermentation typical for the majority of yeasts. The absence of aerobic ethanol formation in this class of yeasts represents a major advantage for the “cell factory” concept and large-scale production of heterologous proteins in K. lactis cells is being applied successfully. First insight into the molecular basis for the different regulatory strategies is beginning to emerge from comparative studies on S. cerevisiae and K. lactis. The absence of glucose repression of respiration, a high capacity of respiratory enzymes and a tight regulation of glucose uptake in K. lactis are key factors determining physiological differences to S. cerevisiae. A striking discrepancy exists between the conservation of regulatory factors and the lack of evidence for their functional significance in K. lactis. On the other hand, structurally conserved factors were identified in K. lactis in a new regulatory context. It seems that different physiological responses result from modified interactions of similar molecular modules.     

Complexity in specificities and expression of Helicoverpa armigera gut proteinases explains polyphagous nature of the insect pest

Helicoverpa armigera is a devastating pest of cotton and other important crop plants all over the world. A detailed biochemical investigation of H. armigera gut proteinases is essential for planning effective proteinase inhibitor (PI)-based strategies to counter the insect infestation. In this study, we report the complexity of gut proteinase composition of H. armigera fed on four different host plants, viz. chickpea, pigeonpea, cotton and okra, and during larval development. H. armigera fed on chickpea showed more than 2.5- to 3-fold proteinase activity than those fed on the other host plants. H. armigera gut proteinase composition revealed the predominance of serine proteinase activity; however, the larvae fed on pigeonpea revealed the presence of metalloproteases and low levels of aspartic and cysteine proteases as well. Gut proteinase activity increased during larval development with the highest activity seen in the fifth instar larvae which, however, declined sharply in the sixth instar. Over 90% of the gut proteinase activity of the fifth instar larvae was of the serine proteinase type, however, the second instar larvae showed the presence of proteinases of other mechanistic classes like metalloproteases, aspartic and cysteine proteases along with serine proteinase activity as evident by inhibition studies. Analysis of fecal matter of larvae showed significant increase in proteinase activity when fed on an artificial diet with or without non-host PIs than larvae fed on a natural diet. The diversity in the proteinase activity observed in H. armigera gut and the flexibility in their expression during developmental stages and depending upon the diet provides a base for selection of proper PIs for insect resistance in transgenic crop plants.     

Compensatory proteolytic responses to dietary proteinase inhibitors from Albizia lebbeck seeds in the Helicoverpa armigera larvae

Plant proteinase inhibitors (PIs) have been shown to reduce the growth rates in larvae of numerous insect species. On the other hand, insects can also regulate their proteinases against plant PIs. In the present study, we report the compensatory activities of Helicoverpa armigera (Hubner) (Lepidoptera: Noctuidae) gut proteinases against the PIs of Albizia lebbeck seeds. Total of ten proteinase inhibitor bands were detected in the seed extract of A. lebbeck. Bioassays were conducted by feeding H. armigera larvae on diet containing partially purified PIs from A. lebbeck seeds. Results show that larval growth and survival was significantly reduced by A. lebbeck PIs. We found that higher activity H. armigera gut proteinase (HGP) isoforms observed in the midgut of control larvae were inhibited in the midgut of larvae fed on test diet. Some HGP isoforms were induced in the larvae fed on PI containing test diet; however, these isoforms showed lower activity in the larvae fed on control diet. Aminopeptidase activities were significantly increased in the midgut of larvae fed on test diet. A population of susceptible and resistant enzymes was observed in the midgut of H. armigera, when fed on diet containing PIs from A. lebbeck seeds. Our initial observations indicate that H. armigera can regulate its digestive proteinase activity against non-host plant PIs, too. It is important to study the exact biochemical and molecular mechanisms underlying this phenomenon in order to develop PI-based insect control strategies.     

Eudesmanes from Pluchea sagittalis. Their antifeedant activity on Spodoptera frugiperda

Eudesmane-type sesquiterpenoids 3-(2,3-epoxy-2-methylbutyryloxy)-4-formoxy-11-hydroxy-6,7-dehydroeudesman-8-one (1) and 3-(2,3-epoxy-2-methylbutyryloxy)-4,7,11-trihydroxyeudesman-8-one (2), together with 10 known structurally related eudesmanes were isolated from the CHCl₃ extract of aerial parts of Pluchea sagittalis (Lamarck) Cabrera. Their structures were deduced by extensive application of 1 and 2D NMR spectroscopic techniques and high and low resolution CIMS. X-ray crystallographic analysis of the known compound 3-(2,3-epoxy-2-methylbutyryloxy)-4-formoxycuauthemone (9) is reported here for the first time, and confirms the structural features for the series of the reported eudesmanes. All eudesmanes were tested for their antifeedant activity by incorporating them to an artificial diet of larvae of the polyphagous insect Spodoptera frugiperda at a concentration of 100 ppm. Our results, from feeding choice tests, indicated that most of the compounds deter larval feeding at the cited concentration.     

Field application of an insect virus in the Mekong Delta: Effects of a Vietnamese nucleopolyhedrovirus on Spodoptera litura (Lepidoptera: Noctuidae) and its parasitic natural enemies

A new Vietnamese isolate of Spodoptera litura nucleopolyhedrovirus (NPV) was applied in local soybean fields, and the effect of its application on S. litura larvae was examined. The virus was propagated in vivo and a crude extract was prepared for spraying at high and low doses (1.7×10⁸ and 3.3×10⁷ occlusion bodies/m², respectively). The percentage of larvae infected with NPV increased from 22.2% on the day before NPV application (Day 0) to 50.8% (Day 6) in the high dose treatment plot, and from 7.9% (Day 0) to 35.7% (Day 6) in the low-dose plot. Microsporidium sp. was observed as another major pathogen of S. litura larvae. Three dominant parasitic natural enemies were found in S. litura larvae: Microplitis manilae (Braconidae), Chelonus sp. (Braconidae), and Peribaea orbata (Tachinidae). The fate of parasitoids developing within virus- and Microsporidium- infected hosts differed between these three parasitoids; more Chelonus sp. emerging from infected hosts died during their larval stage before spinning cocoons, or failed to reach adult eclosion, than did P. orbata. This suggests that the impact of virus application on the survival of parasitoids varies from species to species.     

Dendrosoter protuberans (Hymenoptera: Braconidae), An Important Elm Bark Beetle Parasitoid

The most favourable period for Dendrosoter protuberans development occurred when wasps were introduced 16 days after the beginning of Scolytus multistriatus development (the greatest number of emerged wasps per a single parasitoid female with a very positive sexual index and high percentage of parasitised elm bark beetle larvae). No significant differences were observed in parasitoid efficiency between the 11^th and the 21^st day. The most unfavourable period for elm bark beetle parasitisation was six days after the beginning of S. multistriatus development (a low reproduction of D. protuberans, a negative sexual index and a low number of destroyed S. multistriatus larvae). The reproduction of both the elm bark beetle and D. protuberans was greater in the first, than in the second generation. The developmental period of D. protuberans in the first generation was approximately two days longer than in the second generation. Furthermore, the development of females was 1-2 days longer than the development of males. D. protuberans developed most successfully on S. multistriatus (the most abundant parasitoid reproduction with the longest developmental period and a very positive sexual index that resulted in a high percentage of parasitised larvae) and then on S. ensifer, S. pygmaeus and Pteleobius kraatzi. On the other hand, S. scolytus larvae were the poorest host of all elm species - the reproduction of D. protuberans in this species was the scarcest with the shortest period of development and a negative sexual index, hence larval parasitisation was the lowest.