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PubMed2002

An antibody to the putative aphid recognition site on cucumber mosaic virus recognizes pentons but not hexons.

Cucumber mosaic virus (CMV), the type member of the genus Cucumovirus (family Bromoviridae), is transmitted by aphids in a nonpersistent manner. Mutagenesis experiments identified the betaH-betaI loop of the capsid subunit as a potential key motif responsible for interactions with the insect vector. To further examine the functional characteristics of this motif, we generated monoclonal antibodies that bound to native virions but not to betaH-betaI mutants. Fab fragments from these antibodies were complexed with wild-type CMV and the virus-Fab structure was determined to 12-A resolution by using electron cryomicroscopy and image reconstruction techniques. The electron density attributed to the bound antibody has a turret-like appearance and protrudes from each of the 12 fivefold axes of the icosahedral virus. Thus, the antibody binds only to the pentameric clusters (pentons) of A subunits of the T=3 quasisymmetric virus and does not appear to bind to any of the B and C subunits that occur as hexameric clusters (hexons) at the threefold (quasi-sixfold) axes. Modeling and electron density comparisons were used to analyze the paratope-epitope interface and demonstrated that the antibody binds to three betaH-betaI loops in three adjacent A subunits in each penton. This antibody can discriminate between A and B/C subunits even though the betaH-betaI loop adopts the same structure in all 180 capsid subunits and is therefore recognizing differences in subunit arrangements. Antibodies with such character have potential use as probes of viral assembly. Our results may provide an additional rationale for designing synthetic vaccines by using symmetrical viral particles.

Animals↗
PubMed2002

Two different genes encoding acetylcholinesterase existing in cotton aphid (Aphis gossypii).

Two acetylcholinesterase (AChE) genes, Ace1 and Ace2, have been cloned from cotton aphid, Aphis gossypii Glover, using the rapid amplification of cDNA ends (RACE) technique. To the best of our knowledge, this should be the first direct molecular evidence that multiple AChE genes exist in insects. The Ace1 gene was successfully amplified along its full length of 2371 bp. The open reading frame is 2031 bp long and encodes 676 amino acids (GenBank accession No. AF502082). The Ace2 gene was amplified as a mega-fragment of 2130 bp lacking part of 5'-end untranslated region (UTR). The open reading frame is 1992 bp long and ecodes a protein of 664 amino acids (GenBank accession No. AF502081). Both genes have the conserved amino acids and features shared by the AChE family, but share only 35% identity in amino acid sequence. The Ace1 gene is highly homologous to the AChE gene of Schizaphis graminum (AF321574) with 95% identity, and Ace2 to that of Myzus persicae (AF287291) with 92% identity. Phylogenetic analysis showed that the two cloned AChEs of A. gossypii are different in evolution. The phylogenetic tree generated by the PHYLIP program package inferred that AChE2 of A. gossypii is a more ancestral form of AChE. Homology modeling of structures using Torpedo californica (2ACE_) and Drosophila melanogaster (1Q09:A) native acetylcholinesterase structure as main template indicated that the two AChEs of Aphis gossypii might have different three-dimensional structures. Alternative splicing of Ace1 near the 5'-end resulting in two proteins differing by the presence or absence of a fragment of four amino acids is also reported.

Acetylcholinesterase↗
PubMed2001

Isolation and in vitro cultivation of the aphid pathogenic fungus Entomophthora planchoniana.

Entomophthora planchoniana is an important fungal pathogen of aphids. Although Entomophthora chromaphidis has been considered a synonym for E. planchoniana, the two species are now separated, and E. planchoniana is reported not to grow in vitro. In this paper, we describe for the first time the isolation and cultivation of this species. Entomophthora planchoniana was isolated from a population of Ovatus crataegarius (Homoptera, Aphididae), which was infected by E. planchoniana only. The isolates did not sporulate, but the sequence of the small subunit rDNA and the restriction fragment length polymorphism patterns of the first part of the large subunit rDNA and the ITS II region confirm that the isolates were E. planchoniana. The isolated fungus grew in a medium consisting of Grace's insect cell culture medium supplemented with lactalbumin hydrolysate, yeastolate, and 10% fetal bovine serum or in GLEN medium with 10% fetal bovine serum. Vegetative cells of E. planchoniana were long and club-shaped and did not stain with Calcofluor, thus suggesting that they were protoplasts.

Animals↗
PubMed2006

Germ-plasm specification and germline development in the parthenogenetic pea aphid Acyrthosiphon pisum: Vasa and Nanos as markers.

The germarium, oocytes and embryos of the parthenogenetic viviparous pea aphid Acyrthosiphon pisum are contained within a single ovariole. This species provides an excellent model for studying how maternally-inherited germ plasm is specified and how it is transferred to primordial germ cells. Previous studies have shown that germ cells are first segregated at the embryonic posterior after formation of the blastoderm. We used two cross-reacting antibodies against the conserved germline markers Vasa and Nanos, which specifically identified these presumptive germ cells, to investigate whether germ cells were determined during early development. We observed randomly-distributed weak expression of Vasa signals in the developing oocyte but no localization in the oocyte segregated from the germarium. Localized Vasa was not apparent until it was detected at the posterior in the embryo undergoing the second nuclear division. Nanos, on the other hand, was localized to a nuage-like structure surrounding the nucleus in the developing and segregated oocytes. At the beginning of the oocyte maturation division, Nanos localization shifted to the posterior and could be identified in successive stages until it was incorporated into the germ cells. Taken together, our results suggest that germ plasm is specified in the developing oocyte and that Nanos is an earlier germline marker than Vasa. Germ cells stained for Vasa remained at a dorsal location in the egg during mid-development and then were guided into abdominal segments A1 to A6 during germ-band retraction. We infer that germ cells coalesce with segmented gonadal mesoderm during this period.

Animals↗
PubMed2006

Operating characteristics of full count and binomial sampling plans for green peach aphid (Hemiptera: Aphididae) in potato.

Counts of green peach aphid, Myzus persicae (Sulzer) (Hemiptera: Aphididae), in potato, Solanum tuberosum L., fields were used to evaluate the performance of the sampling plan from a pest management company. The counts were further used to develop a binomial sampling method, and both full count and binomial plans were evaluated using operating characteristic curves. Taylor's power law provided a good fit of the data (r2 = 0.95), with the relationship between the variance (s2) and mean (m) as ln(s2) = 1.81(+/- 0.02) + 1.55(+/- 0.01) ln(m). A binomial sampling method was developed using the empirical model ln(m) = c + dln(-ln(1 - P(T))), to which the data fit well for tally numbers (T) of 0, 1, 3, 5, 7, and 10. Although T = 3 was considered the most reasonable given its operating characteristics and presumed ease of classification above or below critical densities (i.e., action thresholds) of one and 10 M. persicae per leaf, the full count method is shown to be superior. The mean number of sample sites per field visit by the pest management company was 42 +/- 19, with more than one-half (54%) of the field visits involving sampling 31-50 sample sites, which was acceptable in the context of operating characteristic curves for a critical density of 10 M. persicae per leaf. Based on operating characteristics, actual sample sizes used by the pest management company can be reduced by at least 50%, on average, for a critical density of 10 M. persicae per leaf. For a critical density of one M. persicae per leaf used to avert the spread of potato leaf roll virus, sample sizes from 50 to 100 were considered more suitable.

Animals↗
PubMed2006

Categories and inheritance of resistance to Russian wheat aphid (Homoptera: Aphididae) biotype 2 in a selection from wheat cereal introduction 2401.

The Russian wheat aphid, Diuraphis noxia (Kurdjumov) (Homoptera: Aphididae), is one of the most devastating insect pests of wheat (Triticum spp.) and barley (Hordeum spp.) in the world. Yield losses and control costs are valued at several hundred million dollars each year. The use of D. noxia-resistant cultivars is an ecologically, economically, and biologically sound method of managing this pest. Several D. noxia resistance (Dn) genes from wheat have been used to develop cultivars resistant to D. noxia. However, a new U.S. D. noxia biotype (biotype 2) in Colorado is virulent to all known Dn genes except the Dn7 gene from rye (Secale spp.). Hence, there is an immediate need to identify and characterize unique sources of D. noxia resistance to biotypes. In this article, we report resistance to D. noxia biotype 2, identified in a selection from wheat cereal introduction (CItr) 2401, that is controlled by two dominant genes. CItr2401 has a strong antibiosis effect that is exhibited as a reduced intrinsic rate of increase of D. noxia biotype 2. CItr2401 plants also exhibit tolerance to leaf rolling and chlorosis. No antixenosis was detected in CItr2401.

Animals↗
PubMed1996

A characteristic difference among GroEL homologs from intracellular symbionts of closely-interrelated species of aphid.

Nucleotide sequences encoding GroEL homologs of intracellular symbionts in three closely interrelated aphids were compared with one another and that for GroEL. It was suggested that in these proteins a particular position is highly susceptible to amino acid substitution, through which the GroEL homologs of symbionts seemed to have acquired a unique function on top of the activity as molecular chaperone. This may represent a rare example of non-neutral evolution of molecule under the positive selection pressure.

Amino Acid Sequence↗
PubMed1980

Toxicity of [14C] phorate applied systemically to the aphids Myzus persicae (Sulz) and Brevicoryne brassicae (l.) grown on brussels sprout plants.

The effect of foliar application of [14C] phorate on the larvae of M. persicae and B. brassicae was studied. Regression analysis of the toxic components in the foliage and the probit kill showed that B. brassicae was more susceptible to the insecticide than M. persicae. The level of radioactivity extracted from the leaves, aphids and their honeydew shows that there was no correlation between the applied dose and the mortality. The amounts of honeydew produced by colonies before and after application of the insecticide were measured. The ratio of honeydew calculated shows that in M. persicae there was a slight increase in the honeydew production as the insecticide was increased from sublethal doses. At higher doses over the lethal range of the insecticide, honeydew production declined gradually in both the species.

Animals↗
PubMed1998

Aphid species--vectors of plum pox virus.

Plum pox virus (PPV) is widely spread by natural vectors present in plum orchards. The efficiency of transmission is dependent on the frequency of the occurrence of vectors and the cultivar susceptibility to this pathogen. Having in view that PPV has a wide range of annual and multiannual host plants and vectors, there is great concern for obtaining PPV-resistant cultivars. This report deals with the following vectors: Hyalopterus pruni, Brachycaudus cardui, Brachycaudus helichrysi. Myzus persicae and Phorodon humuli aphids, and Aculus fockeni mite. Seven different cultivars of Prunus domestica were utilized. To assess the virus transmission rate, 50-100 individual vectors per tree were used. The treatment of the trees was performed every four weeks and then the disease symptoms were observed. PPV was transmitted by all vectors studied, the rate ranging in dependence on the susceptibility of cultivars used. Thus, in cvs. Centenar, Pescarus, d'Agen, Stanley and Tuleu Gras, the transmission rate ranged from 20% to 60%, while in susceptible cvs. Vanat romanesc and Vanat de Italia--from 40% to 80%.

Animals↗
PubMed2000

Host choice and host leaving in Rhopalosiphum padi (Hemiptera: aphididae) emigrants and repellency of aphid colonies on the winter host.

Host choice and winter-host leaving in emigrants of bird cherry-oat aphid, Rhopalosiphum padi (Linnaeus), were investigated in the laboratory. In settling choice tests, emigrants collected from the winter host, Prunus padus, preferred this plant over a summer host, oats. Emigrants which had left P. padus for up to 24 h did not express a preference as a group, and those which had left for 24-48 h preferred oats. Eighty seven percent of emigrants caged as fourth-instar nymphs on P. padus leaves abandoned the host by the second day of adult life, and apparently did not subsequently return to the leaf. In an olfactometer, P. padus leaves which had supported spring generations of R. padi were repellent to emigrants. Volatiles were entrained from uninfested and R. padi-infested P. padus using cut twigs in the laboratory as well as intact twigs on a tree in the field. Entrainment extracts from uninfested P. padus had no effect on emigrants in the olfactometer, whereas those from twigs infested with nymphal emigrants were repellent. The study indicates that in R. padi, host-alternation is driven by behavioural changes which occur in individuals as well as between morphs.

Animals↗
PubMed2000

An aphid repellent glycoside from Solanum laxum.

A spirostanic saponin was isolated from the ethanolic extract of the aerial parts of Solanum laxum Steud. The compound, named luciamin, was characterised by NMR spectroscopy, mass spectrometry and chemical methods, as (22R, 25S)-spirost-5-en-3 beta, 15 alpha-diol 3-O-[beta-D-glucopyranosyl (1 --> 2)-beta-D-glucopyranosyl-( 1 --> 4)-[alpha-L-rhamnopyranosyl-( 1 --> 2)]-beta-D-galactopyranoside]. The compound was tested against the aphid Schizaphis graminum by incorporation in artificial diets. It showed a deterrent (toxic) activity against the insect and is the first spirostane glycoside reported to have this activity.

Animals↗
PubMed2001

Feeding behaviour of the aphid Rhopalosiphum padi (Hemiptera: Aphididae) on nitrogen and water-stressed barley (Hordeum vulgare) seedlings.

Electrical penetration graphs (EPGs) were used to examine the probing behaviour of adult apterous Rhopalosiphum padi (Linnaeus) on barley seedlings grown under conditions of nitrogen or water stress. Aphids took significantly longer to reach and ingest from sieve elements of nitrogen-deficient seedlings than from nitrogen-sufficient seedlings but there were no such differences between water-stressed or well-watered seedlings. On both nitrogen and water-stressed seedlings the average length of each individual period of salivation into the sieve element was significantly greater compared with their respective unstressed controls.

Animals↗
PubMed2001

[Biomass, sporulation and aphid-infecting virulence of Pandora neoaphidis mycelia produced in repeated liquid culture].

Repeated culture of entomophthoraceous isolates is a suspectable factor leading to their virulence decline of biological variation. In the present study, an isolate of Pandora neoaphidis, F98028, was repeatedly cultured six times at the regime of 20 degrees C and 80 r/min in Sabouraud dextrose broth(SDB) at three inoculation ratio of 1/20, 2/20, and 4/20 (seed culture over fresh SDB). Mycelial biomass(MB), sporulation capacity(SC), and virulence to the green peach aphid, Myzus persicae, were assessed for each of the subcultures. The repeated liquid cultures, initiating from seed culture with MB 8.84 mg/mL ad SC 7.22 x 10(5) conidia/mg, yielded MB and SC in a range of 6.4-10.0 mg/mL and 7.3 x 10(5)-10.8 x 10(5) conidia/mg at the ratio of 1/20(72 h culture), 5.7-8.5 mg/mL and 10.0 x 10(5)-12.1 x 10(5) condia/mg at 2/20(60 h culture), and 5.5-10.9 mg/mL and 6.4 x 10(5)-10.9 x 10(5) conidia/mg at 4/20(48 h culture), respectively. There was no significant difference in both MB and SC among the cultures(F = 0.299, P = 0.903) or the three inoculation ratios (F = 0.561, P = 0.587). Inocula from each of the cultures at the inoculation ratio of 1/20 were repeatedly bioassayed on the second and third instar colonies of M. periscae. Based on time-dose-mortality analysis, the estimates of LD50 s for all batches of the inocula were 22.8-162, 4.7-49.4, 2.8-16.7, 2.3-9.5, and 1.8-5.2 conidia/mm2 3-7 d after inoculation, respectively. All the estimates for the repeated cultures fell within a range previously reported. Thus, the method used for repeated liquid culture in this study did not cause a visible decline in the virulence of P. neoaphidis F98028.

Animals↗
PubMed2002

Evaluation of the pesticidal potential of the congress grass, Parthenium hysterophorus Linn. on the mustard aphid, Lipaphis erysimi (Kalt.).

Petroleum ether extracts of leaves, stem and inflorescence of Parthenium hysterophorus Linn. at 500, 1000, 2000 and 5000 ppm concentrations were tested in the laboratory for their toxic effects on the mean life span and progeny production of adults of the mustard aphid, Lipaphis erysimi (Kalt.). The investigations revealed a significant decrease in life span and progeny production with treatment. Among the three plant parts tested for their efficacy, the leaf extract showed the most significant effect in causing a dose dependent decline in both the life span and progeny production.

Animals↗
PubMed1992

Comparative efficacy of aphid extracts and some juvenoids against the development of mosquitoes.

Comparative efficacy of natural juvenile hormones extracted from Aphis craccivora and A. gosypii and 5 juvenoids, i.e., methoprene, Neporex, OMS 3007, OMS 3019 and DPE-28 on the development of Aedes aegypti, Anopheles stephensi and Culex quinquefasciatus have been evaluated. OMS 3007, OMS 3019, DPE-28 and Neporex show species specific related activities, while methoprene and aphid extracts do not show such activity against these mosquito species. Treatment of mosquito eggs with an EC50 dose of these compounds caused mortality while an EC90 dose completely ceased adult emergence. The fecundity and fertility rates of mosquitoes emerged shows significant reduction (P less than 0.001) when treated with EC50 doses of all the compounds.

Aedes↗
PubMed2004

Phylogenetic and molecular evidence for allochronic speciation in gall-forming aphids (Pemphigus).

Sympatric populations can diverge when variation in phenology or life cycle causes them to mate at distinctly different times. We report patterns consistent with this process (allochronic speciation) in North American gall-forming aphids, in the absence of a host or habitat shift. Pemphigus populi-transversus Riley and P. obesinymphae Aoki form a monophyletic clade within the North American Pemphigus group. They are sympatric on the eastern cottonwood, Populus deltoides (Salicaceae), but have distinctly different life cycles, with sexual stages offset by approximately six months. Field evidence indicates that intermediate phenotypes do not commonly occur, and mitochondrial and bacterial endosymbiont DNA sequences show no maternal gene flow between the two species. Because a genetically distinct population of P. obesinymphae occurs in the southwestern United States on Populus fremontii, we consider the possibility of an initial allopatric phase in the divergence. We discuss the likely origins of the host use patterns in P. obesinymphae, and the larger sequence of evolutionary changes that likely led to the sympatric divergence of P. populi-transversus and P. obesinymphae. A plausible interpretation at this stage of investigation is that a shift in timing of the life cycle in an ancestral population, correlated with an underlying phenological complexity in its host plant, spurred divergence between the incipient species.

Animals↗
PubMed2004

Evaluation of the possible role of five enzymes in the metabolism of IBA in mustard aphid, Lipaphis erysimi (Kalt.).

The enzymatic activity of five enzymes viz. Glutathione S-transferases, Esterases, NADH dehydrogenase, NADH oxidase and Glutathione reductase were assessed under the influence of Indole butyric acid (IBA) (400 ppm) in the nymphs (48-52h old) of mustard aphid, Lipaphis erysimi fed on radish plants treated for 13, 25 and 37h. The activity of Glutathione S-transferases, Esterases and NADH dehydrogenase increased compared to that found in the control of the same age group of nymphs and it was concluded that these enzymes might be involved in the metabolism of IBA. The other two enzymes, NADH oxidase and Glutathione reductase showed no significant increase in their activity compared to that in the control of the same age group. It was hypothesized that the latter enzymes do not play any significant role in the metabolism of IBA.

Animals↗
PubMed2004

Action of some micronutrients on the infestation and yield components of faba bean by the aphid, Aphis craccivora Koch (Aphididae, Homoptera) and the leaf miner, Liriomyza trifolii (Burgess) (Agromyzidae, Diptera).

Field experiments were carried out in the two growing seasons of 1999/2000 and 2000/2001 on faba bean (Vicia faba) plants in the Experimental Farm of Agriculture Research Station at Nubaria region, Alexandria, which is considered as a newly reclaimed calcareous soil. The present investigation aimed to evaluate the effect of spraying faba bean plants with certain micronutrients, i.e. Iron, Manganese and Zinc either in single double or triple combinations on the infestation by the aphid, Aphis craccivora Koch (Aphididae, Homoptera) and the leaf miner, Liriomyza trfolü (Burgess) (Agromyzidae, Diptera). The infestation by these insects was assessed using the parameters of Infestation grades as well as the injury indices. Faba bean plants cv. Giza Blanca were sprayed twice (45 and 66 days) after planting with the above-mentioned micronutrients. However, results of this investigation showed, with no doubt, that Mn, Zn and Fe individually or in double or triple combinations have increased to varied extents the infestation rates (%) of faba bean plants compared to the untreated ones. Such varied increases were mainly due to the metabolic roles of the used foliar sprays and their interactions, which indirectly affect the physio-biological actions of plants that may render them suitable for either A. craccivora or L. trifoii reproduction. This phenomenon might be also due to the different environmental factors. In both seasons, the relationship between nutrients applications and pests Infestation followed the same trend of increase in the percentages of infested plants. This assures and confirms the constant metabolic roles of such micronutrients. The biological seed weight (ton/fed.) was positively affected by the application of the used micronutrients. It is worth mentioning that the maximum response was observed in case of the triple treatment followed by the double and single treatments in a descending order. Application of the investigated micronutrients alone or in mixtures resulted in significant increases in yield and its components. Such increases were due to the fact that ions of Zn, Fe and Mn are cofactors of several enzymes, but rarely if ever with a high degree of specificity.

Animals↗