Poor survival on an artificial diet of two genotypes of the aphid Myzus persicae: a fitness cost of insecticide resistance?

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Does insecticide resistance alone account for the low genetic variability of asexually reproducing populations of the peach-potato aphid Myzus persicae?

The typical life cycle of aphids includes several parthenogenetic generations and a single sexual generation (cyclical parthenogenesis), but some species or populations are totally asexual (obligate parthenogenesis). Genetic variability is generally low in these asexually reproducing populations, that is, few genotypes are spread over large geographic areas. Both genetic drift and natural selection are often invoked to account for this low genetic variability. The peach-potato aphid, Myzus persicae, which encompasses both cyclical and obligate parthenogens, has developed several insecticide resistance mechanisms as a consequence of intense insecticide use since the 1950s. We collected asexually reproducing M. persicae from oilseed rape and examined genetic variability at eight microsatellite loci and three insecticide resistance genes to determine whether their genetic structure was driven by drift and/or selection. We identified only 16 multilocus microsatellite genotypes among 255 individuals. One clone, which combined two insecticide resistance mechanisms, was frequently detected in all populations whatever their location over a large geographical area (the northern half of France). These unexpected findings suggest that drift is not the unique cause of this low variability. Instead, the intensification of both insecticide treatments and oilseed rape cultivation may have favored a few genotypes. Thus, we propose that selective pressures resulting from human activities have considerably modified the genetic structure of M. persicae populations in northern France in a relatively short period of time.     

Annotated expressed sequence tags and xenobiotic detoxification in the aphid Myzus persicae （Sulzer）

Aphids （Hemiptera： Aphididae） are phytophagous insects that are important agricultural pests. The enormous negative economic impacts caused by aphids worldwide are well known, and are mostly due to their high multiplication rate and the transmission of phytopathogenic viruses. Aphid management strategies mainly involve chemical treatments which are pollutants and are increasingly inefficient, since aphids have developed multiple insecticide-resistant mechanisms. Among the most economically important species is the green peach aptfid Myzus persicae Sulzer （Aphididae： Macrosiphini）, which is able to colonize a wide range of host plants belonging to many different families, and transmits numerous plant viruses. Because of its large prevalence, M. persicae has been the target of massive insecticide treatments; consequently, it has evolved several insecticide-resistant mechanisms. In this work, a collection of expressed genes from M. persicae is presented in order to identify putative genes involved in xenobiotic detoxification. After cDNA cloning and sequencing, 959 expressed sequence tags （EST） were annotated. Most sequences matched known genes corresponded to metabolism proteins （26%）, ribosomal proteins （ 23 % ） and structural proteins （8%）. Among them, several sequences corresponded to proteins putatively involved in sensing, degradation or detoxification of plant xenobiotic products.     

Can invasions occur without change? A comparison of G-matrices and selection in the peach-potato aphid,Myzus persicae

Most evolutionary research on biological invasions has focused on changes seen between the native and invaded range for a particular species. However, it is likely that species that live in human‐modified habitats in their native range might have evolved specific adaptations to those environments, which increase the likelihood of establishment and spread in similar human‐altered environments. From a quantitative genetic perspective, this hypothesis suggests that both native and introduced populations should reside at or near the same adaptive peak. Therefore, we should observe no overall changes in the G (genetic variance–covariance) matrices between native and introduced ranges, and stabilizing selection on fitness‐related traits in all populations. We tested these predictions comparing three populations of the worldwide pest Myzus persicae from the Middle East (native range) and the UK and Chile (separately introduced ranges). In general, our results provide mixed support for this idea, but further comparisons of other species are needed. In particular, we found that there has been some limited evolution in the studied traits, with the Middle East population differing from the UK and Chilean populations. This was reflected in the structure of the G ‐matrices, in which Chile differed from both UK and Middle East populations. Furthermore, the amount of genetic variation was massively reduced in Chile in comparison with UK and Middle East populations. Finally, we found no detectable selection on any trait in the three populations, but clones from the introduced ranges started to reproduce later, were smaller, had smaller offspring, and had lower reproductive fitness than clones from the native range.     

The rôle of folic acid in the appearance of alate forms in Myzus persicae

The rôle of folic acid in wing formation was studied using amino-pterin—a folic acid antagonist. The effects of this antivitamin are acute: larviposition ceases in adults and wing formation is depressed in developing larvae. At lower concentrations graded responses are obtained. Omission of methionine and histidine had no effect on wing formation but thymidine did ameliorate the depression of wing formation by aminopterin.Aminopterin is known to inhibit dihydrofolate reductase—thereby inhibiting tetrahydrofolate production. Tetrahydrofolate is known to be involved in thymidine biosynthesis. The activity of dihydrofolate reductase in presumptive alates was 42 per cent higher than in larvae destined to develop as apterates. The significance of folic acid metabolism in wing formation is discussed.     

Super-CHO—A cell line capable of autocrine growth under fully defined protein-free conditions

Chinese Hamster Ovary (CHO) cells are widely used for the large scale production of recombinant biopharmaceuticals. Growth of the CHO-K1 cell line has been demonstrated in serum-free medium containing insulin, transferrin and selenium. In an attempt to get autocrine growth in protein-free medium, DNA coding for insulin and transferrin production was transfected into CHO-K1 cells. Transferrin was expressed well, with clones secreting approximately 1000 ng/10⁶ cells/24h. Insulin was poorly expressed, with rates peaking at 5 ng/10⁶ cells/24h. Characterisation of the secreted insulin indicated that the CHO cells were incompletely processing the insulin molecule. Site-directed mutagenesis was used to introduce a furin (prohormone converting enzyme) recognition sequence into the insulin molecule, allowing the production of active insulin. However, the levels were still too low to support autocrine growth. Further investigations revealed insulin degrading activity (presumably due to the presence of insulin degrading enzymes) in the cytoplasm of CHO cells. To overcome these problems insulin-like growth factor I (instead of insulin) was transfected into the cells. IGF-1 was completely processed and expressed at rates greater than 500 ng/10⁶cells/24h. In this paper we report autonomous growth of the transfected CHO-K1 cell line expressing transferrin and IGF-1 in protein-free medium without the addition of exogenous growth factors. Growth rates and final cell densities of these cells were identical to that of the parent cell line CHO-K1 growing in insulin, transferrin, and selenium supplemented serum-free media.     

Phototactic behaviour of Pachyneuron aphidis (Hymenoptera: Pteromalidae) – hyperparasitoid of Myzus persicae (Hemiptera: Aphidiae)

We investigated the spectral sensitivity and response to light intensity of Pachyneuron aphidis (Hymenoptera: Pteromalidae), which is a common hyperparasitoid of Aphidius gifuensis (Hymenoptera: Braconidae), a key natural enemy of the green peach aphid, Myzus persicae (Hemiptera: Aphididae). To do so, we used 15 monochromatic lights (emitting various specific wavelengths from 340 to 649 nm) and white light. P. aphidis adults are diurnal insects that show a positive phototaxis to a broad spectrum of light. Significant differences were found between sexes in the phototactic responses of P. aphidis to different monochromatic lights. Female P. aphidis showed four peaks of sensitivity at 380, 450, 504 and 589 nm. Male P. aphidis show two peaks of sensitivity, one at 450 nm and second at 628 nm. P. aphidis adults showed an increased phototactic response at low intensities and a decreased phototactic response at high intensities for both UV light and blue light. This experiment will help provide a scientific basis for the development of colour traps for insect pest management.     

Effect of temperature,relative humidity and aphid developmental stage on the efficacy of the mycoinsecticide Mycotal® against Myzus persicae

The green peach aphid, Myzus persicae, is a major pest worldwide. An examination of the impact of temperature, relative humidity (RH) and developmental stages of M. persicae on the efficacy of the whitefly mycoinsecticide Mycotal®, based on Lecanicillium muscarium and the effects of infection on aphid fecundity was evaluated under controlled conditions. Although this fungus can be grown at a broad range of temperatures (15–30°C), the optimum temperature for control of M. persicae ranged between 20 and 30°C. L. muscarium had high efficacy as a microbial control agent against M. persicae between 55% and 90% RH. Total mortality of aphids treated with different spore dosages of L. muscarium varied according to the developmental stage: adults, fourth and third instar nymphs proved more susceptible than first instar nymphs. Although the fungus did not affect the rate of nymph production, the reproductive period of aphids significantly decreased with increasing the spore dosage. Thus, total fecundity of treated aphids was 22.6 ± 1.1 and 31.6 ± 2.4 offspring per adult at the medium (644 ± viable spore/mm²) and low (330 ± 40 viable spore/mm²) dosages, compared with 45.7 ± 4.3 offspring per untreated aphid. The results suggest that L. muscarium has the potential as a biological control agent of M. persicae.     

A superior drug carrier – aponeocarzinostatin in partially unfolded state fully protects the labile antitumor enediyne

Background  

Neocarzinostatin is a potent antitumor drug consisting of an enediyne chromophore and a protein carrier.     

Mapping Rm2 gene conferring resistance to the green peach aphid (Myzus persicae Sulzer) in the peach cultivar ��Rubira?��

The green peach aphid (GPA), Myzus persicae (Sulzer), is a widespread pest insect that significantly reduces yield in peach orchards [Prunus persica (L.) Batsch]. Chemical control of the GPA population in the orchards showed little efficiency because of the development of resistance to most classes of insecticides. Biological control partially gave convincing results. Breeding for resistant peach cultivars is therefore a serious option to take into account for the development of sustainable pest management. Among the few available resistance cultivars, the rootstock peach “Rubira?” shows a strong induced antixenosis-type GPA resistance. This was demonstrated segregating as a single dominant gene. In order to investigate the genetic basis of resistance and develop molecular tools useful in breeding programs, a F₂ population derived from “Rubira?” also segregating for leaf color was grown and scored for GPA resistance under contrasted environmental conditions. An SSR-based genetic linkage map composed of 120 SSR loci spanned over a distance of 497.8 cM was then established. The GPA resistance mapped to a single locus at the bottom end of linkage group 1. We propose to name Rm2 the dominant allele of the underlying gene. Additionally, a reciprocal translocation was identified near the Gr gene controlling leaf color. The red-leaf parent “Rubira?” was demonstrated responsible for the translocation. This study provides the basis for future molecular analysis for the use of Rm2 in peach breeding programs against GPA in peach orchards.     

How important is the statistical approach for analyzing categorical data? A critique using artificial nests

Ecologists rely heavily upon statistics to make inferences concerning ecological phenomena and to make management recommendations. It is therefore important to use statistical tests that are most appropriate for a given data-set. However, inappropriate statistical tests are often used in the analysis of studies with categorical data (i.e. count data or binary data). Since many types of statistical tests have been used in artificial nests studies, a review and comparison of these tests provides an opportunity to demonstrate the importance of choosing the most appropriate statistical approach for conceptual reasons as well as type I and type II errors.
Artificial nests have routinely been used to study the influences of habitat fragmentation, and habitat edges on nest predation. I review the variety of statistical tests used to analyze artificial nest data within the framework of the generalized linear model and argue that logistic regression is the most appropriate and flexible statistical test for analyzing binary data-sets. Using artificial nest data from my own studies and an independent data set from the medical literature as examples, I tested equivalent data using a variety of statistical methods. I then compared the p-values and the statistical power of these tests. Results vary greatly among statistical methods. Methods inappropriate for analyzing binary data often fail to yield significant results even when differences between study groups appear large, while logistic regression finds these differences statistically significant. Statistical power is is 2–3 times higher for logistic regression than for other tests. I recommend that logistic regression be used to analyze artificial nest data and other data-sets with binary data.     

The effect of intra- and interspecific larval competition for food (Myzus persicae) on the development at 20° ofSyrphus ribesii andSyrphus corollae [Diptera,Syrphidae]

Intra- and interspecific competition for food (Myzus persicae) in larvae ofSyrphus ribesii andS. corollae were investigated in the laboratory at 20°, 16 hrs light. A competing unit consisted originally of six newly hatched larvae, trhee of each species or six of one species.S. ribesii had a low larval survival (about 35–40%) and a prolonged larval period (about 16–17 days) under both intra- and interspecific conditions, although food consumption was greater when mixed withS. corollae. InS. corollae, larval survival was significantly smaller when mixed withS. ribesii than under intraspecific conditions (25.0% and 73.1%). Larval period was somewhat increased in the mixed series. The results are explained by different sizes, natural food demands, feeding efficiencies and predatory tendencies of the two larval species.

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Résumé De jeunes larves deSyrphus ribesii et deSyrphus corollae ont été rassemblées par groupe de 6, toutes de la même espèce ou bien à raison de 3 larves de chaque espèce. Au sein de chaque groupe, les larves pouvaient entrer en concurrence les unes avec les autres en raison de la faible quantité de pucerons, qui étaient offertes chaque jour en nombre dépendant de l’age des larves, les mortes n’étant pas remplacées. Dans le cas d’une concurrence intraspécifique, les larves deS. ribesii ont un taux de survie faible (35–40%) et un long cycle de développement (16–17 jours); par contre,S. corollae a une survie élevée (73,1%) et un cycle de développement normal (9,9 jours). Dans le cas d’une concurrence interspécifique, le développement deS. ribesii n’est pas modifié, mis à part une prise de nourriture un peu plus grande en présence deS. corollae, ce qui se traduit par un poids plus élevé des pupes — par contre, les larves deS. corollae ont un taux de survie sensiblement plus faible (25,0%) et une durée de développement un peu plus longue (11,0 jours), lorsqu’elles sont placées dans les conditions d’un comportement interspécifique. Les résultats peuvent être expliqués par le fait que les larves deS. corollae ont, en présence des larves deS. ribesii, un comportement alimentaire plus mauvais que lorsqu’elles sont placées avec des individus de la même espèce. Cela tient vraisemblablement à ce que les larves deS. ribesii sont plus grosses, ont un besoin alimentaire plus élevé et consomment les pucerons plus rapidement queS. corollae.

     

Network genomics – A novel approach for the analysis of biological systems in the post-genomic era

Network Genomics studies genomics and proteomics foundations of cellular networks in biological systems. It complements systems biology in providing information on elements, their interaction and their functional interplay in cellular networks. The relationship between genomic and proteomic high-throughput technologies and computational methods are described, as well as several examples of specific network genomic application are presented.     

Are artificial wetlands good alternatives to natural wetlands for waterbirds? – A case study on Chongming Island, China

Loss of natural wetlands is a global phenomenon that has been a serious threat to the wildlife. A common practice is to construct artificial wetlands to compensate for the loss of natural wetlands. To test whether artificial wetlands as habitats for waterbirds are good alternatives to natural wetlands, we compared species richness, abundance, and seasonal dynamics of waterbird communities of natural (here tidelands) and artificial wetlands (here aquacultural ponds) on Chongming Island, China. Our results indicate that habitat preference of waterbirds showed seasonal difference: most of the shorebirds were found on tidelands in spring, whereas most of the natatorial birds were recorded in aquacultural ponds in winter. Waterbirds preferred the tidelands rather than aquacultural ponds in both spring and autumn, whereas they showed no preference for either the tidelands or the ponds in summer and winter. It is concluded that natural wetlands are better habitats for waterbirds than artificial wetlands on Chongming Island, while the artificial ones are also suitable habitats for waterbirds in winter. The waterbirds might use artificial wetlands only when natural wetlands are unavailable or of poor quality. An over-emphasis that artificial wetlands are suitable habitats for waterbirds might encourage land managers to convert natural wetlands into the artificial ones, resulting in considerable loss of bird diversity. Therefore, for the purpose of bird conservation, it would be a better practice to conserve natural wetlands rather than to construct artificial ones after destruction of natural wetlands.     

Cell salvage using the continuous autotransfusion device CATSmart – an observational bicenter technical evaluation

Background

The use of cell salvage and autologous blood transfusion has become an important method of blood conservation. So far, there are no clinical data about the performance of the continuous autotransfusion device CATSmart.

Methods

In total, 74 patients undergoing either cardiac or orthopedic surgery were included in this prospective, bicenter and observational technical evaluation to validate red cell separation process and washout quality of CATSmart. The target of red cell separation process was defined as a hematocrit value in the packed red cell unit of 55–75% and of washout quality of 80–100% removal ratio.

Results

Hematocrit values measured by CATSmart and laboratory analysis were 78.5% [71.3%; 84.0%] and 73.7% [67.5%; 75.5%], respectively. Removal ratios for platelets 94.7% [88.2%; 96.7%], free hemoglobin 89.3% [85.2%; 94.9%], albumin 97.9% [96.6%; 98.5%], heparin 99.9% [99.9%; 100.0%], and potassium 92.5% [90.8%; 95.0%] were within the target range while removal of white blood cells was slightly worse 72.4% [57.9%; 87.3%].

Conclusion

The new autotransfusion device enables sufficient red cell separation and washout quality.

     

Whakapapa – A Foundation for Genetic Research?

Whakapapa is the foundation of traditional Māori social structure and it perpetuates a value base that locates people through their relationships to the physical and spiritual worlds. As part of a new envirogenomics research programme, researchers at the Institute of Environmental Science and Research (ESR) are developing a study with an iwi (tribe) to identify combinations of genetic and environmental factors that may contribute to current health status. A major objective of this study is to utilise whakapapa (genealogical information) to explore patterns of genetic variation unique to the iwi and to correlate these with potential disease or ill health. Genetic testing and screening raises numerous ethical issues, particularly when indigenous peoples are the subjects. This paper will outline ESR’s strategy for addressing indigenous concerns about genetic testing and how whakapapa forms an integral part of the envirogenomics research programme.     

Dispersal-limited species – A challenge for ecological restoration

In recent years, increasing efforts have been directed to the restoration of natural communities affected by human activities. However, restoration success is often reduced because of the lack of dispersal-limited species in the restored site. Numerous rare species are dispersal-limited, having low probabilities to re-colonize restored sites and to establish viable populations. A high species richness enhances the ability of ecosystems to maintain multiple functions. It has been shown that in highly diverse ecosystems such as alpine meadows, tropical forests and coral reefs, the most distinct combinations of functions are supported predominantly by rare species. Thus, more emphasis should be given to support rare species in restoration actions. I suggest that well-known techniques for increasing plant diversity in restoration projects should be complemented with techniques to re-introduce dispersal-limited animals. Re-establishing ecological connectivity might be of benefit for certain species in the long term. However, for the majority of dispersal-limited animal species, translocations of founder individuals might be the only tool to re-establish populations in restored sites.