Aphid

About: Aphid is a research topic. Over the lifetime, 11380 publications have been published within this topic receiving 229721 citations. The topic is also known as: Aphidoidea & plant lice.

Host-based genetic differentiation in the aphid Aphis gossypii Glover, evidenced from RAPD fingerprints

Abstract: Samples of the aphid Aphis gossypii (Glover) were collected from different host plants at 18 locations in southern France, La Reunion, Portugal and Laos. RAPD (random amplified polymorphic DNA) patterns of the 480 aphids were obtained using three random primers. A large number of RAPD bands were shared by all aphids of the 18 populations, but some RAPD bands appeared to be population specific. Over all aphids, a total of 37 polymorphic bands were identified and defined 142 RAPD phenotypes. A cluster analysis based on genetic distance revealed that the 18 aphid populations were divided into two groups, depending on whether they were collected on a cucurbit host plant. An analysis of molecular variance (AMOVA) was also performed and confirmed the differentiation into two groups. Several RAPD bands that were obtained using random primer A11 could be considered as diagnostic loci as they were fixed in populations collected on cucurbits and were always absent in those collected on noncucurbit host plants. These results represent the first evidence for genetic structuring within the species A. gossypii, according to host-plant type.

Resistance is costly: trade-offs between immunity, fecundity and survival in the pea aphid

Abstract: Parasitoids are among the most important natural enemies of insects in many environments. Acyrthosiphon pisum, the pea aphid, is a common pest of the leguminous crops in temperate regions. Pea aphids are frequently attacked by a range of endoparasitic wasps, including the common aphidiine, Aphidius ervi. Immunity to parasitoid attack is thought to involve secondary symbiotic bacteria, the presence of which is associated with the death of the parasitoid egg. It has been suggested that there is a fecundity cost of resistance, as individuals carrying the secondary symbionts associated with parasitoid resistance have fewer offspring. Supporting this hypothesis, we find a positive relationship between fecundity and susceptibility to parasitoid attack. There is also a negative relationship between fecundity and off-plant survival time (which positively correlates with resistance to parasitoid attack). Taken together, these results suggest that the aphids can either invest in defence (parasitoid resistance, increased off-plant survival time) or reproduction, and speculate that this may be mediated by changes in the aphids' endosymbiont fauna. Furthermore, there is a positive relationship between aphid size and resistance, suggesting that successful resistance to parasitoid attack may involve physical, as well as physiological, defences.

Resistance of Arabidopsis thaliana to the green peach aphid, Myzus persicae, involves camalexin and is regulated by microRNAs

Abstract: Summary Small RNAs play important roles in resistance to plant viruses and the complex responses against pathogens and leaf-chewing insects. We investigated whether small RNA pathways are involved in Arabidopsis resistance against a phloem-feeding insect, the green peach aphid (Myzus persicae). We used a 2-wk fecundity assay to assess aphid performance on Arabidopsis RNA silencing and defence pathway mutants. Quantitative real-time polymerase chain reaction was used to monitor the transcriptional activity of defence-related genes in plants of varying aphid susceptibility. High-performance liquid chromatography-mass spectrometry was employed to measure the accumulation of the antimicrobial compound camalexin. Artificial diet assays allowed the assessment of the effect of camalexin on aphid performance. Myzus persicae produces significantly less progeny on Arabidopsis microRNA (miRNA) pathway mutants. Plants unable to process miRNAs respond to aphid infestation with increased induction of PHYTOALEXIN DEFICIENT3 (PAD3) and production of camalexin. Aphids ingest camalexin when feeding on Arabidopsis and are more successful on pad3 and cyp79b2/cyp79b3 mutants defective in camalexin production. Aphids produce less progeny on artificial diets containing camalexin. Our data indicate that camalexin functions beyond antimicrobial defence to also include hemipteran insects. This work also highlights the extensive role of the miRNA-mediated regulation of secondary metabolic defence pathways with relevance to resistance against a hemipteran pest.

Virus spread and vector dynamics in genetically diverse plant populations

Abstract: Little is known about the influence of genetic diversity in plant populations on the dynamics of plant viruses, particularly those transmitted by insects. For these viruses, plant genetic diversity may affect virus incidence through impacts on the population dy- namics of the vector insects or through impacts on vector feeding behavior, which deter- mines transmission of the virus. This study was designed to explore the influence of plant genetic diversity on virus dispersal by aphid vectors and to examine the biological mech- anisms responsible for that influence. In a set of field experiments using the aphid-transmitted barley yellow dwarf virus, I examined the influence of genetic diversity in oat (Avena sativa L.) populations on the spread of the virus and on the population dynamics and movement behavior of aphid vectors of the virus. Only at relatively high aphid abundance were the densities of aphid vectors influenced by plant genetic diversity. In one year out of three, densities of the oat- bird cherry aphid, Rhopalosiphum padi (L.), were significantly lower in the genetically diverse stand than in the genetically homogeneous stands. In no year were densities of the English grain aphid, Sitobion avenae (F.), influenced by the host-plant population. Despite these weak or absent effects on vector abundance, the incidence of the virus was consistently lower in the genetically diverse oat populations. Disease reduction in the diverse populations appears to depend upon changes in aphid movement behavior that affect the efficiency of virus transmission. Mark-release experi- ments with S. avenae demonstrated that movement rates were significantly higher and plant tenure times were significantly lower in the genetically diverse oat populations. Be- cause the barley yellow dwarf virus requires several hours of aphid feeding for effective transmission, these reduced tenure times and increased travel time among plants led to a reduction of virus transmission. While plant genotype can clearly influence herbivorous insects dramatically, this study suggests that the effects on insects of genetic diversity per se in the host-plant population are likely to be subtle and not easily detected using standard field sampling techniques, except at high insect densities. Yet even at low vector densities, behavioral responses to plant genetic diversity can lead to significant effects on the spread of pathogens.