Showing papers on "Aphid published in 2018"
TL;DR: Light is shed on the possible utilization of the crop residue of industrial hemp as a source of environmental-friendly botanical insecticides to be used in Integrated Pest Management and organic agriculture, particularly to manage aphid and housefly populations.
139 citations
TL;DR: One of very few reports of the compatible use of endophytic fungal entomopathogens with other biological control agents, particularly parasitoids, for aphid suppression under controlled greenhouse conditions as part of an Integrated Pest Management (IPM) approach is presented.
80 citations
TL;DR: Results indicate very high prospects for using the essential oil obtained from F. vulgare in the development of environmentally safe botanical insecticides designed for plant protection against aphids.
Abstract: Aphids are an important agricultural pest that not only damage plants by suction, but can also transmit a number of economically important plant viruses. Protection against aphids is based on the use of synthetic insecticides. However, these products can be dangerous for non-target organisms. Therefore, it is important to develop new, environmentally safe plant protection methods. In this study, we have tested an essential oil (EO) obtained from Foeniculum vulgare for the mortality of Myzus persicae, an important polyphagous pest, its natural predator Harmonia axyridis, and Eisenia fetida as a representative of soil organisms. The EO, with its major compounds trans-anethole (67.9%) and fenchone (25.5%), was found to provide excellent efficacy against M. persicae (LC50 = 0.6 and LC90 = 2.4 mL L−1) while not causing any significant mortality of the tested non-target organisms. On the contrary, application of an insecticide based on the active substance alpha-cypermethrin not only caused mortality in the aphids, but also had a fatal negative effect on both the non-target organisms we tested, resulting in their high mortality. Our results indicate very high prospects for using the essential oil from F. vulgare in the development of environmentally safe botanical insecticides designed for plant protection against aphids.
76 citations
TL;DR: It is demonstrated that selective suppression of insect symbiosis-related gene function can reduce the performance of an insect pest.
59 citations
TL;DR: These results identify the first cuticular proteins ever reported within arthropod mouthparts and distinguish Stylin-01 as the best candidate receptor for the aphid transmission of noncirculative plant viruses.
Abstract: Plant viruses transmitted by insects cause tremendous losses in most important crops around the world. The identification of receptors of plant viruses within their insect vectors is a key challenge to understanding the mechanisms of transmission and offers an avenue for future alternative control strategies to limit viral spread. We here report the identification of two cuticular proteins within aphid mouthparts, and we provide experimental support for the role of one of them in the transmission of a noncirculative virus. These two proteins, named Stylin-01 and Stylin-02, belong to the RR-1 cuticular protein subfamily and are highly conserved among aphid species. Using an immunolabeling approach, they were localized in the maxillary stylets of the pea aphid Acyrthosiphon pisum and the green peach aphid Myzus persicae, in the acrostyle, an organ earlier shown to harbor receptors of a noncirculative virus. A peptide motif present at the C termini of both Stylin-01 and Stylin-02 is readily accessible all over the surface of the acrostyle. Competition for in vitro binding to the acrostyle was observed between an antibody targeting this peptide and the helper component protein P2 of Cauliflower mosaic virus Furthermore, silencing the stylin-01 but not stylin-02 gene through RNA interference decreased the efficiency of Cauliflower mosaic virus transmission by Myzus persicae These results identify the first cuticular proteins ever reported within arthropod mouthparts and distinguish Stylin-01 as the best candidate receptor for the aphid transmission of noncirculative plant viruses.IMPORTANCE Most noncirculative plant viruses transmitted by insect vectors bind to their mouthparts. They are acquired and inoculated within seconds when insects hop from plant to plant. The receptors involved remain totally elusive due to a long-standing technical bottleneck in working with insect cuticle. Here we characterize the role of the two first cuticular proteins ever identified in arthropod mouthparts. A domain of these proteins is directly accessible at the surface of the cuticle of the acrostyle, an organ at the tip of aphid stylets. The acrostyle has been shown to bind a plant virus, and we consistently demonstrated that one of the identified proteins is involved in viral transmission. Our findings provide an approach to identify proteins in insect mouthparts and point at an unprecedented gene candidate for a plant virus receptor.
56 citations
TL;DR: It is proposed that rising global temperatures could promote the widespread breakdown of defensive mutualisms, a prospect with implications for both human and ecosystem health.
Abstract: Environmental factors, including temperature, can have large effects on species interactions, including mutualisms and antagonisms. Most insect species are infected with heritable bacterial symbionts with many protecting their hosts from natural enemies. However, many symbionts or their products are thermally sensitive; hence, their effectiveness may vary across a range of temperatures. In the pea aphid, Acyrthosiphon pisum, the bacterial symbiont Hamiltonella defensa and its associated APSE bacteriophages confer resistance to this aphid's dominant parasitoid, Aphidius ervi. Here, we investigate the effects of temperature on both endogenous and symbiont-based protection against this parasitoid. We also explored the defensive properties of the X-type symbiont, a bacterium hypothesized to shape aphid defence when co-occurring with H. defensa. We show that H. defensa protection fails at higher temperatures, although some aphid genotype and H. defensa strain combinations are more robust than others at moderately warmer temperatures. We also found that a single X-type strain neither defended against parasitism by A. ervi nor rescued lost H. defensa protection at higher temperatures. In contrast, endogenous aphid resistance was effective across temperatures, revealing that these distinct defensive modes are not equally robust to changing environments. Through a survey of field-collected pea aphids, we found a negative correlation between H. defensa frequencies and average daily temperatures across North American locales, fitting expectations for reduced symbiont benefits under warm climates. Based on these findings, we propose that rising global temperatures could promote the widespread breakdown of defensive mutualisms, a prospect with implications for both human and ecosystem health.
55 citations
TL;DR: Comparing aphid-infested with water-stressed plants, most of the observed differences were quantitative and proline and hydroxyproline accumulated dramatically in response to water stress, but not in Response to aphid infestation.
Abstract: Amino acids play a central role in aphid-plant interactions. They are essential components of plant primary metabolism, function as precursors for the synthesis of defense-related specialized metabolites, and are major growth-limiting nutrients for aphids. To quantify changes in the free amino acid content of pepper (Capsicum annuum L.) leaves in response to green peach aphid (Myzus persicae Sulzer) feeding, plants were infested with a low (20 aphids/plant) or a high (200 aphids/plant) aphid density in time-course experiments ranging from 3 hours to 7 days. A parallel experiment was conducted with pepper plants that had been subjected to water stress. Factor Analysis of Mixed Data revealed a significant interaction of time x density in the free amino acid response of aphid-infested leaves. At low aphid density, M. persicae did not trigger a strong response in pepper leaves. Conversely, at high density, a large increase in total free amino acid content was observed and specific amino acids peaked at different times post-infestation. Comparing aphid-infested with water-stressed plants, most of the observed differences were quantitative. In particular, proline and hydroxyproline accumulated dramatically in response to water stress, but not in response to aphid infestation. Some additional differences and commonalities between the two stress treatments are discussed.
50 citations
TL;DR: This study demonstrates that S. symbiotica plays an important role in the ability of aphid hosts to tolerate insecticides, and provides insight into the potential changes in tolerance to insecticides in the field.
Abstract: Background Aphids are agricultural pests that damage crops by direct feeding and by vectoring important plant viruses. Bacterial symbionts can influence aphid biology, e.g. by providing essential nutrients or facilitating adaptations to biotic and abiotic stress. Results We investigated the pea aphid (Acyrthosiphon pisum Harris) and its commonly associated secondary bacterial symbiont Serratia symbiotica to study the effect of this symbiont on host fitness and susceptibility to the insecticides imidacloprid, chlorpyrifos methyl, methomyl, cyantraniliprole and spirotetramat. There is emerging evidence that members of the genus Serratia can degrade and/or detoxify diverse insecticides. Therefore, we hypothesized that S. symbiotica may promote resistance to these artificial stress agents in aphids. Our results showed that Serratia-infected aphids were more susceptible to most of the tested insecticides than non-infected aphids. This probably reflects the severe fitness costs associated with S. symbiotica, which negatively affects development, reproduction and body weight. Conclusion Our study demonstrates that S. symbiotica plays an important role in the ability of aphid hosts to tolerate insecticides. These results provide insight into the potential changes in tolerance to insecticides in the field because there is a continuous and dynamic process of symbiont acquisition and loss that may directly affect host biology. © 2018 Society of Chemical Industry.
47 citations
TL;DR: It is demonstrated that a commercially available resistant sorghum variety provides the most robust protection against this pest in the central High Plains, and an already present assemblage of aphid predators recruits readily to aphid-infested Sorghum and is likely to provide important biological control services particularly in resistant sorks.
46 citations
TL;DR: Results indicated that β-ocimene can activate the defense response of Chinese cabbage against M. persicae, and that M. Persicae can also adjust its detoxifying enzymes machinery to counter the host plant defense reaction.
Abstract: In nature, plants have evolved sophisticated defense mechanisms against the attack of pathogens and insect herbivores. Plant volatile-mediated plant-to-plant communication has been assessed in multitrophic systems in different plant species and different pest species. β-ocimene is recognized as an herbivore-induced plant volatile that play an important role in the chemical communication between plants and pests. However, it is still unclear whether β-ocimene can active the defense mechanism of Chinese cabbage Brassica pekinensis against the peach aphid Myzus persicae. In this study, we found that treatment of Chinese cabbage with β-ocimene inhibited the growth of M. persicae in terms of weight gain and reproduction. Moreover, β-ocimene treatment negatively influenced the feeding behavior of M. persicae by shortening the total feeding period and phloem ingestion and increasing the frequency of stylet puncture. When given a choice, winged aphids preferred to settle on healthy Chinese cabbage compared with β-ocimene-treated plants. In addition, performance of the parasitoid Aphidius gifuensis in terms of Y-tube olfaction and landings was better on β-ocimene-treated Chinese cabbage than on healthy plants. Furthermore, β-ocimene significantly increased the expression levels of salicylic acid and jasmonic acid marker genes and the accumulation of glucosinolates. Surprisingly, the transcriptional levels of detoxifying enzymes (CYP6CY3, CYP4, and GST) in aphids reared on β-ocimene-treated Chinese cabbage were significantly higher than those of aphids reared on healthy plants. In summary, our results indicated that β-ocimene can activate the defense response of Chinese cabbage against M. persicae, and that M. persicae can also adjust its detoxifying enzymes machinery to counter the host plant defense reaction.
46 citations
TL;DR: The obtained results suggest that essential oils from the studied Asteraceae plants can affect important biochemical processes within aphid tissues and may be considered as potent biopesticides in green peach aphid control.
TL;DR: Recommendations for mitigating the challenges resulting from the presence of defensive symbionts for the biological control of pest aphids are derived, including selective breeding of parasitoids as well as clever release strategies, potentially in combination with other biocontrol agents.
TL;DR: Current knowledge on the evolution of aphid genomes is extended and evidence for an as-of-yet unknown shared control mechanism, which underlies effector expression, and ultimately plant parasitism is revealed.
Abstract: Aphids are a diverse group of taxa that contain agronomically important species, which vary in their host range and ability to infest crop plants. The genome evolution underlying agriculturally important aphid traits is not well understood. We generated draft genome assemblies for two aphid species: Myzus cerasi (black cherry aphid) and the cereal specialist Rhopalosiphum padi. Using a de novo gene prediction pipeline on both these, and three additional aphid genome assemblies (Acyrthosiphon pisum, Diuraphis noxia, and Myzus persicae), we show that aphid genomes consistently encode similar gene numbers. We compare gene content, gene duplication, synteny, and putative effector repertoires between these five species to understand the genome evolution of globally important plant parasites. Aphid genomes show signs of relatively distant gene duplication, and substantial, relatively recent, gene birth. Putative effector repertoires, originating from duplicated and other loci, have an unusual genomic organization and evolutionary history. We identify a highly conserved effector pair that is tightly physically linked in the genomes of all aphid species tested. In R. padi, this effector pair is tightly transcriptionally linked and shares an unknown transcriptional control mechanism with a subset of ∼50 other putative effectors and secretory proteins. This study extends our current knowledge on the evolution of aphid genomes and reveals evidence for an as-of-yet unknown shared control mechanism, which underlies effector expression, and ultimately plant parasitism.
TL;DR: This study significantly advances understanding of plant-plant communication by demonstrating the importance of sap-feeding herbivores and herbivore identity, as well as the chemical basis for such effects.
Abstract: It is well known that plant damage by leaf-chewing herbivores can induce resistance in neighbouring plants. It is unknown whether such communication occurs in response to sap-feeding herbivores, whether communication is specific to herbivore identity, and the chemical basis of communication, including specificity. We carried out glasshouse experiments using the California-native shrub Baccharis salicifolia and two ecologically distinct aphid species (one a dietary generalist and the other a specialist) to test for specificity of plant-plant communication and to document the underlying volatile organic compounds (VOCs). We show specificity of plant-plant communication to herbivore identity, as each aphid-damaged plant only induced resistance in neighbours against the same aphid species. The amount and composition of induced VOCs were markedly different between plants attacked by the two aphid species, providing a putative chemical mechanism for this specificity. Furthermore, a synthetic blend of the five major aphid-induced VOCs (ethanone, limonene, methyl salicylate, myrcene, ocimene) triggered resistance in receiving plants of comparable magnitude to aphid damage of neighbours, and the effects of the blend exceeded those of individual compounds. This study significantly advances our understanding of plant-plant communication by demonstrating the importance of sap-feeding herbivores and herbivore identity, as well as the chemical basis for such effects.
TL;DR: There was little evidence of any phytotoxicity caused by any of the biopesticide products tested and the potential to use these products as part of an Insecticide Resistance Management (IRM) programme are discussed.
TL;DR: In this article, the authors identify pepper materials with a good level of resistance to the green peach aphid (GPA), Myzus persicae, and elucidate possible resistance mechanisms.
Abstract: The green peach aphid (GPA), Myzus persicae, is economically one of the most threatening pests in pepper cultivation, which not only causes direct damage but also transmits many viruses. Breeding aphid resistant pepper varieties is a promising and environmentally friendly method to control aphid populations in the field and in the greenhouse. Until now, no strong sources of resistance against the GPA have been identified. Therefore the main aims of this study were to identify pepper materials with a good level of resistance to GPA and to elucidate possible resistance mechanisms. We screened 74 pepper accessions from different geographical areas for resistance to M. persicae. After four rounds of evaluation we identified one Capsicum baccatum accession (PB2013071) as highly resistant to M. persicae, while the accessions PB2013062 and PB2012022 showed intermediate resistance. The resistance of PB2013071 resulted in a severely reduced uptake of phloem compared to the susceptible accession, as determined by Electrical Penetration Graph (EPG) studies. Feeding of M. persicae induced the expression of callose synthase genes and resulted in callose deposition in the sieve elements in resistant, but not in susceptible plants. Three aphid resistant pepper accessions were identified, which will be important for breeding aphid resistant pepper varieties in the future. The most resistant accession PB2013071 showed phloem-based resistance against aphid infestation.
TL;DR: This study collected data on the development, survival, fecundity, and proportion of apterous and alate forms of green peach aphid reared on five commercial pepper cultivars and compared differences in the population growth rate of M. persicae on different pepper cultivARS.
Abstract: The green peach aphid, Myzus persicae (Sulzer) (Hemiptera: Aphididae), is a major pest of pepper. In this study, we collected data on the development, survival, fecundity, and proportion of apterous and alate forms of green peach aphid reared on five commercial pepper cultivars (Amiral, Erciyes, Mert, Mertcan, and Naz) at 25 ± 1°C, 60 ± 5% RH, and a photoperiod of 16:8 (L:D) h. We analyzed the life history raw data by using the age-stage, two-sex life table. The shortest development time (6.66 days) and highest fecundity (62.68 individuals) occurred on the Erciyes cultivar. The highest intrinsic rate of increase (r = 0.332 d−1), finite rate of increase (λ = 1.394 d−1), net reproductive rate (R0 = 62.7 offspring) and shortest mean generation time (T = 12.45 d) also occurred on the Erciyes cultivar; while the lower fitness occurred on the Amiral, Mertcan and Naz cultivars. Our results compared differences in the population growth rate of M. persicae on different pepper cultivars. This information will be useful to individuals working in pest management programs particularly those involving M. persicae.
TL;DR: It is expressed that JA and/or Aphid application induces systemic defenses in oilseed rape that have a negative effect on P. xylostella fitness.
Abstract: The diamondback moth, Plutella xylostella (L.), has become the most destructive insect pest of cruciferous plants, such as B. napus throughout the world including Iran. In this study, the induction of resistance was activated in oilseed rape plants (Brassica napus L.) using foliar application of jasmonic acid (JA) and mealy cabbage aphid either individually or in combination against diamondback moth. Induced resistance by inducers significantly reduced the population growth parameters, as well as the survival rate of immature P. xylostella. Also, the nutritional indices of P. xylostella were studied to evaluate the potential impact of induced resistance on the insect feeding behavior. The values of the efficiency of conversion of ingested food (ECI), the efficiency of conversion of digested food (ECD), relative consumption rate (RCR), and relative growth rate (RGR) of P. xylostella on JA-treated plants were significantly reduced compared to control. These are because glucosinolates and proteinase inhibitors (PIs) are induced following treatment of plants. Also, we found a significantly higher GOX activity in the salivary gland extracts of larvae fed on JA treatment. These results express that JA and/or Aphid application induces systemic defenses in oilseed rape that have a negative effect on P. xylostella fitness. These findings develop our knowledge the effects of induced defenses on P. xylostella.
TL;DR: The results demonstrate that Vg and VgR are involved in various aspects of aphid development and reproduction and could help to elucidate the reproductive mechanism and provide information that will be useful for developing new pest control strategies.
Abstract: Vitellogenin (Vg) and its receptor (VgR) play a key role in the reproductive process and development of insects. Aphids are a group of high-fecundity insect species with pseudoplacental viviparity, but the roles of their Vg and VgR genes have not been investigated yet. The brown citrus aphid, Aphis (Toxoptera) citricidus, is a major insect pest of citrus and the main vector of Citrus tristeza closterovirus. In this study, we identified and characterized these two genes, designated as AcVg and AcVgR, from the brown citrus aphid. We found that AcVg has lost the DUF1943 domain that is present in other insect Vgs. Silencing of AcVg and AcVgR led to a delay in the nymph-adult transition, a prolonged prereproductive period, and a shortened reproductive period, which in turn resulted in slower embryonic development and fewer new-born nymphs. Interestingly, silencing of AcVg decreased the transcript level of AcVgR, but silencing of AcVgR resulted in increased transcript levels of AcVg. In addition, silencing of Vg/VgR had similar phenotypes between alate and apterous morphs, suggesting that the functions of these two genes are the same in the two wing morphs of the aphid. Our results demonstrate that Vg and VgR are involved in various aspects of aphid development and reproduction. Further studies on the synthesis of Vg could help to elucidate the reproductive mechanism and provide information that will be useful for developing new pest control strategies.
TL;DR: In vivo evidence is brought that the membrane-bound Ephrin receptor (Eph) is a novel aphid protein involved in the transmission of the Turnip yellows virus (TuYV, Polerovirus genus, Luteoviridae family) by Myzus persicae and evidence that Eph is likely involved in intestinal uptake of the virion.
Abstract: Aphid-transmitted plant viruses are a threat for major crops causing massive economic loss worldwide. Members in the Luteoviridae family are transmitted by aphids in a circulative and non-replicative mode. Virions are acquired by aphids when ingesting sap from infected plants and are transported through the gut and the accessory salivary gland (ASG) cells by a transcytosis mechanism relying on virus-specific receptors largely unknown. Once released into the salivary canal, virions are inoculated to plants, together with saliva, during a subsequent feeding. In this paper, we bring in vivo evidence that the membrane-bound Ephrin receptor (Eph) is a novel aphid protein involved in the transmission of the Turnip yellows virus (TuYV, Polerovirus genus, Luteoviridae family) by Myzus persicae. The minor capsid protein of TuYV, essential for aphid transmission, was able to bind the external domain of Eph in yeast. Feeding M. persicae on in planta- or in vitro-synthesized dsRNA targeting Eph-mRNA (dsRNAEph) did not affect aphid feeding behavior but reduced accumulation of TuYV genomes in the aphid's body. Consequently, TuYV transmission efficiency by the dsRNAEph-treated aphids was reproducibly inhibited and we brought evidence that Eph is likely involved in intestinal uptake of the virion. The inhibition of virus uptake after dsRNAEph acquisition was also observed for two other poleroviruses transmitted by M. persicae, suggesting a broader role of Eph in polerovirus transmission. Finally, dsRNAEph acquisition by aphids did not affect nymph production. These results pave the way toward an ecologically safe alternative of insecticide treatments that are used to lower aphid populations and reduce polerovirus damages.
TL;DR: It is suggested that for insect-natural enemy interactions, urbanization may affect some groups, while not influencing others, and that local effects will also be key determinants of how urban ecological communities are formed.
Abstract: Urbanization can alter the composition of arthropod communities. However, little is known about how urbanization affects ecological interactions. Using experimental colonies of the black bean aphid Aphis fabae Scopoli reared on Vicia faba L, we asked if patterns of predator-prey, host-parasitoid and ant-aphid mutualisms varied along an urbanization gradient across a large town in southern England. We recorded the presence of naturally occurring predators, parasitoid wasps and mutualistic ants together with aphid abundance. We examined how biotic (green areas and plant richness) and abiotic features (impervious surfaces and distance to town center) affected (1) aphid colony size, (2) the likelihood of finding predators, mutualistic ants and aphid mummies (indicating the presence of parasitoids), and (3) how the interplay among these factors affected patterns of parasitoid attack, predator abundance, mutualistic interactions and aphid abundance. Aphid abundance was best explained by the number of mutualistic ants attending the colonies. Aphid predators responded negatively to both the proportion of impervious surfaces and to the number of mutualistic ants farming the colonies, and positively to aphid population size, whereas parasitized aphids were found in colonies with higher numbers of aphids and ants. The number of mutualistic ants attending was positively associated with aphid colony size and negatively with the number of aphid predators. Our findings suggest that for insect-natural enemy interactions, urbanization may affect some groups, while not influencing others, and that local effects (mutualists, host plant presence) will also be key determinants of how urban ecological communities are formed.
TL;DR: Comparing the strengths and costs of both types of defence in aphids helps elucidate the selective pressures that maintain multi-modal defence mechanisms or that may favour one over the other, and finds that variation in endogenous traits, such as resistance, among host genotypes may offer redundancy and generally limit the invasion potential of mutualistic microbes in insects.
Abstract: The pea aphid, Acyrthosiphon pisum, maintains extreme variation in resistance to its most common parasitoid wasp enemy, Aphidius ervi, which is sourced from two known mechanisms: protective bacterial symbionts, most commonly Hamiltonella defensa, or endogenously encoded defences. We have recently found that individual aphids may employ each defence individually, occasionally both defences together, or neither.
In field populations, Hamiltonella-infected aphids are found at low to moderate frequencies and while less is known about the frequency of resistant genotypes, they show up less often than susceptible genotypes in field collections. To better understand these patterns, we sought to compare the strengths and costs of both types of defence, individually and together, in order to elucidate the selective pressures that maintain multi-modal defence mechanisms or that may favour one over the other.
We experimentally infected five aphid genotypes (two lowly and three highly resistant), each with two symbiont strains, Hamiltonella-APSE8 (moderate protection) and Hamiltonella-APSE3 (high protection). This resulted in three sublines per genotype: uninfected, +APSE8 and +APSE3. Each of the 15 total sublines was first subjected to a parasitism assay to determine its resistance phenotype and in a second experiment, a subset was chosen to compare fitness (fecundity and survivorship) in the presence and absence of parasitism.
In susceptible aphid genotypes, parasitized sublines infected with Hamiltonella generally showed increased protection with direct fitness benefits, but clear infection costs to fitness in the absence of parasitism. In resistant genotypes, Hamiltonella infection rarely conferred additional protection, often further reduced fecundity and survivorship when enemy challenged, and resulted in constitutive fitness costs in the absence of parasitism. We also identified strong aphid genotype × symbiont–strain interactions, such that the best defensive strategy against parasitoids varied for each aphid genotype; one performed best with no protective symbionts, the others with particular strains of Hamiltonella.
This surprising variability in outcomes helps explain why Hamiltonella infection frequencies are often intermediate and do not strongly track parasitism frequencies in field populations. We also find that variation in endogenous traits, such as resistance, among host genotypes may offer redundancy and generally limit the invasion potential of mutualistic microbes in insects.
07 Jun 2018
TL;DR: The results of RNA-Sequencing revealed that overexpression of MYB102 in Arabidopsis promoted ET biosynthesis by upregulation of some 1-aminocyclopropane-1-carboxylate synthase (ACS) genes, which are rate-limiting enzymes of the ET-synthetic pathway.
Abstract: Induction of ethylene biosynthesis by aphids increases the susceptibility of several plant species to aphids. Recent studies have indicated that some MYB transcription factors regulate the phloem-based defense against aphid infestation by modulating ethylene (ET) signaling. Arabidopsis MYB102 has previously been shown to be induced by wound signaling and regulate defense response against chewing insects. However, it remains unclear whether Arabidopsis MYB102 takes part in the defense response of plants to aphids. Here, we investigated the function of MYB102 in the response of Arabidopsis to aphid infestation. Arabidopsis MYB102 was primarily expressed in vascular tissues, and its transcription was remarkably induced by green peach aphids (GPA; Myzus persicae). The results of RNA-Sequencing revealed that overexpression of MYB102 in Arabidopsis promoted ET biosynthesis by upregulation of some 1-aminocyclopropane-1-carboxylate synthase (ACS) genes, which are rate-limiting enzymes of the ET-synthetic pathway. Enhanced ET levels led to reduced Arabidopsis resistance to GPA. Furthermore, dominant suppression of MYB102 inhibited aphid-induced increase of ET levels in Arabidopsis. In agreement with a negative regulatory role for ET in aphid defense responses, the MYB102-overexpressing lines were more susceptible to GPA than wild-type (WT) plants. Overexpression of MYB102 in Arabidopsis obviously repressed aphid-induced callose deposition. Conversely, overexpression of MYB102 failed to increase aphid susceptibility in both the ET-insensitive mutants and plants treated with inhibitors of ET signaling pathways, demonstrating that the ET was critical for promoting aphid performance conferred by overexpression of MYB102. Collectively, our findings indicate that the Arabidopsis MYB102 increases host susceptibility to GPA through the ET-dependent signaling pathways.
TL;DR: The results indicated that EPF and botanical extracts (neem or eucalyptus) caused significant reduction in survival and fecundity of S. avenae and they may be used as promising natural alternatives to synthetic insecticides against the wheat aphid species.
Abstract: Wheat aphid, Sitobion avenae (Fab.), is a serious pest of wheat crop across the world. The present study was conducted to evaluate the potentials of the water plant extracts of Azadirachta indica (neem) or Eucalyptus camaldulensis and the entomopathogenic fungi (EPF); Beauveria bassiana or Metarhizium anisopliae against the aphid species. After 5 days of applications, the combined mixture of B. bassiana and eucalyptus extract caused the maximum mortality rate (87%). While the combination of B. bassiana with neem extract showed the least rate (54%). Fecundity was negatively affected by the single and combined treatments of EPF and botanicals extracts. The lowest fecundity (7 nymphs per female) was recorded when the aphid was treated by the binary mixture of B. bassiana and eucalyptus extract. Correspondent maximum fecundity (29 nymphs per female) in 5 days was recorded in control treatment, while 23 nymphs were produced by a single female when treated with the binary mixture of B. bassiana and neem extract. The results indicated that EPF and botanical extracts (neem or eucalyptus) caused significant reduction in survival and fecundity of S. avenae. Therefore, they may be used as promising natural alternatives to synthetic insecticides against the wheat aphid species.
TL;DR: The combine use of both PGPR strains viz.
TL;DR: A high level of antibiosis in Darab2 compared with the other tested cultivars may decrease the population density of R. padi on wheat and also cause a suppression of cereal viruses and reduce the pesticide application to wheat fields of Iran.
Abstract: Taheri S., Razmjou J., Rastegari N. (2010): Fecundity and development rate of the bird cherry-oat aphid, Rhopalosiphum padi (L) (Hom.: Aphididae) on six wheat cultivars. Plant Protect Sci., 46: 72–78. Rhopalosiphum padi is a polyphagous species with a nearly worldwide distribution. Biological parameters of this aphid on six commonly grown wheat cultivars in the Fars province including Chamran, Darab2, Shiraz, Ghods, Marvdasht and Niknezhad were investigated at the two-leaf stage of wheat. The experiments were carried out at 24 ± 5°C, 65 ± 5% R.H. and a photoperiod of 14:10 h (L:D) in a greenhouse. The number of nymphs per female of R. padi was 62.05, 55.84, 49.89, 47.63, 42.76 and 40.65 (nymphs/female) on Niknezhad, Shiraz, Ghods, Marvdasht, Chamran, and Darab2, respectively. Also, the highest and the lowest rm values of this aphid were obtained on Niknezhad (0.381 per day) and Darab2 (0.328 per day), respectively. In addition, other population growth indices were estimated. In general, a high level of antibiosis in Darab2 compared with the other tested cultivars may decrease the population density of R. padi on wheat and also cause a suppression of cereal viruses (e.g. BYDV) and reduce the pesticide application to wheat fields of Iran.
TL;DR: Feeding on C. australis increased the resistance of the soybean host to subsequent feeding by the leafworm Spodoptera litura and soybean aphid Aphis glycines, resulting in 21% decreased leafworm mass and 41% reduced aphid survival rate, strongly suggest that GPA feeding on Cuscuta induces a systemic signal, which is translocated to hosts and activates defense against herbivores.
Abstract: Dodders (Cuscuta spp.) are shoot holoparasites, whose haustoria penetrate host tissues to enable fusion between the parasite and host vascular systems, allowing Cuscuta to extract water, nutrients and other molecules from hosts. Aphids are piercing-sucking herbivores that use specialized stylets to feed on phloem sap. Aphids are known to feed on Cuscuta, but how Cuscuta and its host plant respond to aphids attacking the parasite was unknown. Phytohormone quantification, transcriptomic analysis and bioassays were performed to determine the responses of Cuscuta australis and its soybean (Glycine max) hosts to the feeding of green peach aphid (GPA; Myzus persicae) on C. australis. Decreased salicylic acid levels and 172 differentially expressed genes (DEGs) were found in GPA-attacked C. australis, and the soybean hosts exhibited increased jasmonic acid contents and 1015 DEGs, including > 100 transcription factor genes. Importantly, GPA feeding on C. australis increased the resistance of the soybean host to subsequent feeding by the leafworm Spodoptera litura and soybean aphid Aphis glycines, resulting in 21% decreased leafworm mass and 41% reduced aphid survival rate. These data strongly suggest that GPA feeding on Cuscuta induces a systemic signal, which is translocated to hosts and activates defense against herbivores.
TL;DR: The data suggest that aphid infestation of potato plants affects the composition of root exudates, with consequential effects on the hatching and gene expression of G. pallida eggs.
Abstract: Plants suffer multiple, simultaneous biotic threats from both above and below ground. These pests and/or pathogens are commonly studied on an individual basis and the effects of above-ground pests on below-ground pathogens are poorly defined. Root exudates from potato plants (Solanum tuberosum L.) were analyzed to characterize the top-down plant-mediated interactions between a phloem-sucking herbivore (Myzus persicae) and a sedentary, endoparasitic nematode (Globodera pallida). Increasing inocula of the aphid, M. persicae, reduced the root mass of potato plants. Exudates collected from these roots induced significantly lower hatching of second-stage juveniles from G. pallida eggs over a 28-day period, than those from uninfested control plants. Inhibition of hatch was significantly positively correlated with size of aphid inoculum. Diminished hatching was partially recovered after treatment with root exudate from uninfested potato plants indicating that the effect on hatching is reversible but cannot be fully recovered. Glucose and fructose content was reduced in root exudates from aphid-infested potato plants compared to controls and these sugars were found to induce hatching of G. pallida, but not to the same degree as potato root exudates (PRE). Supplementing aphid-infested PRE with sugars did not recover the hatching potential of the treatment, suggesting that additional compounds play an important role in egg hatch. The first gene upregulated in the closely related potato cyst nematode Globodera rostochiensis post-exposure to host root exudate, Neprilysin-1, was confirmed to be upregulated in G. pallida cysts after exposure to PRE and was also upregulated by the sugar treatments. Significantly reduced upregulation of Gpa-nep-1 was observed in cysts treated with root exudates from potato plants infested with greater numbers of aphids. Our data suggest that aphid infestation of potato plants affects the composition of root exudates, with consequential effects on the hatching and gene expression of G. pallida eggs. This work shows that an above-ground pest can indirectly impact the rhizosphere and reveals secondary effects for control of an economically important below-ground pathogen.
TL;DR: In this paper, the authors explored the differences in constitutive and aphid-induced defenses in soybeans through the expression of selected defense-related transcripts and the levels of the phytohormones abscisic acid, jasmonic acid (JA), JA-isoleucine (JA-Ile), cis-(+)-12-oxo-phytodienoic acid(OPDA), and salicylic acid (SA) over several time points.
Abstract: Plant resistance can provide effective, economical, and sustainable pest control. Tolerance to the soybean aphid has been identified and confirmed in the soybean KS4202. Although its resistance mechanisms are not fully understood, evidence suggests that enhanced detoxification of reactive oxygen species (ROS) is an active system under high aphid infestation. We further explored tolerance by evaluating the differences in constitutive and aphid-induced defenses in KS4202 through the expression of selected defense-related transcripts and the levels of the phytohormones abscisic acid (ABA), jasmonic acid (JA), JA-isoleucine (JA-Ile), cis-(+)-12-oxo-phytodienoic acid (OPDA), and salicylic acid (SA) over several time points. Higher constitutive levels of ABA and JA, and basal expression of ABA- and JA-related transcripts were found in the tolerant genotype. Conversely, aphid-induced defenses in KS4202 were expressed as an upregulation of peroxidases under prolonged aphid infestation (>7 days). Our results point at the importance of phytohormones in constitutive defense in KS4202 tolerance to the soybean aphid. Understanding the underlying mechanisms of tolerance will assist breeding for soybean with these traits, and perhaps help extend the durability of Rag (Resistance to Aphis glycines)-mediated resistance genes.