Sitobion Avenae Research Articles

Virus-Dependent and -Independent Responses of Sitobion avenae (Homoptera: Aphididae) Feeding on Wheat Infected by Transmitted and Nontransmitted Viruses at Transcriptomic Level

Most plant viruses maintain complex interactions with their vector or nonvector insects and can indirectly (via host plants) or directly affect the fitness of insects. However, little is known about the genes involved in the interactions between insects and transmitted or nontransmitted viruses, particularly nontransmitted viruses. Sitobion avenae (Fabricius) is a vector of barley yellow dwarf virus GAV strains (BYDV-GAV), but not a vector of wheat dwarf virus (WDV), which is transmitted by the leafhopper [Psammotettix alienus (Dahlbom)]. In this study, S. avenae was utilized to determine the transcriptomic responses after feeding on wheat infected by each of the two viruses, respectively, using an Illumina Hiseq sequencing platform. The transcriptomic data presented 61,508 genes, of which 854 differentially expressed. Moreover, in addition to sharing 208 genes, the number of differentially expressed genes (DEGs) in S. avenae exposed to BYDV was higher (800) than that when exposed to WDV (262). The DEGs related to the immune system and fitness of S. avenae in response to BYDV-/WDV-infected plants were identified and analyzed using Gene Ontologies (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG), and the number of related DEGs was lower as nonvector than as vector. This study provides the baseline information to further examine molecular mechanisms of how wheat viruses affect S. avenae fitness and immune response either as a vector for BYDV-GAV or as a nonvector for WDV.

Influence of plant fertilisation on cereal aphid-primary parasitoid-secondary parasitoid networks in simple and complex landscapes

Agricultural intensification can impact agrobiodiversity in several ways such as in terms of population densities, community composition and food web interactions across all trophic levels. This effect can be investigated at two scales: field-scale and landscape scale. Here it was assessed how the impact of fertilisation (within field) and landscape complexity (within landscape) impact cereal aphid-primary parasitoid-secondary parasitoid systems in winter wheat in Germany. A newly developed molecular technique was used to quantify species-specific linkages between aphids, primary parasitoids and secondary parasitoids sampled in fertilised and unfertilised plots in either simple or complex structured landscapes. The results show a stronger effect of fertilisation than landscape complexity on the groups: fertilisation positively affected the crop plants while it negatively affected both the density of the cereal aphid Sitobion avenae and its primary parasitism rates whereas no effect on the level of secondary parasitism rates was observed.Landscape complexity had no effect on plants, aphids, as well as on primary parasitism rate. In case of secondary parasitism rate there was an effect in interaction with sampling date. Field identity accounted for the strongest effect on parasitoid community composition (10.6% of the variance) from all tested variables, while fertilisation and landscape complexity had almost no effect (1.1% and no effect). Nevertheless, a weak cascading effect of both environmental factors could be observed as the primary-secondary parasitoid network structure responded to both. However, these observed effects on food webs strongly depended on species identity, highlighting the need of species-level food web assessment.

The effect of fertilizer‐N on the inter‐specific competition among three wheat aphids under elevated CO2

AbstractIncreasing atmospheric carbon dioxide (ab. CO2) and fertilizer‐nitrogen (ab. N) applications may have marked direct effects on the plant growth of agricultural crops, and in turn affect the higher trophic level of insect herbivores. In this study, the effects of elevated CO2 (i.e., 650 µl/L vs. ambient 400 µl/L) and fertilizer‐N (0, 50, 100, 200 kg/ha) on the population abundances and the inter‐specific competition among three co‐occurring species of wheat aphids, Sitobion avenae, Rhopalosiphum padi and Schizaphis graminum, were studied. The grain weight per ear and the 1,000‐grain weight were generally increased when grown under elevated CO2 and showed a significant effect at the 100 kg/ha (grain weight per ear) and 0, 50 and 100 kg/ha (1,000‐grain weight) N. These two yield indexes increased with increasing fertilizer‐N levels within reasonable limits and reached a maximum at 100 kg/ha. Elevated CO2 combined with fertilizer‐N levels formed complex indirect effects on the three wheat aphids through the wheat crops they fed on. Elevated CO2 significantly decreased the niche overlap index (ab. NOI) between S. avenae and R. padi under 0 and 100 kg/ha and that between R. padi and S. graminum under 0 kg/ha, while significantly increased the three NOIs under 50 kg/ha and that between R. padi and S. graminum under 100 and 200 kg/ha. S. avenae and R. padi had the larger population and stronger competition in low‐N condition (0 and 50 kg/ha), which was harmful to wheat yield and quality when combined with its own poor nutrition. Overall, the 100 kg/ha N level was the best option based on the aphid population, competition and wheat yields. Therefore, the balanced relationship formed among fertilizers, plants and insects under 100 kg/ha N was vital for the interactive ecosystem.

Detecting advanced stages of winter wheat yellow rust and aphid infection using RapidEye data in North China Plain

Yellow rust (Puccinia striiformis f. sp. Tritici) and aphid (Sitobion avenae F.) are two major biotic factors threatening winter wheat growth in the main growing region in northern China. The goal of this study was to develop a remote sensing based approach to reliably detect and discriminate yellow rust and aphid infection. The study was conducted in the North China Plain in 2017 based on RapidEye satellite images using three supervised classification algorithms, the maximum-likelihood classifier, the support vector machine, and the random forest. An overall accuracy of above 60% for aphid and above 70% for yellow rust can be achieved using a single image (May 7 or 10, 2017) with any of the three algorithms. With multi-temporal images, the overall accuracies both increased for aphid and yellow rust (above 70% and above 78%). Using the image acquired on 23 May 2017, joint infections by yellow rust and aphid can be detected with satisfaction (>73% overall accuracy), although confusion exists between the two infections. This study demonstrates that winter wheat disease/pest infection can be detected with remote sensing technologies, providing decision support to farmers, insurance companies, and government organizations in the agriculture sector.

Factors driving susceptibility and resistance in aphids that share specialist fungal pathogens

Pandora neoaphidis and Entomophthora planchoniana are widespread and important specialist fungal pathogens of aphids in cereals (Sitobion avenae and Rhopalosiphum padi). The two aphid species share these pathogens and we compare factors influencing susceptibility and resistance. Among factors that may influence susceptibility and resistance are aphid behavior, conspecific versus heterospecific host, aphid morph, life cycle, and presence of protective endosymbionts. It seems that the conspecific host is more susceptible (less resistant) than the heterospecific host, and alates are more susceptible than apterae. We conceptualize the findings in a diagram showing possible transmission in field situations and we pinpoint where there are knowledge gaps.

Effect of three isolates of Pandora neoaphidis from a single population of Sitobion avenae on mortality, speed of kill and fecundity of S. avenae and Rhopalosiphum padi at different temperatures

We studied the effect of three Pandora neoaphidis isolates from one Sitobion avenae population, three temperatures, and two aphid species namely S. avenae and Rhopalosiphum padi on (i) aphid mortality, (ii) time needed to kill aphids, and (iii) aphid average daily and lifetime fecundity. A total of 38% of S. avenae and 7% of R. padi died and supported fungus sporulation. S. avenae was killed 30% faster than R. padi . Average daily fecundity was negatively affected only in S. avenae inoculated with, but not killed by, P. neoaphidis . Nevertheless, lifetime fecundity of both aphid species inoculated and sporulating with P. neoaphidis was halved compared to lifetime fecundity of surviving aphids in the control. Increased temperature resulted in higher mortality rates but did not consistently affect lethal time or fecundity. Results suggest that (i) temperature effects on virulence differ between isolates, even when obtained within the same host population, and (ii) even though an isolate does not kill a host it may reduce its fecundity. Our findings are important for the understanding of P. neoaphidis epizootiology and for use in pest-natural enemy modelling. • Pandora neoaphidis from Sitobion avenae kills both S. avenae and Rhopalosiphum padi. • P. neoaphidis isolates tested were much more virulent to S. avenae than R. padi. • Temperature influences virulence of isolates from one population differently. • Temperature influences mortality, lethal time and fecundity differently. • S. avenae surviving fungal infection had reduced average daily fecundity.

First evidence of retained sexual capacity and survival in the pyrethroid resistant Sitobion avenae (F.) (Hemiptera: Aphididae) SA3 super-clone following exposure to a pyrethroid at current field-rate

AbstractThe grain aphidSitobion avenaeis a prolific pest of cereal crops worldwide, controlled effectively with pyrethroid insecticides. However, the classic knock down resistance (kdr) mutation, L1014F on theS. avenaesodium channel gene, has been identified as the cause of the recently observed heterozygous (kdr-SR) resistance in the SA3 grain aphid super-clone. Results indicate that the kdr-SR SA3 clone can survive pyrethroid exposure above twice the normal field rate, continuing to reproduce thereafter. Additionally, the SA3 clone was found to be capable of producing sexual oviparous morphs, able to lay eggs following pyrethroid exposure. This demonstrates that possession of the L1014F mutation does not preclude the capacity to produce sexual morphs. This makes the adoption of an effective resistance management strategy imperative, within a wider integrated pest management (IPM) approach to control grain aphid.

Systemically modeling the relationship between climate change and wheat aphid abundance

Climate change influences all living beings. Wheat aphids deplete the nutritional value of wheat and affect the production of wheat in changing climate. In this study, we attempt to explain the ecological mechanisms of how climate change affects wheat aphids by simulating the relationship between climate and the abundance of wheat aphids, which will not only aid in improving wheat aphid forecasting and the effectiveness of prevention and treatment, but also help mitigate food crises. Fuzzy cognitive maps (FCM) are an effective tool for portraying complex systems. Using Sitobion avenae and climatological data collected in China, we made use of differential evolution (DE) algorithms to construct FCM models that directly illustrate the effect of climate on wheat aphid abundance. The relationships among climate and wheat aphids at different growth stages (I–III instar larvae, IV instar larvae with wings, IV instar larvae without wings, adult with wings, adult without wings) were established. The analysis results from the FCM models show that temperature positively influences wheat aphids most. Moreover, these models can be used to determine the numerical value of each climate factor and the abundance of wheat aphids quantitatively. Furthermore, the two overall relationship models between climate and wheat aphids were constructed and the experimental results show that natural enemies and highest daily temperature affect wheat aphids most. Natural enemies and highest daily temperature exert negative and positive impacts on wheat aphids respectively. Some interrelationships among wheat aphids at all growth stages and the internal relationships among climate factors were also shown.

Infection pattern and negative effects of a facultative endosymbiont on its insect host are environment-dependent

Regiella insecticola is a bacterial endosymbiont in insects that exhibits a negative effect on the fitness of hosts. Thus, it is not clear why this costly endosymbiont can persist in host populations. Here, we tested a hypothesis that the infection pattern and negative roles of the endosymbiont were not constant but environmentally dependent. The grain aphids Sitobion avenae, belonging to different genotypes and infected with Regiella or not, were used in this study. We found that S. avenae populations were infected with Regiella, Hamiltonella defensa, Serratia symbiotica and Rickettsia. The predominant endosymbionts in the aphid populations varied with season. Serratia and Rickettsia were predominant from December to February while Regiella predominated from March to May. The vertical transmission of Regiella was poorer at high temperature, but following conditioning for seven generations, the transmission rate improved. Regiella inhibited the production of winged aphids at 25 °C, but it did not affect winged morph production at the higher temperatures of 28 °C and 31 °C. Regiella infection decreased the intrinsic rate of increase (rm) of aphids at 25 °C and 28 °C. However, at 31 °C, the effect of Regiella on the rm varied depending on the aphid genotype and density. Thus, the negative effects of this endosymbiont on its host were environmentally dependent.

The importance of timing of heat events for predicting the dynamics of aphid pest populations.

Heatwaves are increasing in frequency and there is growing interest in their impact on pest organisms. Previous work indicates that effects depend on the timing of the stress event, whose impact needs to be characterized across the full set of developmental stages and exposure periods of an organism. Here, we undertake such a detailed assessment using heat stress (20-35 °C diurnal cycle) across the nymph and adult stages of the English grain aphid, Sitobion avenae (Fabricius). Stress-related mortality increased with stress duration at all stages; effects were less severe at the late nymphal stage. Effects on longevity adults after stress showed a complex pattern with nymphal heat stress, increasing with stress duration at the late nymphal stage, but decreasing with duration at the early nymphal stage. Longevity was also reduced by adult stress although to a lesser extent, and patterns were not connected to duration. Post-stress productivity decreased following adult and nymphal stress and the decrease tended to be correlated with stress duration. The rate of offspring production was more affected by adult stress than nymphal stress. Productivity and longevity effects, when combined, showed that the largest effect of heat stress occurred at the early nymphal stage. These findings highlight the complex ways in which heat stress at a particular life stage influences later fitness and they also emphasize the importance of considering multiple fitness components when assessing stress effects. © 2019 Society of Chemical Industry.

Reproductive adaptation in alate adult morphs of the English grain aphid Sitobion avenae under starvation stress

Adapting their reproductive physiology is a tactic that insects use in responding to conditions of food unavailability. The present study examined the potential effects of starvation periods on the ovarian development and reproduction of alate adult morphs of Sitobion avenae (Fabricius). Morphs both continuously fed and starved aphids contained two telotrophic ovaries, each comprising five ovarioles. As time increase after emergence, the number of offspring produced by the fed aphids increased gradually, whereas the number of embryos in their ovaries decreased gradually. Both the number of mature embryos and the volume of embryos rapidly increased at 24 h after emergence, and then remained at an approximately constant level between 24 and 144 h. Compared to the fed aphids, starved aphids only produced a small number of nymphs, and there was no significant change in the total number of embryos between 24 and 144 h, whereas both the number of mature embryos and volume of embryos increased significantly. Irrespective of starvation period, highly significant relationships between life span and fecundity were found. Adult aphids starved for longer periods presented lower longevity and fecundity, but dead females contained more mature embryos than those starved for shorter periods. These results suggested that, under starvation stress, S. avenae tends to invest in the development of larger embryos at the expense of reducing lifespan and future fecundity. This adaptive reproductive strategy under starvation stress could be one of the factors contributing to the successful establishment of new colonies of alate migratory aphids.

Virulence of Two Entomophthoralean Fungi, Pandora neoaphidis and Entomophthora planchoniana, to Their Conspecific (Sitobion avenae) and Heterospecific (Rhopalosiphum padi) Aphid Hosts.

Pandora neoaphidis and Entomophthora planchoniana (phylum Entomophthoromycota) are important fungal pathogens on cereal aphids, Sitobion avenae and Rhopalosiphum padi. Here, we evaluated and compared for the first time the virulence of these two fungi, both produced in S. avenae cadavers, against the two aphid species subjected to the same exposure. Two laboratory bioassays were carried out using a method imitating entomophthoralean transmission in the field. Healthy colonies of the two aphid species were exposed to the same conidial shower of P. neoaphidis or E. planchoniana, in both cases from a cadaver of S. avenae. The experiments were performed under LD 18:6 h at 21 °C and a successful transmission was monitored for a period of nine days after initial exposure. Susceptibility of both S. avenae and R. padi to fungal infection showed a sigmoid trend. The fitted nonlinear model showed that the conspecific host, S. avenae, was more susceptible to E. planchoniana infection than the heterospecific host R. padi, was. In the case of P. neoaphidis, LT50 for S. avenae was 5.0 days compared to 5.9 days for R. padi. For E. planchoniana, the LT50 for S. avenae was 4.9 days, while the measured infection level in R. padi was always below 50 percent. Our results suggest that transmission from conspecific aphid host to heterospecific aphid host can occur in the field, but with expected highest transmission success to the conspecific host.

Aphids can acquire the nitrogen delivered to plants by arbuscular mycorrhizal fungi

Abstract Above‐ and below‐ground organisms can interact by altering the quality of shared host plants. Arbuscular mycorrhizal fungi (AMF) influence plant nutrient uptake, including nitrogen (N) acquisition. Under low N and phosphorus conditions, AMF delivery of N from organic sources not immediately available to the plant can have large impacts on plant N status, a limiting nutrient in the aphid diet. This study investigated the effect of AMF colonisation upon aphid number and determined the consequences of AMF directly accessing an organic nutrient patch that the plant cannot. We hypothesised that AMF colonisation of plants will increase plant and aphid N status, plant performance and aphid number, but only when the AMF had direct access to the added organic patch. Barley plants hosting the grain aphid Sitobion avenae were colonised by the AMF, Funneliformis mosseae, or no AMF. A two‐compartment microcosm was used to separate the plant roots from a 15N‐labelled organic patch in a second compartment. AMF‐colonised plants, but without access to the second compartment, were used to examine the effect of AMF colonisation on aphid number. In a separate treatment, and to determine whether AMF access to a plant inaccessible N source modified the effect of AMF colonisation on aphid number, AMF hyphae were permitted access to the second compartment containing an organic patch. As a control for AMF accessing a larger substrate volume, AMF were allowed access to a second compartment without an organic patch. When the AMF accessed the organic patch, more N from the patch was delivered to the plant resulting in a higher grain N concentration although plant growth was depressed. More N from the patch was also delivered to the aphids, but the N status of the aphid remained unchanged. Regardless of the level of access to the organic patch, AMF colonisation did not affect aphid number. Our data show that by accessing N sources not readily available to plants, AMF can indirectly deliver N to above‐ground organisms, a finding which has major implications for N‐transfer between higher trophic levels. A plain language summary is available for this article.

Plant-mediated gene silencing of an essential olfactory-related Gqα gene enhances resistance to grain aphid in common wheat in greenhouse and field.

Grain aphid (Sitobion avenae F.) is a dominant pest that limits cereal crop production around the globe. Gq proteins have important roles in signal transduction in insect olfaction. Plant-mediated RNA interference (RNAi) has been widely studied in insect control, but its application for the control wheat aphid in the field requires further study. Here, we used double-stranded (ds)RNA feeding to verify the potential of selected Gqα fragments for host-mediated RNAi, and then evaluated the effect of RNAi on aphid olfaction in transgenic wheat in the greenhouse and field. Gqα gene was expressed in the aphid life cycle, and a 540 bp fragment shared 98.1% similarity with the reported sequence. dsGqα feeding reduced the expression of Gqα, and both reproduction and molting in the grain aphid. Feeding transgenic lines in the greenhouse downregulated expression of aphid Gqα, and significantly reduced reproduction and molting numbers. Furthermore, our field results indicate that transgenic lines have lower aphid numbers and higher 1000-grain weight than an unsprayed wild-type control. Plant-mediated silencing of an essential olfactory-related Gqα gene could enhance resistance to grain aphid in common wheat in both the greenhouse and the field. © 2018 Society of Chemical Industry.

Clonal Diversity and Genetic Differentiation of Sitobion avenae (Hemiptera: Aphididae) From Wheat and Barley in China.

The English grain aphid, Sitobion avenae (Fabricius), is a cosmopolitan insect pest on cereals. Many studies on life-history traits indicate that S. avenae clones from different areas have diverged on various host plants. However, direct genetic evidence for this phenomenon is rare. Thus, S. avenae clones were collected from barley (Hordeum vulgare L.) and wheat (Triticum aestivum L.) in four provinces (i.e., Hubei, Henan, Jiangsu, and Zhejiang) of China, and characterized using six microsatellite markers. In total, 92 multilocus genotypes were found from 302 individuals of S. avenae. Population Jiangsu was found to have relatively high levels of genotypic diversity among the four geographical populations. Substantial long-distance migration of S. avenae was found from Zhejiang to the other three provinces. Thus, relatively low genetic differentiation was found between these geographic populations. Barley clones of S. avenae showed higher gene diversity compared with wheat clones. The gene flow from barley to wheat clones appeared to be more likely than that in the reverse direction. Diversity indices and structure for S. avenae clones suggested highest level of genetic divergence between barley and wheat clones in Jiangsu among all sampling locations. Besides Jiangsu, pairwise FST values indicated moderate levels of genetic divergence between barley and wheat clones in Zhejiang. Thus, compared with geographical factors, plant factors could be relatively more important in promoting genetic differentiation in S. avenae. Our results provide insights into genetic differentiation of S. avenae on different plants, as well as a basis for exploring the molecular mechanism for its differentiation on plants and biotype development.

Laboratory and field tests of predation on the cereal leaf beetle, Oulema melanopus (Coleoptera: Chrysomelidae)

ABSTRACTThe cereal leaf beetle (CLB), Oulema melanopus (L.) (Coleoptera: Chrysomelidae), is an invasive pest in North America recently reported in the Canadian Prairies. We performed a series of laboratory assays to identify potential predators and a field study to quantify predation of CLB eggs. In no-choice Petri dish assays, ground beetles (Carabidae), rove beetles (Staphylinidae), and several common lady beetle species (Coccinellidae) were the most consistent predators of eggs and larvae. Nabis spp. (Hemiptera: Nabidae) and wolf spiders (Araneae: Lycosidae) consumed many larvae, but did not consume eggs. Hippodamia spp., Coccinella septempunctata (L.) (Coleoptera: Coccinellidae), and Pterostichus melanarius (Illiger) (Coleoptera: Carabidae) also fed on CLB eggs on potted plants when an alternative food source was available, Sitobion avenae (Fabricius) (Hemiptera: Aphididae). In our field study, we found an average of 24.5% of sentinel eggs disappeared over a 24 h period, likely due to predation. Our results suggest that generalist predators can play an important role in the biological control of CLB, and warrant further study.

Recruiting on the Spot: A Biodegradable Formulation for Lacewings to Trigger Biological Control of Aphids.

Upon herbivory, plants release herbivore-induced plant volatiles (HIPVs), which induce chemical defenses in the plant as well as recruit natural enemies. However, whether synthetic HIPVs can be employed to enhance biological control in a cultivated crop in the field is yet to be explored. Here we show that a biodegradable formulation loaded with induced and food-signaling volatiles can selectively recruit the common green lacewing, Chrysoperla carnea, and reduce pest population under field conditions. In apple orchards, the new formulation attracted lacewing adults over a 4-week period, which correlated well with independent assessments of the longevity of the slow-release matrix measured through chemical analyses. In barley, lacewing eggs and larvae were significantly more abundant in treated plots, whereas a significant reduction of two aphid species was measured (98.9% and 93.6% of population reduction, for Sitobion avenae and Rhopalosiphum padi, respectively). Results show the potential for semiochemical-based targeted recruitment of lacewings to enhance biological control of aphids in a field setting. Further research should enhance selective recruitment by rewarding attracted natural enemies and by optimizing the application technique.

The complete mitochondrial genome of Indomegoura indica (Hemiptera: Aphididae)

In this study, the complete mitochondrial genome sequence of Indomegoura indica(Hemiptera: Aphididae) was determined. The circular genome was 15220 bp in length and contained 13 protein-coding genes (PCGs), 22 transfer RNA genes (tRNAs), 2 ribosomal RNA genes (rRNAs), and two non-coding regions (control regions). All PCGs were initiated with standard ATN codons and terminated with TAA except for cox1 and nad4. All tRNAs were predicted to contain typical cloverleaf secondary structures except trnS1. The Bayesian phylogenetic analysis indicated that Indomegoura indica was more closely related to Sitobion avenae than to other species.

Population dynamics of wheat aphids and their natural enemies

The abundance of aphids infesting wheat and their natural enemies was studied at the CSKHPKV, Palampur. The aphids (Rhopalosiphum padi and Sitobion avenae) population commenced from first week of January and reached a peak (30.40 aphids/shoot) during third week of March. Seven species of coccinellid beetles were recorded as predators, of which Coccinella septempunctata, Hippodamia variegata and Coccinella transversalis were predominant. Peak population of their adults (8.10 beetles/m2), grubs and pupae was observed during first week of April. As regards the syrphids, peak in population (13.00 adults/5 sweeps-Episyrphus balteatus, E. viridaureus, Ischiodon scutellaris, Sphaerophoria sp. and Melanostoma spp.) was during third week of April. Lacewing Micromus sp. started appearing from first week of March with its peak being during third week of March. The peak activity of Diaeretiella sp. was observed during first week of April with 16.6% parasitization. These natural enemies showed a significant positive correlation with aphid population, while with weather factors mixed results were observed. The predatory potential of coccinellids evaluated revealed that the adults as well as grubs have potential to suppress aphid population.

Biochar applications decrease reproductive potential of the English grain aphid Sitobion avenae and upregulate defense-related gene expression.

The application of biochar as a targeted strategy for managing herbivorous pests is a topic of growing interest. The present study first determined the influence of biochar amendments on the reproductive performance of the English grain aphid Sitobion avenae, and then examined defense-related gene expression in the wheat plant as a function of biochar amendments and aphid feeding. Compared to the control, biocahr amendments decreased aphid lifetime fertility by 9.09% and 20.23% for amending levels at 3% and 5%, respectively; it reduced aphid population by 18.68%, 21.69%, and 28.70% for the levels at 1.5%, 3%, and 5%, respectively. Biochar applications increased silicon content more than 40% in wheat plants. Furthermore, biochar additions increased the expression of four defense-related genes (AOS, LOX, PAL and PR) in wheat plants with extension of feeding time by aphids. Our results suggest that biochar amendments to soils have detrimental consequences on the reproductive potential of the aphid on the wheat, and the effect may result from aphid-induced plant defenses being raised by biochar applications. © 2018 Society of Chemical Industry.