Sitobion Avenae Research Articles

Selection of Reference Genes for RT-qPCR Analysis of Wing Dimorphism in English Grain Aphid, Sitobion avenae (Hemiptera: Aphididae).

The English grain aphid, Sitobion avenae (Fabricius), exhibits classic and dramatic phenotypic plasticity in wing development. Both genetic and environmental inputs contribute to the wing polyphenism in aphids, an extreme form of phenotypic plasticity in which a single genotype produces discrete winged and wingless morphs. Validated reference genes are needed to accurately normalize temporal and spatial variation in gene expression estimates by RT-qPCR. In this research, the stability of 11 candidate reference genes selected from S. avenae transcriptomes was evaluated under an array of abiotic and biotic conditions relevant to wing development. RefFinder, a comprehensive software integrating rankings from delta Ct, BestKeeper, NormFinder, and geNorm, offered a series of reference genes for every experimental condition. Overall, helicase (HEL) and ubiquitin ribosomal protein S27A fusion protein (RpS27) are suited for most of the conditions examined in this study, although exceptions do exist. Specifically, NADH dehydrogenase (Ap-NADH) and 28S ribosomal RNA (28S) are recommended for insecticide and antibiotic treatments, while ribosomal RNA L14 (RPL14) and 18S ribosomal RNA (18S) are selected for density treatment, respectively. This study provides a suite of reference genes to investigate the wing polyphenism in S. avenae, and is important for application of RT-qPCR in future experiments of novel tactics to control aphids.

Impacts of Constitutive and Induced Benzoxazinoids Levels on Wheat Resistance to the Grain Aphid (Sitobion avenae).

Benzoxazinoids are important secondary metabolites in gramineae plants and have inhibitory and toxic effects against a wide range of herbivore pests. However, the relationship between benzoxazinoid level and plant resistance to aphids remains controversial. In this study, we investigated the relationship between benzoxazinoids composition and concentration in wheat leaves and the resistance to the grain aphid Sitobion avenae. Overall, six benzoxazinoids were detected and identified by mass spectrometry based metabolites profiling, including three lactams, two hydroxamic acids, and one methyl derivative. The constitutive levels of these benzoxazinoids were significantly different among the wheat varieties/lines. However, none of these benzoxazinoids exhibited considerable correlation with aphid resistance. S. avenae feeding elevated the level of 2-O-β-D-glucopyranosyloxy-4,7-dimethoxy-(2H)-1,4-benzoxazin-3(4H)-one (HDMBOA-Glc) and reduced the level of 2-O-β-D-glucopyranosyloxy-4-hydroxy-7-(2H)-methoxy-1,4-benzoxazin-3(4H)-one (DIMBOA-Glc) in some of the wheat varieties/lines. Moreover, aphid-induced level of DIMBOA-Glc was positively related with callose deposition, which was closely associated with aphid resistance. Wheat leaves infiltrated with DIMBOA-Glc caused a noticeable increase of callose deposition and the effect was in a dose dependent manner. This study suggests that the constitutive level of benzoxazinoids has limited impact on S. avenae. Aphid feeding can affect the balance of benzoxazinoids metabolism and the dynamic level of benzoxazinoids can act as a signal of callose deposition for S. avenae resistance. This study will extend our understanding of aphid–wheat interaction and provides new insights in aphid-resistance wheat breeding.

Terpene Synthase Gene OtLIS Confers Wheat Resistance to Sitobion avenae by Regulating Linalool Emission.

Sitobion avenae (Fabricius) is a major insect pest of wheat worldwide that reduces crop yield and quality annually. Few germplasm resources with resistant genes to aphids have been identified and characterized. Here, octoploid Trititrigia, a species used in wheat distant hybridization breeding, was found to be repellent to S. avenae after 2 year field investigations and associated with physiological and behavioral assays. Linalool monoterpene was identified to accumulate dominantly in plants in response to S. avenae infestation. We cloned the resistance gene OtLIS by assembling the transcriptome of aphid-infested or healthy octoploid Trititrigia. Functional characterization analysis indicated that OtLIS encoded a terpene synthase and conferred resistance to S. avenae by linalool emission before and after aphid feeding. Our study suggests that the octoploid Trititrigia with the aphid-resistant gene OtLIS may have potential as a target resource for further breeding aphid-resistant wheat cultivars.

Evaluating the impact of pyrethroid insecticide resistance on reproductive fitness inSitobion avenae

AbstractResistance to insecticides used to control pests is an issue of increasing concern for agriculture. The grain aphid,Sitobion avenae, is a pest of cereals and grasses worldwide, and one of growing concern due to the evolution of resistance to certain insecticides. Resistance confers benefits to insects by enabling them to survive exposure to insecticide compounds; however, the mutations conferring resistance may also penalise the insect in pesticide‐free environments due to fitness costs associated with the new phenotype. Here we tested the hypothesis of a reproductive penalty linked to the knockdown resistance mutation (kdr) to pyrethroid insecticides. The mutation occurs predominantly in a single SA3 clone. To date, only heterozygous‐resistant forms (kdr‐SR) have been detected in populations in Ireland and the UK, and this suggests that a fitness penalty may preclude the formation of both male and female heterozygous‐resistant sexual forms. By designing an experiment which included a resistant and a non‐resistant clone, we were able to simulate reduced daylight and temperature conditions which, in nature, trigger sexual reproduction and therefore study the responses of each clone. This allowed us to detect the switch from asexual females to sexual females and males and report on the conditions associated with the production of sexual forms. The results showed that both aphid clones were able to produce sexual forms with no difference in the onset of sexual reproduction, although reproductive strategies differed between clones. The later onset of male forms in the SA3 clone may decrease the likelihood of mating interactions to create fully resistant (kdr‐RR) genotypes and this may constitute a fitness penalty due to pyrethroid resistance.

Biological Activity of Essential Oils of Four Juniper Species and Their Potential as Biopesticides.

The objective of this study was to assess the biological activity of essential oils (EOs) of four Juniperus species obtained via two different distillation methods and their potential as biopesticides. The studied factors were juniper species (Juniperus communis L., J. oxycedrus L., J. pygmaea C. Koch., and J. sibirica Burgsd), plant sex (male (M) and female (F)), and distillation method (hydrodistillation via a standard Clevenger apparatus (ClevA) and semi-commercial (SCom) steam distillation). The hypothesis was that the EO will have differential antioxidant, antimicrobial, and insecticidal activities as a function of plant species, plant sex, and distillation method. The two distillation methods resulted in similar EO composition within a given species. However, there were differences in the EO content (yield) due to the sex of the plant, and also differences in the proportions of some EO components. The concentration of α-pinene, β-caryophyllene, δ-cadinene and δ-cadinol was dissimilar between the EO of M and F plants within all four species. Additionally, M and F plants of J. pygmaea, and J. sibirica had significantly different concentrations of sabinene within the respective species. The EOs obtained via ClevA extraction showed higher antioxidant capacity within a species compared with those from SCom extraction. All of the tested EOs had significant repellent and insecticidal activity against the two aphid species Rhopalosiphum padi (bird cherry-oat aphid) and Sitobion avenae (English grain aphid) at concentrations of the EO in the solution of 1%, 2.5%, and 5%. The tested EOs demonstrated moderate activity against selected pathogens Fusarium spp., Botrytis cinerea, Colletotrichum spp., Rhizoctonia solani and Cylindrocarpon pauciseptatum. The results demonstrate that the standard ClevA would provide comparable EO content and composition in comparison with SCom steam distillation; however, even slight differences in the EO composition may translate into differential bioactivity.

INSECTICIDAL STRAIN OF THE GENUS LECANICILLIUM FOR PLANT BIOLOGICAL CONTROL

Presented are the results of studies of the biological activity of a strain of the genus Lecanicillium, which is in the collection of the Engineering and Technological Institute “Biotechnika” NAAS of Ukraine. The biological activity of the strain of the genus Lecanicillium under laboratory conditions was compared with the biological activity of control samples. Actofit (Streptomyces avermitilis) and Metarizin (Metarhizium anisopliae) were used as control samples. The studies carried out to assess the fungus of the genus Lecanicillium indicate that after two treatments at 1.0 % concentration of the working solution, the population density of the large cereal aphid (Sitobion avenae Fabricius, 1775) decreased. Thus, the introduction of a strain of the genus Lecanicillium into the natural biocenosis will make it possible to regulate the number of harmful insects, limiting outbreaks of their mass reproduction.

Prevalence and management of aphids (Hemiptera: Aphididae) in different wheat genotypes and their impact on yield and related traits.

Wheat (Triticum aestivum L.) production is significantly altered by the infestation of sucking insects, particularly aphids. Chemical sprays are not recommended for the management of aphids as wheat grains are consumed soon after crop harvests. Therefore, determining the susceptibility of different wheat genotypes and selecting the most tolerant genotype could significantly lower aphid infestation. This study evaluated the susceptibility of six different wheat genotypes (‘Sehar-2006’, ‘Shafaq-2006’, ‘Faisalabad-2008’, ‘Lasani-2008’, ‘Millat-2011’ and ‘Punjab-2011’) to three aphid species (Rhopalosiphum padi Linnaeus, Schizaphis graminum Rondani, Sitobion avenae Fabricius) at various growth stages. Seed dressing with insecticides and plant extracts were also evaluated for their efficacy to reduce the incidence of these aphid species. Afterwards, an economic analysis was performed to compute cost-benefit ratio and assess the economic feasibility for the use of insecticides and plant extracts. Aphids’ infestation was recorded from the seedling stage and their population gradually increased as growth progressed towards tillering, stem elongation, heading, dough and ripening stages. The most susceptible growth stage was heading with 21.89 aphids/tiller followed by stem elongation (14.89 aphids/tiller) and dough stage (13.56 aphids/tiller). The genotype ‘Punjab-2011’ recorded the lower aphid infestation than ‘Faisalabad-2008’, ‘Sehar-2006’, ‘Lasani-2008’ and ‘Shafaq-2006’. Rhopalosiphum padi appeared during mid-February, whereas S. graminum and S. avenae appeared during first week of March. Significant differences were recorded for losses in number of grains/spike and 1000-grain weight among tested wheat genotypes. The aphid population had non-significant correlation with yield-related traits. Hicap proved the most effective for the management of aphid species followed by Hombre and Husk among tested seed dressers, while Citrullus colocynthis L. and Moringa oleifera Lam. plant extracts exhibited the highest efficacy among different plant extracts used in the study. Economic analysis depicted that use of Hombre and Hicap resulted in the highest income and benefit cost ratio. Therefore, use of genotype Punjab-2011’ and seed dressing with Hombre and Hicap can be successfully used to lower aphid infestation and get higher economic returns for wheat crop.

Intron-containing hairpin RNA interference vector for OBP8 show promising mortality in peach potato aphid

Myzus persicae is a devastating pest affecting potato production. Intron-containing hairpin RNA (ihpRNA) silenced the odorant-binding protein 8 (OBP8) for enhanced protection against Myzus persicae in potatoes. OBP8 was isolated from M. persicae, sequenced, with the allotment of GenBank ID. ERNAi was used to design siRNA targets from OBP8 with no off-targets. Multiple Sequence Alignment show M. persicae OBP8 resemblance with Acyrthosiphon pisum, Rhopalosiphum maidis, Aphis fabae, and Sitobion avenae. dsRNA-OBP8 (7 µg/µL) oral feeding resulted in a 69% mortality, and 58% OBP8 reduced expression 8D post-feeding compared to control. Golden Gate cloning is used for RNA interference taking advantage of type IIs restriction enzyme Eco31I. ihpRNA-OBP8 introduced by agroinfiltration in Solanum tuberosum. Transgenic S. tuberosum fed Myzus show 57.6% mortality and 49% reduction in OBP8 expression 8D post-feeding, compared to control. This work proves OBP8 as promising ihpRNA targets in potato and related crops for whom Myzus is a destructive pest.

The complete mitochondrial genome of Oenopia sauzeti (Coleoptera: Coccinellidae)

Oenopia sauzeti Mulsant are predators of various aphids, such as Myzus persicae, Rhopalosiphum maidis, and Sitobion avenae. We sequenced the mitochondrial genome (mitogenome) of O. sauzeti. Consistent with other mitogenomes of Coleoptera, the circular mitogenome of O. sauzeti consists of 17,630 bp, including 13 PCG genes, 2 rRNA genes, and 22 tRNA genes. The mitogenome differs in 2 long non-coding regions of 1285 bp and 1843 bp. The 22 tRNA genes products are folded into the typical cloverleaf secondary structure, except trnS1, which lacks the dihydrouridine (DHU) arm. The base composition is AT-biased (80.1%). The phylogenetic tree confirms monophyly at the genus level within the Coccinellinae and supports O. sauzeti as a sister group to Aiolocaria hexaspilota.

Wheat-Fusarium graminearum Interactions Under Sitobion avenae Influence: From Nutrients and Hormone Signals.

The English grain aphid Sitobion avenae and phytopathogen Fusarium graminearum are wheat spike colonizers. “Synergistic” effects of the coexistence of S. avenae and F. graminearum on the wheat spikes have been shown in agroecosystems. To develop genetic resistance in diverse wheat cultivars, an important question is how to discover wheat–F. graminearum interactions under S. avenae influence. In recent decades, extensive studies have typically focused on the unraveling of more details on the relationship between wheat-aphids and wheat-pathogens that has greatly contributed to the understanding of these tripartite interactions at the ecological level. Based on the scientific production available, the working hypotheses were synthesized from the aspects of environmental nutrients, auxin production, hormone signals, and their potential roles related to the tripartite interaction S. avenae–wheat–F. graminearum. In addition, this review highlights the relevance of preexposure to the herbivore S. avenae to trigger the accumulation of mycotoxins, which stimulates the infection process of F. graminearum and epidemic of Fusarium head blight (FHB) in the agroecosystems.

Multi-generational Effects of Different Resistant Wheat Varieties on Fitness of Sitobion avenae (Hemiptera: Aphididae).

Crop resistance plays a role in preventing aphid damage, benefiting food production industries, but its effects are limited due to aphid adaptation and phenotypic plasticity. Therefore, furthering understanding of aphid–crop interactions will improve our ability to protect crops from aphids. To determine how aphids adapt to resistant varieties of wheat, Triticum aestivum L. over time, we performed a laboratory experiment to assess the multi-generational effects of three wheat varieties, Batis, Ww2730, and Xiaoyan22, with different resistance levels on the fitness of Sitobion avenae (Fab.) (Hemiptera: Aphididae). The results showed that Ww2730 and Xiaoyan22 were more resistant than Batis to S. avenae, regardless of whether the aphids were newly introduced or had been acclimated before being introduced to the three wheat varieties. However, the effect of resistance on aphid life-history traits was time dependent. Aphid weigh gain increased and they development faster of the acclimated generation compared to the newly introduced generation on all three varieties. And the fecundity on the three varieties and net reproduction rates on Batis and Xiaoyan22 significantly decreased. Aphid fitness in terms of individual life-history parameters improved, whereas aphid fitness in terms of reproductive decreased, and a convergence effect, the difference gaps and standard errors of all life-history traits among the three acclimated populations had narrowed and were less than those in the three first-generation populations, was observed during the 3-mo experimental period. We suggested that S. avenae could rapidly respond to wheat resistance through life-history plasticity.

Bacillus subtilis (Bacillales, Bacillaceae) Spores Affect Survival and Population Growth in the Grain Aphid Sitobion avenae (Hemiptera, Aphididae) in Relation to the Presence of the Facultative Bacterial Endosymbiont Regiella insecticola (Enterobacteriales, Enterobacteriaceae).

The grain aphid Sitobion avenae (Fabricius) is one of the most important cereal pests, damaging crops through sap sucking and virus transmission. Sitobion avenae harbors the secondary endosymbiont Regiella insecticola, which is highly prevalent in populations in south-central Chile and other regions of the world. In order to develop ecological alternatives for biological control, we studied the effect of applying the spores of a strain of the bacterium Bacillus subtilis on the survival and fecundity of the most prevalent genotype of S. avenae in central Chile. The strain selected was one that in previous studies had shown the ability to outcompete other bacteria. Using clones of this aphid genotype infected and uninfected with R. insecticola, we found that applying B. subtilis spores through artificial diets and spraying on leaves decreased both adult survival and nymph production. The detection of spores within the aphid body was negatively correlated with nymph production and was lower in the presence of R. insecticola when applied in diets. B. subtilis spores applied on leaves reduced the number of aphids, an effect that was stronger on aphids harboring R. insecticola. A possible interaction between endosymbiotic bacteria and bacterial antagonists within the aphid body is discussed.

Nitrogen and plant growth regulator affect plant detoxification metabolism and tritrophic interactions among Triticum aestivum, Sitobion avenae and Aphelinus asychis

Nitrogen and plant growth regulator affect plant detoxification metabolism and tritrophic interactions among Triticum aestivum, Sitobion avenae and Aphelinus asychis

Bio-fertilizers and micronutrients affect the digestibility, detoxification, and intermediary metabolisms of English grain aphid, Sitobion avenae, in greenhouse

• Bio-fertilizers as key players in pest management by improving the plant tolerance. • Plant growth promoting rhizobacteria such as Biofarm showed great effect on physiology English grain aphid. • Bio-fertilizers could be a proper alternative to chemical fertilizers. • Sitobion avenae reared on wheat treated with Biofarm showed the highest activities of antioxidant enzymes. • Digestive enzymes had the highest activities in Sitobion avenae fed on Biofarm treated wheat plants. The English grain aphid, Sitobion avenae (Fabricius) (Hemiptera: Aphididae), is one of the most serious pests of cereals as the transmitter of viral diseases, mainly in wheat, Triticum aestivum . This agricultural pest is controlled with chemical insecticides, which is environmental pollutants and toxic for human. This study evaluated the potential of alternative environmentally friendly compounds to control this insect pest. The activities of digestive, antioxidants, and intermediary metabolism enzymes of S. avenae reared on wheat plants treated with bio-fertilizers (Biofarm and Probio96) and micronutrients (Librel Zinc and α-Iron) in the greenhouse were evaluated. The results reveal that α-amylase, total protease, trypsin, chymotrypsin, amino- and carboxypeptidases, alanine- and aspartate- aminotransferases, and acid phosphatase enzymes had lower activities in S. avenae reared on Biofarm treated plants compared to control. On the other hand, aphids reared on treated plants with Biofarm had the highest activities of antioxidant enzymes superoxide dismutase, catalase, peroxidase, and ascorbate oxidase, γ- glutamyl transferase, as well as lactate dehydrogenase. Moreover, the oxidized/reduced thiols ratio and malondialdehyde indicated higher activity in the aphids reared on Biofarm-treated plants than control. These results suggest that the bio-fertilizer Biofarm may compromise the physiology of S. avenae as a potential alternative toll in the integrated pest management of this aphid.

Effects of Long-Term Exposure to Electrostatic Radiation on the Mean Relative Growth Rate and Feeding Behavior of Sitobion avenae (Hemiptera: Aphididae)

Abstract Previous research has indicated that electrostatic radiation may induce biological and physiologic changes in plants and aphids. This study was conducted to determine effects of long-term exposure of electrostatic radiation on biology and feeding behavior of Sitobion avenae (F.). To imitate the natural electrostatic radiation stress, both wheat seeds and S. avenae nymphs (produced within 12 h) were exposed to an electrostatic radiation of 4 kV/cm for 20 min and 5 kV/cm intensity for 40 min, respectively. Controls received no treatment (0 kV/cm). Then, the mean relative growth rate (MRGR) and feeding behavior of the 5th-, 10th-, 15th-, 20th-, 27th-, 33rd-, and 39th-generation aphids were examined, respectively. Data showed that electrostatic radiation exposure within a certain period of time can promote weight increases of S. avenae, but long-term exposure of electrostatic radiation had an adverse effect on the weight gain of aphids. The comparison of the two treatment intensities showed that electrostatic radiation at the intensity of 4 kV/cm for 20 min had a significant influence on the probing behavior of S. avenae. This study initially evaluated the effect of electrostatic radiation on S. avenae from the aspect of nutrient feeding behavior, which further verifies the biological characteristics of electrostatic radiation.

Identifying aphid resistance in the ancestral wheat Triticum monococcum under field conditions

Wheat is an economically, socially, and nutritionally important crop, however, aphid infestation can often reduce wheat yield through feeding and virus transmission. Through field phenotyping, we investigated aphid resistance in ancestral wheat Triticum monococcum (L.). Aphid (Rhopalosiphum padi (L.), Sitobion avenae (F.) and Metopolophium dirhodum (Wlk.)) populations and natural enemy presence (parasitised mummified aphids, ladybird adults and larvae and lacewing eggs and larvae) on two naturally susceptible wheat varieties, Triticum aestivum (L.) var. Solstice and T. monococcum MDR037, and three potentially resistant genotypes T. monococcum MDR657, MDR045 and MDR049 were monitored across three years of field trials. Triticum monococcum MDR045 and MDR049 had smaller aphid populations, whereas MDR657 showed no resistance. Overall, natural enemy presence was positively correlated with aphid populations; however, MDR049 had similar natural enemy presence to MDR037 which is susceptible to aphid infestation. It is hypothesised that alongside reducing aphid population growth, MDR049 also confers indirect resistance by attracting natural enemies. The observed resistance to aphids in MDR045 and MDR049 has strong potential for introgression into commercial wheat varieties, which could have an important role in Integrated Pest Management strategies to reduce aphid populations and virus transmission.

Functional divergence of three glutathione transferases in two biotypes of the English grain aphid, Sitobion avenae

AbstractThe English grain aphid, Sitobion avenae (Fabricius) (Hemiptera: Aphididae), is a significant pest of cereal crops, but molecular factors and mechanisms that underpin its ability to develop differential biotypes on variable host plants are still not well understood. In this study, we investigated the interactions between two plant secondary metabolites (i.e., gramine and gallic acid) and three glutathione S‐transferases (GSTs) of S. avenae. Using artificial diets complemented or not with one of these two plant compounds, we found that gramine had relatively stronger negative effects on fitness of S. avenae biotype 3 (adapted to barley), and gallic acid on that of biotype 4 (adapted to wheat). Gramine significantly induced overexpression of SaveGST1 and SaveGST2 in biotype 4, but not in biotype 3. Gramine also reduced SaveGST3 expression in biotype 4, but not in biotype 3, suggesting biotype‐specific effect of GSTs’ regulation. In the treatments with gallic acid, the overexpression of SaveGST1, but not SaveGST2 or SaveGST3, was significantly induced in both biotypes, suggesting a critical role of SaveGST1 in detoxification of phenolic compounds such as gallic acid. The total constitutive GST activity was much higher in biotype 4 than in biotype 3. Significant increase in GST activity was obtained by the addition of both secondary metabolites in biotype 4, but not in biotype 3, showing significantly higher expression plasticity of GSTs in biotype 4. Thus, both constitutive and induced expression of GSTs could affect the adaptability of S. avenae on plants with variable secondary compounds, and thus contribute to the divergence of biotypes in this aphid species.

The role of plant labile carbohydrates and nitrogen on wheat-aphid relations\xa0

Interactions between plants and herbivores are key drivers of evolution and ecosystem complexity. We investigated the role of plant labile carbohydrates and nitrogen on wheat-aphid relations in a 22 factorial combining [CO2] and nitrogen supply. We measured life history traits (assay 1) and feeding behaviour (assay 2) of bird-cherry oat aphid (Rhopalosiphum padi L.) and English grain aphid (Sitobion avenae F.) forced to feed on single leaf laminae, and reproduction of R. padi in a setting where insects moved freely along the plant (assay 3). Experimental setting impacted aphid traits. Where aphids were constrained to single leaf, high nitrogen reduced their fitness and discouraged phloem feeding. Where aphids could move throughout the plant, high nitrogen enhanced their reproduction. Aphid responses to the interaction between nitrogen and [CO2] varied with experimental setting. The number of R. padi adults varied tenfold with plant growing conditions and correlated negatively with molar concentration of sugars in stem (assay 3). This finding has two implications. First, the common interpretation that high nitrogen favours insect fitness because protein-rich animal bodies have to build from nitrogen-poor plant food needs expanding to account for the conspicuous association between low nitrogen and high concentration of labile carbohydrates in plant, which can cause osmotic stress in aphids. Second, the function of labile carbohydrates buffering grain growth needs expanding to account for the osmotic role of carbohydrates in plant resistance to aphids.

Complex delayed and transgenerational effects driven by the interaction of heat and insecticide in the maternal generation of the wheat aphid, Sitobion avenae.

Experience of an earlier environment plays an important role in the induction of delayed and even intergenerational phenotypes of an organism. Evidence suggests that rapid adaptation to an environmental stressor can change the performance of organisms, and even enable them to deal with other stressors. The goal of this study was to determine the effects of adult imidacloprid exposure on life-history traits within and between generations of the cereal aphid, Sitobion avenae, under three developmental conditions: constant temperature, 22°C; a low-intensity thermal condition, 22 + 34°C for 2h per day; and a high-intensity thermal condition, 22 + 38°C for 2h per day. Early thermal experience not only changed the tolerance of S. avenae to the insecticide, imidacloprid, but also caused adults to incur fitness costs: the higher the heat intensity, the higher the costs. Negative transgenerational impacts of combined heat and insecticide stressors were limited to the developmental stage, whereas positive stimulation of heat intensity was observed during the adult stage. Overall, nymphal thermal experience exacerbated the detrimental effects of adult insecticidal exposure on the intrinsic rate of population increase in the maternal generation, but stimulated a net reproductive rate in the succeeding offspring generation. These findings underpin the importance of considering the experience of the early developmental environment, but also enhance our understanding of the transgenerational effects of combined thermal and insecticide stressors on the population fate of S. avenae. They also help to assess the efficacy of chemical control in a warming world. © 2021 Society of Chemical Industry.

Extreme climate shifts pest dominance hierarchy through thermal evolution and transgenerational plasticity

Abstract Dominance hierarchy, the dominance ranking of members in a community, is determined by the relative population fitness of coexisting species. Climate change can shift dominance hierarchies depending on how species respond to changing climate, but ecological mechanisms underlying such shifts remain largely unknown. Specifically, dominance hierarchy shifts under climate change have rarely been linked to eco‐evolutionary responses to thermal extremes, which we consider in this study. We conducted an 8‐year field survey to link extreme high‐temperature events to the shift in dominance hierarchy of two worldwide cereal aphid species (Rhopalosiphum padi and Sitobion avenae), which may respond rapidly through evolutionary or plastic responses to thermal extremes due to their short generation duration, clonal structure and high thermal sensitivity. To further understand the mechanism involved in this change in species' dominance, we characterised aphid heat tolerance and demography of the two species sourced from relatively mild (Xinxiang) and hot (Wuhan) locations in a common garden design and compared the same measures in up‐ and down‐selected lines of the two aphid species. We found that accumulation of extreme high‐temperature events (EHTs) affected per capita growth rate of S. avenae but not R. padi, driving a shift in annual relative dominance of these two common species in wheat fields. Furthermore, evidence from common garden tests and artificial thermal selection revealed that evolutionary and plastic changes in thermal tolerance under EHTs were species‐dependent; R. padi evolved higher heat tolerance without reducing fitness while S. avenae did not evolve heat tolerance but showed detrimental transgenerational plastic changes under thermal extremes. Rhopalosiphum padi may take over the dominant position of S. avenae in a warmer future, due to a higher evolutionary potential of heat tolerance and less detrimental plasticity following selection. Field surveys and laboratory experiments together point to a shift in species dominance related to interspecific differences in species' evolutionary rates and transgenerational plasticity of thermal traits during selection events associated with extreme climatic conditions. This study highlights that eco‐evolutionary dynamics can contribute to community responses to natural thermal extremes. A free Plain Language Summary can be found within the Supporting Information of this article.