Genome-Wide Identification of the Odorant Receptor Gene Family and Revealing Key Genes Involved in Sexual Communication in Anoplophora glabripennis.

Insects use a powerful and complex olfactory recognition system to sense odor molecules in the external environment to guide behavior. A large family of odorant receptors (ORs) mediates the detection of pheromone compounds. Anoplophora glabripennis is a destructive pest that harms broad-leaved tree species. Although olfactory sensation is an important factor affecting the information exchange of A. glabripennis, little is known about the key ORs involved. Here, we identified ninety-eight AglaORs in the Agla2.0 genome and found that the AglaOR gene family had expanded with structural and functional diversity. RT-qPCR was used to analyze the expression of AglaORs in sex tissues and in adults at different developmental stages. Twenty-three AglaORs with antennal-biased expression were identified. Among these, eleven were male-biased and two were female-biased and were more significantly expressed in the sexual maturation stage than in the post-mating stage, suggesting that these genes play a role in sexual communication. Relatively, two female-biased AglaORs were overexpressed in females seeking spawning grounds after mating, indicating that these genes might be involved in the recognition of host plant volatiles that may regulate the selection of spawning grounds. Our study provides a theoretical basis for further studies into the molecular mechanism of A. glabripennis olfaction.

Cloning and Molecular Characterization of Hsp Genes from Anoplophora glabripennis and Their Responses to Cold Stress.

Anoplophora glabripennis (Agla) is an important global quarantine pest due to its highly destructive impacts on forests. It is widely distributed in many countries in Asia, Europe, and North America. The survival of A. glabripennis larvae has been facilitated by its high adaptability to low temperature. When insects are subjected to temperature stress, heat shock proteins (Hsps) limit cell damage and improve cell tolerance via their protein folding, localization, and degradation activities. However, the temperature adaptation mechanisms of A. glabripennis Hsps remain unclear. In this study, four A. glabripennis Hsp genes, AglaHsp20.43, AglaHsp71.18, AglaHsp82.09, and AglaHsp89.76, were cloned. Sequence analysis showed that all four Hsps had specific conserved domains. Phylogenetic analysis revealed that Hsps from different subfamilies were evolutionarily conserved, and that AglaHsps were highly similar to those of Coleoptera species. Protein expression vectors (pET30a-AglaHsps) were constructed and used to express AglaHsps in E. coli, where all four proteins were expressed in inclusion bodies. Western blot analysis showed that AglaHsps were expressed at a range of temperatures, from -10 °C to 25 °C. AglaHsp82.09 and AglaHsp89.76 showed high expressions with treatment at 0 °C. Our results will facilitate clarification of the molecular mechanisms underlying A. glabripennis responses to environmental stress.

Comparative transcriptome analysis of the newly discovered insect vector of the pine wood nematode in China, revealing putative genes related to host plant adaptation.

BACKGROUND: In many insect species, the larvae/nymphs are unable to disperse far from the oviposition site selected by adults. The Sakhalin pine sawyer Monochamus saltuarius (Gebler) is the newly discovered insect vector of the pine wood nematode (Bursaphelenchus xylophilus) in China. Adult M. saltuarius prefers to oviposit on the host plant Pinus koraiensis, rather than P. tabuliformis. However, the genetic basis of adaptation of the larvae of M. saltuarius with weaken dispersal ability to host environments selected by the adult is not well understood. RESULTS: In this study, the free amino and fatty acid composition and content of the host plants of M. saltuarius larvae, i.e., P. koraiensis and P. tabuliformis were investigated. Compared with P. koraiensis, P. tabuliformis had a substantially higher content of various free amino acids, while the opposite trend was detected for fatty acid content. The transcriptional profiles of larval populations feeding on P. koraiensis and P. tabuliformis were compared using PacBio Sequel II sequencing combined with Illumina sequencing. The results showed that genes relating to digestion, fatty acid synthesis, detoxification, oxidation-reduction, and stress response, as well as nutrients and energy sensing ability, were differentially expressed, possibly reflecting adaptive changes of M. saltuarius in response to different host diets. Additionally, genes coding for cuticle structure were differentially expressed, indicating that cuticle may be a potential target for plant defense. Differential regulation of genes related to the antibacterial and immune response were also observed, suggesting that larvae of M. saltuarius may have evolved adaptations to cope with bacterial challenges in their host environments. CONCLUSIONS: The present study provides comprehensive transcriptome resource of M. saltuarius relating to host plant adaptation. Results from this study help to illustrate the fundamental relationship between transcriptional plasticity and adaptation mechanisms of insect herbivores to host plants.

Projecting the Global Potential Distribution of Cydia pomonella (Lepidoptera: Tortricidae) Under Historical and RCP4.5 Climate Scenarios.

The codling moth Cydia pomonella (L.) (Lepidoptera: Tortricidae) is a destructive pest of apple (Malus domestica (Rosales: Rosaceae)), pear (Pyrus spp. (Rosales: Rosaceae)), and other pome tree fruits; outbreaks cause significant ecological and economic losses. In this study, we used CLIMEX model to predict and evaluate the global risk of C. pomonella based on historical climate data (1989-2018) and simulated future climate data (2071-2100) under the RCP4.5 scenarios. Cydia pomonella exhibited a wide distribution under both historical and future climate conditions. Climate change is predicted to expand the northern boundary of the potential distribution from approximately 60°N to 75°N. Temperature was the most dominant factor in climatic suitability for the pest. Combinations of multiple meteorological factors (relative humidity and precipitation) associated with a failure to break diapause in certain regions also affect suitability, particularly in northern South America and central Africa. Irrigation only had a slight impact on species favorability in some areas. The projections established in our study present insight into the global potential suitability of C. pomonella under climate change scenarios by the end of the 21st century. Farmers should be aware of the risk associated with the pest based on the results, which would provide guidance for quarantine agencies and trade negotiators worldwide.

Supercooling capacity and cryoprotectants of overwintering larvae from different populations of Holcocerus hippophaecolus.

BACKGROUND: Holcocerus hippophaecolus is the most serious pest occurred in seabuckthorn forest of three north areas. OBJECTIVE: The primary aims of the current study were to explore the physiological mechanisms and adaptability of H. hippophaecolus to low temperatures. MATERIALS AND METHODS: Assessing supercooling point, freezing point, and cryoprotectants of different larval instars from three different populations. RESULTS: Supercooling capacity of larvae from the 8-13 instar groups was relatively independent of temperature and other indicators such as latitude. Larvae from the 14-16 instar groups were sensitive to temperature and latitude, with generally lower limits and a wider range of SCPs than those of the other instar groups. CONCLUSION: For each population, the differences in the supercooling capacity of different instar stages for the identical period were not significant. The metabolism of fat and glycogen might not be the primary factors affecting the supercooling capacity.

Modeling the pest-pathogen threats in a warming world for the red turpentine beetle (Dendroctonus valens) and its symbiotic fungus (Leptographium procerum).

BACKGROUND: Dendroctonus valens along with its symbiotic fungi have caused unprecedented damage to pines in China. Leptographium procerum, its primary symbiotic fungus, facilitates the invasion and colonization of the pest, thereby aggravating ecological threats. Assessing shifts in the niches and ranges of D. valens and its symbiotic fungus could provide a valuable basis for pest control. Here, we conducted niche comparisons between native and invasive populations of D. valens. Then, we employed standard ecological niche models and ensembles of small models to predict the potential distributions of D. valens and L. procerum under climate change conditions and to estimate areas of overlap. RESULTS: The niche of invasive population of D. valens in Chinese mainland only occupied a limited portion of the niche of native population in North America, leaving a substantial native niche unfilled and without any niche expansion. The suitable regions for D. valens are predicted in central and southern North America and central and northeastern Chinese mainland. The overlap with the suitable regions of L. procerum included eastern North America and the central and northeastern Chinese mainland under historical climatic scenarios. The regions susceptible to their symbiotic damage will shift northward in response to future climate change. CONCLUSIONS: Projected distributions of D. valens and its symbiotic fungus, along with areas vulnerable to their symbiotic damage, provide essential insights for devising strategies against this association. Additionally, our study contributes to comprehending how biogeographic approaches aid in estimating potential risks of pest-pathogen interactions in forests within a warming world. © 2024 Society of Chemical Industry.

Impacts of climate change and host plant availability on the potential distribution of Bradysia odoriphaga (Diptera: Sciaridae) in China.

BACKGROUND: Chinese chives (Allium tuberosum Rottler ex Sprengel) are favored by consumers because of its delicious taste and unique fragrance. Bradysia odoriphaga (Diptera: Sciaridae) is a main pest that severely harms Chinese chives and other Liliaceae's production. Climate change may change the future distribution of B. odoriphaga in China. In this study, the CLIMEX was employed to project the potential distribution of B. odoriphaga in China, based on China's historical climate data (1987-2016) and forecast climate data (2021-2100). RESULTS: Bradysia odoriphaga distributed mainly between 19.8° N-48.3° N and 74.8° E-134.3° E, accounting for 73.25% of the total mainland area of China under historical climate conditions. Among them, the favorable and highly favorable habitats accounted for 30.64% of the total potential distribution. Under future climate conditions, B. odoriphaga will be distributed mainly between 19.8° N-49.3° N and 73.8° E-134.3° E, accounting for 84.89% of China's total mainland area. Among them, the favorable and highly favorable habitats will account for 35.23% of the total potential distribution, indicating an increase in the degree of fitness. Areas with relatively appropriate temperature and humidity will be more suitable for the survival of B. odoriphaga. Temperature was a more important determinant of the climatic suitability of the pest B. odoriphaga than humidity. Host plants (Liliaceae) availability also had impact on climate suitability in some regions. CONCLUSIONS: These projected potential distributions will provide supportive information for monitoring and early forecasting of pest outbreaks, and to reduce future economic and ecological losses. © 2024 Society of Chemical Industry.

Unveiling winter survival strategies: physiological and metabolic responses to cold stress of Monochamus saltuarius larvae during overwintering.

BACKGROUND: Monochamus saltuarius is a destructive trunk-borer of pine forest and an effective dispersal vector for pinewood nematode (PWN), a causative agent of pine wilt disease (PWD), which leads to major ecological disasters. Cold winter temperatures determine insect survival and distribution. However, little is known about the cold tolerance and potential physiological mechanisms of M. saltuarius. RESULTS: We demonstrated that dead Pinus koraiensis trunks do not provide larvae with insulation. The M. saltuarius larvae are freeze-tolerant species. Unlike most other freeze-tolerant insects, they can actively freeze extracellular fluid at higher subzero temperatures by increasing their supercooling points. The main energy sources for larvae overwintering are glycogen and the mid-late switch to lipid. The water balance showed a decrease in free and an increase in bound water of small magnitude. Cold stress promoted lipid peroxidation, thus activating the antioxidant system to prevent cold-induced oxidative damage. We found eight main pathways linked to cold stress and 39 important metabolites, ten of which are cryoprotectants, including maltose, UDP-glucose, d-fructose 6P, galactinol, dulcitol, inositol, sorbitol, l-methionine, sarcosine, and d-proline. The M. saltuarius larvae engage in a dual respiration process involving both anaerobic and aerobic pathways when their bodily fluids freeze. Cysteine and methionine metabolism, as well as alanine, aspartate, and glutamate metabolism, are the most important pathways linked to antioxidation and energy production. CONCLUSIONS: The implications of our findings may help strengthen and supplement the management strategies for monitoring, quarantine, and control of this pest, thereby contributing to controlling the further spread of PWD. © 2024 Society of Chemical Industry.

Cold tolerance and metabolism of red-haired pine bark beetle Hylurgus ligniperda (Coleoptera: Curculionidae) during the overwintering period.

Hylurgus ligniperda invaded Shandong, China, through imported forest timber, posing a threat to China's forest health. Exotic insects with broad environmental tolerance, including low temperatures, may have a better chance of surviving the winters and becoming invasive. Understanding the cold-tolerance strategies of H. ligniperda may help to design sustainable pest management approaches. In this study, we aim to investigate the cold-tolerance ability and relevant physiological indicators in overwintering H. ligniperda adults to determine any possible overwintering strategies. Supercooling points (SCPs) for adults H. ligniperda differed significantly across months and reached the lowest level in the mid- and post-overwintering period, the minimum SCPs -6.45 ±â€…0.18 °C. As the cold exposure temperature decreased, the survival rate of adults gradually decreased, and no adult survived more than 1 day at -15 °C, and the LLT50 for 1 day was -7.1 °C. Since H. ligniperda adults can survive internal ice formation, they are freeze-tolerant insects. Throughout the overwintering period, the SCPs and the water, protein, sorbitol, and glycerol content in adults decreased initially and then increased. We reported significant correlations between total protein, sorbitol, trehalose, and glycerol content in the beetles and SCPs. Glycogen, lipid, protein, trehalose, and sorbitol content in adult beetles may directly affect their cold-tolerance capacity and survival during winter. This study provides a physiological and biochemical basis for further study of metabolism and cold-tolerance strategies in H. ligniperda adults, which may help predict population dynamics and distribution potential of pests.

Chromosome-level genome assembly of the Japanese sawyer beetle Monochamus alternatus.

The Japanese sawyer beetle Monochamus alternatus (Coleoptera: Cerambycidae) is a pest in pine forests and acts as a vector for the pine wood nematode Bursaphelenchus xylophilus, which causes the pine wilt disease. We assembled a high-quality genome of M. alternatus at the chromosomal level using Illumina, Nanopore, and Hi-C sequencing technologies. The assembled genome is 767.12 Mb, with a scaffold N50 of 82.0 Mb. All contigs were assembled into ten pseudo-chromosomes. The genome contains 63.95% repeat sequences. We identify 16, 284 protein-coding genes in the genome, of which 11,244 were functionally annotated. The high-quality genome of M. alternatus provides an invaluable resource for the biological, ecological, and genetic study of this beetle and opens new avenues for understanding the transmission of pine wood nematode by insect vectors.

cDNA cloning and sequence determination of the pheromone biosynthesis activating neuropeptide from the seabuckthorn carpenterworm, Holcocerus hippophaecolus (Lepidoptera: Cossidae).

The PBAN (pheromone biosynthesis activating neuropeptide)/pyrokinin peptides comprise a major neuropeptide family characterized by a common FXPRL amide at the C-terminus. These peptides are actively involved in many essential endocrine functions. For the first time, we reported the cDNA cloning and sequence determination of the PBAN from the seabuckthorn carpenterworm, Holcocerus hippophaecolus, by using rapid amplification of cDNA ends. The full-length cDNA of Hh-DH-PBAN contained five peptides: diapause hormone (DH) homolog, α-neuropeptide (NP), ß-NP, PBAN, and γ-NP. All of the peptides were amidated at their C-terminus and shared a conserved motif, FXPR (or K) L. Moreover, Hh-DH-PBAN had high homology to the other members of the PBAN peptide family: 56% with Manduca sexta, 66% with Bombyx mori, 77% with Helicoverpa zea, and 47% with Plutella xylostella. Phylogenetic analysis revealed that Hh-DH-PBAN was closely related to PBANs from Noctuidae, demonstrated by the relatively higher similarity compared with H. zea. In addition, real-time quantitative PCR (qRT-PCR) analysis showed that Hh-DH-PBAN mRNA expression peaked in the brain-subesophageal ganglion (Br-SOG) complex, and was also detected at high levels during larval and adult stages. The expression decreased significantly after pupation. These results provided information concerning molecular structure characteristics of Hh-DH-PBAN, whose expression profile suggested that the Hh-DH-PBAN gene might be correlated with larval development and sex pheromone biosynthesis in females of the H. hippophaecolus.

Molecular cloning and expression profile of a Halloween gene encoding Cyp307A1 from the seabuckthorn carpenterworm, Holcocerus hippophaecolus.

20-Hydroxyecdyone, an active form of ecdysteroid, is the key hormone in insect growth and development. Halloween genes encode ecdysteroidogenic enzymes, including cytochrome P450 monooxygenase. CYP307A1 (spook) is accepted as an enzyme acting in the so-called 'black box' that includes a series of hypothetical and unproven reactions that finally result in the oxidation of 7-dehydrocholesterol to diketol. In this study, the Holcocerus hippophaecolus Hua (Lepidoptera: Cossidae) CYP307A1 (HhSpo) gene was identified and characterized. The obtained cDNA sequence was 2084 base pairs with an open reading frame of 537 animo acids, in which existed conserved motifs of CYP450 enzymes. The transcript profiles of HhSpo were analyzed in various tissues of final instar larvae. The highest expression was observed in the prothoracic gland, while expression level was low but significant in other tissues. These results suggest that the sequence character and expression profile of HhSpo were well conserved and provided the basic information for its functional analysis.

Development of semiochemical attractants for monitoring and controlling Chlorophorus caragana.

Chlorophorus caragana is an important wood-boring pest that infests Caragana korshinskii. The larvae bore into the stems to the point of hollowing them out, causing the whole tree to wither and even die. To control these infestations, volatile compounds were collected from C. korshinskii and used in electroantennography to ascertain which plant semiochemicals could be used to trap adult C. caragana in the field. Isophorone, cis-3-hexen-1-ol, 3-pentanone, dibutyl phthalate, and diisobutyl phthalate were the main volatile compounds produced by C. korshinskii. These compounds induced dose-dependent electrophysiological responses in the antennae of adult C. caragana to some degree. Accordingly, 58 different compound mixtures were tested in field trapping experiments over two consecutive years. Isophorone was most attractive to adult insects. In the field, the best traps were funnel-shaped ones hanging at a height of 1 m. The trapping efficiency was 63.8%. Adult beetles appear between mid June and late August, with an eclosion peak in mid July. The prototype trapping system developed could be used as a tool to monitor and control C. caragana adults.

Comparative study of the volatiles' composition of healthy and larvae-infested Artemisia ordosica.

Volatiles emitted by healthy Artemisia ordosica (Asteraceae) and plants infested with larvae of Sphenoptera sp. (Coleoptera: Buprestidae) or Holcocerus artemisiae (Lepidoptera: Cossidae) were obtained using a dynamic headspace method and analysed by automatic thermal desorption/gas chromatography/mass spectrometry (ATD/GC/MS). Twenty-eight major compounds were identified, and qualitative and quantitative differences were compared. The novel green leaf volatiles 2-hexenal, (Z)-3-hexen-1-ol, 2-hexen-1-ol 1-hexanol, and (Z)-3-hexen-1-ol acetate, the terpenoids alpha-copaene, beta-cedrene, and (E,E)-alpha-farnesene, and the ester methyl salicylate were present in all infested plants. Volatiles from healthy plants were dominated by D-limonene (32.14%), beta-pinene (16.63%), beta-phellandrene (16.06%), and sabinene (12.88%). Volatiles from Sphenoptera sp. larvae-infested plants were dominated by D-limonene (24.74%), beta-pinene (21.05%), alpha-pinene (19.39%), and sabinene (11.64%), whereas volatiles from H. artemisiae larvae-infested plants were dominated by D-limonene (31.76%), sabinene (18.49%), ocimene (15.93%), and beta-phellandrene (10.59%). In addition to the qualitative variation, a larvae-induced quantitative change in the proportion of terpenoids in the blends was also a noticeable feature.

Identification of volatile compounds emitted by Artemisia ordosica (Artemisia, Asteraceae) and changes due to mechanical damage and weevil infestation.

Volatiles emitted by healthy, mechanically damaged, and weevil-infested Artemisia ordosica (Asteraceae) were obtained through a dynamic headspace method and analysed by automatic thermal desorption/gas chromatography/mass spectrometry (ATD/GC/MS). Twenty-eight compounds in all were identified, and the qualitative as well as quantitative differences were compared. The green leaf volatiles 2-hexenal, (Z)-3-hexen-1-ol, 2-hexen-1-ol, 1-hexanol, and (Z)-3-hexen-1-ol acetate were present in all of the damaged plants, but in relatively lower portions when plants were infested by the weevil Adosopius sp., while the terpenoids alpha-copaene, beta-cedrene, and (E,E)-alpha-farnesene and the ester methyl salicylate were only present in weevil-damaged plants. The volatiles from healthy and weevil-infested leaves were dominated by D-limonene, whereas mechanically damaged leaves emitted beta-pinene as the dominant compound.

Host-plant adaptation in xylophagous insect-microbiome systems: Contributionsof longicorns and gut symbionts revealed by parallel metatranscriptome.

Adaptation to host plants is of great significance in the ecology of xylophagous insects. The specific adaptation to woody tissues is made possible through microbial symbionts. We investigated the potential roles of detoxification, lignocellulose degradation, and nutrient supplementation of Monochamus saltuarius and its gut symbionts in host plant adaptation using metatranscriptome. The gut microbial community structure of M. saltuarius that fed on the two plant species were found to be different. Plant compound detoxification and lignocellulose degradation genes have been identified in both beetles and gut symbionts. Most differentially expressed genes associated with host plant adaptations were up-regulated in larvae fed on the less suitable host (Pinus tabuliformis) compared to larvae fed on the suitable host (Pinus koraiensis). Our findings indicated that M. saltuarius and its gut microbes respond to plant secondary substances through systematic transcriptome responses, allowing them to adapt to unsuitable host plants.

Niche shifts and range expansions after invasions of two major pests: the Asian longhorned beetle and the citrus longhorned beetle.

BACKGROUND: In recent years, the quarantine forestry pests the Asian longhorned beetle (ALB) Anoplophora glabripennis and the citrus longhorned beetle (CLB) Anoplophora chinensis have spread across the Northern Hemisphere, triggering concern about their potential distribution. However, little is known about the niche shifts of the pests during the invasion, making it difficult to assess their potential ranges. We thus employed two distinct approaches (i.e., ordination-based and reciprocal model-based) to compare the native and invaded niches of ALB and CLB after their spread to new continents based on global occurrence records. We further constructed models with pooled occurrences from both the native and invaded ranges to analyze the effects of occurrence partitioning on predicted ranges. RESULTS: We detected expansions in the invaded niches of both pests, indicating that the niches shifted to varying extents after the invasion. Large shares of the native niches of ALB and CLB remained unfilled, revealing the potential for further invasion in new regions. The models calibrated with pooled occurrences clearly underestimated the potential ranges in invaded regions compared with the projections based on partitioned models considering native and invaded areas separately. CONCLUSIONS: These results emphasize the importance of elucidating the niche dynamics of invasive species for obtaining accurately predicted ranges, which may help identify risk areas masked by the assumption of niche conservatism. Furthermore, prevention and quarantine measures for ALB and CLB are clearly needed to avoid future serious damage to forest ecosystems. © 2023 Society of Chemical Industry.

Comparative mitochondrial genomic analysis provides new insights into the evolution of the subfamily Lamiinae (Coleoptera: Cerambycidae).

The genus Monochamus within the subfamily Lamiinae is the main vector of Bursaphelenchus xylophilus, which causes pine wilt disease and induces substantial economic and ecological losses. Only three complete mitochondrial genomes of the genus Monochamus have been sequenced to date, and no comparative mitochondrial genomic studies of Lamiinae have been conducted. Here, the mitochondrial genomes of two Monochamus species, M. saltuarius and M. urussovi, were newly sequenced and annotated. The composition and order of genes in the mitochondrial genomes of Monochamus species are conserved. All transfer RNAs exhibit the typical clover-leaf secondary structure, with the exception of trnS1. Similar to other longhorn beetles, Lamiinae mitochondrial genomes have an A + T bias. All 13 protein-coding genes have experienced purifying selection, and tandem repeat sequences are abundant in the A + T-rich region. Phylogenetic analyses revealed congruent topologies among trees inferred from the five datasets, with the monophyly of Acanthocinini, Agapanthiini, Batocerini, Dorcaschematini, Pteropliini, and Saperdini receiving high support. The findings of this study enhance our understanding of mitochondrial genome evolution and will provide a basis for future studies of population genetics and phylogenetic investigations in this group.

Cradle for the newborn Monochamus saltuarius: Microbial associates to ward off entomopathogens and disarm plant defense.

The Japanese pine sawyer, Monochamus saltuarius, as a beetle vector of Bursaphelenchus xylophilus (pine wood nematode), is an economically important forest pest in Eurasia. To feed on the phloem and xylem of conifers, M. saltuarius needs to overcome various stress factors, including coping with entomopathogenic bacteria and also various plant secondary compounds (PSCs). As an important adaptation strategy to colonize host trees, M. saltuarius deposit eggs in oviposition pits to shield their progeny. These pits harbor bacterial communities that are involved in the host adaptation of M. saltuarius to the conifers. However, the composition, origin, and functions of these oviposition pit bacteria are rarely understood. In this study, we investigated the bacterial community associated with M. saltuarius oviposition pits and their ability to degrade PSCs. Results showed that the bacterial community structure of M. saltuarius oviposition pits significantly differed from that of uninfected phloem. Also, the oviposition pit bacteria were predicted to be enriched in PSC degradation pathways. The microbial community also harbored a lethal strain of Serratia, which was significantly inhibited. Meanwhile, metatranscriptome analysis indicated that genes involved in PSCs degradation were expressed complementarily among the microbial communities of oviposition pits and secretions. In vitro degradation showed that bacteria cultured from oviposition pits degraded more monoterpenes and flavonoids than bacteria cultured from uninfected phloem isolates. Disinfection of oviposition pits increased the mortality of newly hatched larvae and resulted in a significant decrease in body weight in the early stages. Overall, our results reveal that M. saltuarius construct oviposition pits that harbor a diverse microbial community, with stronger PSCs degradation abilities and a low abundance of entomopathogenic bacteria, resulting in the increased fitness of newly hatched larvae.

Effects of fungicides on fitness and Buchnera endosymbiont density in Aphis gossypii.

BACKGROUND: Several agricultural fungicides are known to affect insect pests directly and these effects may be transgenerational and mediated through impacts on endosymbionts, providing opportunities for pest control. The cotton aphid Aphis gossypii is a polyphagous pest that can cause large crop yield losses. Here, we tested the effects of three fungicides, pyraclostrobin, trifloxystrobin and chlorothalonil, on the fitness and Buchnera endosymbiont of A. gossypii. RESULTS: The formulations of trifloxystrobin and pyraclostrobin, and the active ingredient of pyraclostrobin produced dose-dependent mortality in A. gossypii, whereas there was no dose-dependent mortality for chlorothalonil. The formulations of trifloxystrobin and pyraclostrobin significantly reduced the lifespan and fecundity of A. gossypii, and increased the density of Buchnera in the parental generation but not the (unexposed) F1 . When the active ingredient of pyraclostrobin was tested, the lifespan of the F0 generation was also reduced, but the density of Buchnera was not, indicating that non-insecticidal chemicals in the fungicide formulation may affect the density of the endosymbiont of A. gossypii. There was no transgenerational effect of the active ingredient of pyraclostrobin on the lifespan and Buchnera of (unexposed) F1 . CONCLUSIONS: Our results suggest that formulations of two strobilurin fungicides have immediate impacts on the fitness of A. gossypii, and chemicals in the formulation impact the density of the primary Buchnera endosymbiont. Our study highlights the potential effects of non-insecticidal chemicals of fungicides on aphid pests and their primary endosymbionts but direct connections between fitness and Buchnera densities remain unclear. © 2023 Society of Chemical Industry.