Delia Antiqua Research Articles

Population variability of three Delia species (Diptera: Anthomyiidae) from the same agricultural habitat in Québec, Canada

AbstractLong-term trap catches of seedcorn maggot, Delia platura (Meigen), onion maggot, Delia antiqua (Meigen), and cabbage maggot, Delia radicum (Linnaeus) (Diptera: Anthomyiidae), were used to test the hypothesis that related species have more similar population variability than unrelated ones. Annual abundance was estimated from trap catches for 32 years (two species) or 17 years (one species). Population variability was quantified as PV, a proportion between 0 and 1. The three Delia Robineau-Desvoidy species had PV values of 0.51–0.55 that did not differ significantly. These PV values were found to differ significantly from two unrelated species studied over the same time period in the same habitat, which had PV values of 0.39 and 0.67. The hypothesis that related species have more similar population variabilities than unrelated species in the same habitat was supported. These data strengthen the view that PV is a species-specific trait reflecting the adaptation of life histories to their habitat, with related species showing more similar adaptations than unrelated species. The polyphagous and saprophagous seedcorn maggot had PV similar to the two oligophagous herbivores, casting doubt on the hypothesis that more generalist feeders have less variable populations than more specialised feeders.

Influence of larval experience on preference of a subterranean insect Delia antiqua on Allium hosts

AbstractNumerous studies have reported that larval experience can affect subsequent host plants selection and future oviposition decisions of many different species, but the investigation of pre‐imaginal experiences on host preference of adults has rarely been tested for soil‐dwelling insects. In this study, we present evidence that larval feeding experience can affect adult host preference in the onion maggot, Delia antiqua. By rearing D. antiqua on different host plants, we were able to examine the role of the natal host of different generations and the effect of larval density on host‐choice behaviour. We also performed bioassays by means of switched host treatment to evaluate the host‐selection principle. Choice bioassays among the three host species demonstrated that D. antiqua females preferred to oviposit on their natal host in each generation and host‐switching treatments. Additionally, increasing larval density could intensify this ovipositional preference on the natal host. The overall results showed that host preference of female D. antiqua is determined by larval experience and density. These findings also add support for the controversial Hopkins’ host‐selection principle.

Development of insect life tables: comparison of two demographic methods of Delia antiqua (Diptera: Anthomyiidae) on different hosts

In this study, we first construct an age-stage, two-sex life table for onion maggot, Delia antiqua, grown on three host plants: onion, scallion, and garlic. We found that onion is the optimal host for this species and populations grown on onion have maximum fecundity, longest adult longevity and reproduction period, and the shortest immature developmental time. In contrast, the fecundity on other hosts was lower, particularly on garlic, but these crops can also serve as important secondary hosts for this pest. These data will be useful to the growers to develop specific integrated management programs for each of hosts. We also compared the demographic analyses of using individually-reared and group-reared methods. These two methods provided similar accurate outcomes for estimating insect population dynamics for this species. However, for gregarious species, using the individually-reared method to construct insect life tables produces inaccurate results, and researchers must use group-reared method for life table calculations. When studying large groups of insect, group-reared demographic analysis for age-stage, two-sex life table can also simplify statistical analysis, save considerable labor, and reduce experimental errors.

Predicting the current potential and future world wide distribution of the onion maggot, Delia antiqua using maximum entropy ecological niche modeling.

Climate change will markedly impact biology, population ecology, and spatial distribution patterns of insect pests because of the influence of future greenhouse effects on insect development and population dynamics. Onion maggot, Delia antiqua, larvae are subterranean pests with limited mobility, that directly feed on bulbs of Allium sp. and render them completely unmarketable. Modeling the spatial distribution of such a widespread and damaging pest is crucial not only to identify current potentially suitable climactic areas but also to predict where the pest is likely to spread in the future so that appropriate monitoring and management programs can be developed. In this study, Maximum Entropy Niche Modeling was used to estimate the current potential distribution of D. antiqua and to predict the future distribution of this species in 2030, 2050, 2070 and 2080 by using emission scenario (A2) with 7 climate variables. The results of this study show that currently highly suitable habitats for D.antiqua occur throughout most of East Asia, some regions of North America, Western Europe, and Western Asian countries near the Caspian sea and Black Sea. In the future, we predict an even broader distribution of this pest spread more extensively throughout Asia, North America and Europe, particularly in most of European countries, Central regions of United States and much of East Asia. Our present day and future predictions can enhance strategic planning of agricultural organizations by identifying regions that will need to develop Integrated Pest Management programs to manage the onion maggot. The distribution forecasts will also help governments to optimize economic investments in management programs for this pest by identifying regions that are or will become less suitable for current and future infestations.

Day-to-day variations in the amplitude of the soil temperature cycle and impact on adult eclosion timing of the onion fly.

The onion fly Delia antiqua advances its eclosion timing with decreasing temperature amplitude to compensate for a depth-dependent phase delay of the zeitgeber. To elucidate whether or not naturally occurring day-to-day variations in the amplitude of soil temperature cycle disturb this compensatory response, we monitored daily variations in the temperature amplitude in natural soils and evaluated the impact on adult eclosion timing. Our results indicated that both median and variance of the soil temperature amplitude become smaller as depth increases. Insertion of a larger temperature fluctuation into the thermoperiod with smaller temperature amplitude induced a stronger phase delay, while insertion of a smaller temperature fluctuation into the thermoperiod with larger temperature amplitude had a weaker phase-advancing effect. It is therefore expected that larger diurnal temperature fluctuations disturb the compensatory response, particularly if they occur at deeper locations, while smaller temperature fluctuations do so only at shallower locations. Under natural conditions, however, the probability of occurrence of smaller or larger temperature fluctuations in shallower or deeper soils, respectively, is relatively small. Thus, naturally occurring day-to-day variations in the temperature amplitude rarely disturb the compensatory response, thereby having a subtle or negligible impact on adult eclosion timing.

Sterilization Effects of Adult-targeted Baits Containing Insect Growth Regulators on Delia antiqua.

The onion maggot, Delia antiqua, is a devastating pest of liliaceous crops and current control measures fail to avert pesticide residues, threats to agroecosystem, and costly expenditures. Insect growth regulators (IGRs) are used as trypetid pest chemosterilants for their suppression on adult fertility and fecundity, but their effects on onion flies are unknown. Here, three IGRs (lufenuron, cyromazine, pyriproxyfen) were incorporated into baits to evaluate their effects on onion fly survival, fecundity, fertility, susceptibility of adults in different ages and offspring development. Lufenuron and cyromazine did not affect survival of new-emerged adults, but lufenuron inhibited adult fertility without affecting fecundity, and cyromazine reduced fertility and fecundity. Differently, pyriproxyfen enhanced fecundity within 10 days after treatment, while it reduced adult survival without affecting fertility. The fertility of younger adults was affected by lufenuron and cyromazine whereas the fecundity was affected with cyromazine and pyriproxyfen. For offspring of onion flies treated with lufenuron or cyromazine, most of larvae died within 5 days after hatch, but surviving larvae pupated and emerged normally. Pyriproxyfen did not affect offspring larval survival or pupation but affected pupal emergence. Thus, lufenuron and cyromazine could be potential chemosterilants for onion flies.

Harmfulness of Delia antiqua (Diptera: Anthomyiidae) in Garlic in Southeast and Central Moravia

The aim of the three year research was to determine the first occurrence of Delia antiqua (Meigen, 1826) (Diptera: Anthomyiidae), specify its bionomics, compare its harmfulness on different garlic varieties, find out the effect of temperature on their life cycle and how their abundance influences garlic yield in regional agriculture areas traditionally growing garlic such as southeast and central Moravia. There was a significantly higher infestation of Delia antiqua on the edge (32.3 larvae) of study plot than in the middle (16.3 larvae) from 2010 to 2012. Intensive laying eggs of D. antiqua takes place between 9–11 a.m. and 16–18 p.m. hours at the edges of the study plot. The highest number of laid eggs was of 28 per one plant in Nedakonice. The development lasted 15 days at 21 °C under laboratory conditions.

Insight into the possible mechanism of the summer diapause of Delia antiqua (Diptera: Anthomyiidae) through digital gene expression analysis.

The onion fly, Delia antiqua, is a major underground agricultural pest that can enter pupal diapause in the summer and winter seasons. However, little is known about its molecular regulation due to the lack of genomic resources. To gain insight into the possible mechanism of summer diapause (SD), high-throughput RNA-Seq data were generated from non-diapause (ND) and SD (initial, maintenance and quiescence phase) pupae. Three pair-wise comparisons were performed and identified, 1380, 1471 and 435, and were significantly regulated transcripts. Further analysis revealed that the enrichment of several functional terms related to juvenile hormone regulation, cell cycle, carbon hydrate and lipid metabolism, innate immune and stress responses, various signalling transductions, ubiquitin-dependent proteosome, and variation in cuticular and cytoskeleton components were found between ND and SD and between different phases of SD. Global characterization of transcriptome profiling between SD and ND contributes to the in-depth elucidation of the molecular mechanism of SD. Our results also offer insights into the evolution of insect diapause and support the importance of using the onion fly as a model to compare the molecular regulation events of summer and winter diapauses.

Temperature cycle amplitude alters the adult eclosion time and expression pattern of the circadian clock gene period in the onion fly

Soil temperature cycles are considered to play an important role in the entrainment of circadian clocks of underground insects. However, because of the low conductivity of soil, temperature cycles are gradually dampened and the phase of the temperature cycle is delayed with increasing soil depth. The onion fly, Delia antiqua, pupates at various soil depths, and its eclosion is timed by a circadian clock. This fly is able to compensate for the depth-dependent phase delay of temperature change by advancing the eclosion time with decreasing amplitude of the temperature cycle. Therefore, pupae can eclose at the appropriate time irrespective of their location at any depth. However, the mechanism that regulates eclosion time in response to temperature amplitude is still unknown. To understand whether this mechanism involves the circadian clock or further downstream physiological processes, we examined the expression patterns of period (per), a circadian clock gene, of D. antiqua under temperature cycles that were square wave cycles of 12-h warm phase (W) and 12-h cool phase (C) with the temperature difference of 8°C (WC 29:21°C) and 1°C (WC 25.5:24.5°C). The phase of oscillation in per expression was found to commence 3.5h earlier under WC 25.5:24.5°C as compared to WC 29:21°C. This difference was in close agreement with the eclosion time difference between the two temperature cycles, suggesting that the mechanism that responds to the temperature amplitude involves the circadian clock.

Chemosensory proteins involved in host recognition in the stored-food mite Tyrophagus putrescentiae.

Chemosensory proteins (CSPs) have been proposed to transport a range of aliphatic compounds, esters and other long-chain compounds. A large number of CSPs from different gene subfamilies have been identified and annotated in arthropods; however, the CSP genes in mites remain unknown. Tyrophagus putrescentiae Schrank is an important stored-product and house-dust pest. By analysing the transcriptome, two putative CSPs were identified, namely TputCSP1 and TputCSP2 (14.9 kDa and 12.1 kDa respectively). The phylogenetic tree showed that the two TputCSPs shared most homology with CSPs in Ixodes scapularis and partially with Diptera, including Anopheles gambiae, Drosophila melanogaster, D. pseudoobscura, D. simulans, Delia antiqua and Culex quinquefasciatus. Additionally, they had similar secondary structure. The 3D models revealed that there are six α-helices enclosing the hydrophobic ligand binding pocket. Based on a docking study, we found that three ligands, (-)-alloaromadendrene, 2-methylnaphthalene and cyclopentadecane, had high binding affinities for TputCSP1. Moreover, the TputCSP2 protein had a higher inhibition constant with different affinities to all test ligands from host volatile substances. The two CSPs have distinct physiological functions. TputCSP1 may mediate host recognition. © 2015 Society of Chemical Industry.

The Complete Mitochondrial Genome of Delia antiqua and Its Implications in Dipteran Phylogenetics.

Delia antiqua is a major underground agricultural pest widely distributed in Asia, Europe and North America. In this study, we sequenced and annotated the complete mitochondrial genome of this species, which is the first report of complete mitochondrial genome in the family Anthomyiidae. This genome is a double-stranded circular molecule with a length of 16,141 bp and an A+T content of 78.5%. It contains 37 genes (13 protein-coding genes, 22 tRNAs and 2 rRNAs) and a non-coding A+T rich region or control region. The mitochondrial genome of Delia antiqua presents a clear bias in nucleotide composition with a positive AT-skew and a negative GC-skew. All of the 13 protein-coding genes use ATN as an initiation codon except for the COI gene that starts with ATCA. Most protein-coding genes have complete termination codons but COII and ND5 that have the incomplete termination codon T. This bias is reflected in both codon usage and amino acid composition. The protein-coding genes in the D. antiqua mitochondrial genome prefer to use the codon UUA (Leu). All of the tRNAs have the typical clover-leaf structure, except for tRNA Ser(AGN) that does not contain the dihydrouridine (DHU) arm like in many other insects. There are 7 mismatches with U-U in the tRNAs. The location and structure of the two rRNAs are conservative and stable when compared with other insects. The control region between 12S rRNA and tRNA Ile has the highest A+T content of 93.7% in the D. antiqua mitochondrial genome. The control region includes three kinds of special regions, two highly conserved poly-T stretches, a (TA)n stretch and several G(A)nT structures considered important elements related to replication and transcription. The nucleotide sequences of 13 protein-coding genes are used to construct the phylogenetics of 26 representative Dipteran species. Both maximum likelihood and Bayesian inference analyses suggest a closer relationship of D. antiqua in Anthomyiidae with Calliphoridae, Calliphoridae is a paraphyly, and both Oestroidea and Muscoidea are polyphyletic.

Comprehensive identification of odorant-binding protein genes in the seed fly, Delia platura (Diptera: Anthomyiidae)

Insect odorant-binding proteins (OBPs) function in the perception of chemical cues such as pheromones and host-plant odors. Comparative genomic analysis has shown that OBP genes underwent the birth-and-death process through the evolution of Hexapoda, resulting in diverged OBP repertoires between distantly related species. On the other hand, comparisons between closely related species, particularly those species with different degrees of host specialization, are limited. In this study, 20 novel OBP genes were identified from Delia platura (Meigen) by transcriptome analysis in the antennae and legs. The repertoire of OBP genes was compared with that of a closely related species, Delia antiqua (Meigen). Although D. platura is a generalist while D. antiqua is a specialist in regard to their host utilization, expression profiles of these OBPs were almost identical between the two species. Evolutionary analysis showed that at least 14 OBPs have been under purifying selection, suggesting that they have a similar function in both species. These results suggest that the repertoire of OBPs was relatively independent from host specialization in these species.

Gene cloning, characterization and expression and enzymatic activities related to trehalose metabolism during diapause of the onion maggot Delia antiqua (Diptera: Anthomyiidae)

Trehalose represents the main hemolymph sugar in many insects, and it functions in energy metabolism and protection in extreme environmental conditions. To gain an insight into trehalose functions in Delia antiqua diapausing pupae, genes encoding trehalose-6-phosphate synthase (TPS), trehalose-6-phosphatase (TPP) and trehalase (TRE) were identified and characterized. Analysis of the deduced amino acid sequences indicated that these genes were highly similar to each homolog from Diptera insects. Gene expressions and their enzyme activities were also investigated. The differential expressions of TPS and TPP shared very similar trends for summer and winter diapausing pupae. Their enzyme activities were consistent with the gene expressions. Trehalose concentrations in summer- and winter-diapausing pupae were lower at the initial phase (4.37–5.09μg/mg) but increased gradually and peaked in the maintenance phase (10.59–14.36μg/mg); the concentrations then declined in the quiescence phase. We speculated that a higher trehalose content during the maintenance stage may contribute to protein and/or biological membrane stabilization in winter or to desiccation resistance in the summertime. Diapause termination requires a decrease in the trehalose concentration to promote pupal–adult development. The glucose content also varied during the diapausing processes. Our results provide an overview of the differential expression levels of trehalose metabolic enzymes, confirming the important roles of trehalose in diapausing pupae of the onion maggot. Further work remains to explore its actual functions.

Evaluation of insecticides and application methods to protect onions from onion maggot, Delia antiqua, and seedcorn maggot, Delia platura, damage

Onion maggot, Delia antiqua (Meigen), and seedcorn maggot, Delia platura (Meigen), are important pests of spring-sown onions, Allium cepa L. Larvae of both species feed on developing epicotyls and roots of young onion plants often resulting in seedling mortality. Cultural controls used in combination with the insecticide chlorpyrifos are currently the standard practice for maggot control in the western USA. However, cultural controls are only partially effective and reliance on chlorpyrifos has several potential problems including future availability and development of resistance. Insecticides including clothianidin, imidacloprid, spinosad, and thiamethoxam were evaluated in California, USA in 2011–2013 to identify efficacious alternatives to chlorpyrifos. Some insecticides were applied in multiple ways including seed treatment, in-furrow application at planting, and rototiller incorporation prior to planting. Onion plant population, vigor, and yield were measured to assess insecticide efficacy. Maggots reduced onion plant populations by more than 65% of the seeding rate in the untreated controls. Seed treatments with spinosad or clothianidin + imidacloprid were the best alternative to chlorpyrifos for minimizing onion mortality from maggot feeding. Onions treated with both seed treatments had similar or higher plant populations and bulb yields compared to chlorpyrifos. The efficacy of spinosad was greatly improved when applied as a seed treatment compared to an in-furrow application at planting or when incorporated into the soil with a rototiller prior to planting. Spinosad seed treatment increased onion plant populations by 256%, 76%, and 853% compared to untreated controls in 2011, 2012, and 2013, respectively. Conversely, in-furrow and rototill-incorporated applications of spinosad were similar to the untreated control in terms of onion plant population and yield. Seed treatments with newer chemistries could provide an efficacious alternative to chlorpyrifos for protecting onions from maggot damage in western onion production systems.

The de novo Transcriptome and Its Analysis in the Worldwide Vegetable Pest, Delia antiqua (Diptera: Anthomyiidae)

The onion maggot Delia antiqua is a major insect pest of cultivated vegetables, especially the onion, and a good model to investigate the molecular mechanisms of diapause. To better understand the biology and diapause mechanism of the insect pest species, D. antiqua, the transcriptome was sequenced using Illumina paired-end sequencing technology. Approximately 54 million reads were obtained, trimmed, and assembled into 29,659 unigenes, with an average length of 607 bp and an N50 of 818 bp. Among these unigenes, 21,605 (72.8%) were annotated in the public databases. All unigenes were then compared against Drosophila melanogaster and Anopheles gambiae. Codon usage bias was analyzed and 332 simple sequence repeats (SSRs) were detected in this organism. These data represent the most comprehensive transcriptomic resource currently available for D. antiqua and will facilitate the study of genetics, genomics, diapause, and further pest control of D. antiqua.

Quantitative evaluation of the host-colonizing capabilities of the enteric bacterium Pantoea using plant and insect hosts

The genus Pantoea is a highly diverse group comprising free-living, and both pathogenic and non-pathogenic host-associating species. Pathogenic isolates have been found to infect insects, plants and humans, yet it is unclear whether these isolates have similar pathogenic potential to the free-living environmental populations. Using MLSA of six housekeeping genes, we evaluated the phylogenetic relationships among 115 environmental and clinical (human) isolates representing 11 Pantoea species. An overlay of the location of isolation onto the resulting tree revealed that clinical and environmental isolates are interspersed, and do not form distinctive groups. We then conducted quantitative growth assays of our isolates using maize, onion and fruit flies as hosts. Notably, most clinical isolates were able to grow in both plant hosts often comparably or even better than the environmental isolates. There were no obvious growth or host colonization patterns that could distinguish those isolates with clinical potential. Growth of an isolate in one host could not be predicted based on its performance in another host, nor could host growth be predicted by phylogeny or source of isolation. This work demonstrates that the host-colonizing capabilities of all Pantoea species groups is unpredictable, indicating a broader host range and pathogenic potential than currently assumed.

Identification of odorant-binding protein genes expressed in the antennae and the legs of the onion fly, Delia antiqua (Diptera: Anthomyiidae)

The onion fly, Delia antiqua (Meigen), is a pest specialized to the onion, Allium cepa L., and some other Allium plants. Host odorants play an important role in the attraction of D. antiqua adults and stimulation of oviposition in females. Odorant-binding proteins (OBPs) may serve as a first step in the perception of these chemical cues. In this study, to identify all OBP genes expressed in the chemosensory tissues in D. antiqua, RNA-seq analysis was carried out. In addition to the seven OBP genes previously identified, we found eight novel OBPs. Comparisons with Drosophila melanogaster Meigen OBP genes revealed that these 15 D. antiqua OBPs cover the structural variety observed in D. melanogaster OBPs, including Plus C and Minus C OBPs. These results suggest that a relatively large repertoire of chemosensory genes is maintained even in a specialist feeder.

Effects of background light conditions on thermoperiodic eclosion rhythm of onion fly Delia antiqua

AbstractTo elucidate the effects of light on thermoperiodic regulation of adult eclosion rhythm in the onion fly, Delia antiqua, the responses to two thermoperiods, 29°C (12 h):21°C (12 h) and 25.5°C (12 h):24.5°C (12 h), with different amplitude and same average temperature, were examined in continuous darkness (DD) and continuous light (LL). Irrespective of the temperature step between warm phase (W) and cool phase (C), temperature cycles effectively entrained the adult eclosion rhythm in both DD and LL. Eclosion peaks, however, varied with light conditions and temperature step between W and C. It advanced by approximately 2–3 h in DD than in LL and at smaller temperature step. Background light conditions and temperature step also affect the amplitude of eclosion rhythm. It became lower in LL than in DD and at smaller temperature steps. On transfer to constant temperature (25°C), eclosion rhythm was elicited earliest in the pupae at 8°C temperature step in DD and latest in those at 1°C temperature step in LL. Pupae at 1°C temperature step in DD and at 8°C temperature step in LL demonstrated intermediate responses, but the eclosion rhythm was elicited 1 day earlier in the former than in the latter. This might be ascribed to the interaction between background light and temperature step under thermoperiodic conditions. The results suggest that continuous light and a smaller temperature step weaken the coupling strength between eclosion rhythm and thermoperiod, but the light effect is stronger than the temperature step effect.

Cloning, Characterization and Bioinformatic Analysis of the Gene Encoding the Larval Serum Protein 2 in Diapause of the Onion Maggot, Delia Antiqua

The full-length cDNA encoding Larval serum protein 2 (LSp-2) in the onion maggot, Delia antiqua, was cloned and sequenced by rapid amplification of cDNA ends methods. The result showed that the cDNA was 2203 bp long and the open reading frame (ORF) of 2106 bp encoded 701 amino acid with a calculated molecular weight of 80.5 kDa and an isoelectric point of 5.87. The onion maggot LSp-2 shows highest homology (83%) to that of Calliphora vicina at amino acid level. Its signal peptides, domains and structures were predicted and analyzed by using bioinformatic methods. The amino acid sequence of LSP-2 suggests that it would be a typical hexamerin.

Differential gene expression between summer and winter diapause pupae of the onion maggot Delia antiqua, detected by suppressive subtractive hybridization

To gain a better understanding of the molecular mechanisms regulating pupal diapause of the onion maggot Delia antiqua, PCR-based suppressive subtractive hybridization was performed to identify genes involved in summer and/or winter diapause. A total of 209 unique sequences were obtained including 89 in forward library for winter diapausing pupae and 120 in the reverse library for summer diapausing pupae. 76.4% (68/89) and 68.3% (82/120) unique sequences had significant hits to non-redundant proteins database. Gene functional annotation showed these non-redundant sequences are involved in stress response and innate immunity, metabolism and energy, information processing and regulation, binding, food storage, morphogenesis and development, cell skeleton and cycle, protein synthesis and folding. Approximately 28.2% (59/209) transcripts showed no significant similarity to any other sequence in the public databases, probably representing unique genes of the onion maggot. Semi-quantitative RT-PCR revealed that the relative expression levels of 18 genes were comparable between summer and winter diapause. This study elucidates the temporal expression of diapause-related genes in onion maggot, also provides new insights into the differences in the physiological changes in summer and winter pupae. Functional characterization of some candidate genes will further enhance the understanding of the generating, maintaining, and breaking mechanism of diapause.