Scholarly Literature

This is a database of scholarly literature that concentrates currently on natural and engineered selfish genetic elements (gene drives).  The latest are shown here.
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Assessing potential hybridization between a hypothetical gene drive-modified Drosophila suzukii and nontarget Drosophila species

24610
S. Wolf, J. Collatz, J. Enkerli, F. Widmer and J. Romeis,  Risk Analysis,  2023-01-24 09:02:35.
Genetically engineered gene drives (geGD) are potentially powerful tools for suppressing or even eradicating populations of pest insects. Before living geGD insects can be released into the environment, they must pass an environmental risk assessment to ensure that their release will not cause unacceptable harm to non-targeted entities of the environment. A key research question concerns the likelihood that nontarget species will acquire the functional GD elements; such acquisition could lead to reduced abundance or loss of those species and to a disruption of the ecosystem services they provide. The main route for gene flow is through hybridization between the geGD insect strain and closely related species that co-occur in the area of release and its expected dispersal. Using the invasive spotted-wing drosophila, Drosophila suzukii, as a case study, we provide a generally applicable strategy on how a combination of interspecific hybridization experiments, behavioral observations, and molecular genetic analyses can be used to assess the potential for hybridization.

Complicated expansion trajectories of insertion sequences and potential association with horizontal transfer of Wolbachia DNA

24573
Y. H. Miao, D. W. Huang and J. H. Xiao,  Zoological Research,  44:273-275. 2023-01-22 08:41:24.
Insertion sequences (ISs) are the simplest structural transposable elements (TEs) in prokaryotes, consisting only of a transposase coding sequence and its bilateral short terminal inverted repeats. Due to their gradually streamlined genomic construction, TEs rarely exist in the genomes of obligate endosymbionts. However, TE content, especially ISs, is abundant in the genome of Wolbachia bacteria, obligate endosymbionts widespread in arthropods and nematodes. Although IS indels are reported to affect genome structure and gene function in Wolbachia, the distribution patterns, sources, and transfer trajectories of ISs remain poorly understood. Furthermore, whether IS transposition is associated with dynamic horizontal transfer of Wolbachia DNA is still unclear. Based on distribution patterns in supergroup A Wolbachia strains, ISs accounted for 11% of the genome of the Wolbachia strain wWpum, one of the highest IS genome coverages reported for Wolbachia to date. Three types of ISs showed rapid expansion in wWpum, possibly due to horizontal transfer from other Wolbachia strain supergroups or more distant prokaryotes. We also found the first evidence that ISs can carry flanking Wolbachia sequences for transposition, resulting in the horizontal transfer of Wolbachia DNA into the eukaryotic genome, thus implying a potential association between ISs and horizontal gene transfer from endosymbionts to eukaryotes.

Closing the gap to effective gene drive in Aedes aegypti by exploiting germline regulatory elements

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M. A. E. Anderson, E. Gonzalez, J. X. D. Ang, L. Shackleford, K. Nevard, S. A. N. Verkuijl, M. P. Edgington, T. Harvey-Samuel and L. Alphey,  Nature Communications,  14:338. 2023-01-20 09:00:46.
CRISPR/Cas9-based homing gene drives have emerged as a potential new approach to mosquito control. While attempts have been made to develop such systems in Aedes aegypti, none have been able to match the high drive efficiency observed in Anopheles species. Here we generate Ae. aegypti transgenic lines expressing Cas9 using germline-specific regulatory elements and assess their ability to bias inheritance of an sgRNA-expressing element (kmo(sgRNAs)). Four shu-Cas9 and one sds3-Cas9 isolines can significantly bias the inheritance of kmo(sgRNAs), with sds3G1-Cas9 causing the highest average inheritance of ~86% and ~94% from males and females carrying both elements outcrossed to wild-type, respectively. Our mathematical model demonstrates that sds3G1-Cas9 could enable the spread of the kmo(sgRNAs) element to either reach a higher (by ~15 percentage point) maximum carrier frequency or to achieve similar maximum carrier frequency faster (by 12 generations) when compared to two other established split drive systems.

Both male and female meiosis contribute to non-Mendelian inheritance of parental chromosomes in interspecific plant hybrids (Lolium x Festuca)

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J. Majka, M. Glombik, A. Dolezalova, J. Knerova, M. T. M. Ferreira, Z. Zwierzykowski, M. Duchoslav, B. Studer, J. Dolezel, J. Bartos and D. Kopecky,  NEW PHYTOLOGIST,  2023-01-19 08:34:11.
Some interspecific plant hybrids show unequal transmission of chromosomes from parental genomes to the successive generations. It has been suggested that this is due to a differential behavior of parental chromosomes during meiosis. However, underlying mechanism is unknown. We analyzed chromosome composition of the F-2 generation of Festuca x Lolium hybrids and reciprocal backcrosses to elucidate effects of male and female meiosis on the shift in parental genome composition. We studied male meiosis, including the attachment of chromosomes to the karyokinetic spindle and gene expression profiling of the kinetochore genes. We found that Lolium and Festuca homoeologues were transmitted differently to the F-2 generation. Female meiosis led to the replacement of Festuca chromosomes by their Lolium counterparts. In male meiosis, Festuca univalents were attached less frequently to microtubules than Lolium univalents, lagged in divisions and formed micronuclei, which were subsequently eliminated. Genome sequence analysis revealed a number of non-synonymous mutations between copies of the kinetochore genes from Festuca and Lolium genomes. Furthermore, we found that outer kinetochore proteins NDC80 and NNF1 were exclusively expressed from the Lolium allele. We hypothesize that silencing of Festuca alleles results in improper attachment of Festuca chromosomes to karyokinetic spindle and subsequently their gradual elimination.

Joint FAO/IAEA Coordinated Research Project on Mosquito Handling, Transport, Release and Male Trapping Methods in Support of SIT Application to Control Mosquitoes

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M. Gómez, B. J. Johnson, H. C. Bossin and R. Argilés-Herrero,  Insects,  14. 2023-01-19 08:14:17.
The research carried out in the framework of this CRP generated key achievements in areas relevant to the SIT application to control mosquitoes. Among these outcomes, particular mentions must be given to the following: (1) Novel and efficient self-marking techniques were established to improve our understanding of male movement, competitiveness, survival, and potential interaction with closely related species post-release [7,8]. As the next step, these new marking systems will be upscaled and validated under operational conditions in SIT field projects targeting the Aedes species. (2) One of the techniques evaluated included the novel large-scale marking of male mosquitoes via administration of Rhodamine B via sugar feeding. The mentioned technique brings the advantage of marking all of the tissues of the mosquitoes, including sperm and seminal fluid, such that the mark can be retrieved and identified in mated females. Thus, the use of Rhodamine B enables researchers to estimate the sexual competitiveness of sterile male mosquitoes under field conditions [9,10].

Wolbachia Promotes Its Own Uptake by Host Cells

24576
L. B. Nevalainen, E. M. Layton and I. L. G. Newton,  Infection and Immunity,  e0055722. 2023-01-17 08:49:38.
Wolbachia pipientis is an incredibly widespread bacterial symbiont of insects, present in an estimated 25 to 52% of species worldwide. Wolbachia is faithfully maternally transmitted both in a laboratory setting and in the wild. In an established infection, Wolbachia is primarily intracellular, residing within host-derived vacuoles that are associated with the endoplasmic reticulum. However, Wolbachia also frequently transfers between host species, requiring an extracellular stage to its life cycle. Indeed, Wolbachia has been moved between insect species for the precise goal of controlling populations. The use of Wolbachia in this application requires that we better understand how it initiates and establishes new infections. Here, we designed a novel method for live tracking Wolbachia cells during infection using a combination of stains and microscopy. We show that live Wolbachia cells are taken up by host cells at a much faster rate than dead Wolbachia cells, indicating that Wolbachia bacteria play a role in their own uptake and that Wolbachia colonization is not just a passive process. We also show that the host actin cytoskeleton must be intact for this to occur and that drugs that disrupt the actin cytoskeleton effectively abrogate Wolbachia uptake. The development of this live infection assay will assist in future efforts to characterize Wolbachia factors used during host infection.

Wolbachia RNase HI contributes to virus blocking in the mosquito Aedes aegypti

24468
M. Hussain, G. Zhang, M. Leitner, L. M. Hedges and S. Asgari,  iScience,  26:105836. 2023-01-15 08:41:00.
The endosymbiotic bacterium Wolbachia pipientis blocks replication of several arboviruses in transinfected Aedes aegypti mosquitoes. However, the mechanism of virus blocking remains poorly understood. Here, we characterized an RNase HI gene from Wolbachia, which is rapidly induced in response to dengue virus (DENV) infection. Knocking down w RNase HI using antisense RNA in Wolbachia-transinfected mosquito cell lines and A. aegypti mosquitoes led to increased DENV replication. Furthermore, overexpression of wRNase HI, in the absence of Wolbachia, led to reduced replication of a positive sense RNA virus, but had no effect on a negative sense RNA virus, a familiar scenario in Wolbachia-infected cells. Altogether, our results provide compelling evidence for the missing link between early Wolbachia-mediated virus blocking and degradation of viral RNA. These findings and the successful pioneered knockdown of Wolbachia genes using antisense RNA in cell line and mosquitoes enable new ways to manipulate and study the complex endosymbiont-host interactions.

Engineered symbiotic bacteria interfering Nosema redox system inhibit microsporidia parasitism in honeybees

24493
H. Lang, H. Wang, H. Wang, X. Xie, X. Hu, X. Zhang and H. Zheng,  bioRxiv,  2023.01.13.524015. 2023-01-14 16:42:03.
Nosema ceranae is an emergent microsporidia parasite of the European honey bee (Apis mellifera), which causes serious nosemosis implicated in honeybee colony losses worldwide. N. ceranae is an obligate intracellular eukaryotic parasite that mainly invades the midgut of honeybees. Recent studies find that bee gut microbiota is potentially involved in protecting against parasitism. Here, using laboratory-generated bees mono-associated with gut members, we find that Snodgrassella alvi inhibited microsporidia proliferation, potentially via the stimulation of host oxidant-mediated immune response. Accordingly, N. ceranae employs the thioredoxin and glutathione systems to defend against oxidative stress and maintain a balanced redox equilibrium, which is essential for the infection process. We knocked down the gene expression using nanoparticle-mediated RNA interference, which targets the γ-glutamyl-cysteine synthetase and thioredoxin reductase genes of microsporidia. It significantly reduces the spore load, confirming the importance of the antioxidant mechanism for the intracellular invasion of the N. ceranae parasite. Finally, we genetically modified the symbiotic S. alvi to deliver dsRNA corresponding to the genes involved in the redox system of the microsporidia. The engineered S. alvi induces RNA interference and represses parasite gene expression, thereby inhibits the parasitism by up to 99.8%. Specifically, N. ceranae was most suppressed by the recombinant strain corresponding to the glutathione synthetase or by a mixture of bacteria expressing variable dsRNA. Our findings extend our previous understanding of the protection of gut symbionts against N. ceranae and provide a symbiont-mediated RNAi system for inhibiting microsporidia infection in honeybees.Competing Interest StatementThe authors have declared no competing interest.

Dynamics of an impulsive reaction-diffusion mosquitoes model with multiple control measures

24571
Y. Li, H. Zhao and K. Wang,  Mathematical Biosciences and Engineering,  20:775-806. 2023-01-14 08:34:08.
It is well-known that mosquito control is one of the effective methods to reduce and prevent the transmission of mosquito-borne diseases. In this paper, we formulate a reaction-diffusion impulsive hybrid model incorporating Wolbachia, impulsively spraying of insecticides, spatial heterogeneity, and seasonality to investigate the control of mosquito population. The sufficient conditions for mosquito extinction or successful Wolbachia persistence in a population of natural mosquitoes are derived. More importantly, we give the estimations of the spraying times of insecticides during a period for achieving the mosquito extinction and population replacement in a special case. A global attractivity of the positive periodic solution is analyzed under appropriate conditions. Numerical simulations disclose that spatial heterogeneity and seasonality have significant impacts on the design of mosquitoes control strategies. It is suggested to combine biological control and chemical pulse control under certain situations to reduce the natural mosquitoes. Further, our results reveal that the establishment of a higher level of population replacement depends on the strain type of the Wolbachia and the high initial occupancy of the Wolbachia-infected mosquitoes.

Bypassing Mendel’s First Law: Transmission Ratio Distortion in Mammals

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G. Friocourt, A. Perrin, P. A. Saunders, E. Nikalayevich, C. Voisset, C. Coutton, G. Martinez and F. Morel,  International Journal Molecular Sciences,  24. 2023-01-13 10:43:58.
Mendel's law of segregation states that the two alleles at a diploid locus should be transmitted equally to the progeny. A genetic segregation distortion, also referred to as transmission ratio distortion (TRD), is a statistically significant deviation from this rule. TRD has been observed in several mammal species and may be due to different biological mechanisms occurring at diverse time points ranging from gamete formation to lethality at post-natal stages. In this review, we describe examples of TRD and their possible mechanisms in mammals based on current knowledge. We first focus on the differences between TRD in male and female gametogenesis in the house mouse, in which some of the most well studied TRD systems have been characterized. We then describe known TRD in other mammals, with a special focus on the farmed species and in the peculiar common shrew species. Finally, we discuss TRD in human diseases. Thus far, to our knowledge, this is the first time that such description is proposed. This review will help better comprehend the processes involved in TRD. A better understanding of these molecular mechanisms will imply a better comprehension of their impact on fertility and on genome evolution. In turn, this should allow for better genetic counseling and lead to better care for human families.

Single-cell transcriptome sequencing reveals Wolbachia-mediated modification in early stages of Drosophila spermatogenesis

24466
W. Dou, B. Sun, Y. Miao, D. Huang and J. Xiao,  Proceedings of the Royal Society B: Biological Sciences,  290:20221963. 2023-01-11 08:36:44.
Wolbachia are the most widely distributed intracellular bacteria, and their most common effect on host phenotype is cytoplasmic incompatibility (CI). A variety of models have been proposed to decipher the molecular mechanism of CI, among which the host modification (HM) model predicts that Wolbachia effectors play an important role in sperm modification. However, owing to the complexity of spermatogenesis and testicular cell-type heterogeneity, whether Wolbachia have different effects on cells at different stages of spermatogenesis or whether these effects are linked with CI remains unknown. Therefore, we used single-cell RNA sequencing to analyse gene expression profiles in adult male Drosophila testes that were infected or uninfected by Wolbachia. We found that Wolbachia significantly affected the proportion of different types of germ cells and affected multiple metabolic pathways in germ cells. Most importantly, Wolbachia had the greatest impact on germline stem cells, resulting in dysregulated expression of genes related to DNA compaction, and Wolbachia infection also influenced the histone-to-protamine transition in the late stage of sperm development. These results support the HM model and suggest that future studies on Wolbachia-induced CI should focus on cells in the early stages of spermatogenesis.

Heterogeneous distribution of sex ratio distorters in natural populations of the isopod Armadillidium vulgare

24464
S. Durand, B. Lheraud, I. Giraud, N. Bech, F. Grandjean, T. Rigaud, J. Peccoud and R. Cordaux,  Biology Letters,  19:20220457. 2023-01-11 08:32:10.
In the isopod Armadillidium vulgare, many females produce progenies with female-biased sex ratios, owing to two feminizing sex ratio distorters (SRD): Wolbachia endosymbionts and the f element. We investigated the distribution and population dynamics of these SRD and mitochondrial DNA variation in 16 populations from Europe and Japan. Confirming and extending results from the 1990s, we found that the SRD are present at variable frequencies in populations and that the f element is overall more frequent than Wolbachia. The two SRD never co-occur at high frequency in any population, suggesting an apparent mutual exclusion. We also detected Wolbachia or the f element in some males, which probably reflects insufficient titer to induce feminization or presence of masculinizing alleles. Our results are consistent with a single integration event of a Wolbachia genome in the A. vulgare genome at the origin of the f element, which contradicts an earlier hypothesis of frequent losses and gains. We identified strong linkage between Wolbachia strains and mitochondrial haplotypes, but no association between the f element and mitochondrial background. Our results open new perspectives on SRD evolutionary dynamics in A. vulgare, the evolution of genetic conflicts and their impact on the variability of sex determination systems.

Effects of gamma radiation on the vector competence of Aedes aegypti (diptera: Culicidae) to transmit Zika virus

24462
E. B. da Silva, C. M. de Mendonça, D. R. D. Guedes, M. H. S. Paiva, J. d. A. Mendonça, E. S. F. Dias, S. G. L. Florêncio, A. Amaral, A. M. Netto, C. F. J. A. Lopes and M. A. V. de Melo-Santos,  Acta Tropica,  239:106831. 2023-01-11 08:27:34.
One of the limitations of the Sterile Insect Technique (SIT), conventionally performed by ionizing radiation, regards separating males from females, which is not 100% effective. Some irradiated females may be released together with males in the field at SIT. The present study aimed to evaluate the influence of ionizing radiation on the ability of Aedes aegypti mosquitoes to transmit the Zika virus after exposing female pupae to a 40 Gy of gamma radiation. The results suggest that the genetic damage induced by exposure of females to this dose level promotes their total sterility, but it does not influence their vector competence. However, our data point out that ionizing radiation may decrease the proportion of infective mosquitoes.

Trust in science and scientists: Effects of social attitudes and motivations on views regarding climate change, vaccines and gene drive technology

24622
H. G. W. Dixson, A. F. Komugabe-Dixson, F. Medvecky, J. Balanovic, H. Thygesen and E. A. MacDonald,  Journal of Trust Research,  2023-01-10 09:31:54.
Trust in science and scientists (TSS) is an increasingly important topic with respect to how science is applied within society. However, its role regarding specific issues may vary depending upon other psychosocial factors. In this study, we investigated how trust interacts with social attitudes and motivations to shape views on scientific issues in New Zealand (N = 8,199; 74.7% New Zealand European, 55.1% female). The study went beyond TSS by including broader institutional trust alongside measures relating to support for inequality, status quo preservation and fear of the unknown. We focused on their effects on three issues: vaccines, climate change and genetic technology (gene drive). Although TSS was strongly associated with lower vaccine skepticism (B = -0.497, p < 0.01), and moderate support for gene drive (B = 0.231, p < 0.01), it had no meaningful effect on climate skepticism. Furthermore, trust differentially mediated the relationship between social motivations and responses to all three issues. Trust in science and scientists is therefore unlikely to represent a one-size-fits-all variable. We conclude that future research should consider what effects trust in institutions and TSS have with social attitudes and motivations over a range of technologies across the sciences.

Sterility of Aedes albopictus by X-ray Irradiation as an Alternative to γ-ray Irradiation for the Sterile Insect Technique

24424
L.-M. Wang, N. Li, C.-P. Ren, Z.-Y. Peng, H.-Z. Lu, D. Li, X.-Y. Wu, Z.-X. Zhou, J.-Y. Deng, Z.-H. Zheng, R.-Q. Wang, Y.-N. Du, D.-Q. Wang and S.-Q. Deng,  Pathogens,  12. 2023-01-06 10:18:19.
The mosquito Aedes albopictus can transmit various arboviral diseases, posing a severe threat to human health. As an environmentally friendly method, sterile insect technology (SIT) is considered an alternative to traditional methods such as chemical pesticides to control Ae. albopictus. In SIT, the sterility of male mosquitoes can be achieved by γ-ray or X-ray radiation. Compared with γ-rays, X-rays are easier to obtain, cheaper, and less harmful. However, there is a lack of comparative assessment of these two types of radiation for SIT under the same controlled conditions. Here, we compared the effects of X-ray and γ-ray radiation on the sterility of Ae. albopictus males under laboratory-controlled conditions. Neither type of radiation affected the number of eggs but significantly reduced the survival time and hatch rate. The same dose of γ-rays caused a higher sterility effect on males than X-rays but had a more significant impact on survival. However, X-rays could achieve the same sterility effect as γ-rays by increasing the radiation dose. For example, X-rays of 60 Gy induced 99% sterility, similar to γ-rays of 40 Gy. In the test of male mating competitiveness, the induced sterility and the male mating competitiveness index were also identical at the same release ratio (sterile males/fertile males). At a release ratio of 7:1, nearly 80% of eggs failed to hatch. Sterile males produced by X-ray and γ-ray radiation had similar male competitiveness in competition with field males. In conclusion, a higher dose of X-rays is required to achieve the same sterility effect, compared to γ-rays. When γ-rays are not readily available, high-dose X-rays can be used instead. This study provides data supporting the selection of more suitable radiation for the field release of sterile male mosquitoes.

Assessment of distant-site rescue elements for CRISPR toxin-antidote gene drives

24363
J. Chen, X. Xu and J. Champer,  bioRxiv,  2023.01.06.522951. 2023-01-06 09:33:07.
New types of gene drives promise to provide increased flexibility, offering many options for confined modification or suppression of target populations. Among the most promising are CRISPR toxin-antidote gene drives, which disrupt essential wild-type genes by targeting them with Cas9/gRNA, resulting in their removal. This increases the frequency of the drive in the population. All these drives, plus homing modification rescue drives, rely on having an effective rescue element, which consists of a recoded version of the target gene. This rescue element can be at the same site as the target gene, which maximizes the chance of efficient rescue, or at a distant site, which allows some other useful options, such as easily disrupting another essential gene or achieving greater confinement. Previously, we developed a homing rescue drive targeting a haplolethal gene and a toxin-antidote drive targeting an essential but haplosufficient gene. These successful drives had functional rescue elements but suboptimal drive efficiency. Here, we attempted to construct new toxin-antidote drives targeting these genes with a distantsite configuration from three different loci. We found that use of additional gRNAs increased cut rates to nearly 100%. However, all distant-site rescue elements failed for both haplolethal and haplosufficient target genes. Furthermore, one rescue element with a minimally recoded rescue element was used as a template for homology-directed repair for the target gene on a different chromosomal arm, resulting in the formation of functional resistance alleles at high frequency. Together, these results can inform the design of future CRISPR-based toxin-antidote gene drives.Competing Interest StatementThe authors have declared no competing interest.

The Possibilities of Gene Drives for Managing Populations and Controlling Diseases

27641
J. Vijay Upadhye, U. N. Shah and B. Mudhol,  Salud, Ciencia y Tecnologia,  3. 2023-01-01 07:51:35.
The technical limitations and the use of gene drives to address ecological problems by modifying all populations of wild species remain primarily speculative. Here, we examine the possibility that RNA-guided gene drives based on the CRISPR nuclease Cas9 could be used as an all-encompassing approach for introducing changed features into natural populations over a long period. We outline potential capabilities and possible disadvantages and offer new preventative measures to stem from the propagation of genes and undo genetic modifications. Editing the sexual animal population would significantly benefit both people and the environment. For instance, RNA-guided gene drives may stop the spread of illness, assist farming by correcting bug and weed chemicals and resistance to herbicides, and manage harmful invasive species. However, each prospective use needs to be carefully evaluated due to the likelihood of unfavorable ecological repercussions and the near inevitability of dissemination beyond political boundaries. To investigate the responsible application of this now hypothetical technology, we want serious, inclusive, educated public conversations. © 2023; Los autores.

Gene drive designs for efficient and localisable population suppression using Y-linked editors

24339
R. Geci, K. Willis and A. Burt,  PLOS Genetics,  18:e1010550. 2022-12-27 08:45:03.
Author summary Some pest populations can be successfully controlled by the inundative release of sterile males, but this approach is not practicable when the target population is large or the species difficult to rear. Computer modelling has previously demonstrated that releasing males with a genomic editor on their Y chromosome that kills or sterilises female descendants could be much more efficient, particularly if combined with a sex ratio distorter. Here we extend this work to show that Y-linked editors can also be used in even more efficient gene drive designs that would spread over successive generations beyond the region of release. Such spread could nonetheless be controlled by exploiting relatively small pre-existing differences in gene frequency between populations to restrict the spread and impact of the constructs, if desired. The proposed design does not require high rates of recombinational repair of DNA breaks or expression off the Y chromosome during meiosis, potentially expanding the range of species in which such low release rate control is possible. Y-linked editors may therefore form the basis of a highly flexible set of genetic strategies for population control.

Survival-Larval Density Relationships in the Field and Their Implications for Control of Container-Dwelling Aedes Mosquitoes

24714
K. G. Evans, Z. R. Neale, B. Holly, C. C. Canizela and S. A. Juliano,  Insects,  14. 2022-12-23 10:10:37.
Population density can affect survival, growth, development time, and adult size and fecundity, which are collectively known as density-dependent effects. Container Aedes larvae often attain high densities in nature, and those densities may be reduced when larval control is applied. We tested the hypothesis that density-dependent effects on survival are common and strong in nature and could result in maximal adult production at intermediate densities for Aedes aegypti, Aedes albopictus, and Aedes triseriatus. We surveyed naturally occurring densities in field containers, then introduced larvae at a similar range of densities, and censused the containers for survivors. We analyzed the survival-density relationships by nonlinear regressions, which showed that survival-density relationships vary among seasons, sites, and species. For each Aedes species, some sites and times yielded predictions that larval density reduction would yield the same (compensation), or more (overcompensation), adults than no larval density reduction. Thus, larval control targeting these Aedes species cannot always be assumed to yield a reduction in the number of adult mosquitoes. We suggest that mosquito control targeting larvae may be made more effective by: Imposing maximum mortality; targeting populations when larval abundances are low; and knowing the shape of the survival-density response of the target population.

Mating Competitiveness of Irradiated Lobesia botrana (Lepidoptera: Tortricidae) in Male-Only and Both Sex Release Strategies under Laboratory Cage Conditions

24324
G. Saour, A. Hashem and I. Jassem,  Insects,  14. 2022-12-23 09:03:18.
This laboratory study explored the concept of whether irradiated male-only releases are more or equally efficient as releases of both irradiated males and females in the context of using the sterile insect technique/inherited sterility (SIT/IS) for the management of the European grapevine moth Lobesia botrana. The current study examined the mating competitiveness of 150-Gy-treated L. botrana male and female moths or 150-Gy-treated male moths only, with untreated moths in laboratory cages. Our results showed that the release of both sexes significantly increased the competitiveness value (C) and the biological efficiency index (BE) as compared with male-only release, and this was independent of the male to untreated male ratio. Moreover, a single release of 150-Gy-treated and untreated males and females at a 1:1:10:10 ratio (untreated male:untreated female: treated male:treated female) significantly reduced egg hatch, and the number of first-generation offspring (F1) was small. The emergence of F2-moths per untreated F1 male and female moth was low, but these undesired fertile moths should be eliminated in order to achieve effective control. The results presented herein provide useful information on the impact of 150-Gy-treated male-only, versus releases of both treated males and females on untreated moths, which is essential to managing L. botrana populations with SIT/IS.

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