Enterobacter sp. AA26 as a Protein Source in the Larval Diet of Drosophila suzukii

The Spotted-Wing Drosophila fly, Drosophila suzukii, is an invasive pest species infesting major agricultural soft fruits. Drosophila suzukii management is currently based on insecticide applications that bear major concerns regarding their efficiency, safety and environmental sustainability. The sterile insect technique (SIT) is an efficient and friendly to the environment pest control method that has been suggested for the D. suzukii population control. Successful SIT applications require mass-rearing of the strain to produce competitive and of high biological quality males that will be sterilized and consequently released in the wild. Recent studies have suggested that insect gut symbionts can be used as a protein source for Ceratitis capitata larval diet and replace the expensive brewer’s yeast. In this study, we exploited Enterobacter sp. AA26 as partial and full replacement of inactive brewer’s yeast in the D. suzukii larval diet and assessed several fitness parameters. Enterobacter sp. AA26 dry biomass proved to be an inadequate nutritional source in the absence of brewer’s yeast and resulted in significant decrease in pupal weight, survival under food and water starvation, fecundity, and adult recovery

How the mighty have adapted: Genetic and microbiome changes during laboratory adaptation in the key pest Drosophila suzukii

International audienceAdaptation of wild insects to an artificial laboratory environment goes hand in hand with changes in their genetic diversity and symbiotic communities. This can have a profound effect on mass rearing of insects since their biological quality and mating competitiveness might be reduced. Patterns of genetic and symbiotic variation associated with laboratory adaptation vary among species and identifying the agents of selection that drive such patterns can be extremely helpful for pest control programmes. In the present study, we profiled the genetic and symbiotic structure of a wild Drosophila suzukii population and monitored their changes during laboratory adaptation. We employed sixteen microsatellite markers and tracked the fluctuation of their frequencies as domestication was progressing. We also used 16S rRNA sequencing to depict changes in the microbiota structure. Changes in effective and observed allele numbers and heterozygosity became evident from F10, while between F0 and F6 a gradual decline was observed. The microbiota profile of D. suzukii also formed distinct clusters during adaptation as F0 and F1 were differentiated by the rest generations and presented the highest bacterial diversity. Overall, our results showed that laboratory adaptation strongly affects both genetic diversity and bacterial communities of D. suzukii. These results can serve as a reference for the design of an area-wide integrated pest management approach with a Sterile Insect Technique (SIT) component. Rearing productivity, biological quality, and mating competitiveness of a SIT mass-reared strain should be assessed in connection with genetic and symbiotic changes occurring during laboratory adaptation

Deep orange gene editing triggers temperature-sensitive lethal phenotypes in Ceratitis capitata

Abstract Background The Mediterranean fruit fly, Ceratitis capitata, is a significant agricultural pest managed through area-wide integrated pest management (AW-IPM) including a sterile insect technique (SIT) component. Male-only releases increase the efficiency and cost-effectiveness of SIT programs, which can be achieved through the development of genetic sexing strains (GSS). The most successful GSS developed to date is the C. capitata VIENNA 8 GSS, constructed using classical genetic approaches and an irradiation-induced translocation with two selectable markers: the white pupae (wp) and temperature-sensitive lethal (tsl) genes. However, currently used methods for selecting suitable markers and inducing translocations are stochastic and non-specific, resulting in a laborious and time-consuming process. Recent efforts have focused on identifying the gene(s) and the causal mutation(s) for suitable phenotypes, such as wp and tsl, which could be used as selectable markers for developing a generic approach for constructing GSS. The wp gene was recently identified, and efforts have been initiated to identify the tsl gene. This study investigates Ceratitis capitata deep orange (Ccdor) as a tsl candidate gene and its potential to induce tsl phenotypes. Results An integrated approach based on cytogenetics, genomics, bioinformatics, and gene editing was used to characterize the Ccdor. Its location was confirmed on the right arm of chromosome 5 in the putative tsl genomic region. Knock-out of Ccdor using CRISPR/Cas9-NHEJ and targeting the fourth exon resulted in lethality at mid- and late-pupal stage, while the successful application of CRISPR HDR introducing a point mutation on the sixth exon resulted in the establishment of the desired strain and two additional strains (dor 12del and dor 51dup), all of them expressing tsl phenotypes and presenting no (or minimal) fitness cost when reared at 25 °C. One of the strains exhibited complete lethality when embryos were exposed at 36 °C. Conclusions Gene editing of the deep orange gene in Ceratitis capitata resulted in the establishment of temperature-sensitive lethal mutant strains. The induced mutations did not significantly affect the rearing efficiency of the strains. As deep orange is a highly conserved gene, these data suggest that it can be considered a target for the development of tsl mutations which could potentially be used to develop novel genetic sexing strains in insect pests and disease vectors

Irradiation dose response under hypoxia for the application of the sterile insect technique in Drosophila suzukii.

Treating insects with a lower oxygen atmosphere before and during exposure to radiation can mitigate some of the negative physiological effects due to the irradiation. The irradiation of pupae under oxygen-reduced environment such as hypoxia or anoxia is routinely used in the sterile insect technique (SIT) of some tephritid species as it provides radiological protection. This treatment allows to have the sterile pupae already in sealed containers facilitating the shipment. SIT is an environment friendly control tactic that could be used to manage populations of Drosophila suzukii in confined areas such as greenhouses. The objectives of this study were to assess the effect of irradiation on the reproductive sterility in D. suzukii males and females under low-oxygen atmosphere (hypoxia) and atmosphere conditions (normoxia). Additionally, we assessed the differences in radiological sensitivity of pupae treated under hypoxia and normoxia conditions. Finally, the effect on emergence rate and flight ability of the irradiated D. suzukii adults exposed to doses that induced >99% of sterility were assessed. Pupae needed a 220 Gy irradiation dose to achieve >99% of egg hatch sterility in males irrespective of the atmosphere condition. For females the same level of sterility was achieved already at 75 Gy and 90 Gy for the normoxia and hypoxia treatments, respectively. Radiation exposure at 170 and 220 Gy under the two atmosphere treatments did not have any effect on the emergence rate and flight ability of D. suzukii males and females. Therefore, hypoxia conditions can be used as part of an area-wide insect pest management program applying SIT to facilitate the protocols of packing, irradiation and shipment of sterile D. suzukii pupae

Temperature Sensitivity of Wild-Type, Mutant and Genetic Sexing Strains of Ceratitis capitata

Area-wide integrated pest management (AW-IPM) programmes with a sterile insect technique component (SIT) are used to control populations of insect pests worldwide, including the Mediterranean fruit fly, Ceratitis capitata. SIT consists of the mass rearing, radiation-induced sterilization, handling, and release of sterile insects over the target area. Although SIT can be performed by using both sterile males and females, male-only releases significantly increase the efficiency and cost-effectiveness of SIT applications. Male-only releases can be achieved by using genetic sexing strains (GSS). The medfly VIENNA 8 GSS is based on two selectable markers, the white pupae (wp) gene, and the temperature-sensitive lethal (tsl) genes. The latter allows the elimination of females by exposing embryos to elevated temperatures. This study assessed the temperature sensitivity of twenty-seven medfly strains through a TSLT. Our results indicated significant differences among the strains regarding egg hatching as well as pupal and adult recovery rates due to the presence or absence of the tsl mutation and/or the genetic background of the strains. Our findings are discussed in the context of SIT applications, the importance of the tsl gene for developing genetic sexing strains, and climate change

Mass-Rearing of Drosophila suzukii for Sterile Insect Technique Application: Evaluation of Two Oviposition Systems

Drosophila suzukii (Diptera: Drosophilidae) is an invasive pest of a wide range of commercial soft-skinned fruits. To date, most management tactics are based on spraying of conventional and/or organic insecticides, baited traps, and netting exclusion. Interest has been expressed in using the sterile insect technique (SIT) as part of area-wide integrated pest management (AW-IPM) programs to control D. suzukii infestations. Mass-rearing protocols are one of the prerequisites for successful implementation of the SIT. To establish mass-rearing methods for this species, two different egg-collection systems were developed and compared with respect to the number of eggs produced, egg viability, pupa and adult recovery, adult emergence rate, and flight ability. Female flies kept in cages equipped with a wax panel produced significantly more eggs with higher viability and adult emergence rate, as compared to the netted oviposition system. The wax panel system was also more practical and less laborious regarding the collection of eggs. Furthermore, the wax panel oviposition system can be adapted to any size or design of an adult cage. In conclusion, this system bears great promise as an effective system for the mass production of D. suzukii for SIT

Data from: Back and forth Wolbachia transfers reveal efficient strains to control spotted wing drosophila populations

1.Since its recent invasion of the European and American continents, the spotted wing Drosophila Drosophila suzukii has become a burden of the fruit industry. Armed with a highly sclerotized ovipositor, females can lay eggs in a wider variety of ripening and healthy fruits than other Drosophila species. Economic losses due to Drosophila suzukii reach millions of dollars annually and methods to control natural populations in the field mainly rely on the use of chemical pesticides. 2.We tested if Wolbachia bacteria represents a potential ally to control this pest. These symbionts are naturally present in many insects and often induce a form of conditional sterility called Cytoplasmic Incompatibility (CI): the offspring of infected males die, unless the eggs are rescued by the compatible infection, inherited from the mother that protects the embryo. A long-recognised, a strategy called the Incompatible Insect Technique (IIT) makes use of the CI phenotype to control insect populations through the mass release of infected males. To implement this technique in D. suzukii, we used back and forth Wolbachia transfers between D. suzukii and D. simulans to identify Wolbachia strains that can sterilize D. suzukii females despite the presence of wSuz, a natural Wolbachia infection in this species. 3.We identified two Wolbachia strains as potential candidates for developing IIT in D. suzukii. Both induce a very high level of CI in this pest which is not attenuated by the presence of wSuz in females. Moreover, the newly transferred Wolbachia do not affect the fitness or the mating competitiveness of the sterilizing males. 4.Synthesis and applications. Although several critical steps still need to be tested and developed outside the laboratory to achieve the control of Drosophila suzukii using Incompatible Insect Technique. By an experimental approach in large population cage, we showed that releases of transinfected males limits population size. Thus, we provide in this study the proof of concept that this technique can be a very promising approach to control D. suzukii populations

Sterile insect technique and Wolbachia symbiosis as potential tools for the control of the invasive species Drosophila suzukii

International audienceDrosophila suzukii, a vinegar fly originated from Southeast Asia, has recently invaded western countries, and it has been recognized as an important threat of a wide variety of several commercial soft fruits. This review summarizes the current information about the biology and dispersal of D. suzukii and discusses the current status and prospects of control methods for the management of this pest. We highlight current knowledge and ongoing research on innovative environmental-friendly control methods with emphasis on the sterile insect technique (SIT) and the incompatible insect technique (IIT). SIT has been successfully used for the containment, suppression or even eradication of populations of insect pests. IIT has been proposed as a stand-alone tool or in conjunction with SIT for insect pest control. The principles of SIT and IIT are reviewed, and the potential value of each approach in the management of D. suzukii is analyzed. We thoroughly address the challenges of SIT and IIT, and we propose the use of SIT as a component of an area-wide integrated pest management approach to suppress D. suzukii populations. As a contingency plan, we suggest a promising alternative avenue through the combination of these two techniques, SIT/IIT, which has been developed and is currently being tested in open-field trials against Aedes mosquito populations. All the potential limiting factors that may render these methods ineffective, as well as the requirements that need to be fulfilled before their application, are discussed

Sterile insect technique and Wolbachia symbiosis as potential tools for the control of the invasive species Drosophila suzukii

International audienceDrosophila suzukii, a vinegar fly originated from Southeast Asia, has recently invaded western countries, and it has been recognized as an important threat of a wide variety of several commercial soft fruits. This review summarizes the current information about the biology and dispersal of D. suzukii and discusses the current status and prospects of control methods for the management of this pest. We highlight current knowledge and ongoing research on innovative environmental-friendly control methods with emphasis on the sterile insect technique (SIT) and the incompatible insect technique (IIT). SIT has been successfully used for the containment, suppression or even eradication of populations of insect pests. IIT has been proposed as a stand-alone tool or in conjunction with SIT for insect pest control. The principles of SIT and IIT are reviewed, and the potential value of each approach in the management of D. suzukii is analyzed. We thoroughly address the challenges of SIT and IIT, and we propose the use of SIT as a component of an area-wide integrated pest management approach to suppress D. suzukii populations. As a contingency plan, we suggest a promising alternative avenue through the combination of these two techniques, SIT/IIT, which has been developed and is currently being tested in open-field trials against Aedes mosquito populations. All the potential limiting factors that may render these methods ineffective, as well as the requirements that need to be fulfilled before their application, are discussed