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Improvement of Colony Management in Insect Mass-rearing for SIT Applications
Closed for proposals
Project Type
Project Code
D42017CRP
2191Approved Date
Status
Start Date
Expected End Date
Completed Date
9 October 2024Participating Countries
Description
Sterile Insect Technique (SIT) applications against major insect pests and disease vectors rely on the cost-effective production of high quality sterile males. This largely depends on the optimal management of target pest colonies by maximizing the benefits provided by a genetically rich and pathogen-free mother colony, the presence of symbiotic microorganisms, and an efficient domestication and mass-rearing process, while at the same time minimizing or even eliminating the outbreak of microbial (bacteria, fungi, microsporidia) and viral pathogens, as well as the use of hazardous chemicals. The optimization of the colony management for different SIT target insects will ensure a standardized high quality mass-rearing process and the cost-effective production of sterile males with enhanced field performance and male mating competitiveness. The proposed CRP aims to develop best practices for insect colony management for the cost-effective production of high quality sterile males for SIT applications against major insect pests and disease vectors through a multidisciplinary approach involving entomologists, geneticists, ecologists, microbiologists, pathologists, virologists, and mass-rearing experts.
Objectives
The objective of this CRP is to develop the best practices for insect colony management for improved SIT applications against major insect pests by exploiting existing as well as novel knowledge and tools to address problems associated with mother colony deterioration and strain breakdown, symbionts and pathogens, and potential health issues.
Specific objectives
Prevent potential human health issues related to disease transmission to staff and reduce the staff exposure to hazardous materials, allergens, etc.
Manage insect colonization procedures to overcome problems such as loss of genetic diversity, pathogen presence and low performance.
Avoid or minimize the loss of strain stability or purity of specially designed or selected strains
Prevent or minimize colony deterioration in terms of loss of genetic diversity, important symbiotic organisms, mating competitiveness, predator avoidance, longevity and change in circadian rhythm.
Avoid or minimize the infection or build-up of microbial and viral pathogens in mass rearing facilities and the emergence of resistance against anti-microbial compounds and to overcome the lack of pathogen detection tools
Prevent potential human health issues related to disease transmission to staff and reduce the staff exposure to hazardous materials, allergens, etc.
Manage insect colonization procedures to overcome problems such as loss of genetic diversity, pathogen presence and low performance.
Avoid or minimize the loss of strain stability or purity of specially designed or selected strains
Prevent or minimize colony deterioration in terms of loss of genetic diversity, important symbiotic organisms, mating competitiveness, predator avoidance, longevity and change in circadian rhythm.
Avoid or minimize the infection or build-up of microbial and viral pathogens in mass rearing facilities and the emergence of resistance against anti-microbial compounds and to overcome the lack of pathogen detection tools
Impact
1. Multiple new RNA viruses infecting SIT-related species have been identified, highlighting the importance of viral covert infection in insect mass production.
2. Quantitative PCR has been implemented for each of the viruses identified in C. capitata, tsetse species, and S. exigua, allowing a routine surveillance of their presence.
3. Novel molecular techniques based on PCR and Nanopore (MinION) sequencing and new bioinformatic pipelines for insect pathogen diagnostics were developed and applied to different insects.
4. CpGV resistance appeared not stable if resistance was not reselected by exposing larvae of codling moth to CpGV for several generations
5. The identity of CpGV in covert infections of codling moth could be identified by SNP mapping of RNA-Seq data.
6. The C. pomonella SIT colony was found to have very low apparent levels of CpG using current pathogen control methods. However, another pathogen (B. thuringiensis kurstaki) previously unknown was found to be present in the colony.
7. The gut bacteriome of A. fraterculus sp. 1 larvae was described in samples from different environments and host fruit. Both factors significantly conditioned the bacteriome diversity. The most abundant symbionts were characterized based on the sequence of the 16S rRNA gene.
8. The gut bacteriome of A. fraterculus sp. 1 adults from a wild population and a laboratory colony were characterized. The negative effect of domestication to laboratory conditions on the genetic diversity and the gut bacteria diversity was evidenced for this species.
9. The impact of laboratory adaptation on the insect-gut microbiome relationship was assessed in wild-type and V8 strains of C. capitata. Distinct bacterial communities developed over 13 generations, varying between strains and developmental stages. These findings guide colonization protocol design to enhance SIT effectiveness.
10. A collection of bacterial isolates from the gut and the crop of A. fraterculus sp. 1 has been made available, with all the strains identified based on the 16S rRNA gene sequence. This collection will be used to test for the function (probiotic, pathogenic, attractive, etc.) opening new opportunities for R&D in the field of fruit fly SIT.
11. Improvements of the mass-rearing protocols for a number of fruit fly species and for tsetse flies have been made.
12. Colonies of the mutant black pupae GSS-89 of A. fraterculus sp. 1 were successfully established in Brazil and Argentina.
13. Enrichment environmental conditions in temperature luminosity and relative humidity were tested, showing that CABIM can provide a closer to natural conditions that could improve the sexual performance and oviposition behaviour of fruit fly species.
14. Two sources of hydrolyzed yeast (MP biomedicals and Lallemand) for adult diet were tested as a part of the protocol for the maintenance of the filter colony.
15. New cages for colony management were designed and installed in the CABIM.
16. A new cage design (bi-environmental cage) for colony maintenance of A. ludens showed that it can contribute to improving the field performance of released sterile males.
17. Directional selection for pupal size was assessed as an alternative for colony management in A. ludens.
18. No significant differences in genetic diversity were observed between long-term mass-reared strains and a wild population of A. ludens.
19. Significant differences in genetic diversity were observed between long-term mass-reared strains and a wild population of A. fraterculus sp. 1.
20. Demonstrated that levels of genetic variation in mass-reared strains of A. ludens can be monitored using RAPDs as genetic markers after “refreshment” of the strain by crossing in wild material.
21. Demonstrated that levels of genetic variation in mass-reared strains of A. fraterculus can be monitored using microsatellites as genetic markers after “refreshment” of the strain by crossing in wild material.
22. Characterized the relationship between tsetse’s bacterial microbiota and the fitness of colonized flies to reduce tsetse vectorial capacity.
23. Virulence factors have been identified in several insect symbionts.
24. Type VI secretion system was identified in several bacterial symbionts, which indicates that bacteria can affect the host and the relative abundance of other symbionts.
25. The whole genome sequence of Spiroplasma and other gut microbiota was completed.
Relevance
The activities done in the frame of this CRP are of high relevance as the mass-rearing is a fundamental need for the implementation of SIT programmes to control insects of agricultural and medical importance in the IAEA Member States.
The results of the CRP are very relevant to ongoing technology transfer activities in support of technical cooperation projects in Sub-Saharan Africa for tsetse and all the world for fruit flies. The technical information generated by this CRP will contribute to improving SIT technology through a better understanding of the role that microbes, domestication and handling process play in the small- and large-scale rearing facilities of tsetse flies and fruit flies. The goal is to improve the quality of released sterile insects. The emphasis on the field component of the CRP will ensure the effective transfer of technology and effective capacity building.