Genetic changes during laboratory domestication of an olive fly SIT strain

Abstract

Early attempts to apply the SIT on the olive fly, Bactrocera oleae, were unsuccessful, mainly due to the low competitiveness of the sterile mass‐reared males compared with the wild ones. Recently, new efforts are underway in Israel to develop a vigorous and efficient mass‐reared olive fly laboratory strain. To understand the genetics of the adaptation process and possibly link the corresponding loss of competitiveness to genetic markers, we followed the fluctuation of genotypic frequencies of ten microsatellite markers during the course of 22 generations of the colonization of a wild Israeli population in laboratory conditions. Effective and observed allele number is halved after 11 generations, so is mean heterozygosity. Practically, there is very little change between F0 and F1, there are substantial changes between F1 and F2–F5, and there is a virtual complete adaptation to the new laboratory environment by F11, because no more changes are observed between F11 and F22. If we assume that the loss of allele number and heterozygosity also reflects the loss of the ‘wild’ character of the colonized strain and, possibly, the loss of a substantial part of its natural vigour, our results indicate that there is an apparent need to refresh a mass‐reared colony with wild material at about every five to eight generations. Furthermore, simulation models indicated that while most of the observed allele frequency fluctuations were due to random drift, some alleles were probably under selection.

Cytogenetic and symbiont analysis of five members of the B. dorsalis complex (Diptera, Tephritidae): no evidence of chromosomal or symbiont-based speciation events

“…On the other hand, results obtained from laboratory colonies must be verified in larger samples of different origin before elevating to species level. As it has been shown by different studies (Gilchrist et al 2012; Parreño et al 2014, Zygouridis et al 2014), lab colonization is accompanied by an adaptation process including severe bottlenecks, hitch-hiking effects and extended inbreeding. This can affect the genetic structure of the populations and, possibly, their symbiotic communities.…”

The Anopheles arabiensis genetic sexing strain ANO IPCL1 and its application potential for the sterile insect technique in integrated vector management programmes

“…Generally, competitiveness of the male insects decreases with every generation in the insectary and therefore the mass-reared strains occasionally need to be refreshed by integrating wild genetic material (Gilchrist et al, 2012;Zygouridis et al, 2014). This has been successfully applied in fruit fly programmes (Calkins and Parker, 2005).…”

A review of plant protection against the olive fly (Bactrocera oleae (Rossi, 1790) Gmelin) and molecular methods to monitor the insecticide resistance alleles

“…However, due to their adaptation to factory, laboratory, and irradiation, flies have significantly reduced fitness (Leftwich et al, 2016). Zygouridis et al (2014) observed a substantial loss of variability between F1 and F2-F5 generations in the laboratory, while in F11 a complete adaptation to the new laboratory environment occurs. It was suggested that loss of variability is responsible for the loss of wild characters like low competitiveness of the sterile mass-reared males compared with the wild ones.…”

“…Loss of variability was shown with microsatellite markers. Authors suggested a solution to refresh a mass-reared colony with wild material at about every five to eight generations (Zygouridis et al, 2014). Efforts to develop a vigorous and efficient mass-reared laboratory olive fly strain is underway.…”

“…An environmentally safe alternative to insect pest control is the sterile insect technique (SIT) (Zygouridis et al, 2014). This is a species-specific method of insect suppression in which insects are mass-reared under factory conditions, sterilized by irradiation, and then released (Leftwich et al, 2016).…”