Wolbachia-induced cytoplasmic incompatibility (CI) in the parasitoid wasp, Habrobracon hebetor
عنوان دوره: دومین کنگره بین المللی حشره شناسی ایران
نویسندگان
چکیده
Wolbachia are common intracellular bacteria that generally found in arthropods, including a high proportion of insects, and also some nematodes. This intracellular symbiont can affect sex ratio with a variety of reproductive anomalies in its host, including cytoplasmic incompatibility (CI) between populations and parthenogenesis induction in parasitoid wasps. In this study, we questioned if the parasitoid wasp Habrobracon hebetor (Hym.: Braconidae), which is one of the most important biological control agents of many lepidopteran larvae is infected with Wolbachia. To test this hypothesis, different populations of the wasp were collected from Karaj and Isfahan; DNA was extracted from the adult insects and subjected to Real-Time PCR (qPCR) using specific primers targeting Wolbachia ftsZ gene. The results showed Wolbachia infection in the both populations. To see if Wolbachia are present in different developmental stages of H. hebetor, DNA samples of each developmental stage (i.e. egg, larva, pupa, and adults) were screened by qPCR. We found that Wolbachia were present in all developmental stages of the parasitoid wasp. Wolbachia densities in both egg and adult stages were higher than other stages of the parasitoid wasps that supported vertical transmission of Wolbachia. To find out the biological function of Wolbachia in H. hebetor, two isolines of this insect (i.e. Wolbachia infected (W+) and Wolbachia cured (W-)) were generated from Karaj population using tetracycline treatment and maintained for ten generations in the laboratory. Then, the insects from these isolines were used for crossing experiments: W+ ♀×W+ ♂, W+ ♀×W- ♂, W ̶ ♀×W ̶ ♂ and W- ♀×W+ ♂. Results of the crossing experiments revealed that Wolbachia induced CI in H. hebetor in which W- ♀×W+ ♂ produced only males (average number of males: 161.33), while in W+♀×W- ♂ both sexes (average number of males:137.66 + average number of females: 148) were observed. In the progeny of other two crosses, both males and females were observed. CI is commonly expressed when CI Wolbachia-infected males mate with uninfected females and caused male production in haplodiploid insects which is in consistent with these results. In conclusion, Wolbachia-induced CI was consistently detected in H. hebetor that biases sex ratio by increasing male progeny in the population. This phenomenon may affect success of biological control programs based on H. hebetor.
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