| Summary: | Sterile insect release technique (SIT) is effective for eradicating quarantine insects including various tephritid fruit flies. When SIT is used for fruit flies, it is challenging to remove females from sterile males due to oviposition-associated piercing damage. This study developed a sex transition technique by feeding double-stranded RNA (dsRNA) specific to a sex-determining gene, <i>Transformer-2</i> (<i>Zs-Tra2</i>) of the striped fruit fly, <i>Zeugodacus scutellata</i>. <i>Zs-Tra2</i> is homologous to other fruit fly orthologs. It is highly expressed in female adults. RNA interference (RNAi) of <i>Zs-Tra2</i> by injecting or feeding its specific dsRNA to larvae significantly increased male ratio. Recombinant <i>Escherichia coli</i> cells expressing dsRNA specific to <i>Zs-Tra2</i> were prepared and used to feed larvae to suppress <i>Zs-Tra2</i> gene expression levels. When these recombinant bacteria were fed to larvae during the entire feeding stage, the test population was significantly male-biased. Some females treated with such recombinant <i>E. coli</i> exhibited mosaic morphological characters such as the presence of male-specific abdominal setae in females. This study proposes a novel technique by feeding dsRNA specific to <i>Transformer-2</i> to reduce female production during mass-rearing of tephritid males for SIT.
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