Abstract: Wolbachia are common bacteria found in arthropods. Trichogramma ostriniae is the major Trichogramma species in maize fields in China and it has been reported that Trichogramma species harbored Wolbachia. In this study, the Wolbachia wsp and 16s rDNA gene sequences were used to detect the infection of Wolbachia in natural populations of T. ostriniae. The results indicated that T. ostriniae was triply infected with three strains of Wolbachia based on the wsp gene, i.e., wOstGDAa (GenBank accession no. EU157103), wOstGDAb (GenBank accession no. EU157104) and wOstGDB (GenBank accession no. EU157105). Phylogenetic analyses showed that wOstGDAa and wOstGDAb belong to supergroup A, while wOstGDB belongs to supergroup B. An extensive survey of Wolbachia infection in natural populations of T. ostriniae revealed that nearly all individuals tested were infected with wOstGDAa, wOstGDAb and wOstGDB. This is the first report that nearly 100% of the individuals in the population were triply infected with Wolbachia. According to our results, we suppose that Wolbachia may transfer among different Trichogramma species when they share a host egg.

Key words: Trichogramma ostriniae, Wolbachia, triple infection, wsp gene