A Wolbachia strain in the flour moth, Ephestia kuehniella, causes moderate cytoplasmic incompatibility but has little impact on host fitness

Abstract

The flour moth, Ephestia kuehniella Zelter 1979 (Pyralidae: Phycitinae) is well known as a pest of stored products and serves as an important host for parasitoids in commercial rearing. In this study, we detected and characterized a Wolbachia infection in E. kuehniella from a local Australian commercial strain used to rear parasitoids. Identification of Wolbachia by PCR and a phylogenetic reconstruction using the wsp gene showed that the Wolbachia strain belongs to Supergroup A. After generating a cured line, we found that flour moths from this commercial line suffered partial cytoplasmic incompatibility, where around 50% of eggs hatched in incompatible crosses. The infection did not generate large host fitness effects once inbreeding and maternal effects were controlled. This contrasts with previous studies demonstrating costs of Wolbachia, suggesting that Wolbachia strains in the flour moth may have different fitness effects depending on the strain or host genotype. This research suggests that commercial insectaries do not gain much by clearing Wolbachia from their production stocks but should be mindful of inbreeding depression when establishing cultures.