Closely Related Male-Killing and Nonmale-Killing Wolbachia Strains in the Oriental Tea Tortrix Homona magnanima

Wolbachia are inherited intracellular bacteria that cause male-specific death in some arthropods, called male-killing. To date, three Wolbachia strains have been identified in the oriental tea tortrix Homona magnanima (Tortricidae, Lepidoptera); however, none of these caused male-killing in the Japanese population. Here, we describe a male-killing Wolbachia strain in Taiwanese H. magnanima . From field-collected H. magnanima , two female-biased host lines were established, and antibiotic treatments revealed Wolbachia ( w Hm-t) as the causative agent of male-killing. The wsp and MLST genes in w Hm-t are identical to corresponding genes in the nonmale-killing strain w Hm-c from the Japanese population, implying a close relationship of the two strains. Crossing the Japanese and Taiwanese H. magnanima revealed that Wolbachia genotype rather than the host genetic background was responsible for the presence of the male-killing phenotype. Quantitative PCR analyses revealed that the density of w Hm-t was higher than that of other Wolbachia strains in H. magnanima , including w Hm-c. The densities of w Hm-t were also heterogeneous between host lines. Notably, w Hm-t in the low-density and high-density lines carried identical wsp and MLST genes but had distinct lethal patterns. Furthermore, over 90% of field-collected lines of H. magnanima in Taiwan were infected with w Hm-t, although not all host lines harboring w Hm-t showed male-killing. The host lines that showed male-killing harbored a high density of Wolbachia compared to the host lines that did not show male-killing. Thus, the differences in the phenotypes appear to be dependent on biological and genetic characteristics of closely related Wolbachia strains.