Abstract: To clarify the effect of Cardinium on the reproductive traits of the infected carmine spider mites, Tetranychus cinnabarinus (Boisduval), the experiments were performed in the Shanxi and Gansu populations of China to test for the cytoplasmic incompatibility (CI) phenotype previously reported to be caused by Cardinium. The infected and uninfected mites from each population were crossed with each other in the following four cross combinations: Cardinium infected ♀ × Cardinium infected ♂, Cardinium infected ♀ × uninfected ♂, uninfected ♀ × Cardinium infected ♂, uninfected ♀ × uninfected ♂. The results showed that CI was induced in both populations when the infected males were crossed with the uninfected females. Furthermore, the two populations tested showed the different types of CI. In Shanxi population, CI resulted in severe reduction in the hatchability of eggs and the number of F1 females, while in Gansu population, CI resulted in a 100% hatchability of eggs, but the F1 generation contained no female mite. The Cardinium strains in these two populations share very close relationship, but their different CI performance suggests that closely related strains may have different phenotypes of CI. Our results will be proved useful in future studies on the infection mechanism and reproductive manipulation of Cardinium.

Key words: Tetranychus cinnabarinus, symbiont, Cardinium, reproduction manipulation, cytoplasmic incompatibility, crossing experiment