Abstract: [Objective]There exists reproductive incompatibility between the Castanea mollissima population from Shandong Province (TSBL) and the Cunninghamia lanceolata population from Zhejiang Province (ZJSM) of Oligonychus ununguis. However, Wolbachia or Cardinium, as the insect's endosymbiont, has the ability to alter the reproductive capabilities of its host. This study aims to analyze the distribution of Wolbachia and Cardinium in different O. ununguis populations, and to reveal the effects of endosymbionts on O. ununguis reproductive incompatibility.[Method]Primers were designed according to the sequences of the gene encoding a surface protein of Wolbachia (wsp) and the Cardinium's 16S rRNA gene, and PCR was performed using the genomic DNA extracted from a single adult female O. ununguis. Purified PCR fragments were sequenced and blasted against the databases. Phylogenetic tree was constructed based on these sequences.[Result]Neither the C. mollissima population from Shandong Province (TSBL) nor the C. lanceolata population from Zhejiang Province (ZJSM) was infected with Wolbachia. In all the detected 12 populations of O. ununguis, the infection rates of Wolbachia and Cardinium were 0 and 8.3%, respectively. Cardinium was detected only in the Quercus acutissima population from Hebei Province, but the intrapopulation infection rate was high with 66.7%.The Cardinium infecting O. ununguis was closer to that from Teranychus urticae in phylogenetic relationship.[Conclusion]The infection rate of Wolbachia might be very low in O. ununguis in China. The reproductive incompatibility between the C. mollissima population from Shandong Province (TSBL) and the C. lanceolata population from Zhejiang Province (ZJSM) of O. ununguis was independent of Wolbachia and Cardinium.

Key words: Oligonychus ununguis, population differentiation, Wolbachia, Cardinium, phylogeny