Detection And Phylogenetic Analysis Of Some Endosymbionts In The Parasitoid Wasps Of Chilo Suppressalis (Walker)(Lepidoptera:Pyralididae)

Bacterial symbionts can play important roles in the reproduction and other processes of insects. Parasitoid wasps are one of the key beneficial factors contributing to natural control of insect pests. Studies on these beneficial insects would greatly better our understanding of their population development mechanisms, and expectedly provide some cues for the searching of novel symbiont-based approaches to enhance natural control efficiency. The striped stem borer, Chilo suppressalis (Walker), is one of the most serious pests of rice in Asia. A high number of parasitoid wasps have ever been discovered from this pest, but little is known about their bacterial symbionts. In this study, Wolbachia and Cardinium, which are well known for their capacity of regulating host reproduction, and the phage of Wolbachia (WO), were detected for their infection status, strain diversity and possible lateral transfers. Five parasitoid wasp species, Apanteles chilonis, Microgaster russata, Eriborus terebrans, Gambrus wadai and Chelonus munakatae, which were collected from six locations of China, were used.By using PCR, a total of32different nucleotide sequences (496-594bp in length) of Wolbachia surface protein (wsp) gene were cloned, indicating that Wolbachia have a high diversity in these insects. Double and multiple infections were found to be relatively common with77.8%of A. chilonis and31.3%of M. russata female adults tested being doubly infected. The Wolbachia strains belong to supergroup A and B, and according to the phylogenetic analysis they can be subdivided into at least six distinct groups. Many strains were speculated to have experienced lateral transfers among parasitoid wasp species, or between parasitoid wasps and other insect species. Intragenic recombination was detected for the gene ftsZ of Wolbachia. As new findings,15novel wsp alleles and26new MLST gene (ftsZ, gatB, cox A, hcpA, fbpA) alleles were identified, and subsequently14new sequence types (STs) were established.Fragments of orf7genes in Wolbachia phage (WO) were cloned, and thereby two WO strains were identified. One WO strain occurs in most of the geographic populations of A. chilonis and M. russata, and one population of C. munakatae, and the other occurs only in a few of populations of A. chilonis and M. russata. Possible lateral transfers were also detected among various parasitoid wasps.By using the primers reported in literatures, we tried to clone16S rRNA fragments from Cardinium. Fragments displayed expected length were obtained, but sequencing and blasting results indicated that all of the cloned sequences were not from these bacteria, while instead from species of another bacterial genus, Sphingobacterium. Thus, all of the five species appeared to be not infected with Cardinium. These results increase our knowledge of the Wolbachia/WO infection status and diversity in parasitoid wasps of C. suppressalis. In particular, as many strains were discovered for the first time, our results would serve as an important basis for further studies in future.