Infection density of Wolbachia and incompatibility level in two planthopper species, Laodelphax striatellus and Sogatella furcifera.

Wolbachia, a bacterial endosymbiote of arthropods, causes cytoplasmic incompatibility (CI) in many insect species. CI traits were studied in two planthopper species, Laodelphax striatellus and Sogatella furcifera, and Wolbachia densities in these planthopper species were calculated by quantitative PCR methods. The CI level of L. striatellus was quite high and even aged males strongly caused CI. In contrast, S. furcifera showed partial CI, and males lost their ability to cause CI with age. Wolbachia infecting these two planthopper species were the same with respect to the nucleotide sequences of Wolbachia genes, 16S rDNA, ftsZ gene, groE genes, and wsp gene. Two methods for quantitative PCR, one using a DNA sequencer and the other a real-time sequence detection system, were established to calculate the amount of Wolbachia in the planthoppers. The density of Wolbachia in S. furcifera males was quite low. The difference in CI levels between the two planthopper species seems to be due to different amounts of Wolbachia infecting males.