Abstract: To determine the species of the yeast-like symbiont (YLS) in the rice planthoppers, the YLS was first isolated and purified by ultracentrifugation from the fat bodies of the small brown planthopper, Laodelphax striatellus (Fallén), and then 18S rDNA and 5.8S-ITS rDNA sequences of the YLS were amplified with the general primers for fungi. Sequence homology analysis showed that 18S rDNA and 5.8S-ITS rDNA obtained were different from the strain that Noda et al. had identified previously, but showed high homology (99.8%) with those of Pichia guilliermondii. The results of in situ hybridization (ISH) and nested PCR proved that this kind of Pichia-like symbiont existed in the body of L. striatellus and involved in the transovarial transmission. The results suggest that there exist other YLS in L. striatellus besides the kind of YLS identified by Noda et al.

Key words: Laodelphax striatellus, yeast-like symbiont (YLS), Pichia guilliermondii, molecular identification, nested PCR, in situ hybridization