Cultivation, identification and quantification of one species of yeast-like symbiotes, Candida, in the rice brown planthopper, Nilaparvata lugens

The brown planthopper (BPH), Nilaparvata lugens Stål, which is one of the most destructive pests of rice, has been confirmed to harbor yeast-like symbiotes (YLS) in the fat body. Several morphologically different YLS have been previously isolated and cultured in vitro from BPH, but direct evidence is lacking to further clarify whether the cultured YLS were from BPH. In this study, one species of YLS was successfully cultured in vitro and simultaneously verified to exist in the fat body of BPH by sequence analysis and nested polymerase chain reaction (PCR). The cultured YLS isolate in vitro was identified as a member of the genus Candida on the basis of 18S rDNA (ribosomal DNA) and 5.8S-ITS (internal transcribed spacer) rDNA sequence and a phylogenetic analysis of ITS sequences from yeast. Therefore, this yeast isolate was named as Candida-like symbiotes. Candida-like symbiotes was found to exist in fat bodies, ovaries and newly laid eggs of the BPH, but not in the heads, thoraxes and mid-guts. In addition, the number of Candida-like symbiotes in 1 × 10 ⁶ of purified YLS from BPH fat bodies was speculated to be (5.32 ± 0.22) × 10 ⁴ on the basis of a quantitative PCR analysis.