The brown planthopper(BPH,Nilaparvata lugens St(a)l)is an important pest of rice,and it has a record of quickly overcoming rice resistance,possibly associated with its transovarially transmitted yeast-like symbionts(YLSs).Based on the sequence analysis of internal transcribed spacer,we isolated and identified Cryptococcus-like and Pichia-like YLSs and also successfully cultured a Candida-like YLS in vitro.Using the PCR-DGGE technology,we found YLS composition was complicated,including at least other eight different YLSs besides Hypomyces chrysospermus.In terms of the results of PCR-DGGE and ITS sequence analysis,three of these YLSs,Hypomyces chrysospermus,Meyerozyma guilliermondii and Candida quercitrusa,were chosen to test their population dynamics during BPH adaptation to various resistant rice varieties by qPCR.The number of the above three YLSs significantly decreased in the 2nd generation in BPH transferred from susceptible rice variety(TN1)to resistant ones(Mudgo,ASD7,or RH),but their numbers recovered in the 3rd generation.Besides,the ratio of these three YLSs in BPH on different varieties changed,even though H.chrysospermus was always dominant while C.quercitrusa was the least common.These results proved the close relation of YLSs and BPH virulence change.