中文摘要：

为研究水稻3种主要害虫灰飞虱Laodelphax striatellus、褐飞虱Nilaparvata lugens和白背飞虱Sogatella furcifera体内类酵母共生菌（yeast-like symbiotes,YLS）的种属地位及与寄主的进化关系,测定了其体内YLS的18S rDNA及ITS-5.8Sr DNA的全长序列。基于3种稻飞虱体内YLS的18SrDNA序列比对表明,褐飞虱YLS和白背飞虱YLS的一致性比其与灰飞虱YLS的高（褐飞虱YLS和白背飞虱YLS为98.91%,灰飞虱YLS和褐飞虱YLS为95.74%,灰飞虱YLS和白背飞虱YLS为96.02%）,而基于ITS-5.8SrDNA序列比对,灰飞虱YLS和白背飞虱YLS的一致性比其与褐飞虱YLS的要高（白背飞虱YLS和灰飞虱YLS为99.57%,灰飞虱YLS和褐飞虱YLS为91.91%,白背飞虱YLS和褐飞虱YLS为90.46%）。基于真菌18SrDNA和ITS-5.8SrDNA的系统发育树均表明,3种稻飞虱体内YLS与其他已知真菌进化关系较远。本研究证实了昆虫真菌类共生菌与寄主形成了长期的进化关系,从而形成了不同于已知真菌的分类地位。

英文摘要：

In order to study the species status of yeast-like symbiotes（YLS） from three rice planthoppers（Laodelphax striatellus,Nilaparvata lugens and Sogatella furcifera） and the evolutionary relationship of YLS with insect hosts,the complete sequences of 18S rDNA and ITS-5.8S rDNA of YLS from the three planthoppers were determined.Sequence identity comparison of YLS from rice planthoppers was conducted based on 18S rDNA and ITS-5.8S rDNA sequences.The results showed that YLS of N.lugens has a higher identity to that of S.furcifera（98.91%） than to that of L.striatellus（95.74%） according to 18S rDNA sequences,but YLS of L.striatellus has a higher identity to that of S.furcifera（99.57%） than that to N.lugens（91.91%） according to the ITS-5.8S rDNA sequences.Phylogenetic analysis based on both 18S rDNA and ITS-5.8S rDNA showed that YLS from three rice planthoppers has no obvious identity to other known fungi.The results suggest that insect YLS have a close evolutionary relationship with hosts and form a taxonomic group different from other fungi.