Abstract: For the preliminary study oninfluence of different citrus cultivars on the composition of Citrus tristeza virus (CTV) isolates, the HinfⅠRFLP and SSCP of p25 gene of 9 CTV isolates collected from sweet orange shown stempitting symptom were comparatively analysed as those isolates were graft inculated from Xinhui sweet orange to Fenghuang pummelo.The results of RFLP revealed that the HinfⅠRFLP group of the isolates CT90 and CT20 were kept the same as in Xinhui sweet orange and in Fenghuang pummelo; RFLP groups of other 6 isolates shown mixed groups in Xinhui sweet orange and single group in Fenghuang pummelo. DNA bands of p25/SSCP of the isolate CT90 kept the same as in Xinhui sweet orange and in Fenghuang pummlo but DNA bands of other 8 isolates maintained in Fenghuang pummlo were less than that of which maintained in Xinhui sweet orange.It seems that the replication of some composition of above 8 CTV isolates collected from sweet orange were inhibited in Fenghuang pummelo.

Key words: Citrus, Citrus tristeza virus, Composition of isolate, Host