从印度木薯花叶病毒（ＩＣＭＶ）侵染的植物中纯化特异的核酸，经ＲＮＡａｓｅ，ＤＮＡａｓｃ，Ｎｕｃｌｅ－ａｓｅＳｌ，ＥｘｏｎｕｃｌｅａｓｅⅢ和ＥｃｏＲＩ酶切，Ｓｏｕｔｈｅｒｎ和Ｄｏｔｂｌｏｔｓ杂交证实，在感病的植株中，存在两种形式的病毒核酸：环状双链ＤＮＡ和环状单链ＤＮＡ，后者可能是病毒ＤＮＡ的（－）链，环状双链ＤＮＡ经限制性内切酶作用可得２．７ｋｂ的线性双链ＤＮＡ纯化的病毒核酸含ＤＮＡ１和ＤＮＡ２两个分子量相近的组份。

J.Rovinson B.D.Harrison(Scottish Crop research Institute, Dundee,DD2 5DS,U.K.)Nucleic acids extracted from Indian cassava mosaic geminivirus infected plant leaves(Nicotiana ben thamiana)and further purified through 1.0% LMT agarose gel electrophoresis were treated with RNA ase,DNAase,Nuclease Sl,Exonuclease Ⅲ and restriction endonuclease EcoR I.Two kinds ofvirus-specific DNA existed in infected plants as shown by Southern and Dot blotting using virus ssDNAprobes synthesized by nick translation,These two DNAs were circu lar double stranded and singlestranded DNA(dsDNA and ssDNA)respectively.The dsDNA was in the form of open circular and covalently closed circular molecules(ee and ccc dsDNA).Both oc and ccc dsDNA were digested byEcoR I to produce lincar molecules of abeut 2.7 kb,The virus genome contained two components(DNA1 and DNA2)Furthermore,the circular viral ssDNA in plants was largely the miunus strandednot the plus stranded ssDNA reported from particles,This may be an important clue to the understandin