Abstract: The homology among fifteen RGAs of cucumber cloned in authorsplaboratory and the homology between the RGAs and N gene from tobacco, and L6 gene from flax, and RPS2 gene from A rabidopsiswas analyzed using ClustalW and DNAMAN 310 p rogram. The fifteen RGAs were identified by PCR and Southern hybridization. The results showed that the highest homology of nucleotide sequence existed between CsRGA2,CsRGA4 and CsRGA5. Higher homology existed between CsRGA6, CsRGA7, CsRGA8 and CsRGA9, also existed between CsRGA1 and CsRGA3, Less homology existed in the other RGAs. The amino acid sequence homologies of the products translated from the RGAs were also similar to the above. The highest homology,46% , and the lowest homology, 22% , between the RGAs and three novel disease resistance genes, N, L6 and RPS2, were exhibited. The RGAswere identified using PCR with fifteen pairs of special p rimers based on the nucleotide sequence of the RGAs. CsRGA3 showed polymorphism in cucumber varieties. The fifteen digoxin (D IG) labeling probe, which produced by performing special primer PCR, hybridized with genomic DNA of 215, 129 and L18, digested by EcoRⅤ, using Southern blotmethod. The existence of the RGAs in cucumber genome was certified. CsRGA9, CsRGA11-CsRGA15 had multi copies, respectively, CsRGA3 had single copy, the others had two copies.

Key words: Cucumber, Cucumis sativus L., RGA, Homology, Southern hybridization