Development And Appliaction Of Molecular Marker System Based On TY1-Copla Retrotransposon In Cucumis

Retrotransposons are the most abundant and widespread class of transposable elements (TEs) in plant kingdom. Tyl-copia-like retrotransposon is one of the most deeply studied types, which transpose through a RNA intermediate by a "copy-paste" mechanism. They play an important role in plant genome size, structure, evolution, and so on. Because of their extensive distribution, high copy number, they are used in genetic diversity analysis, phylogenetic and genetic mapping and so on.Cucumber is one of the most important vegetables not only in china but also in the world. Due to artificial selection and hybridization of cultivars, the diversity of cucumber germplasm resources was thereatened and the genetic background became increasingly narrow. So the reaserch on the development and application of molecular marker systems in Cucumis based on retrotransposon will provide much help for genetic analysis and the discovery genes of resistant to dease and gei us a new mothod for the breeding in cucumis.1. Development of IRAP Molecular Marker System in CucumisIRAP (inter-retrotransposon amplified polymorphism) marker system was developed based on the long terminal repeat (LTR) sequence of Ty1-copia retrotransposon in Cucumis. Twenty-three cultigens in Cucumis were analyzed with this system and the results indicated it can efficiently detect polymorphism among different materials. Thus it can be used for cultivar identification and fingerprinting in Cucumis.2. Development and Application of REMAP Molecular Marker System in CucumisREMAP (retrotransposon-microsatellite amplified polymorphism) marker system was developed based on the long terminal repeat (LTR) sequence of Tyl-copia retrotransposon in Cucumis and combination of the ISSR primer sequence. Forty six cultigens in Cucumis were analyzed with this system and the results indicated it can efficiently detect polymorphism among different materials. Thus it can be used for cultivar identification and fingerprinting in Cucumis. 3. The discovery of the resistance gene to downy mildew used retrotransposon-based molecular marker and interspecific introgression lines58special expressed cDNA segments were found from C. hytrix and resistant introgression lines (ILDM10-4) after inoculated used cDNA-SSAP based on retrotransposon. BLAST analysis revealed that they were homologous partly to tyrosine-protein kinase, Cucumis sativus cultivar407catalase, Glycine max probable lysine-specific demethylase JMJ14. Further analysis on expression show that the3fragments were closely related with the resistance to Downy Mildew in cucumber by RT-PCR.