Genomics of grapevine: From genomics research on model plants to crops and from science to grapevine breeding

A large number of grape cultivars are commercialised, and the breeding industry is particularly dynamic, with new cultivars being released annually. In recent years there has been an interest in breeding new grape cultivars with two main objectives: one, to develop a genotype with wider ecological adaptation and second, to provide a response to the menace of viral pathogens that are causing severe damage in most cultivars. To achieve these goals biotechnological approaches for plant disease are employed to find solutions within a reasonable time frame. These challenges are represented by the need for a correct identification of genetic resources and the determination of genetic diversity to be applied either in conservation and utilisation of valuable germplasm, e.g. in breeding programs. Since the process from hybridization to cultivar release can span decades, genomic studies and genetic markers can significantly speed up the selection of putative resistant seedlings. Natural virus resistance may be exploited by the identification of resistant genotypes, followed by the transfer of genes into new germplasm through hybridization. New breeding goals and genetically improved solutions are part of the biotechnological benefits, e.g. resistance against biotic and abiotic stress factors. Plant transformation has become an essential tool for plant molecular biologists and genetically improved plants have become a major focus of many breeding programs. Since grapes are long-lived, they represent an excellent tool for long-term expression studies for genetically improved sequences. The isolation, cloning and moving of genes from diverse biological sources into grape genomes holds promise to broaden the gene pool of crops and tailor plant varieties for specific traits that determine yield, quality and resistance to biotic and abiotic stresses. The molecular characterization and localization of T-DNA insertion in genetically improved grapevines carrying structural and non-structural genes of viral origin in different vectors constructed under ecological consideration is presented. Genetically improved plants were analyzed for a correlation between transgene expression, siRNAs production and DNA methylation. The detailed analyses revealed the complex arrangements of T-DNA and integrated binary vector sequences as crucial factors that influence transgene expression. Inoculation of genetically improved and untransformed plants produced short siRNAs indicating that the plants responded to infection by activating a post-transcriptional gene silencing mechanism.