Breeding virus resistant potatoes (Solanum tuberosum): a review of traditional and molecular approaches.

Tetraploid cultivated potato (Solanum tuberosum) is the World's fourth most important crop and has been subjected to much breeding effort, including the incorporation of resistance to viruses. Several new approaches, ideas and technologies have emerged recently that could affect the future direction of virus resistance breeding. Thus, there are new opportunities to harness molecular techniques in the form of linked molecular markers to speed up and simplify selection of host resistance genes. The practical application of pathogen-derived transgenic resistance has arrived with the first release of GM potatoes engineered for virus resistance in the USA. Recently, a cloned host virus resistance gene from potato has been shown to be effective when inserted into a potato cultivar lacking the gene. These and other developments offer great opportunities for improving virus resistance, and it is timely to consider these advances and consider the future direction of resistance breeding in potato. We review the sources of available resistance, conventional breeding methods, marker-assisted selection, somaclonal variation, pathogen-derived and other transgenic resistance, and transformation with cloned host genes. The relative merits of the different methods are discussed, and the likely direction of future developments is considered.