Repetitive Sequences in the Potato and Related Genomes

Repetitive sequence elements refer to sequences which are repeated a number of times in the genome and are generally composed of either the interspersed elements or tandem repeats, which may be coding or non-coding. Solanum genomes, like that of potato and tomato, are exceptionally rich in repetitive elements and have evolved by the multidirectional activities of the repetitive elements. Interspersed elements, in particular, have contributed to the evolution of Solanum genomes, not only by their amplification in the genome, but also by their association with different genes. The genomic proximity of interspersed elements to genes may influence the expression patterns, development of alternative functions, emergence of new genes or elimination of existing genes. Long terminal repeat (LTR) retrotransposons represent the most abundant class of repetitive elements among all the repeats and they are also considered the progenitors of some genes and other types of repeats such as microsatellites. Centromeric, telomeric, minisatellites and microsatellites constitute tandem repeats, which are abundant in the Solanum genomes. The patterns of occurrence and abundance of repeats vary among different species of Solanum, although a careful analysis reveals a number of perceptible evolutionary trends. Tandem repeats, particularly microsatellites, have frequently been exploited for the development of molecular markers for diverse applications in potato. The present chapter deals with the occurrence and distribution of different categories of repetitive elements in potato and the related Solanum genomes.