Cytogenetics of Potato and Tomato Wild Relatives

Cytogenetics has historically contributed to the taxonomy, genetics, and breeding of cultivated and wild Solanum species. This chapter summarizes the contributions of cyto- genetic research to our understanding of genome structure and evolution of potato and tomato wild relatives. We focus on the advances in cytogenetics, going from the classical chromosome morphological analysis of species and their hybrids to the recent oligonucleotide-based chromosome paints, which are helping to identify and compare chromosomes and genomes of the wild Solanum relatives, detect large-scale changes among these species, and clarify the parental origin of polyploid potatoes. Given the large number of species, comparative fluorescence in situ hybridization (FISH) mapping and genome size data are still sparse. However, these studies are helping uncover the karyotypic differences among cultivated and wild Solanum species, a diversity with a significant impact on introgression and pre-breeding programs, and characterize their rich reper- toire of tandem satellite sequences. In addi- tion, this chapter summarizes how the analysis of the centromeres of several Solanum species has provided a new model system to study the centromere evolution and the accumulation of satellite repeats in these specialized chromo- somal regions.