Linkage and quantitative trait locus (QTL) mapping allow regions of the genome conferring adaptive traits to be identified; this is often an early step in identifying the genetic basis of said trait. In addition, comparative mapping, i.e. using orthologous genetic markers to create linkage and QTL maps, allows genome structure (translocations, inversions and so on) to be identified as well as to provide insight into the extent to which the same genes may confer the same trait in different crops. Extensive comparative mapping in the Solanaceae (especially eggplant, tomato, potato and pepper) has revealed how genome organisation takes place during species evolution and suggests that up to 40% of agronomically important traits in eggplant may be controlled by orthologous genes in tomato, potato and/or pepper.