ABSTRACT
Despite its considerable distribution and great economic importance, the origin and evolution of plant species of the genus Citrus are still unclear; indeed these species hybridize easily and naturally through cross-pollination. The phylogeny and taxonomy are somewhat controversial; often the differences between species, new botanical variants, or varieties cultivated in a different way can be extremely small. In the case of varieties and hybrids in existence for a long time, only the new methods of molecular investigation are able to distinguish different species, although often this type of response is far from unique (Nicolosi et al. 2000).
