Saffron (Crocus sativus) is an autotriploid hybrid derived from wild Crocus cartwrightianus cytotypes

Saffron crocus (Crocus sativus) is the source of the most expensive spice of the world, produced from manually harvested stigmas, thus serving as prime cash crop for many rural communities. However, despite its economic importance, its genome and chromosomes are poorly studied. C. sativus is a sterile triploid harboring eight chromosome triplets (2n=3x=24), and is propagated only vegetatively by corms. Saffron's evolutionary origin, parental species and allo- or autotriploidy has been the matter of discussion for almost a century.We sequenced the saffron genome and identified cytogenetic landmark sequences consisting of major tandem repeats, which we used as probes in six-color fluorescent in situ hybridization (FISH). We labeled 92 chromosomal positions and resolved the chromosomal composition of saffron triplets. By comparative FISH karyotyping of closely related Crocus species we demonstrate that C. sativus is an autotriploid hybrid derived from highly heterogeneous C. cartwrightianus cytotypes, of which one must have contributed unreduced gametes. The knowledge of the parental origin offers a route towards the resynthesis of this clonally propagated crop from C. cartwrightianus cytotypes to broaden the gene pool of saffron.