Phylogeny of the saffron-crocus species group, Crocus series Crocus (Iridaceae)

Adding color to a century‐old enigma: multi‐color chromosome identification unravels the autotriploid nature of saffron (Crocus sativus) as a hybrid of wild Crocus cartwrightianus cytotypes

“…(2n = 2x = 16) presumably played a major role in saffron evolution, and it has been suggested that changes of its ploidy resulted in autotriploid saffron (Karasawa, 1933(Karasawa, , 1943Chichiricc o, 1984). Very recently, Nemati et al (2018) performed single nucleotide polymorphism analyses of an intron of the nuclear topoisomerase gene, and genotyping-by-sequencing, and found that saffron and C. cartwrightianus show very high allele similarity, concluding that C. cartwrightianus genotypes formed the autotriploid saffron. By contrast, other reports consider saffron crocus as an allotriploid species involving diploid progenitors with 2n = 2x = 16 chromosomes, such as C. cartwrightianus, Crocus hadriaticus Herb., Crocus oreocreticus Burtt., Crocus pallasii Goldb.…”

Saffron (Crocus sativus) is an autotriploid that evolved in Attica (Greece) from wildCrocus cartwrightianus

“…Taking into account the high genetic diversity in C. cartwrightianus , we hypothesized that this could have influenced the outcome of earlier phylogenetic studies where C. cartwrightianus and C. sativus were included but did not result as sister species. We used DNA sequences of five single-copy genes that were amplified from C. cartwrightianus, C. sativus and their four closest relatives C. hadriaticus, C. oreocreticus, C. pallasii and C. thomasii (Nemati et al, 2018), which all share the same chromosome base number of x = 8. Where initial direct sequencing provided evidence for the presence of more than one copy of a gene within an individual, amplicons were cloned and six clones per individual were sequenced.…”

“…The sampling of C. cartwrightianus covered its entire distribution range (Figure 1A). Crocus oreocreticus , the closest relative of C. cartwrightianus and C. sativus (Nemati et al, 2018), is endemic to Crete, where it was collected in two different populations with four individuals each. In addition we used single individuals of the other Crocus series Crocus species sharing the chromosome number of 2 n = 2 x = 16 with C. cartwrightianus , which were often named as parents of triploid C. sativus (2 n = 3 x = 24).…”

“…if it originated through autopolyploidization from a single progenitor (Brighton, 1977; Ghaffari, 1986) or allopolyploidization involving two parental species (Tsaftaris et al, 2011; Harpke et al, 2013) has been debated. In a recent study inferring phylogenetic relationships of the species of Crocus series Crocus , that is the taxonomic group to which C. sativus belongs, we found that C. cartwrightianus is the closest relative of the saffron crocus and hypothesized that no other species might have contributed to the formation of the triploid (Nemati et al, 2018).…”

“…However, there are other similar species and molecular data were inconsistent regarding the contribution of possible parental taxa. Although C. cartwrightianus has been postulated several times as parent or one of the parental species, also C. almehensis, C. hadriaticus, C. haussknechtii, C. mathewii, C. michelsonii, C. pallasii, C. thomasii and C. serotinus have been proposed as possible parents (see Nemati et al, 2018). However, none of the analyses conducted to date have allowed for the safe inference of the parent(s), partly due to study designs that did not include the relevant species, and partly due to methodological shortcomings (Nemati et al, 2018).…”