Ancient Artworks and Crocus Genetics Both Support Saffron's Origin in Early Greece

Abstract

Saffron crocus (Crocus sativus) is a male-sterile, triploid flower crop, and source of the spice and colorant saffron. For over three millennia, it was cultivated across the Mediterranean, including ancient Greece, Persia, and other cultures, later spreading all over the world. Despite saffron crocus' early omnipresence, its origin has been the matter of a century-old debate, in terms of area and time as well as parental species contribution. While remnants of the ancient arts, crafts, and texts still provide hints on its origin, modern genetics has the potential to efficiently follow these leads, thus shedding light on new possible lines of descent. In this review, we follow ancient arts and recent genetics to trace the evolutionary origin of saffron crocus. We focus on the place and time of saffron domestication and cultivation, and address its presumed autopolyploid origin involving cytotypes of wild Crocus cartwrightianus. Both ancient arts from Greece, Iran, and Mesopotamia as well as recent cytogenetic and comparative next-generation sequencing approaches point to saffron's emergence and domestication in ancient Greece, showing how both disciplines converge in tracing its origin.

Keywords: #ArtGenetics; Crocus sativus; Genome; Minoan frescoes; cytogenetics; historical art; saffron.

Figure 1

Cultivation of saffron (Crocus sativus L.) as traced by historic arts and modern genetics. (A) The timeline and map show four exemplary time-points (1–4) and their corresponding geographic locations. (B) The earliest evidence of “historic saffron” (any crocus species with at least partially similar traits as today’s cultivated saffron and used by humans for this particular trait) use was found in pigments from cave wall paintings. These contained crocin (structure shown) that was derived from Crocus flowers. These cave paintings were found in today’s north western Iraq and were created about 50,000 years ago (tya). (C,D) The first signs of saffron cultivation were found in Aegean Bronze Age frescoes from Crete and Santorini, dating back to 1700 to 1500 before the common era (BCE). Shown here is a part of “The Saffron Gatherers” (C) and “Adorants” frescos (D), both found in Xeste 3 (Akrotiri, Santorini) from around 1600 BCE. (E) The first mentioning of saffron crocus propagation through corms was documented in Historia Plantarum by Theophrastus around 300 BCE. Shown here is the front cover of the Latin translation (1644). (F,G) Recent studies investigating the origin of saffron crocus using modern genetic approaches [multicolor FISH (F) and genotyping-by-sequencing GBS (G)] also point to early Greece as the place of origin, with Attica as the most likely region of origin. Countries that are major saffron-producers today are colored in red and purple on the map (Rukšāns, 2017). [Image sources: (A) The map was generated with Natural Earth (https://www.naturalearthdata.com/); (B) Crocin structure was made with ChemSketch; (C,D) “The Saffron Gatherers” and “Adorants” pictures from Doumas (1992) p. 152/Figure 116, p. 136/Figure 100 (contrast and brightness enhanced, layered); (E) Historia Plantarum belongs to the public domain, image provided by Andrew Dalby (Wiki commons); (F) FISH image reused from Schmidt et al. (2019), Figure 2Q with permission from John Wiley and Sons; (G) Phylogenetic tree and cluster analysis reused from Nemati et al. (2019) under CC-BY]. The timeline is not to scale.

Figure 2

Scenarios for the auto- or allotriploid origin of saffron crocus (Crocus sativus L.). Saffron crocus is triploid and sterile and, hence, can only be propagated vegetatively through corms. How this triploidy emerged has been debated for over a century, with two main hypotheses being brought forward: On the one hand, saffron may have originated with genome contributions from a single species, likely Crocus carthwrightianus (autotriploid scenario). On the other hand, at least two species may have contributed to the genome of saffron crocus, with one likely being C. cartwrightianus (allotriploid scenario). Both scenarios represent extreme cases along a gradual spectrum from auto- toward allopolyploidy, as indicated by the gradual arrangement in the figure. The current position of saffron supported by several recent studies tends to be more on the autotriploid side of the spectrum of polyploidy (Nemati et al., 2019; Schmidt et al., 2019). The capital letters represent sub-genomes from different species, with different cytotypes being represented by different typefaces. The representation of the spectrum of polyploidy using letter triplets only serves as symbolic visualization and may not represent all possible scenarios.