Saffron (Crocus sativus L.) breeding: Opportunities and challenges

Abstract

Saffron (Crocus sativus L.) is an autumnal herbaceous flowering plant belonging to the Iridaceae family. It is considered the most expensive spice in the world and a valuable medicinal herb. The origin of saffron is unclear. The probable center of origin of the plant is Asia Minor (Greece) and/or the Middle East (Iran). From the historical point of view, use of saffron for medical treatment, perfume, food and dye dates back 4000 years. Saffron stigmas contain three important secondary metabolites, crocin, picrocrocin and safranal that are responsible for the saffron color, taste and aroma, respectively. Saffron's adaptation to hot and dry climates has led to widespread cultivation in arid regions, notably Iran where it is a primary income source for many people. The triploid genome of saffron causes the production of abnormal pollen triggering self-sterility. With respect to the clonal nature of saffron, it is believed that there is only one cultivar worldwide. Lack of genetic variation restricts the use of traditional plant breeding based on selection. Probable wild relatives could be an excellent source of genes to alter saffron traits by cross-pollination. In addition, an induced mutation approach with various mutagen agent treatments is an alternative to produce genetic variations. Recent advances in sequencing methods and next-generation sequencing (NGS), provide efficient approaches such as transcriptome sequencing along with proteome and metabolome information, which would help to exploit functional genomics toward genetic engineering of the economic traits of saffron.