Chromosome number variation of phytoestrogen-producing Curcuma (Zingiberaceae) from Thailand

Wan-chak-motluk is a Thai local name for native species of Curcuma (Zingiberaceae) that produce phytoestrogen in their rhizomes. Wan-chak-motluk has long been used in Thai traditional medicine for treatment of illness in the uterus and ovarian hormone deficit, and therefore it is cultivated for economic purposes throughout Thailand. The rhizome morphology of wan-chak-motluk is highly variable and this may be related to its medicinal properties. Thus, this study aimed to identify and classify wan-chak-motluk collected from cultivation sites in 16 provinces of Thailand. Chromosome numbers, together with inflorescent, floral, and leaf morphology, were used to separate wan-chak-motluk into five cultivars belonging to three species: C. comosa, C. elata, and C. latifolia. Curcuma comosa has short (2–5 cm) peduncle, glabrous lower leaf, and consists of two cultivars. One cultivar has a cylindrical spike 13–17 cm long and 5–8 cm wide, whereas the cylindrical spike of the other cultivar is shorter (10–15 cm) but larger (8–12 cm). The former cultivar has 2n = 42 and the latter has 2n = 63, seldom 2n = 62 or 64. Both C. elata and C. latifolia have long (10–25 cm) peduncle and pubescent lower leaf. They differ in that C. latifolia has 2n = 63 and 84 with a red path along the midrib, whereas C. elata has 2n = 63 without a red path along the midrib. This study shows that chromosome numbers can be used to accurately verify the taxonomic identification of wan-chak-motluk.