The 2012 ASHS Annual Conference

The genus Curcuma L. is a member of the family Zingiberaceae consisting of about 70 species distributing mainly in South and Southeast Asia including China, India, Indonesia, Malaysia, Myanmar, and Thailand. Some species are also found in Australia and the South Pacific. Curcuma is an economically important genus; many species have been used as medicinal, spicy, and ornamental plants. It is estimated that there are more than 10 species occurring in China. However, highly morphological variation has led to a continuous debate on the exact number of species in China. To pursue a better understanding of species variation, a karyomorphologycal study was conducted on11 species collected from China. Results showed that there was only one species (Curcuma flaviflora S. Q. Tong) that was diploid with 2n = 2x = 42, one species was tetraploid (C. kwangsiensis S. G. Lee & C. F. Liang) with 2n = 4x = 84; and the rest were triploid (2n = 3x = 63). The basic chromosome number is x = 21. The chromosome sizes of all studied species are very small, ranging from 0.5 to 2.0 μm, creating a great challenge for karyotype analysis. Diploid C. flaviflora produces viable seeds, which are the main source for propagation. Tetraploid C. kwangsiensis can reproduce asexually and sexually whereas triploids are unable to produce seed and therefore rhizomes are their primary organ for propagation. This study suggests that polyploidy is common in Curcuma. The fact that majority of species are triploid indicates that triploidy may have some type of competitive advantage over diploids and tetraploids; triploid individuals do not require seed production to survive because of asexual rhizome propagation and therefore advantageous traits become fixed in natural populations.