Ribosomal FISH mapping reveals hybridity in phytoestrogen producing Curcuma species from Thailand

Abstract

Species in the genus Curcuma (Zingiberaceae) that are cultivated widely in Thailand for their phytoestrogen-producing rhizomes are called wan-chak-motluk. Five cultivars belonging to Curcuma comosa (cultivars with 2n = 42 and 63) and Curcuma elata (2n = 63) were examined using the molecular cytogenetic method of fluorescence in situ hybridisation (FISH) in order to identify genetic relationships among these cultivars based on chromosomal maps of the 18S-25S ribosomal loci. The results revealed hybrid features in this Curcuma species group and a significant similarity among wan-chak-motluk cultivars. The main features included: (1) the presence of the single largest ribosomal site, assigned the Cc1 marker site, in the somatic 2n complement of all cultivars, and (2) the odd numbers of ribosomal sites in the complements, most often in sets of three. We therefore propose that the cultivar with 2n = 42 (C. comosa) is a homoploid hybrid species comprised of two different ancestral genomes and has a diploid status with the basic chromosome number x = 21. The cultivars with 2n = 63 (C. comosa and C. elata) are most probably triploids arising within the 2n = 42 diploid species/cultivars via a meiotic modification, rather than from hybridisation between diploid and tetraploid plants. The knowledge about genetic and genomic relationships among wan-chak-motluk cultivars will be important in the research projects that aim to explore and promote new plant materials for cultivation. © 2011 Springer-Verlag.