Chromosome number variation and polyploidy in 19 Kaempferia (Zingiberaceae) taxa from Thailand and one species from Laos

Abstract

Several Kaempferia species, endemic to Thailand, are rare and therefore entitled to conservation status; other species are widely cultivated. We conducted extensive cytogenetic investigation of this genus to elucidate the botanical and taxonomic characterization of these plants. The study included 42 accessions belonging to 15 Kaempferia species and four undescribed taxa from regions throughout Thailand, and one species from Laos. We determined chromosome numbers from root‐tip cells collected from germinating rhizomes ex situ, but examined meiosis in flowers collected from the wild. The mitotic analyses verify that 2n chromosome numbers range from 22 (diploid, 15 taxa), 33 (triploid, three species), 44 (tetraploid, five taxa) to 55 (pentaploid, one species). Four taxa included accessions with different ploidy levels. The meiotic analyses demonstrated that all 14 diploid accessions investigated displayed normal meiosis, forming 11 bivalents, indicating the base chromosome number x = 11 for this genus. Meiotic figures were obtained from one triploid and four tetraploid accessions. The triploid showed 11 trivalents, most likely indicating autotriploidy. Two tetraploid accessions showed regular meiotic figures consisting of 22 bivalents, probably indicating allopolyploidy originating from interspecific hybrids, a hypothesis that is consistent with observations of plant morphology. The other two tetraploid accessions belong to the same species and show mostly irregular meiotic figures. Cytogenetic information is useful for evaluating fertility and hybridity in the genus. Good seed set was observed among diploid and tetraploid accessions. Triploid and pentaploid plants, on the other hand, do not set seeds, but produce large clusters of vegetatively‐propagated rhizomes.

Cytogenetic verification of Curcuma candida (Zingiberaceae) from Thailand and Myanmar

“…Different base chromosome numbers of Curcuma have been reported. Based on direct chromosome counting, the base chromosome number of x = 16 was reported by Sharma & Bhattacharya (1959), whereas Sato (1960) suggested that it could be x = 7 and 8. Leong-Škorničková et al (2007) proposed, based on genome size data, that x = 7 should be considered a "primary" base chromosome number in Curcuma.…”

“…Preparation of meiotic metaphase chromosomes from microsporocytes was performed using the aceto-carmine smear technique described in Nopporncharoenkul et al (2017). Samples of at least twenty young flower buds from each accession were collected in the field and from local markets.…”

“…Baker and K. pulchra Ridl. are also edible or ornamental plants (Chuakul & Boonpleng, 2003;Picheansoonthon & Koonterm, 2008).…”

“…The conservation status of C. candida has been assigned as vulnerable . This species produces substantial and attractive inflorescences, which are traditionally used as a vegetable eaten with native food, as well as having the potential to be developed as an ornamental or medicinal plant (Jenjittikul & Larsen, 2000;Picheansoonthon & Koonterm, 2008). Taxonomically, this species was initially classified into the genus Kaempferia, based on morphology of specimen from Myanmar, and was given the name K. candida by Wallich (1830).…”

“…Chromosome numbers of Kaempferia have also been reported. Most Kaempferia species are diploid having 2n = 22 (base number x = 11), whereas other ploidy levels exist within the genus, such as 2n = 33 (triploid), 44 (tetraploid) and 55 (pentaploid) (Raghavan & Venkatasubban, 1943;Chakravorti, 1948;Ramachandran, 1969;Mahanty, 1970;Eksomtramage & Boontum, 1995;Eksomtramage et al, 1996;Saensouk & Jenjittikul, 2001;Eksomtramage et al, 2002;Saensouk & Saensouk, 2004;Nopporncharoenkul et al, 2017. ) Ploidy level variation within species is also common in Kaempferia: for example, K. angustifolia Roscoe (2n = 22 and 33); K. elegans (2n = 22, 33 and 44); and K. galanga (2n = 22, 44 and 55) (Nopporncharoenkul et al, 2017).…”