Comparative Karyotype Analysis and Chromosome Evolution in the Genus Ocimum L. from Thailand


  • Paweenuch Lekhapan Biological Sciences Program, Faculty of Science, Chulalongkorn University, Bangkok 10330, THAILAND
  • Kesara Anamthawat-Jónsson Institute of Life and Environmental Sciences, School of Engineering and Natural Science, University of Iceland, Reykjavik IS-102, ICELAND
  • Ploenpit Chokchaichamnankit Department of Botany, Faculty of Science, Chulalongkorn University, Bangkok 10330, THAILAND


basil, chromosomal rearrangement, diploidization, genome downsizing, karyotype asymmetry, polyploidy


Ocimum L. (Lamiaceae) is one of the best-known genera of aromatic herbs in the world for its economic and medicinal importance. Most species are polyploids, harboring a large variation in genome and chromosome compositions. This study reports the comparative karyotype analysis among O. americanum L. and four accessions each of O. basilicum L., O. africanum Lour., O. gratissimum L. and O. tenuiflorum L. from Thailand. We found chromosome numbers of O. americanum, O. basilicum, O. africanum, O. gratissimum and O. tenuiflorum to be 2n=26, 52, 78, 40 and 36, respectively. All these species have asymmetric karyotypes, but O. tenuiflorum exhibited higher level of asymmetry than the other species. Although the chromosome numbers of all the studied species were stable among accessions, differences were found in the karyotypic constitutions. Intra-specific variation in karyotype formulae and satellite chromosomes of O. basilicum and O. africanum suggest that chromosomal rearrangements are involved in the chromosome evolution of these karyotypically unstable species, indicating that they may be newly formed polyploids. On the other hand, the disproportionate rise between ploidy level and the total karyotype length in the derived and stable polyploids, O. gratissimum and O. tenuiflorum, points towards a process of diploidization via genome downsizing.


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How to Cite

Lekhapan, P. , Anamthawat-Jónsson, K. and Chokchaichamnankit, P. 2021. Comparative Karyotype Analysis and Chromosome Evolution in the Genus Ocimum L. from Thailand. Tropical Natural History. 21, 1 (Mar. 2021), 27–40.



Original Articles