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

Paweenuch Lekhapan, Kesara Anamthawat-Jónsson, Ploenpit Chokchaichamnankit*

*Corresponding author for this work

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1 Citation (Scopus)


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.

Original languageEnglish
Pages (from-to)27-40
Number of pages14
JournalTropical Natural History
Issue number1
Publication statusPublished - 2021

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© 2021 by Chulalongkorn University

Other keywords

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


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