Karyotype analysis and DNA content in some species of Chrysolaena (Vernonieae, Asteraceae)

Abstract

Cytogenetic characterization by karyotyping and determination of DNA content by flow cytometry of five species of Chrysolaena (Vernonieae, Asteraceae) was performed. This is the first study of nuclear DNA content realized in the genus. The 2C-values were compared with the ploidy level and the total karyotype length (TKL) of each species. Mitotic analysis revealed a base chromosome number x = 10 for all entities and different ploidy levels, from diploid (2n = 2x = 20) to octoploid (2n = 8x = 80). All species showed bimodal karyotypes composed of metacentric and submetacentric chromosomes. The average chromosome size (ML) varied from 1.86 μm to 2.70 μm, while the TKL ranged from 18.65 μm to 80.55 μm. The intrachromosomal asymmetry index (A₁) varied from 0.27 to 0.38, while the interchromosomal asymmetry index (A₂) ranged from 0.19 to 0.25. A new cytotype is reported for the first time for C. propinqua. Accessory chromosomes found in C. verbascifolia, C. cognata, C. flexuosa, and C. propinqua are also reported as new.

Keywords::

• Chromosomes
• Compositae
• flow cytometry
• Vernonia

Acknowledgements

The authors wish to thank Eduard Schilling from the University of Tennessee (USA) for the language review and helpful suggestions and comments on the manuscript. This work has been supported by grants from the Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) and the Secretaría General de Ciencia y Técnica of the Universidad Nacional del Nordeste, which are greatly appreciated.