Silva et al. 2015 (Conference Paper) Fosterella

Chromosomal features of Fosterella L. (Bromeliaceae, Pitcairnioideae) species

Author(s):—H. Silva, A.M. Benko-Iseppon, N. Wagner, D.S. Pinagé, R. Gonçalves-Oliveira, K. Weising & A.C. Vidal in Benko-Iseppon, A.M.; Alves, M. & Louzada, R. (2015) An overview and abstracts of the First World Congress on Bromeliaceae Evolution. Rodriguésia 66(2): A1-A66.

Publication:— (2015).

Abstract:—The genus Fosterella L. comprises 31 species of terrestrial herbs with leaves in rosettes and mostly small, whitish flowers. Previous karyological studies on the genus were restricted to chromosome counts of four taxa, including diploid (2n = 50) and polyploid (2n = 100, 150) individuals. Besides chromosome counts, the present work analyzed other karyomorphological markers, including fluorochrome staining (DAPI/CMA; Chromomycin A3/ 4,6-diamino-2-fenilindol) and Fluorescent In Situ Hybridization (FISH) using 45S and 5S rDNA probes, generating data on mitotic metaphase for eight taxa. The observed chromosome numbers 2n = 50, 100 and 150 were in accordance with literature data and also regarding the basic chromosome number x = 25. Staining CMA /DAPI enabled the identification of a chromosome pair with CMA+/DAPI- (GC-rich) band in all diploid (2n = 2x = 50) species in the terminal (F. christophii, F. micrantha, F. spectabilis and F. robertreadii), subterminal (F. rusbyi) or proximal (F. gracilis) position. Considering the tetraploid (2n = 4x = 100) species, in F. hatschbachii one chromosome pair exhibited a CMA+ proximal band, while F. yuvinkaepresented two pairs with proximal bands. For the polyploid F. hatschbachii (2n = 100), additional CMA+ bandswere expected, but a single pair was observed, indicating that this sequence was lost after polyploidization. Moreover, the presence of two CMA+/DAPI- in F. yuvinkae may indicate a recent polyploidization event. The application of in situ hybridization is unprecedented for Bromeliaceae. For F. robertreadii, F. spectabilis and F. christophii FISH using 45S rDNA probes revealed a colocalization of these sites with CMA+/
DAPI- bands. In addition, a pair of 5S rDNA proximal sites was found in a second chromosome pair for F.
spectabilis and F. christophii. Considering the data, it is evident that polyploidy plays an important role in the
evolution of this genus. In addition, the results indicate that all species are poor in heterochromatin, except
for NOR-associated sites that may vary in their position. Thus, the differences in sizes of the chromosomes
can be attributed to the variation of dispersed repetitive elements.

Keywords:—Fosterella; Chromosome Number; Polyploidy.