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- Title
Comparative cytogenetic study on Trifolium subterraneum (2 n = 16) and Trifolium israeliticum (2 n = 12).
- Authors
Falistocco, Egizia; Marconi, Gianpiero; Falcinelli, Mario; Scoles, G.J.
- Abstract
Changes in chromosome number have played an important role in the evolution of the genus Trifolium. Along with a few species of polyploid origin there are several cases of dysploidy as evidenced by the presence of four basic chromosome numbers ( x = 8, 7, 6, 5). Trifolium subterraneum and Trifolium israeliticum are related species with chromosome complements 2 n = 16 and 2 n = 12, respectively. Although they represent an interesting case of speciation based on chromosome number reduction, no attempts to demonstrate their cytogenetic affinity have been carried out to date. With this study we performed a comparative cytogenetic study with the purpose of clarifying the evolutionary relationship between these species and to verify whether genomic rearrangements, other than modification of the chromosome number, are associated with the speciation process. Although karyomorphological analysis supports the hypothesis that chromosome rearrangements had a role in the reduction of the chromosome number, the physical mapping of the rDNA sequences revealed a significant remodelling of the 45S and 5S rDNA sites that greatly contributed to the differentiation of the 2 n = 16 and 2 n = 12 karyotypes. The nucleotide analysis of 5S rDNA repeats confirmed that the two species are related but constitute distinct entities. The observed genomic changes lead to the hypothesis that the 2 n = 12 species is the result of an evolutionary pathway that passed through intermediate forms. It cannot be excluded that the most direct ancestor of T. israeliticum is a species with 2 n = 14.
- Subjects
CYTOGENETICS; GENETICS; CHROMOSOMES; POLYPLOIDY; KARYOTYPES; SUBTERRANEAN clover
- Publication
Genome, 2013, Vol 56, Issue 6, p307
- ISSN
0831-2796
- Publication type
Article
- DOI
10.1139/gen-2013-0055