The genus Cynara L., Asteraceae, Cardueae, is distributed mainly in the Mediterranean region and includes eight species: C. cardunculus, C. syriaca, C. auranitica, C. cornigera, C. algarbiensis, C. baetica, C. cyrenaica, and C. humilis. The cultivated artichoke and the cultivated leafy cardoon are two varieties included in the species Cynara cardunculus, also containing the wild variety C. cardunculus var. sylvestris, which is fully interfertile with the cultivated types and is therefore considered the direct progenitor of the cultigroup. The phyletic relationships among the species of this genus are still not completely understood, although examined by various authors using different approaches. Moreover, the domestication of the two crops is still largely indefinite. In plants, the 18S-5.8S-25S rDNA locus has frequently been used for molecular systematic studies. The mature rRNA-coding regions of the gene are quite conserved in the evolution; on the contrary, the two internal transcribed spacers (ITS1 and ITS2) evolve more rapidly so that they are well fit for comparison of closely related taxa. To this end, also a portion of the external transcribed spacer (ETS), a part of the Intergenic Spacer immediately upstream of the 18S rDNA sequence, has been largely employed. In order to contribute to a better understanding of the phylogeny of the genus Cynara as a whole and in particular of the origin of the two cultivated forms, a study of the nucleotide sequence divergence of ITS1, ITS2 and part of the ETS was undertaken. Genomic DNA from the three varieties of C. cardunculus, from C. syriaca, C. cornigera, C. baetica, and C. humilis was amplified by means of PCR using appropriate primer pairs. The amplicons were cloned and ten clones per sample subjected to automated sequencing. The sequences so obtained were aligned using CLUSTAL and analysed for phylogenetic divergence. The results clearly indicate that the C. cardunculus group is more evolved with respect to the other wild species of Cynara. Nevertheless, some relationships remain unclear; the presence of specific autapomorphisms in the cultivated artichoke suggests an influence of the domestication process on its evolutionary history.
Variable rDNA regions provide suggestions on artichoke domestication and evolutionary history
Sonnante G;Carluccio AV;Pignone D
2006
Abstract
The genus Cynara L., Asteraceae, Cardueae, is distributed mainly in the Mediterranean region and includes eight species: C. cardunculus, C. syriaca, C. auranitica, C. cornigera, C. algarbiensis, C. baetica, C. cyrenaica, and C. humilis. The cultivated artichoke and the cultivated leafy cardoon are two varieties included in the species Cynara cardunculus, also containing the wild variety C. cardunculus var. sylvestris, which is fully interfertile with the cultivated types and is therefore considered the direct progenitor of the cultigroup. The phyletic relationships among the species of this genus are still not completely understood, although examined by various authors using different approaches. Moreover, the domestication of the two crops is still largely indefinite. In plants, the 18S-5.8S-25S rDNA locus has frequently been used for molecular systematic studies. The mature rRNA-coding regions of the gene are quite conserved in the evolution; on the contrary, the two internal transcribed spacers (ITS1 and ITS2) evolve more rapidly so that they are well fit for comparison of closely related taxa. To this end, also a portion of the external transcribed spacer (ETS), a part of the Intergenic Spacer immediately upstream of the 18S rDNA sequence, has been largely employed. In order to contribute to a better understanding of the phylogeny of the genus Cynara as a whole and in particular of the origin of the two cultivated forms, a study of the nucleotide sequence divergence of ITS1, ITS2 and part of the ETS was undertaken. Genomic DNA from the three varieties of C. cardunculus, from C. syriaca, C. cornigera, C. baetica, and C. humilis was amplified by means of PCR using appropriate primer pairs. The amplicons were cloned and ten clones per sample subjected to automated sequencing. The sequences so obtained were aligned using CLUSTAL and analysed for phylogenetic divergence. The results clearly indicate that the C. cardunculus group is more evolved with respect to the other wild species of Cynara. Nevertheless, some relationships remain unclear; the presence of specific autapomorphisms in the cultivated artichoke suggests an influence of the domestication process on its evolutionary history.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
