Microsatellite and AFLP markers in an artichoke world collection.

Artichoke, Cynara cardunculus L. var. scolymus (L.) Fiori is a diploid outcrossing species, originated in the Mediterranean basin, which has been much appreciated both for its tasting heads and pharmaceutical properties since ancient times. In order to assess genetic variation and relationships among artichoke varieties and between these and their wild relatives, microsatellite (SSR) and AFLP markers were developed. Microsatellite sequences were isolated from a genomic library produced from "Locale di Mola" cultivar. Hundreds of recombinant phages were screened by using oligonucleotides containing SSR sequences labelled with digoxygenin. Some positive clones were obtained with (CAT)8 and (GATA)5 probes. The nucleotide sequence of the insert was determined and the repetitive stretches of di- and tri- nucleotides were identified. Primers specific to SSR flanking regions were designed and and used for DNA amplification. The expected fragments, comprised between 150 and 300 bp, were separated, purified and sequenced. A selected group of wild and cultivated artichoke accessions belonging to different clusters detected on a morphological basis and from various geographical origins was chosen to amplify the isolated microsatellite regions and ascertain length variation. Twenty-four primer combinations for AFLP were used to evaluate their ability to detect polymorphism between samples. Six primer combinations were chosen for further analysis on 38 cultivated and wild artichoke accessions. A high level of polymorphism was observed especially for AFLP markers. The polymorphic bands obtained from AFLP and microsatellite analyses were scored and used to assess genetic similarity between wild and cultivated accessions and finally to construct a UPGMA dendrogram based on Jaccard's similarity index. The dendrogram obtained generally grouped the accessions on the basis of the morphological characteristics of their capitula. The artichoke wild progenitor was quite distantly related to the cultigen and occupied a separated branch in the dendrogram. The usefulness of these markers to distinguish artichoke varieties is discussed.