Relationships among artichoke cultivars and some related wild taxa based on AFLP markers

Abstract

AbstractArtichoke,Cynara cardunculusvar.scolymusis a diploid outcrossing species, originated in the Mediterranean basin, which has been much appreciated both for its tasty heads and pharmaceutical properties since ancient times. The species includes two more botanical varieties:C. cardunculusvar.altilis, the cultivated leafy cardoon andC. cardunculusvar.sylvestris, the presumed wild progenitor of artichoke, which are completely interfertile with the cultivated globe artichoke and all together they form the primary gene pool of artichoke. The secondary gene pool includes at least seven wildCynaraspecies. A high level of morphological variation, essentially in head shape and size, is observed in artichoke varieties. Amplified fragment length polymorphism (AFLP) markers were used in order to assess genetic variation and relationships among artichoke varieties and between these and some of their wild relatives. 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 for the analysis. Twenty-four primer combinations were initially tested to evaluate their ability to detect polymorphism between samples. Nine primer combinations were chosen for further analysis on 39 cultivated artichokes, two wild progenitors, one cultivated cardoon, one sample ofC. cornigera, one ofC. humilisand two samples ofC. syriaca. A high level of polymorphism was observed for AFLP markers. The polymorphic bands obtained were scored and used to assess genetic similarity among wild and cultivated accessions and finally to construct a UPGMA dendrogram and principal co-ordinate (PCO) analysis based on Jaccard's similarity index. The artichoke wild progenitor was quite distantly related to the cultigen and occupied a separate branch in the dendrogram. However, wildC. cardunculuswas more similar to the artichoke than were the other wild species, corroborating the idea that it is the wild progenitor of cultivated artichokes. Within the cultivated artichoke, the dendrogram derived from AFLP analysis produced branches which roughly corresponded to the groups obtained on the basis of morphological and physiological characteristics. The groups were homogeneous enough, except for the ‘Romaneschi’ types, which proved to be quite genetically variable, and did not cluster in a single branch. This is interpreted on the grounds of the possible selection pathway of this more modern morpho-group.