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

Abstract

Artichoke, Cynara cardunculus var. scolymus is 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. cardunculus var. altilis, the cultivated leafy cardoon and C. cardunculus var. 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 wild Cynara species. 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 of C. cornigera, one of C. humilis and two samples of C. 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, wild C. cardunculus was 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.

Genetic Diversity Assessment in European Cynara Collections

“…fragments present in only one accession) found by Crinò et al (2008) in 'Romanesco' clones is comparable to that observed by Lanteri et al (2004b) and Sonnante et al (2004Sonnante et al ( , 2007 in collections with all the global artichoke types. The predicted heterozygosity was different (0.37 versus 0.67) from that estimated in wild cardoon using SSR markers , probably because SSR loci are associated with a high number of detectable alleles, whereas AFLP and ISSR loci are dominant.…”

“…Studies based on variation of isozymes and molecular markers such as RAPDs and AFLPs (Rottenberg et al 1996;Sonnante et al 2002Sonnante et al , 2004Lanteri et al 2004a;) have confirmed that both crops evolved from the wild cardoon gene pool, thereby confirming that it is the progenitor of both cultivated types. AFLP marker studies have shown that all C. cardunculus samples share a high genetic similarity compared with the other Cynara wild species.…”

“…23.3). Sonnante et al (2004) considered the two cultivated forms to be the result of concurrent directional selection for distinct traits, and not disruptive selection.…”

On the origin of artichoke and cardoon from the Cynara gene pool as revealed by rDNA sequence variation

“…Hybridization experiments have shown that wild cardoon is fully interfertile with cultivated material and therefore it belongs to the primary genepool of artichoke and leafy cardoon (Basnizki and Zohary 1994;; this evidence together with other ones, such as isozymes, RAPDs, and AFLPs Sonnante et al 2002Sonnante et al , 2004, have suggested that the two crops have evolved from the wild cardoon genepool, which can therefore be considered their progenitor.…”

“…Among the other wild species recognised, C. syriaca was initially considered as a possible donor of genes to the cultivated artichoke (Zohary and Bazniski 1975), however some other evidences , including a recent analysis based on AFLP markers (Sonnante et al 2004) do not support this hypothesis.…”