Genetic diversity and accession structure in European Cynara cardunculus collections

Understanding the distribution of genetic variations and accession structures is an important factor for managing genetic resources, but also for using proper germplasm in association map analyses and breeding programs. The globe artichoke is the fourth most important horticultural crop in Europe. Here, we report the results of a molecular analysis of a collection including globe artichoke and leafy cardoon germplasm present in the Italian, French and Spanish gene banks. The aims of this study were to: (i) assess the diversity present in European collections, (ii) determine the population structure, (iii) measure the genetic distance between accessions; (iv) cluster the accessions; (v) properly distinguish accessions present in the different national collections carrying the same name; and (vi) understand the diversity distribution in relation to the gene bank and the geographic origin of the germplasm. A total of 556 individuals grouped into 174 accessions of distinct typologies were analyzed by different types of molecular markers, i.e. dominant (ISSR and AFLP) and co-dominant (SSR). The data of the two crops (globe artichoke and leafy cardoon) were analyzed jointly and separately to compute, among other aims, the gene diversity, heterozygosity (He, Ho), fixation indexes, AMOVA, genetic distance and structure. The findings underline the huge diversity present in the analyzed material, and the existence of alleles that are able to discriminate among accessions. The accessions were clustered not only on the basis of their typology, but also on the basis of the gene bank they come from. Probably, the environmental conditions of the different field gene banks affected germplasm conservation. These outcomes will be useful in plant breeding to select accessions and to fingerprint varieties. Moreover, the results highlight the particular attention that should be paid to the method used to conserve the Cynara cardunculus germplasm and suggest to the preference of using accessions from different gene banks to run an association map.