Abstract
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.
Highlights
Cynara cardunculus is a diploid species with 2n = 2x = 34 belonging to the Asteraceae family
Globe artichoke germplasm can be classified according to different criteria, the most important of which are (i) the harvesting time and (ii) the head shape. (i) The first divides the globe artichoke into (a) autumn and spring or (b) only spring. (ii) The second criterion classifies the globe artichoke on the basis of the morphology of its commercial part, the immature flowers called “capitula” or “heads”
The accessions are divided according to the four typologies described in the introduction and identified by Porceddu et al [2]: Romanesco (225 individuals), Violet (34 individuals), Catanese (116 individuals) and Spiny (11 individuals), plus the accessions belonging to leafy cardoon (72 individuals)
Summary
A recent botanical classification grouped two vegetable crops and their wild progenitor, which were previously considered distinct species, under C. cardunculus. The three taxa within the species are: wild cardoon Scolymus (L.) Fiori), and cultivated or leafy cardoon In line with this classification, the updated CPVO/UPOV protocol (entered into force on 27.02.2013) to tests on distinctness, uniformity and stability, has become the same for both the globe artichoke and the leafy cardoon [1]. Globe artichoke germplasm can be classified according to different criteria, the most important of which are (i) the harvesting time and (ii) the head shape. Spiny and Catanese types are normally re-blooming typologies, while Violet and Romanesco varieties are usually harvested in spring
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