RAPD variation within and among populations of globe artichoke cultivar `Spinoso sardo' S. L ANTERI ANTERI 1 , I. DI DI L EO EO 2 , L. L EDDA EDDA 1 , M. G. M AMELI AMELI 1 and E. P ORTIS ORTIS 2 1 Dipartimento di Scienze Agronomiche e Genetica Vegetale Agraria, UniversitaÁ degli Studi di Sassari, via E. De Nicola, I±07100 Sassari, Italy. E-mail: lanteri@ssmain.uniss.it; 2 DI.VA.P.R.A. settore Genetica Agraria, UniversitaÁ degli Studi di Torino, via L. Da Vinci 44, I±10095 Grugliasco (Turin), Italy With 2 ®gures and 3 tables Received August 26, 2000/Accepted January 15, 2001 Communicated by M. Heun Abstract Globe artichoke is a vegetable native to the Mediterranean basin. Its commercial production is mainly based on perennial cultivation of vegetatively propagated clones, which are highly heterozygous and segregate widely when progeny-tested. The aim of this study was to measure genetic variation using random ampli®ed polymorphic DNA (RAPD) in ®ve populations of `Spinoso sardo', the most widely grown and economically important cultivar in Sardinia (Italy). Analysis of molecular variance (AMOVA AMOVA) gave highly signi®cant dierences between populations (28.1% of the total genetic diversity); substantial within-population variation was detected (71.8% of total genetic diversity). The RAPD results show the need to apply clonal selection to narrow the broad genetic variability within the cultivar and to address important questions on the most suitable strategies for germplasm preservation. Key words: Cynara scolymus Ð `Spinoso sardo' Ð genetic variability Ð RAPD Globe artichoke (Cynara cardunculus L. var. scoly- mus  Cynara scolymus L.), a perennial and predominantly cross-pollinated species (de Vos 1992, Wiklund 1992, PeÂcaut 1993), is native to the Mediterranean basin (Rottemberg and Zohary 1995). Cytogenetic as well as isozyme relationships between cultivated artichoke and wild relatives (Rottemberg and Zohary 1995) show that the wild cardoon C. cardunculus var. sylvestris is the ancestor of the cultivated artichoke. They are also cross-compatible and their F 1 hybrids are fully fertile. Italy is the richest source of variation for this species (Bianco 1990) and numerous distinct clonal cultivars, adapted to local environments and local tastes, are grown. By measuring cultivar divergence using multivariate analysis, Porceddu et al. (1976) and Vannella et al. (1981 1 ) identi®ed four dierent groups: (1) the `Spinosi' group, containing cultivars with long sharp spines on bracts and leaves, to which the cv. `Spinoso sardo' belongs; (2) the `Violetti' group, with medium-sized, violet-coloured heads; (3) the `Romaneschi' group, which contains cultivars with spherical or subspherical heads; and (4) the `Catanesi' group, with relatively small, elongated heads. Recently, cluster analysis based on discrimination of eight quantitative characters among 104 artichoke accessions (Elia and Miccolis 1996) has identi®ed ®ve large groups having similar characters and presumably similar genomes. Artichoke breeding is limited to a few studies on the inheritance of a few main characters (PeÂcaut 1993 2 , LoÂpez Anido et al. 1998 3 ). Breeding programmes have traditionally aimed at improving earliness, yield and quality based on interclonal hybridization (Miller 1975, Scarascia Mugnozza and Pacucci 1976, Tesi 1976) and intraclonal selection (Deidda 1967, Abbate and Noto 1981 4 ). Commercial production of artichoke is now mainly based on perennial cultivation of vegetatively propagated clones, which are usually highly heterozygous and segregate widely when progeny-tested (Foury 1969, PeÂcaut 1993). Seed-propagated cultivars are becoming popular in some parts of the world, but relatively few populations have been developed with commercially acceptable phenotypic uniformity (Basnizki and Zohary 1987, 1994). There is a lack of information available on the level of variation within artichoke cultivars and knowledge of the extent of random ampli®ed polymorphic DNA (RAPD) variation 5 in artichoke cultivars is extremely limited (Tivang et al. 1996). The aim of this study was to measure DNA variation among and within ®ve artichoke populations of `Spinoso sardo', the most widely grown and economically important cultivar in Sardinia (Italy). At present, `Spinoso sardo' is grown on about 74% of a total of 9890 ha planted with artichoke in Sardinia, with 21% of the cv. `Violet de Provence' and 5% of the cv. `Terom' (1996, Agrosarda, HTTP://www.agrosarda.it) 6 . Materials and Methods Plant materials: Thirty plants were randomly chosen within ®ve Sardinian populations of globe artichoke, C. scolymus L., in Valled- oria, Usini, Oristano, Samassi and Tratalias (Fig. 1), with diering soils and climate. The choice was also based on self-production of the propagating material by the farmers themselves; no exchange of material usually occurs among them. Primer selection, DNA extraction and ampli®cation: Each of the 30 randomly chosen plants, within each population, was evaluated for polymorphism using 30 RAPD (Welsh and McClelland 1990, Williams et al. 1990) primers (Operon Technologies, Alameda CA, USA). After an initial screening of 30 primers, 20 were selected on the clarity of polymorphic bands and are listed in Table 1. Approximately 0.15 g fresh tissue, obtained from young leaves, was ground in liquid nitrogen and transferred to 0.8 ml lysis buer (2% cetyltrimethylammonium bromide (CTAB), 0.1 M Tris-HCl pH 9, 20 mM ethylenediaminetetraacetic acid (EDTA), pH 8, 1.4 M NaCl). The mixture was incubated at 60°C for 90 min and thereafter mixed with an equal volume of chloroform±isoamyl alcohol (24 : 1) and then centrifuged at 16 000 g 7 for 15 min. The supernatant was transferred to a clean 1.5 ml microfuge tube and DNA was Plant Breeding 120, 243Ð246 (2001) ã 2001 Blackwell Wissenschafts-Verlag, Berlin ISSN 0179-9541 U. S. Copyright Clearance Center Code Statement: 0179±9541/2001/2003±0243 $ 15.00/0 www.blackwell.de/synergy