Genetic variability in wild vs. cultivated Eruca vesicaria populations as assessed by morphological, agronomical and molecular analyses Catalina Egea-Gilabert a, *, Juan A. Ferna ´ ndez b,c , Daniele Migliaro b , Juan J. Martı ´nez-Sa ´ nchez b,c , Marı ´a Jose ´ Vicente b a Ciencia y Tecnologı´a Agraria, E.T.S. Ingenierı´a Agrono ´mica, Universidad Polite ´cnica de Cartagena, C/Paseo Alfonso XIII 52, 30203 Cartagena, Spain b Produccio ´n Vegetal, E.T.S. Ingenierı´a Agrono ´mica, Universidad Polite ´cnica de Cartagena, C/Paseo Alfonso XIII 52, 30203 Cartagena, Spain c Unidad Asociada CSIC ‘‘Horticultura sostenible en zonas a ´ridas’’, (UPCT-CEBAS), C/Paseo Alfonso XIII 52, 30203 Cartagena, Spain 1. Introduction Rocket is a collective name to indicate many species within the Brassicaceae whose leaves are characterized by a more or less pungent taste. One of the rocket species in the Mediterranean Region is Eruca vesicaria (L.) Cav., which is sometimes cultivated, although its domestication cannot be considered complete (Go ´ mez-Campo and Prakash, 1999). Rocket is widely used in Europe and in other parts of the world as a special food or even a delicacy. The main use is for fresh consumption as a salad, although it is also considered as a medicinal plant with many reported properties, such as its depurative effect, vitamin C and iron contents (Kim and Ishii, 2007). Among its different production modalities, the baby leaf form (small leaves) has grown in popularity in recent years as a ready-to-eat vegetable. Its presentation is mainly as whole leaves, 8–12 cm long, with only a very small section exposed to oxidation, the petiole, thus increasing its postharvest life (Gonza ´lez et al., 2004). The floating system is one of the easiest and cheapest hydro- ponic methods used to produce baby-leaf vegetables. This system shortens the cultivation cycle compared with soil-based culture and is very interesting for growers because of its low installation and manpower costs; weeds are avoided and harvesting is straightforward. Plants can be grown in high densities and the resulting products (leaf vegetables) are clean and ready to be packed (Gonnella et al., 2004). This system offers good control of the nutrient solution, so that vegetables with a low nitrate content can be produced (Santamaria et al., 2001). This is important because rocket is one of the leafy vegetables that most accumulates nitrates (Santamaria et al., 1999), which it absorbs very quickly to such an extent that the nitrate concentration in leaves can be higher than in the nutrient solution itself (Santamaria, 2006). These days, the genetic characterization of phytogenetic resources is considered to be very important in order to identify the wild material with the aim of maintaining biodiversity and in Scientia Horticulturae 121 (2009) 260–266 ARTICLE INFO Article history: Received 3 December 2008 Received in revised form 23 February 2009 Accepted 25 February 2009 Keywords: Rocket ISSR markers Genetic diversity Agronomical traits Nitrate content ABSTRACT In this study, the genetic diversity of 50 individuals of rocket, Eruca vesicaria, from five accessions, four of them wild type collected from different parts of Spain and one commercial, were evaluated using morphological, agronomical and inter simple sequence repeat DNA (ISSR) data. Molecular analysis was carried out using the ISSR technique with 20 primers. Out of these 20 primers, nine were polymorphic, producing a total of 395 DNA bands, 247 of which were polymorphic among the accessions. A dendrogram drawn on the basis of a similarity matrix using the UPGMA algorithm revealed that the 50 samples of rocket plants could be classified into three major clusters at a Nei’s genetic distance of 0.36. The experiment shows that molecular markers such as ISSR are a good instrument for distinguishing and selecting rocket accessions to group different wild populations. In general, a high variation was observed for most of the 16 morphological and 6 agronomical traits showing significant differences. Some morphological traits such as leaf length, petiole length and lamina width explained 69.1% of the whole variation observed in the populations, and some agronomical traits such as leaf area, nitrate and chlorophyll contents accounted for 65.7%, but the clusters generated by means of agronomical and morphological variables were less evident than when ISSR markers used. Some accessions showed good qualities, such as small leaves, high chlorophyll content, late-flowering or low nitrate content. All these parameters, together with the high degree of genetic homogeneity found, could make the local accessions good candidates for a future breeding programme. ß 2009 Elsevier B.V. All rights reserved. * Corresponding author. Tel.: +34 968 32 55 20; fax: +34 968 32 54 33. E-mail address: catalina.egea@upct.es (C. Egea-Gilabert). Contents lists available at ScienceDirect Scientia Horticulturae journal homepage: www.elsevier.com/locate/scihorti 0304-4238/$ – see front matter ß 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.scienta.2009.02.020