Comparison of morphological, AFLP and SSR markers for the protection of eggplant germplasm.

Germplasm of local materials of vegetable crops can be protected in several ways, by registering it as a conservation variety, or also by means of a Protected Designation of Origin (PDO) or Protected Geographical Indication (PGI) status. An effective protection requires devising tools to characterize and distinguish the materials from other related or similar materials. Here, we study the utility of morphological and molecular characterizations for the protection of eggplant (Solanum melongena) germplasm. In this respect, we have made morphological and molecular (AFLP and SSR) characterizations in Spanish local materials of eggplant corresponding to three varietal groups with different characteristics: Almagro (protected by a PGI status), Listada de Gandía (internationally known striped local variety), and Spanish Black (conglomerate of different local varieties from different origins). Morphological data are useful to distinguish the local landraces from related materials. However, within each varietal group there is some morphological variation among the different germplasm accessions of each group, and also there is variation in the morphological characterization among trials performed in different years. The use of AFLP and SSR markers has confirmed the existence of genetic variation within each group. In this respect, SSRs are more reliable than AFLPs to distinguish closely related eggplant materials and have allowed detect specific universal SSR markers for the Almagro and Listada de Gandía landraces. Correlation coefficients between distances based on morphological, AFLP and SSR markers are moderate, reflecting the different genetic information provided by these three markers. The results show that morphological and molecular markers provide complementary information, and when used in combination can be very useful for the protection of local materials of eggplant. INTRODUCTION Germplasm enhancement can be achieved by using it as a source of variation in breeding programmes for developing new varieties, or by using it per se for obtaining high quality or speciality products with high added value. In this latter case, the germplasm used mainly corresponds to local varieties or landraces which are reputed for having a high organoleptic and/or nutritional quality, or that are associated with special production processes (Sequi et al., 2007; Muñoz-Falcón et al., 2009a). In this respect, for a satisfactory enhancement of the germplasm for this type of use, it is necessary to develop tools that allow the differentiation and protection of the plant material. In the European Union, protection of local varieties can be achieved through a conservation variety status (Commission of the European Communities, 2008), or in the case of agricultural products with specific characteristics associated to a high quality and originating from a certain geographical region by a Protected Designation of Origin (PDO) or a Protected Geographical Indication (PGI) (Commission of the European Communities, 2006a, b). The main difference between PDO and PGI is that in PDO the final product must be produced, processed and prepared in a certain geographical area using recognized knowledge, while in the PGI it is just required that at least one of the stages of production, processing or preparation has a link with a certain geographical area. Proc. V IS on Seed, Transplant and Stand Establishment of Hort. Crops Eds.: J.A. Pascual and F. Pérez-Alfocea Acta Hort. 898, ISHS 2011 124 On many occasions, the production of PDO or PGI products requires the use of local varieties with special characteristics that are essential for achieving a high quality. Morphological and molecular characterizations of the local varieties can be of great utility to develop tools that allow the protection of the germplasm. In this respect, we have worked with three different Spanish local materials of eggplant (Solanum melongena L.) that differ in their characteristics: Almagro, Listada de Gandía, and Spanish Black. The Almagro eggplant is the only eggplant officially protected in Europe with a PGI status, which was granted in 1994 (Castro, 2005). The Almagro eggplant is an heirloom landrace from the center of Spain used for making pickles. Almagro materials are characterized by having small fruits covered by an acrescent and prickly calyx (Muñoz-Falcón et al., 2009a). On occasion, pickling eggplants from the neighbouring region of Andalusia (Pickling Andalusian) are used instead of the Almagro landrace because of the higher yield and lower prickliness of the former. However, these Pickling Andalusian materials give a low quality product, as the internal texture of the processed pickled fruits is soft, and this is an undesirable characteristic for Almagro PGI eggplants (Prohens et al., 2007). The Listada de Gandía eggplant is another heirloom from the Mediterranean coast of the region of Valencia, and is native to the countryside around the city of Gandía, which is situated 70 km south of Valencia. Listada de Gandía fruits have obovate to oblong shape and white background colour covered by narrow purple stripes (MuñozFalcón et al., 2008). The Listada de Gandía is internationally known for its white flesh, excellent texture and cooking quality. Listada de Gandía eggplant materials might be candidates for being registered as a conservation variety or for being granted a PDO or PGI status. However, there are many striped varieties of eggplant, which on many occasions are being sold as Listada de Gandía and do not correspond to the authentic Listada de Gandía materials. The Spanish Black eggplants correspond to a group of local varieties with different origins and with different shapes and sizes, and which are characterized for having uniformly coloured black skin (Muñoz-Falcón et al., 2009b). This type of local eggplant with black skin is having an increased demand for several reasons, including the fact that consumers are used to this typ black colored type of eggplant, and that anthocyanins giving the black color are reported to present healthy properties (Noda et al., 2000). Protection of the group of Spanish Black eggplants as a whole with a PDO or PGI status does not seem realistic, as it includes many different types of eggplants from different origins. However, some of these local varieties could be granted a conservation variety status. Morphological characterizations allow descriptions of the phenotypic characteristics of the plant material and, currently, morphological traits constitute the tools used for the distinctness, uniformity and stability (DUS) tests required for protection of plant materials (UPOV, 2002). Despite their evident usefulness, morphological traits may be subject to environmental variation and require the cultivation of plants. In this respect, molecular markers represent an additional tool for protecting and characterizing the plant material. In this paper we present the results obtained with morphological and molecular (AFLPs and SSRs) characterizations of Almagro, Listada de Gandía and Spanish Black eggplants and the implications for the protection of local materials of this crop. MATERIALS AND METHODS Trials and Plant Material Three characterization trials were performed in open field cultivation during three consecutive years. Each of the characterization trials was focused on comparing morphological and molecular (AFLP and SSR) markers for the protection of Almagro, Listada de Gandía and Spanish Black eggplants. Each of these trials was labeled as ALM,