Agronomic and molecular analyses for the characterisation of accessions in Tunisian olive germplasm collections

Electronic Journal of Biotechnology ISSN: 0717-3458 © 2006 by Pontificia Universidad Católica de Valparaíso -- Chile Vol.9 No.5, Issue of October 15, 2006 Received April 5, 2006 / Accepted May 23, 2006 RESEARCH ARTICLE DOI: 10.2225/vol9-issue5-fulltext-12 Agronomic and molecular analyses for the characterisation of accessions in Tunisian olive germplasm collections Wael Taamalli Laboratoire Caractérisation et Qualité de l’Huile d’Olive Centre de Biotechnologie Technopole de Borj Cedria BP 901, 2050, Hammam-Lif, Tunisia Tel: 216 71 855430 Fax: 216 71 855934 E-mail: Filippo Geuna Dipartimento di Produzione Vegetale Università degli Studi di Milano Via Celoria 2, 20133, Milano, Italy Tel: 39 02 50316550 Fax: 39 02 50316553 E-mail: Riccardo Banfi Dipartimento di Produzione Vegetale Università degli Studi di Milano Via Celoria 2, 20133, Milano, Italy Tel: 39 02 50316550 Fax: 39 02 50316553 E-mail: Daniele Bassi Dipartimento di Produzione Vegetale Università degli Studi di Milano Via Celoria 2, 20133, Milano, Italy Tel: 39 02 50316550 Fax: 39 02 50316553 E-mail: Douja Daoud Laboratoire Caractérisation et Qualité de l’Huile d’Olive Centre de Biotechnologie Technopole de Borj Cedria BP 901, 2050, Hammam-Lif, Tunisia Tel: 216 71 855430 Fax: 216 71 855934 E-mail: Mokhtar Zarrouk* Laboratoire Caractérisation et Qualité de l’Huile d’Olive Centre de Biotechnologie Technopole de Borj Cedria BP 901, 2050, Hammam-Lif, Tunisia Tel: 216 71 855430 Fax: 216 71 855934 E-mail: Financial support: The present work has been done in the framework of a research programme (2002-2005) funded by the Tunisian Ministry of Science Research, Technology and Competency Development. Keywords: agronomic traits, AFLP, Olea europaea, SSR. Abbreviations: AFLP: amplified fragment length polymorphisms ISSR: intermicrosatellites PCA: perform principal component PCoA: principal coordinates analysis SSR: microsatellites UPGMA: unweighted pair group method based on arithmetic averages *Corresponding author This paper is available on line at http://www.ejbiotechnology.info/content/vol9/issue5/full/12/ Taamalli, W. et al. In this study, a total of 14 agronomic traits, five AFLP primer combinations and ten SSR loci were used to describe and to classify a group of Tunisian olive genotypes into groups based on molecular profiles and agronomic traits. The analysis of variance of the agronomical data revealed significant differences among accessions for all measured traits. The mean phenotypic dissimilarity (0.34 with a range of 0.08-0.6) was low in comparison to dissimilarity calculated using AFLP (0.50 with a range of 0.16-0.70) and SSR markers (0.76 with a range 0.35-0.94). The correlation between the agronomical dissimilarity matrix and the matrices of genetic dissimilarity based on SSR and AFLP markers was very weak: 0.156 (p = 0.05) and 0.185 (p = 0.05), respectively. The SSR-AFLP dendrogram based on unweighted pair-group cluster analysis using Jaccard’s index revealed that the genetic diversity was predominantly structured according to fruit size. A trend of clustering together of accessions originating from the same or adjacent regions was also observed. The data obtained can be used for the varietal survey and construction of a database of all olive varieties grown in Tunisia and providing also additional information that could form the basis for the rational design of breeding programs. The olive tree (Olea europaea L.) is a subtropical species typical of the Mediterranean basin where it represents the most important oil-producing crop. It is a diploid, out crossing species with a very wide genetic patrimony. Since the beginning of its domestication, olive has been propagated vegetatively to exploit the best combination of genes which arose by random crosses or mutations (Carriero et al. 2002). As a result, a great number of varieties are present in all the countries where this species is cultivated, raising several problems for germplasm management and preservation (Carriero et al. 2002). Evaluation and characterisation of olive genetic resources is therefore crucial, since identification of olive cultivars is complicated by the large number of varietal synonyms and homonyms, the intensive exchange of plant material, the presence of varietal clones, and problems of varietal certification in nurseries (Bandelj et al. 2002). Morphological and biological characters have been widely used for descriptive purposes and are commonly used to distinguish olive cultivars (Cantini et al. 1999). Agronomic characterization also allowed the classification of different olive cultivars (Barranco and Rallo, 2000). In order to supplement and refine the initial phenotypical based descriptions, different genetic markers such as randomly amplified polymorphic DNA (RAPD) markers (Fabbri et al. 1995; Wiesman et al. 1998; Belaj et al. 2001; Besnard et al. 2001b; Sanz-Cortés et al. 2001; Nikoloudakis et al. 2003), amplified fragment length polymorphisms (AFLP) (Angiolillo et al. 1999; Rotondi et al. 2003; Sanz-Cortés et al. 2003; Sensi et al. 2003), microsatellites (SSR) (Carriero et al. 2002; Cipriani et al. 2002) and intermicrosatellites (ISSR) (Hess et al. 2000) have been applied to identify and characterize different cultivars or genotypes and in order to provide information on olive origin and dispersal. Tunisia occupies the fourth place on world scale in terms of olive oil production. Tunisian olive plantations count about 63 million trees covering 1.6 million of hectares and estimated to include more than 50 cultivars. Despite this economic importance, little is known about the olive germplasm of this country and about the genetic relationships among them. In fact Tunisian olive tree is dominated by the variety-population ‘Chemlali’ that occupies more than 2/3 of the total olive growing area. It is a cultivar for oil production, well adapted to arid and semiarid zones but its oil shows physico-chemical drawbacks (high saturated-fatty acids content, notably the palmitic acid, a high level of linoleic acid and a low level of oleic acid). Whereas a wide range of minor cultivars are cultivated around their presumed areas of origin and have a limited diffusion outside these areas. The study of these less-common cultivars appears of particular interest because they may have agronomic characteristics which can be relevant to olive growers. The objectives of this paper are: to describe relationships among Tunisian olive cultivars using agronomic and molecular markers, to assess the correlation between distance estimates based on agronomic characterisation and AFLP and SSR molecular markers, and to classify the cultivars into groups based on molecular profiles and agronomic traits. MATERIALS AND METHODS Plant material Agronomic and molecular analyses were performed on 26 olive (Olea europaea L.) accessions: 25 accessions belonging to 25 cultivars and one accession without denomination. These were obtained from four c (...truncated)