The First Molecular Identification of an Olive Collection Applying Standard Simple Sequence Repeats and Novel Expressed Sequence Tag Markers

Abstract

Germplasm collections of tree crop species represent fundamental tools for conservation of diversity and key steps for its characterization and evaluation. For the olive tree, several collections were created all over the world, but only few of them have been fully characterized and molecularly identified. The olive collection of Perugia University (UNIPG), established in the years’ 60, represents one of the first attempts to gather and safeguard olive diversity, keeping together cultivars from different countries. In the present study, a set of 370 olive trees previously uncharacterized was screened with 10 standard simple sequence repeats (SSRs) and nine new EST-SSR markers, to correctly and thoroughly identify all genotypes, verify their representativeness of the entire cultivated olive variation, and validate the effectiveness of new markers in comparison to standard genotyping tools. The SSR analysis revealed the presence of 59 genotypes, corresponding to 72 well known cultivars, 13 of them resulting exclusively present in this collection. The new EST-SSRs have shown values of diversity parameters quite similar to those of best standard SSRs. When compared to hundreds of Mediterranean cultivars, the UNIPG olive accessions were splitted into the three main populations (East, Center and West Mediterranean), confirming that the collection has a good representativeness of the entire olive variability. Furthermore, Bayesian analysis, performed on the 59 genotypes of the collection by the use of both sets of markers, have demonstrated their splitting into four clusters, with a well balanced membership obtained by EST respect to standard SSRs. The new OLEST (Olea expressed sequence tags) SSR markers resulted as effective as the best standard markers. The information obtained from this study represents a high valuable tool for ex situ conservation and management of olive genetic resources, useful to build a common database from worldwide olive cultivar collections, also based on recently developed markers.

Reply to Saumitou‐Laprade et al. (2017) “Controlling for genetic identity of varieties, pollen contamination and stigma receptivity is essential to characterize the self‐incompatibility system of Olea europaea L.”. Eva:https://doi.org/10.1111/eva.12498

“…Moreover, morphological characterization, with or without molecular characterization, is at the basis of the controls for variety correspondence for the registration of primary sources in the certification process of plants produced by nurseries (for which the identity of the cultivar is essential) (Baldoni et al., ,b). In addition, the overall validity of using morphological characteristics to recognize cultivars is also demonstrated by the fact that the identity of the majority of varieties classified by examining morphological characteristics (Farinelli et al., , ) has also been confirmed by genetic characterization (Mousavi et al., ). This furtherly confirms that errors in identifying cultivars using morphological characterization only represent exceptions and not the rule.…”

The newly developed genomic-SSR markers uncover the genetic characteristics and relationships of olive accessions

“…There are plenty of olive germplasm, represented by a high number of cultivars and unknown accessions (Díez et al, 2015;Mousavi et al, 2017;Belaj et al, 2018;Sion et al, 2019). The rich diversity of this species is a consequence of its allogamous nature, a remarkable tree longevity, multiple domestication events such as crosses among cultivars and local selection, as well as a lack of turnover with new breeding genotypes (Díez et al, 2015;Belaj et al, 2016;Besnard, Terral & Cornille, 2018).…”

“…During the long-term cultivation of olive, wrong naming of cultivars such as homonymy or synonymy and mistakes in labeling and propagation of cultivars have often led to misleading classification and misinterpreting relationships among cultivars (Beghè et al, 2015;Mariotti et al, 2016). Furthermore, the high degree of kinship among many cultivars mainly in cases of geographic proximity and the possible appearance of clonal variation increase the difficulty of cultivar identification (Caruso, Marra & Costa, 2014;Ipek et al, 2015;Mousavi et al, 2017).…”

Biochemical and molecular profiling of unknown olive genotypes from central Italy: determination of major and minor components

“…The aim of this research was to perform a complete characterization of local olive types from different areas of Umbria, based on a multidisciplinary approach, including the molecular characterization by using best ranked SSRs (Simple Sequence Repeats), widely applied to determine their genetic identity [4,35,51] and evaluating fatty acid, phenol, sterol, tocopherol and pigment content and composition. The work provides a useful contribution towards the differentiation of local, traditional and typical olive oils, from the perspective of diversity conservation and large-scale plantations of the most promising genotypes.…”