Pollen-mediated gene flow and fine-scale spatial genetic structure inOlea europaeasubsp.europaeavar.sylvestris

Abstract

Background and Aims Wild olive (Olea europaea subsp. europaea var. sylvestris) is important from an economic and ecological point of view. The effects of anthropogenic activities may lead to the genetic erosion of its genetic patrimony, which has high value for breeding programmes. In particular, the consequences of the introgression from cultivated stands are strongly dependent on the extent of gene flow and therefore this work aims at quantitatively describing contemporary gene flow patterns in wild olive natural populations.Methods The studied wild population is located in an undisturbed forest, in southern Spain, considered one of the few extant hotspots of true oleaster diversity. A total of 225 potential father trees and seeds issued from five mother trees were genotyped by eight microsatellite markers. Levels of contemporary pollen flow, in terms of both pollen immigration rates and within-population dynamics, were measured through paternity analyses. Moreover, the extent of fine-scale spatial genetic structure (SGS) was studied to assess the relative importance of seed and pollen dispersal in shaping the spatial distribution of genetic variation.Key Results The results showed that the population under study is characterized by a high genetic diversity, a relatively high pollen immigration rate (0Á57), an average within-population pollen dispersal of about 107 m and weak but significant SGS up to 40 m. The population is a mosaic of several intermingled genetic clusters that is likely to be generated by spatially restricted seed dispersal. Moreover, wild oleasters were found to be selfincompatible and preferential mating between some genotypes was revealed.Conclusions Knowledge of the within-population genetic structure and gene flow dynamics will lead to identifying possible strategies aimed at limiting the effect of anthropogenic activities and improving breeding programmes for the conservation of olive tree forest genetic resources.

Paternity tests support a diallelic self‐incompatibility system in a wild olive (Olea europaea subsp. laperrinei, Oleaceae)

“…Long‐distance pollen dispersals have been reported in natural populations of olive trees (>3 km), but relatively high differences in mean pollination distance were observed between sites, depending, especially, on the topography or positioning of mature, compatible individuals (Beghè, Piotti, Satovic, de la Rosa, & Belaj, ; Besnard et al, ; Kassa, Konrad, & Geburek, ). In the specific conditions of our 1‐year experiment (i.e., blooming during early summer, with limited wind in a high‐density orchard), we observed a highly significant reduction of the pollination distance within the Laperrine's olive collection compared to a random process (3.29 vs. 5.85 m on average; Figure ), with ca.…”

“…Such mechanisms that affect gene flow are of great importance for the in situ conservation of endangered populations and for the management of ex situ collections. In the wild, crosses between compatible individuals can be indeed limited in fragmented and low‐density populations that may result in preferential mating between some genotypes (Beghè et al, ; Besnard et al, ; Kassa et al, ). In a nursery orchard that aims to produce seeds, the assemblage of individuals should be also carefully thought in order to avoid the production of high levels of inbreeded seedlings (as shown in the present study).…”

Recent developments in olive (Olea europaea L.) genetics and genomics: applications in taxonomy, varietal identification, traceability and breeding

“…Recently, Beghè et al (2017) used SSRs and paternity analysis to investigate the pollen flow, measuring pollen immigration rate and dispersal distance, and the spatial genetic structure in an endemic wild olive forest in Andalusia (southern Spain). The study was carried out to understand the mechanisms shaping the spatial distribution of genetic variation in Olea europaea subsp.…”

Genetic Identification of the Wild Form of Olive (Olea europaea var. sylvestris) Using Allele-Specific Real-Time PCR

“…Wild-type olive oil has higher antioxidant activity, as well as phenolic, tocopherolic and orthodiphenolic contents equal to or higher those in extra virgin cultivated olive oil [2]. Moreover, wild-type olive is a valuable natural resource due to its resistance to certain environmental and climatic conditions and diseases [3]. For the above reasons, its genetic characteristics have to be evaluated, and reliable molecular tools have to be developed for olive oil origin traceability (genetically and geographically) and wild-type olive oil identification.…”

“…This research led to the discovery that there was a large degree of diversity among olive cultivated trees, but that they were more or less related to the local oleasters [9,10]. Moreover, ISSR and SSR markers have been utilized by many researchers to investigate the relation and differentiation of cultivated olives from wild-type olives [3,[11][12][13][14][15][16]. Genome size estimation based on double-stranded DNA staining followed by flow cytometric analysis was also used for screening purposes between Olea europaea var Sylvestris and Olea europaea L. var Europaea species [17], while flow cytometry in combination with SSR profiles was used for the taxonomy of four olive subspecies, namely Olea europaea ssp.…”