Elucidation of the Origin of the Monumental Olive Tree of Vouves in Crete, Greece.

Aureliano Bombarely,Evi Margaritis,Katerina K. Lambrou,Georgios Koubouris,Christos Zioutis,Andreas G. Doulis

doi:10.3390/plants10112374

Abstract

The olive tree of Vouves in Crete, is considered the oldest producing olive tree in the world with an estimated age exceeding 4000 years. In the present study, we sequenced two samples (from the bottom and the top of the tree) to elucidate the genetic relation of this ancient tree with other olive cvs as well as to gain some insights about its origin. Our results showed that both samples have different genetic origins, proving that this ancient tree has been grafted at least one time. On the basis of whole genome sequences the sample from the top of the Vouves tree showed relation of the same order than half-siblings to one accession corresponding to the present-day Greek cv ‘Mastoidis’. Nevertheless, in the framework of a microsatellite analysis it was found to cluster with the ‘Mastoidis’ samples. The Vouves rootstock (bottom sample) showed a clear grouping with the oleaster samples in a similar way to that of ‘Megaritiki’ Greek cv although it does not show any signal of introgression from them. The genomic analyses did not show a strong relation of this sample with the present-day Greek cvs analyzed in this study so it cannot be proved that it has been used as a source for cultivated olive tree populations represented by available genome sequences. Nevertheless, on the basis of microsatellite analyses, the Vouves rootstock showed affinity with two present-day Greek cvs, one “ancient” rootstock from continental Greece as well as monumental trees from Cyprus. The analysis of the impact of the variants in the gene space revealed an enrichment of genes associated to pathways related with carbohydrate and amino acid metabolism. This is in agreement with what has been found before in the sweep regions related with the process of domestication. The absence of oleaster gene flow, its old age and its variant profile, similar to other cultivated populations, makes it an excellent reference point for domestication studies.

Highlights

Olive (Olea europaea subsp. europaea) is the dominant tree crop in the Mediterranean countries
The top of the Vouves tree sample has an Ajk statistics value of 0.53 with the ‘Mastoidis’ accession indicating a relation of the same order than half-siblings, and verifying that the Vouves tree was grafted with a present-day cv
Greek cvs whose genomes were available for inclusion in the present study (Table 1; ‘Kalamon’, ‘Koroneiki’, ‘Mastoidis’, ‘Mavreya’, ‘Megaritiki’, ‘Myrtolia’) didn’t show any high Ajk values with the Vouves bottom sample so it cannot be documented that the original monumental tree has a special role in the development of these present-day Greek varieties

Summary

Introduction

Olive (Olea europaea subsp. europaea) is the dominant tree crop in the Mediterranean countries. Europaea) is the dominant tree crop in the Mediterranean countries. Over the 90% of the global olive production is realized in this region [1]. The products of this emblematic crop, namely olive oil and table olives are popular in the framework of a healthy lifestyle [2,3]. Even in parts of the world far from its traditional cultivation area, such as Eastern Asia, Australia and America, there is a strong interest in growing olive trees and consuming its nutritional and rich in biological value products. It is common belief that the wild olive Olea europaea var. Sylvestris is the ancestor of the cultivated olive Olea europaea var. Wild olive trees still survive in some Mediterranean forests [11]

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