Genetic Resources of Olea europaea L. in the Garda Trentino Olive Groves Revealed by Ancient Trees Genotyping and Parentage Analysis of Drupe Embryos

Abstract

The area of the Garda Lake within the Trentino province (north of Italy) is the northernmost part of Europe where the Mediterranean species Olea europaea L. is traditionally cultivated. ‘Casaliva’ is claimed as the main variety traditionally grown in the Garda Trentino area (GT) from which a world renowned niche extra virgin olive oil is produced. Since a dominant presence of ‘Casaliva’ would link the fruit set success and yield to a self-pollination compatibility system, a deep genetic survey of the olive tree population in the GT has been performed with the aim of establishing the actual varietal composition and of understanding from which pollen donor the ‘Casaliva’ olives originate. Forty-four different genetic profiles were observed among the 205 leaf samples collected from 106 ancient trees through the analysis of 20 nuclear microsatellite markers. The varietal composition in modern orchards was also explored and the vast majority of the additional 151 trees analyzed showed the same genotype as the ancient accessions of ‘Casaliva’. The results support the long historical link of ‘Casaliva’ with the GT and, besides a high varietal homogeneity, they also revealed the presence of olive genetic resources essential to fruit production. In fact, the parentage analysis of 550 embryos from drupes of ‘Casaliva’ evidenced that a cross-fertilization system is favored and a list of candidate cultivars most suitable as local pollinizers of ‘Casaliva’ was identified.

Diallelic self‐incompatibility is the main determinant of fertilization patterns in olive orchards

“…A phenomenon, generally thought to be a consequence of environmental factors interfering with the SI reaction or to result from the action of modifier genes (Busch & Schoen, 2008;Levin, 1996), is reported as 'leaky' SI. As already discussed in Saumitou-Laprade, Vernet, Vekemans, Billiard, et al (2017), it is observed in some olive cultivars like Koroneiki (Marchese et al, 2016) and Casaliva a homonym of Frantoio (Moreno-Sanz et al, 2020). These cultivars belong to a SI group (Table S1) and present a low rate of selfing.…”

Utility of EST-SNP Markers for Improving Management and Use of Olive Genetic Resources: A Case Study at the Worldwide Olive Germplasm Bank of Córdoba

“…In agreement with previous morphological [ 5 , 6 ] and molecular [ 3 , 6 , 16 ] studies, our results revealed that the redundant genotypes corresponded mainly to synonymy cases. In addition, most of them included cultivars from the same country, followed by pairs or groups of cultivars from close neighbouring countries, as previously reported [ 3 , 33 , 34 ]. However, although to a less extent, synonymy cases between cultivars from distant Mediterranean olive growing countries, as well as in the New World, have also been observed [ 6 ].…”

The Monumental Olive Trees as Biocultural Heritage of Mediterranean Landscapes: The Case Study of Sicily

“…Traditional olive groves with monumental specimens host a high number of varieties. The importance of this latter genetic resource and the potential it holds for agriculture is also a common element in other European and Mediterranean contexts, as shown by the recent studies on centenary olive trees conducted in several Mediterranean countries [50][51][52][53][54][55]. The cataloging, characterization, and in situ conservation of secular olive trees is, in fact, a priority to safeguard their genetic, natural, and agricultural value and to protect ancient genotypes threatened with extinction [56,57].…”