Evaluation of early vigor traits in wild olive germplasm

Abstract

The control of the olive tree vigor is a critical factor to ensure adequate production and longevity of high-density olive cultivation. To deal with this problem, we intend to take advantage of the genetic variability present in the wild subspecies of Olea europaea to identify genotypes of reduced vigor with optimal adaptability to diverse soils and adverse environmental conditions. In this work, early vigor traits have been characterized in different wild olive subspecies that could potentially be used as rootstocks to control the vigor of grafted cultivars. Significant differences between genotypes were obtained for all vigor traits and high values of broad sense heritability were obtained for most of them, indicating strong genetic effect and therefore good possibilities for selection. Compared to 'Arbequina' and 'Picual' cultivars, some of the wild genotypes evaluated showed a Preprint submitted to Elsevier 2 clear lower vigor at the end of the experimental period. These genotypes could be tested as dwarfing rootstocks for high-density olive plantations.

SILVOLIVE, a Germplasm Collection of Wild Subspecies With High Genetic Variability as a Source of Rootstocks and Resistance Genes for Olive Breeding

“…Around 3.3 times variability was observed in the basal stem diameter of the wild olives collection. In general, genotypes with greater heights have thicker trunks, showing a positive correlation in potted plants (R 2 = 0.7581), as reported also in SILVOLIVE genotypes grown in the field (León et al, 2020). However, some varieties such as FRA1, AMS15, AMK26 and DHO6A, showed thicker primary stems despite having low vigor traits according to other morphological features.…”

“…However, genotypes with low vigor are frequently discarded in olive breeding programs because of their long juvenile period (De la Rosa et al, 2006). This wide variability of vigor features was also observed in wild olive genotypes from the SILVOLIVE collection grown in the field for a longer time (León et al, 2020). Thus, similarly to the phenotype observed in potted plants, AMK genotypes showed low vigor when grown in the field, supporting the fact that morphological features observed in young plants grown in pots, like vigor, are still observed in field-grown plants.…”

“…A higher genetic diversity is still observed in the wild genepool (Lumaret et al, 2004;Baldoni et al, 2009;Belaj et al, 2010;Besnard et al, 2013a;Chiappetta et al, 2017;Kassa et al, 2019). Wild olives therefore represent an important source of genes for crop improvement of resistance to abiotic stresses [e.g., salinity (Cantos et al, 2002), water deficit (Hernández-Santana et al, 2019), soil pollution (Murillo et al, 2005)], vigor (León et al, 2020), crop yield and quality (Hannachi et al, 2008;Baccouri et al, 2011;León et al, 2018), as well as for resistance to biotic factors such as the Verticillium wilt (Colella et al, 2008;Arias-Calderon et al, 2015b;Trapero et al, 2015;Jimenez-Fernandez et al, 2016). Wild olive genotypes have been tested in limited breeding studies, showing potential to shorten the juvenile period or to increase flower production (Klepo et al, 2014), to improve oil composition (Hannachi et al, 2008;León et al, 2018) and to improve resistance to soil-borne diseases (Arias-Calderon et al, 2015a).…”

“…Some studies indicate that certain olive cultivars used as rootstocks can regulate vigor traits like the canopy volume, stem section and production of the grafted scion (Baldoni and Fontanazza, 1990;Pannelli et al, 2002;Del Río and Caballero, 2006;Tous et al, 2012;Romero et al, 2014;Rugini et al, 2016). The use of wild genotypes to control the vigor of the grafted cultivar is also a matter of great interest (León et al, 2020), but no rootstocks of proven quality are currently available at either commercial or experimental levels.…”

Morphological, Molecular and Genomic Characterization of Two Inter-Subspecific Hybrids between Olive Cultivars and Olive Subspecies

“…cuspidata) have also been identified as a possible source of tolerance to abiotic stress [11][12][13]. A wide genetic diversity has been reported for wild olives, which could be particularly interesting for the introgression of some agronomic traits and resistance to biotic and abiotic stresses in breeding programs [14][15][16][17][18]. Crossbreeding between olive cultivars and wild olive with specific characters might represent a useful strategy to exploit the enormous gene pool represented by the wild olive and olive subspecies for plantations in traditional and new olive-growing countries [9,15,[19][20][21][22].…”