Micropropagation Effects on Juvenile Traits, Flower Differentiation, and Tree Architecture in Young Olive Trees

Davide Neri,Tonino Cioccolanti,Oriano Navacchi,Giuseppe Zuccherelli,Veronica Giorgi,Enrico Maria Lodolini

doi:10.3390/agronomy10111742

Davide Neri, Tonino Cioccolanti + Show 4 more

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https://doi.org/10.3390/agronomy10111742

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Abstract

Olive micropropagation is nowadays possible but knowing if it induces juvenile traits and how juvenility, vigor and fruit productivity are affected is pivotal. Three trials were carried out during micropropagation and afterwards in the field. Three varieties were characterized during multiplication in vitro, after several subcultures. ‘Arbequina’ revealed higher shoot miniaturization than ‘Coratina’ and ‘Frantoio’, and likely-juvenile shoots with three or four leaves per node. The ‘Arbequina’ trees obtained from two- and three-leaves-per-node in vitro plantlets were compared to cuttings in the field. Two years after planting, flower-differentiated shoots were found in the apical part of the canopy in all tested trees while in this position the ramification was more intense on three-leaves-per-node trees. Architecture of ‘Arbequina’ trees from micropropagation and cuttings was finally characterized in a high-density commercial grove. Micropropagated trees showed a well distributed and deep root system, a regular conical shape of the canopy, a higher number of primary branches, and a reproductive ability equivalent to cuttings. In conclusion, some juvenile traits and vigor may appear in vitro and last after ex vitro acclimation, but no more than two years in the field.

Highlights

Micropropagated plants delay the onset of flowering capacity by only one year. These results showed that the micropropagated trees did not regress to the juvenile stage, but only to a higher level of vigor that ensures a very rapid growth in the post-implant phase with times of onset into production, comparable to those propagated with cuttings
Micropropagated trees recovered from this growth delay in the following year (2011), reaching a plant height of about 2.8 m. We concede that this might be attributable to a superior vigor of the trees from micropropagation, when compared to those from cuttings
No statistically significant differences were found between micropropagated trees and cuttings regarding the longitudinal and transversal diameters of the canopy in 2010 and 2011, as both types of trees had already exceeded their fixed limits

Summary

Introduction

Olive (Olea europaea L.) is one of the oldest and most important fruit tree species cultivated in the Mediterranean region. Olive production according to FAO [2] is classified as follows; world 20.9 Mt, EU 12.9 Mt of which, Spain 6.5 Mt, Greece 2.7 Mt, Italy 2.6 Mt, and Portugal 0.8 Mt. traditional olive groves are becoming less competitive in Europe due to the lack of mechanization matched by a high demand for intensive labor. Traditional olive groves are becoming less competitive in Europe due to the lack of mechanization matched by a high demand for intensive labor For these reasons, in the four leading EU countries, Spain, Italy, Greece, and Portugal, olives have been planted as high-density hedgerow systems ( known as super-high-density orchards, SHDO) since the early

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