Abstract
Several olive cultivars, characterized by high-quality olive oil show agronomical issues such as excessive vigor, high susceptibility to biotic and abiotic stresses, and low propagation ability. They are strong candidates for breeding based on new technologies to improve their performance in a short period of time. For this reason, the first step is developing efficient somatic embryogenesis (SE) protocols. Somatic embryogenesis in olive is highly genotype-dependent for both adult tissues and mature embryos as initial explants, requiring the development of specific protocols for each genotype. Trials using cotyledons and radicles as initial explants, isolated from ripe seeds from the Portuguese olive cv. ‘Galega vulgar’, gave more than 95% calli development. Radicles proved to be the most responsive tissue for SE induction, with an average of 2 embryos per callus after callus transfer to expression medium, and 14 embryos per callus after subculture on the olive cyclic embryogenesis medium (ECO). Embryogenic competence could be recovered after several subcultures on ECO medium that maintained cyclic embryogenesis for an indeterminate period of time. Embryo conversion and plant acclimatization were also attained with high success rates. Media management for cyclic embryogenesis maintenance is of general importance for SE protocols in any olive genotype. Somatic embryogenesis was thus attained for the first time in embryo-derived explants of cv. ‘Galega vulgar’.
Highlights
Olive trees are one of the oldest and most economically relevant fruit trees and oilseed crops in the Mediterranean region, being most of the cultivars used for olive oil production [1]
There are currently more than 2000 olive cultivars and this genetic diversity is the main factor contributing to the olive oil singularity of each country and region [4,5]
Mature embryo structures were extracted from fruits collected from trees of the Portuguese olive cv
Summary
Olive trees are one of the oldest and most economically relevant fruit trees and oilseed crops in the Mediterranean region, being most of the cultivars used for olive oil production [1]. The first report is known from Capelo and co-authors [38], which demonstrated the possibility to use petioles/leaf tissues taken from plants established under greenhouse conditions (no juvenile or rejuvenated material), to induce SE response with efficient differentiation of somatic embryos. Narváez and co-authors [39] described a protocol focused on different olive wild genotypes differing in their response to defoliating Verticillium dahlia, in which was stated the use of shoot apex collected from in vitro plantlets as the most appropriated tissue to induce SE and further efficient embryos conversion. Results reported by Narváez and co-authors [39] emphasize this dependence, showing SE induction efficiency in two olive wild genotypes from the four initially considered, and embryos conversion from a single one. The present research reveals the establishment of an efficient protocol that will make available plant material to be used in genetic transformation and gene editing of olive varieties
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