Olive (Olea europaea L.) Genetic Transformation: Current Status and Future Prospects

Abstract

Olive (Olea europaea L.) is the most characteristic and important oil crop of the Mediterranean region. Traditional olive cultivation is based on few tens cultivars of ancient origin. To improve this crop, novel selections with higher tolerance to biotic and abiotic stress, adaptable to high-density planting systems and resilient to climate change are needed; however, breeding programs are hindered by the long juvenile period of this species and few improved genotypes have been released so far. Genetic transformation could be of great value, in the near future, to develop new varieties or rootstocks in a shorter time; in addition, it has currently become an essential tool for functional genomic studies. The recalcitrance of olive tissues to their in vitro manipulation has been the main bottleneck in the development of genetic transformation procedures in this species; however, some important traits such as fungal resistance, flowering or lipid composition have successfully been manipulated through the genetic transformation of somatic embryos of juvenile or adult origin, providing a proof of the potential role that this technology could have in olive improvement. However, the optimization of these protocols for explants of adult origin is a prerequisite to obtain useful materials for the olive industry. In this review, initially, factors affecting plant regeneration via somatic embryogenesis are discussed. Subsequently, the different transformation approaches explored in olive are reviewed. Finally, transgenic experiments with genes of interest undertaken to manipulate selected traits are discussed.

The Status of Genetic Resources and Olive Breeding in Tunisia

“…The information generated using SNP-based approaches may allow us to discover genes/alleles useful for enhancing target traits, while new advanced biotechnologies, such as transformation-based editing methods, allow us to transfer them to elite cultivars. Improvements in transformation and regeneration protocols in a recalcitrant species such as the olive are continually reported, and important traits such as resistance to fungi, flowering, or lipid composition, have already been successfully manipulated [96][97][98].…”

Efficient Transformation of Catalpa bungei Shows Crystal Genes Conferring Resistance to the Shoot Borer Omphisa plagialis

“…Types Were Involved in the Embryogenic Calli Protocol of Catalpa bungei Embryogenic calli induction and regeneration is a process that limits the establishment of efficient genetic transformation systems (Palomo-Rios et al, 2021). Genotype is considered the determinant factor in the success of this process in plant species because protocols suitable for one embryogenesis line or clones may not necessarily apply to others (Petri and Burgos, 2005).…”

“…Genotype is considered the determinant factor in the success of this process in plant species because protocols suitable for one embryogenesis line or clones may not necessarily apply to others (Petri and Burgos, 2005). Only one or two EC genotypes were developed in previous genetic transformation protocols of woody plants, such as Paulownia elongata (Bajaj et al, 2021), olive (Olea europaea L.) (Narvaez et al, 2019;Palomo-Rios et al, 2021), Cork oak (Quercus suber L.) (Alvarez et al, 2004;Cano et al, 2021), European chestnut (Corredoira et al, 2016), and tea (Camellia sinensis) (Mondal et al, 2001). In this study, we obtained five EC genotypes, including two types of EC initiated from mature seed explants and three types from stem segment explants, which indicated that our constructed EC protocol was independent of genotype; therefore, it might be able to be extended to elite cultivars.…”

Effect of heterologous expression of FT gene from Medicago truncatula in growth and flowering behavior of olive plants

“…Biotechnological approaches to improve this crop are also difficult to apply due to the recalcitrance of olive tissues to regenerate in vitro . Along this line, few transgenic olive plants have been generated ( Palomo-Ríos et al., 2021 ).…”