Multi-Omics approaches for identifying Salt- and Drought-tolerant Olive Cultivars

Introduction: Salinity and drought could be considered the most common environmental constraints in the Mediterranean area. Olive is a tree that is adapted to long dry periods and saline soil, but the degree of tolerance to these two adverse situations is cultivar-dependant. However, drought and salinity are two abiotic stresses that are increasingly present in the Mediterranean region, and identifying olive cultivars that can tolerate these adversities is a research priority.

Goals: As salinity and drought are limiting factors for olive production, the goals of this research were to detect consistent descriptors that could be used for underlying genotype-dependent performance under conditions of environmental disturbance that will occur in the future due to climate change, such as drought and salinity stress for olive plants.

Methodology: The multi-omics approach was used for screening olive cultivars that are well adapted to drought and salinity, including ‘Phenomic’, ‘Ionomic’, ‘Transcriptomic’ and ‘Metabolomic’ approaches. Using the ‘Phenomic’ approach, the physiological responses to the photosynthetic process in terms of gas exchange regulation and chlorophyll a fluorescence can be investigated. Moreover, visible symptoms of salt and drought stress, including foliar chlorosis and necrosis, reduced growth, and a general reduction in leaf area, can be monitored. Using the ‘Ionomic’ approach, the macro- and micro-element imbalance in all organs of olive trees were evaluated. Finally, the ‘Transcriptomic’ and ‘Metabolomic’ approaches were used to reveal the genes and metabolic pathways that are regulated in olives and determine their sensitivity or tolerance under drought and salinity conditions.

Conclusions: Considering recent research on olive under drought and salinity conditions, an overview of the principal mechanisms that olive plants adopt to overcome these two abiotic stresses is provided, examining anatomical, physiological, and metabolic traits. The selection of these traits could be used as a rapid olive screening method for selecting cultivars that can keep up with climate change without losing productivity.