Insights on Physiological, Biochemical and Genetic Responses of Tomato (Solanum lycopersicum L.) to Drought Conditions

With global warming and climate change, drought stress is nowadays a threatening problem for growing vegetable crops worldwide. The introduction of more resilient and less water-demanding varieties is a key aspect for sustainable vegetable production, especially in Mediterranean countries where water availability for agricultural uses is progressively decreasing. This review highlights different mechanisms of tomato plant, as one of the most important crops of the Mediterranean countries, which are activated at physiological, biochemical and molecular levels in response to drought. With regard to the root system architecture modification, osmotic adjustments, and hormonal and antioxidant regulations are discussed. For vegetative organs, plant architecture, leaf morphology adjustments and stomatal regulation are described. Major genetic traits related to drought stress, along with responsive genes, are listed. The metabolic pathways, which determine the tolerance to drought stress, are reported and their related molecular markers used for the molecular-assisted selection (MAS) are listed. Novel growing systems and techniques which can improve efficiency for mitigating drought are highlighted; in addition, different breeding methods, both conventional and new gene-editing ones, are mentioned.