Under drought conditions plants may find strategies to escape the stress (accelerating the life cycle) or to avoid it (controlling stomatal conductance, investing in the development of the root system, reducing canopy, etc.), or still to activate strategies of osmotic adjustment to increase tolerance to low tissue water potential (for instance accumulating compatible solutes).
The efficiency of photosynthetic carbon gain relative to the rate of water loss can be used as indicator (Ennaheli and Earl 2005; Jiménez et al., 2013). In the seasonally dry and variable environment of the Mediterranean region, the ability of species like almond to cope with water scarcity is not only dependent on the variety, but also very dependent on the rootstock on which it is grafted.
The characterization of drought resistance in almond cultivars and the rest of fruit crops is therefore linked to efficiently use of water (Yadollahi et al. 2011), together with the ability of the root system to access water. Collecting materials for future research and breeding are helpful tools to reduce drought losses, but this is a lengthy process (Neale et al., 2017). However, development of improved production systems using drought resistant almonds may be possible utilizing native germplasm. These materials allow a more sustainable production, particularly in the marginal areas of harsh climate conditions found around the Mediterranean basin (Gouta et al. 2010; 2017). This starting material has proven to be more efficient and resilient than wild species that, moreover, show poorer agronomical behaviour (Sorkheh et al., 2009).
However, an integrated approach evaluating varieties/clones/biotypes which are more drought resistant but are also productive and giving good yield and nutraceutical quality has not been developed as far as we know.