Phenotypic and molecular traits determine the tolerance of olive trees to drought stress

Abstract

Olive trees are known for their capacity to adapt to drought through several phenotypic and molecular variations, although this can vary according to the different provenances of the same olive cultivar. We confronted the same olive cultivar from two different location in Spain: Freila, in the Granada province, with low annual precipitation, and Grazalema, in the Cadiz province, with high annual precipitation, and subjected them to five weeks of severe drought stress. We found distinctive physiological and developmental adaptations among the two provenances. Thus, trees from Freila subjected to drought stress exhibited increasing root dry weights and decreasing leaf numbers and relative stem heights. On the other hand, the treatment with drought in Grazalema trees reduced their leaf chlorophyll contents, but increased their relative stem diameter and their root hydraulic conductivity. The physiological responses of Freila tree roots to drought were linked to different molecular adaptations that involved the regulation of genes related to transcription factors induced by ABA, auxin and ethylene signaling, as well as, the action of a predicted membrane intrinsic protein (MIP). On the other hand, the responses of Grazalema trees were related with different root genes related to oxidation-reduction, ATP synthesis, transduction and posttranslational regulation, with a special mention to the cytokinins signaling through the transcript predicted as a histidinecontaining phosphotransfer protein. Our results show that olive trees adapted to dry environments will adjust their growth and water uptake capacity through transcription factors regulation, and this will influence the different physiological responses to drought stress.

Water Stress, Irrigation and Concentrations of Pentacyclic Triterpenes and Phenols in Olea europaea L. cv. Picual Olive Trees

“…In Jaén, the main olive-oil-producing Spanish province, olive trees are mainly rain fed. When water is scarce, plants develop different physiological responses to avoid desiccation, such us regulation of root water uptake and transpiration [2], induction of antioxidant activity and osmotic adjustments [3], and alteration of hormonal content [4]. Several transduction pathways are implicated in the synchronisation of the stress gene response mediated by different transcription factors [5].…”

“…In order to prevent important economic losses in this region, increased irrigation is required. In recent years, many studies have shown how olive trees have adapted to these conditions [1,2,7]. Water availability affects the overall development of the tree and fruit composition, leading to changes in the flavour of olive oil [8,9,10].…”

Evaluation of Indigenous Olive Biocontrol Rhizobacteria as Protectants against Drought and Salt Stress

“…Changes in gs are a response to water deficit that causes a decline in rate of photosynthesis thereby reducing plant growth rate, root functionality and crop yield [11,101]. Most of the studies reported that Chl content decreases in plants subjected to water stress [21,102]. However, in our experiments, an increase in Chl was observed in plant subjected to stress compared to non-stressed plants (Table 2).…”

Effect of three water-regimes on morpho-physiological, biochemical and yield responses of local and foreign olive cultivars under field conditions

“…In the study of Calvo-Polanco et al [44], the drought treatment induced a significant reduction in the leaf Chl content of olive trees. These pigments are crucial components for Photosystems II and I and light-harvesting complexes (LHC), and oxidative stress can cause their photo-oxidation and degradation, affecting photosynthesis more than the restriction of CO 2 caused by stomatal closure during water deficit [45,46].…”