Comprehensive study of the hormonal, enzymatic and osmoregulatory response to drought in Prunus species

Nowadays, climate change is creating new challenges all over the planet and altering the availability of water resources. Agriculture is one of the most affected sectors, as water is a fundamental requirement for the sustainability of agriculture and future demands. Recurrent drought periods have pushed breeding programs to develop and select genotypes tolerant to water stress. Understanding the mechanisms involved in drought response is essential in facilitating the selection of such genotypes. In this study, we have characterized the levels of enzymatic antioxidants, the soluble sugars content (osmotic response) and the hormone profile of four genotypes of the genus Prunus (P. webbi, P. elaeagnifolia, P. dulcis var. 'Garrigues', and P. persica var. 'Montclar') and one P. dulcis x P. persica hybrid ('GF677') subjected to three different water irrigation conditions (control, drought and recovery). Results show that P. webbi and P. elaeagnifolia, and, to a lesser extent, the cultivar 'Garrigues', seem to be the most tolerant to water stress. Drought and recovery treatments led to a differential response in terms of the levels of enzymatic antioxidants depending on the genotype. Elevated levels of the osmotic regulators glucose and fructose and a parallel decrease in sucrose were also observed. Finally, a finetuned regulation of abscisic acid (ABA), jasmonic acid (JA), salicylic acid (SA), and cytokinins (trans-zeatin, tZ, and isopentenyl adenine, iP) took place in P. webbi, P. elaeagnifolia and 'Garrigues'. In summary, deciphering the tolerance response to water stress of these almond genotypes together with proper breeding efforts could contribute to the development of new drought-tolerant almond cultivars and rootstocks. In this sense, we strongly suggest the use of more unexplored wild almond species in breeding programs to increase diversity and improve environmental stress tolerance-related traits.