Abstract

production is one of the agricultural items with greater dynamism and growth in Chile, being one of the engines of the export industry. In this context, stone fruit tree orchards (apricot, cherry, plum, peach, nectarine and almond) are one of the most important fruit producers in Chile representing a 25% of the total area planted with fruit trees. However, there are environmental problems (such abiotic stresses) imposed by the actual global climate scenario that restrict or will constrain the cultivation of species of the Prunus genus. The Intergovernmental Panel on Climate Change (IPCC) reports that studies in Chile and other countries forecast future yield reductions for a number of crops, and that in the more arid zones such as northern and central Chile, climate change could lead to the salinization and desertification of agricultural land. Beside adverse environmental conditions, unsuitable irrigation managements could exacerbate the soil salinization process. The inability of stone fruit trees to tolerate root salinity could result in substantial yield losses (reduced number of fruits per tree) and decreased fruit quality (reduced fruit size). In general, stone fruit trees are grafted on rootstocks, which either belong to the same or other species or interspecific hybrids of the Prunus genus. The influences of rootstock system on the development of the scion are remarkable. Several horticultural attributes of the stone-fruit tree may be substantially influenced by the stock, such as vigor, blossom initiation, fruit set, and phenology. Also, rootstocks are known by to confer tolerance to salt stress and other abiotic stresses. Prunus species are considered as salt-sensitive species, although differences between genotypes as to their ability to tolerate this stress have been reported. The genetic determinants that shape the plant response to salt stress interact in a very complex network whose finely coordinated action defines the development, survival and, eventually, the plant yield in high salinity conditions. To dissect this complexity will allow identifying the key genetic determinants for salt tolerance in this genus. In this proposal research, I hypothesize that the tolerant phenotype to salt stress in Prunus rootstocks is determined by particular transcriptomes ruled by gene regulatory networks genotype-dependent. The General Objective of this project is to identify "master regulators" responsible for the phenotypic and transcriptomic contrasting response of Prunus rootstocks to salt stress. To reach this, two Prunus rootstocks with contrasting salinity tolerance will be submitted to salt stress by saline irrigation and their phenotypic response will be characterized with a multi-level approach involving physiological (gas interchange parameters, relative growth rate and electrolyte leakage), biochemical (contents of chlorophyll, proline, H2O2 and MDA) and ionomics evaluations. These results will be used to determine the optimal time points for isolating RNA in order to perform the RNA-Seq analysis needed to determine the gene regulatory networks (GRNs) of the transcriptomic responses of Prunus rootstocks with contrasting tolerance to salt stress. Finally, from GRNs constructed one of the master regulators identified will be selected with the aim of to evaluate its functional role in a heterologous plant model system (Arabidopsis thaliana) under salt stress. This approach, that conjugates wide-scale analysis tools, such as transcriptomics and ionomics, beside the the functional characterization of candidate genes though functional genomics and plant physiology will validate the identification of master regulators with most influential and massive effect in to determine the salt-tolerant phenotype. Such information is susceptible to transfer to the Prunus rootstocks breeding program that takes place in the Center for Advanced Research in Fruticulture-CEAF, in order to lead a more efficient and predictable early selection of Prunus genotypes tolerant to soil salinity.