Combination of arbuscular mycorrhizal fungi and natural compounds for improving tomato tolerance to water and salt stress

The Mediterranean area is particularly susceptible to the incidence of adverse abiotic and biotic conditions derived from climate change that will severely impact agricultural production. Priming modulates plant stress responses before the stress factor appears, increasing the ability of the primed plant to endure the adverse conditions and thrive. This can be achieved by the application of different compounds and/or microorganisms (chemical and biological priming, respectively). In this context, we are investigating the priming effect of different natural compounds (i.e., salicylic acid alone or in combination with chitosan) and biological (i.e., arbuscular mycorrhizal fungi, AMF) agent combinations against the incidence of water deficit and salinity on a commercial tomato genotype to improve its stress tolerance. To optimize the use of the considered priming agents, a seed priming protocol has been developed to generate more resilient and climate-flexible plants. As a first step, the effect of the chemical priming compounds on the AMF colonization has been evaluated, demonstrating the possibility of using them in combination. Next, plant responses to water and salt stress have been evaluated on primed seeds. The trials were carried out on potted plants by subjecting them to water deficit (by withholding irrigation up to 35% of water holding capacity) and salt stress (by exposing plants to progressively higher NaCl concentrations up to 200 mM). The impact on plant fitness of the several treatments has been studied using a combined approach, including eco-physiological and biochemical analyses, transcriptomics, and untargeted metabolomics.