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Processes at the soil-root interface shaping soil functions (Communication session)

EUROSOIL2020CONT-1722

STRIGOLACTONES INVOLVEMENT IN TOMATO PLANTS RESPONSE TO LOW P LEVELS

Veronica Santoro^{* 1}, Michela Schiavon ¹, Luisella Celi¹

¹DISAFA, Università degli Studi di Torino, Torino, Italy

Content: Phosphorus (P) is an essential macronutrient required by plants but, in most soils, its concentration can be very low because of abiotic processes that immobilize it, reducing its mobility and limiting fertilizers diffusion. Plants have evolved several strategies to exploit localized sources of P to cope with P deficiency, including modifications of root architecture, exudation of organic acids and electron-rich species, production of enzymes able to hydrolyse organic P-compounds and higher expression of high-affinity P-transporters encoding genes. Recently, strigolactones (SL), a class of plant hormones involved in the regulation of plant architecture and establishment of symbiosis with AM-fungi, have been suggested to be involved in plants response to P availability. In the context of TOMRES project, aiming at enhancing tomato resilience to combined water and nutrient stress, we studied how SLs control plants adaptation to low P conditions. We grew up wild-type (WT) tomato plants and plants with gene for SL synthesis silenced (SL-). After a period of normal nutrient conditions, plants were moved to aerated hydroponic systems and kept in P stress regimen for two weeks. Root exudates were collected at regular time intervals and analysed for P, protons (H⁺), dissolved organic carbon (DOC) and organic acids content. Biomass parameters were measured, and roots were analysed for P, C and nitrogen (N) content, enzymatic activity and P transporters. Root architecture was also investigated via X-ray computed tomography and microscopy. SL silencing prevented leaf senescence symptoms in SL- plants, while SLs promoted internode elongation and induced early leaf senescence especially in P-starved WT plants, probably to facilitate internal P reallocation under P shortage. Under normal P provision, SL- plants preferentially allocated P in the aerial part, possibly to maintain their more shoot-branched phenotype. This higher P content of SL- plants under normal P provision was related to the greater consumption of P from the nutrient solution compared to the WT, and was probably due to an altered perception of exogenous P, which could be responsible for altered sensitivity responses to this nutrient. In line with this, SL- showed a constitutive transcriptional up-regulation of the high-affinity P transporters encoding genes LePT1, LePT4 and LePT7 and greater production of phytases and phosphatases under normal P conditions. The main exudates diversities were instead found in organic acids amount and composition and in the kinetics and levels of H⁺ release. 

This work has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 727929 (TOMRES).

Disclosure of Interest: None Declared

Keywords: nutrient availability, phosphorus, root architecture, Root exudates, strigolactones, tomato plants