SELECTION OF RESILIENT TOMATO GENOTYPES IN NUTRIENT AND DROUGHT STRESS CONDITIONS

In the frame of the EU project TOMES, we have tested under environmental stress conditions 27 Solanum lycopersicum L. genotypes, chosen among a large international core collection. The plants were grown in 15L pots containing river sand in a semi controlled glasshouse. Four separated treatments were applied: Control (10.2 mM NO3-), Low Nitrate (2.88 mM NO3-), Drought (50% water) and CombinedStress (2.88 mM NO3- with 50% water). Physiological parameters (chlorophyll content, stomatalconductance and relative water content) were monitored during the growth cycle, whereas impact oftreatments on growth (plant height, shoot fresh/dry weight, leaf area, number of floral trusses, root lengthand dry weight) and proline content was measured five weeks after treatment differentiation. Threeoutstanding genotypes were selected based on tolerance traits: T292, T150, T327. Growth of genotypesT292 and T150 was scarcely reduced under nitrogen and water deficit conditions, respectively. T150 alsoaccumulated the lowest absolute amount of proline in drought-stressed condition. T327 showed the smallestdecrease in stomatal conductance in drought treatment compared to the control. We measured reactiveoxygen species (ROS) H2O2 and lipid peroxidation marker malondialdehyde (MDA), as well as ROSscavenger Ascorbic acid (AsA), known to protect organelles and cells from ROS damage. Consistent with ahigher stress tolerance, all the identified genotypes showed lower membrane damage in all tested stressconditions compared to control genotype M82. In detail T292 showed virtually no increase in H2O2 and hadthe highest AsA level in all conditions, indicating a higher accumulation of antioxidant compounds in thisgenotype. The gene expression pattern of APX, CAT and SOD6 in leaves is consistent with ROS content.We also analyzed the expression of LEA in T150 and T327 genotypes, and consistent with a lowerperception of stress, both genotypes had lower induction of LEA compared to M82. P5CS (ProlineBiosynthesis gene) and P5CDH (Proline Catabolic gene) gene expressions are consistent with the low levelsof proline measured in these two genotypes. In conclusion, we have selected three candidate genotypes thatshow resilience to environmental stresses and identified molecular mechanisms that may contribute to theobserved tolerant phenotypes. This work was supported by the European Union's Horizon 2020 research and innovation programme under the Grant Agreement No. 727929.