Physiological response of tomato to saline irrigation in long-term salinized soils

On an experimental field that had been irrigated with saline water for more than 10 years, we assessed the effects of saline irrigation on water relations and yield of a processing tomato crop (Lycopersicon lycopersicum Mill., Cois HC01). Three NaCl concentrations (43, 86 and 171 mM) and a non-salinized control were compared. Total (Ψt), osmotic (Ψ) and pressure (Ψp) potentials decreased at increasing salinity, in both leaf and roots. Leaf osmotic adjustment (OA) throughout the growth seasonwas proportional to the salinity of the irrigation water. However, diurnal osmotic adjustment was more pronounced in non-salinized relatively to moderately salinized (43 and 86 mM) plants, indicating that the latter were somehow pre-adapted to further stress. Salinity inhibited leaf area and root density, which are both possibly associated to functional adaptation to saline environments. However, it did not significantly affect (up to 86mM NaCl) the commercial yield, rather tomato quality was improved in terms of total soluble solids. Although salinized tomato fruits were smaller than non-salinized control fruits, they had higher acidity, increased soluble solids and higher sugar content, which all are highly requested qualities by the processing tomato industry. Overall, the reduced yield of moderately salinized plants (86mM NaCl) was compensated by enhanced quality of tomato fruits.