Application of drought and salt stress can improve tomato fruit quality without jeopardising production

Abstract

High-tech tomato greenhouse systems, which are the standard in Northern Europe (especially in Belgium and the Netherlands), mainly aim for high yields, up to 60 kg m-2. However, quality should be considered equally important, as consumers are willing to pay higher prices per kg for a high quality product. Influencing the plant water status is acknowledged to strongly influence fruit quality, as water deficit or increased salinity may result in higher dry matter content, a main determinant of tomato quality. Unfortunately, this increase in quality is often associated with a decrease in fresh yield, making a thorough insight on the controlling factors of both aspects critical if one aspires to optimise the final product value. The objective of the current research was therefore to combine plant water status monitoring with the assessment of an array of fruit quality parameters and yield, for both drought and salinity treatments in order to further clarify this interrelationship. To this end, we set up an experiment in a controlled greenhouse environment, where tomato plants (Solanum lycopersicum 'Dirk') were exposed to four different treatments: control, drought stress, and two levels of salt stress (EC levels of 4 and 6 dS cm-1). Plant water status was monitored by measuring stem water potential. Furthermore, fruit yield, as well as a set of fruit quality parameters (hexose sugars content, organic acids content, and firmness) was evaluated. Results showed that fruit quality does benefit from both drought and increased salinity, and that the highest salinity level scored the best on all measured quality aspects. Moreover, we observed that even small water deficits, induced either by mild drought or salt stress, improved fruit quality, without jeopardising yield. The acquired insights, combined with mechanistic modelling, may ultimately lead to a more efficient greenhouse management with higher quality tomatoes.