Effects of nutrient solution management modes on fruit production and quality of tomatoes grown in extremely root restriction

Tomatoes (Solanum lycopersicum L.) are popular worldwide due to their unique flavor and abundant nutrients. To explore a suitable nutrient solution management mode for high quality production of tomato grown in extremely root restriction, we analyzed the effect of drainage rate and electric conductivity (EC) of nutrient solution on plant growth and fruit production of tomatoes. To reveal the diversity of flavor in tomato fruits under four modes, we focused on sugars, organic acids, amino acids, fatty acids and volatile compounds. In total, 831 metabolites were identified by metabolome analysis. The results displayed that low drainage (0–5%) significantly repressed plant growth, reduced photosynthesis and fruit production. Normal drainage (20%) combined with high EC markedly promoted the accumulation of soluble sugar and most of aromatic amino acids as well as fatty acids. The treatment of increasing EC by adding NaCl (EC1.2/4.8(1.2+3.6Na)/3.2(1.2+2.0Na)) markedly promoted the level of 5 compounds of (glucose-1p, glucose-6p, glyceric acid-3p, phosphoenolpyruvate and sedoheptuiose-7p), 1 compound (α-ketoglutaric acid) involved in tricarboxylic acid cycle and 1 volatile (2-phenylethanol). Therefore, the increase of EC from 1.2 to 4.8 dS/m by adding NaCl is an ideal pathway to ensure fruit production and high-quality tomatoes grown in extremely root restriction.