Quantitative responses of tomato yield, fruit quality and water use efficiency to soil salinity under different water regimes in Northwest China

Reduced irrigation and high soil salinity are widely recognized to decrease tomato yield, but they can improve fruit quality and water use efficiency (WUE) when imposed appropriately. However, the response of plant to their interaction is still unclear, and the quantitative relationship of WUE and fruit quality with salinity under different water regimes is also lacking. This study investigated the responses of tomatoes in terms of yield, fruit quality, and WUE based on yield (WUEy), biomass (WUEb), and leaf (iWUE) to twelve treatments, consisting of combinations of three water regimes relative to the field capacity (FC) (W0, W1, and W2 refer to 95 % FC, 75 % FC, and 60 % FC, respectively) and four soil salinity levels (0 g, 2 g, 4 g, and 6 g salt mixtures added to 1000 g air-dried soil, respectively). Results showed that WUEy and WUEb had a negative correlation with salinity under different water regimes. Salinity resulted in a greater reduction in yield and biomass than water consumption compared to the control treatment. Therefore, lower water consumption of plants under W2 treatment alleviated the decrease of WUEy induced by salinity to a certain extent. From the leaf scale, iWUE was positively and linearly related with salinity, indicating that stomatal regulation was more prone to reduced stomatal conduc-tance than the net photosynthetic rate under W0 and W1. Whilst it showed a quadratic relationship under W2, the results supported that a highly salinity-induced iWUE was dependent on water supply. In addition, although salinity had a negative correlation with fruit fresh mass (FM), dry matter content, and water content (WC) under W0 and W1, fruit titratable acidity (TA) and total soluble solids (TSS) were proportional to salinity regardless of water regimes. The results also showed that W1 increased the sensitivity of TA and TSS to salinity, but W2 resulted in weak sensitivity of FM and WC to salinity. Thus, we deduced that mildly reduced irrigation was an appropriate strategy to regulate iWUE and fruit quality under high salinity conditions. This study provides a water regime management basis for comprehensive changes in yield, WUE, and fruit quality of tomatoes grown in saline soils.