As the concentrations of essential vitamins and minerals and a number of other health‐promoting compounds are often low in stable crops, research is under way to understand and increase synthesis of phytochemicals in order to improve crop nutritional quality. The question addressed in this study is whether shoot genotypes or root genotypes with tolerant drought character are able to increase the fruit quality and production under moderate water stress. Zarina (drought tolerant) and Josefina (drought sensitive) were grafted self and reciprocally. The results showed that the use of cv. Zarina (drought tolerant) as rootstock (Zar × Jos) results in a greater number of fruits under water‐stress conditions, a moderate increase in some antioxidant compounds, such as ascorbic acid, phenols and flavonoids and lycopene and β‐carotene, and Zar × Jos showed high levels of sugars and organic acids, sweetness index and sugars : acids ratio, as well as important minerals, such as K and Mg, which could increase its nutritional quality under stress conditions. Overall, the use of drought‐tolerant rootstock could provide a useful tool to improve fruit yield and quality of cherry tomato fruit under moderate water stress, which in turn could mean lower costs in the use of irrigation water.

The response of grafted vegetables to stress conditions owing to the nutrient status may be different than that of self-rooted plants, depending mainly on the rootstock genotype. The aim of the present work is to determine the response of reciprocal grafts made between cherry tomato cultivars (Solanum lycopersicum) to moderate water stress, examining uptake and concentration of nutrient. The tomato cultivars Zarina (drought-tolerant) and Josefina (drought-sensitive) were reciprocal grafted and selfgrafted, and ungrafted were used as control. The total content and uptake fluxes of macro-and micronutrients were determined in leaves. Our results show that the use of drought-tolerant cv. Zarina like rootstocks (ZarxJos) showed improve ionome, with increases in nitrogen (N), phosphorus (P) and potassium (K) concentration and uptake fluxes, and an increase in iron (Fe) and copper (Cu) concentration and uptake under water stress. Besides, the vigorous root system of rootstocks is often capable of absorbing plant nutrients more efficently than scion root, and we have showed that cv. Zarina and ZarxJos develop a better radicular system. This result confirms the hypothesis that grafted plants on vigorous rootstocks can improve mineral nutrition and nutrient uptake with respect to ungrafted plants, especially under water stress conditions.

Strigolactones (SLs) are plant hormones that modulate morphological, physiological and biochemical changes as part of the acclimation strategies to phosphorus (P) deficiency, but an in-depth description of their effects on tomato P-acquisition strategies under P shortage is missing. Therefore, in this study, we investigate how SLs impact on root exudation and P uptake, in qualitative and quantitative terms over time, in wild-type and SL-depleted tomato plants grown with or without P. Under P shortage, SL-depleted plants were unable to efficiently activate most mechanisms associated with the P starvation response (PSR), except for the up-regulation of P transporters and increased activity of P-solubilizing enzymes. The reduced SL biosynthesis had negative effects also under normal P provision, because plants overactivated high-affinity transporters and enzymatic activities (phytase, acidic phosphatase) to sustain elevated P uptake, at great carbon and nitrogen costs. A shift in the onset of PSR was also highlighted in these plants. We conclude that SLs are master kinetic regulators of the PSR in tomato and that their defective synthesis might lead both to suboptimal nutritional outcomes under P depletion and an unbalanced control of P uptake when P is available.

For the production and nutritional parameters measured, it is postulated that the fogging system treatment offers a better balance between production and nutritional quality. This treatment proved to be best in terms of productivity, vitamin C and lycopene contents and antioxidant capacity.