Tomato Cultivar and Rootstock Evaluation Under Mg Deficiency: Growth, Mg Uptake, and Leaf Gas Exchange

The importance of magnesium (Mg) is often overlooked in modern crop production. Tomato (Solanum lycopersicum L.) is commonly grafted onto appropriate rootstock to improve the nutrient uptake, which may have a negative effect on the tomato Mg leaf concentration and possibly influence the carbohydrate partitioning required for optimal crop yield and quality. The aim of this study was to screen tomato cultivars and rootstocks under Mg deficiency using two experiments. The first experiment included a panel of 14 tomato cultivars and 10 rootstocks grown with 1 or 0.1 mM Mg in nutrient solution. The second experiment consisted of four cultivars either self-grafted or grafted onto four rootstocks chosen from the first experiment. In both experiments, most of the plants grown under low-Mg conditions, on average, had a higher biomass production. The magnesium concentrations in the leaves and stems (but not in the roots) of both cultivars and rootstocks, non-grafted or grafted, were significantly higher under optimal Mg supply. Regarding the Mg content, the differences between the Mg supplies were up to three-fold for cultivars, up to two-fold for the rootstocks, and up to five-fold for the combinations of grafted plants. Our results showed that genotypic differences between used tomato cultivars and rootstocks in response to Mg can be observed at early developmental stages and can possibly serve as a tool in screening programs, but further research is needed to assess their relationship with long-term cultivation.