Variation in tomato fruit ascorbate levels and consequences of manipulation of ascorbate metabolism on drought stress tolerance

Tomato is an important crop worldwide and one of the major sources of vitamin C (ascorbate) in the human diet. Ascorbate contributes both to tomato nutritional quality and has roles in stress tolerance and adaptation to the environment. In this study we show the variability that exists in tomato germplasm in terms of ascorbate content (10 to 90 mg/100 g fwt) which could be starting point for evaluating correlations with physiological traits potentially linked to ascorbate. We have then manipulated genes involved in ascorbate metabolism, using RNA interference, to investigate their influence on fruit ascorbate levels, fruit physiology and yield under both normal and drought stress conditions. There is some evidence that one of the genes chosen affects fruit size and yield under different conditions, but clear effects on the fruit ascorbate pool are not seen. We conclude that ascorbate metabolism is complex and can also have wider effects on fruit physiology and growth