AbstractRibes nigrum is a woody perennial crop grown across Europe for its fruit which contain high levels of l-ascorbic acid (AsA). Significant variation is observed in fruit AsA content dependent on plant genotype and although significant year on year variation is observed regarding absolute AsA content, genotypic ranking is maintained.As part of a study into the mechanisms controlling AsA content of blackcurrant fruit we examined physiological and biochemical factors associated with AsA accumulation in low (cv. Hedda),
medium (cv. Baldwin) and high (genotype 8982/6) fruit AsA
genotypes. Measurement of the AsA content of individual plant
tissues over the course of a growing season demonstrated lack of AsA storage and remobilisation and showed that differences in tissue AsA concentrations between genotypes were primarily confined to fruit. In agreement with our previous work in other species, AsA was present in the phloem of R. nigrum however, no differences in phloem AsA content could be detected and source leaves of each genotype showed a similar capacity for AsA biosynthesis. AsA accumulated during the very early stages of fruit development and this coincided with the highest AsA biosynthetic capacity within the fruit. The biosynthetic capacity of individual genotypes closely resembled their ranking for AsA concentration in ripe fruit. We conclude that in R. nigrum import of AsA via the phloem has a limited impact in determination of ripe fruit AsA content and that the major determinant of fruit AsA content is the capacity of fruit tissues to synthesise the antioxidant from carbohydrates.