Colour differentiation of high-lycopene tomato fruit through the addition of the colourless-epidermis (y) mutation
High-lycopene tomatoes (Solanum lycopersicum) are characterised by an intense red flesh-colour, due to an elevated concentration of the carotenoid, lycopene. However, this characteristic is only visible once fruit are cut open, making it impossible to differentiate intact high-lycopene fruit from standard tomato fruit, a clear market disadvantage. The reason that fruit colour of both high-lycopene and standard fruit looks almost identical from the outside is because tomato fruit normally contain the yellow flavonoid LSQUOnaringenin chalconeRSQUO in a thin layer of epidermal cells. It is this combination of naringenin chalcone and the underlying lycopene in the flesh that gives tomatoes their characteristic orange-red colour. By incorporation of the recessive colourless epidermis mutant allele LSQUOyRSQUO (which prevents naringenin chalcone accumulation) into high-lycopene fruit, we have been able to create high-lycopene tomatoes (hp1.ogc.y) exhibiting a deep-pink colour visible from the outside. Hue angle of the skin of the high-lycopene LSQUOyRSQUO mutant and a regular high-lycopene tomato (hp1.ogc.Y) was 30 and 38°, respectively, while flesh values were similar at 31 and 32°, respectively. Removal of naringenin chalcone from the epidermis appeared to improve the visibility of underlying lycopene, such that fruit outer colour became a subsequent indicator of underlying flesh colour. The removal of epidermal pigmentation means that high-lycopene fruit can now be differentiated from standard tomato fruit in the market place without the need to cut fruit open.
O'Hare, T.J., McGrath, D.J., Dillon, N.L. and Walker, I.O. (2015). Colour differentiation of high-lycopene tomato fruit through the addition of the colourless-epidermis (y) mutation. Acta Hortic. 1106, 9-14
biofortification, MYB12, naringenin-chalcone, pink tomato, breeding, Solanum lycopersicum