How sweet it is: Link found between ripening, colour and taste

ITHACA, N.Y. – For many grocery shoppers, those perfect, red tomatoes from the store just can’t match the flavour from the home garden. Now, researchers at Boyce Thompson Institute for Plant Research at Cornell University, USDA and the University of California at Davis have decoded a gene that contributes to the level of sugar, carbohydrates and carotenoids in tomatoes. (Science, June 29, 2012)

Cuong Nguyen, a Cornell University graduate student in plant breeding working at the Boyce Thompson Institute (BTI), along with colleagues at BTI, USDA, University of California at Davis, Universidad Politecénica de Valencia (Spain), Universidad de Málaga (Spain) and University of Suleyman Demiral (Turkey) revealed the gene that underlies the uniform ripening mutation.

This gene also influences how tomato fruits ripen and is used by commercial breeders to create tomatoes that develop into perfectly red, store-ready fruit. “Practically, it is a very important trait,” says James Giovannoni, a plant molecular biologist with BTI and the U.S. Department of Agriculture, Agricultural Research Service, who is a senior author on the paper. “It’s a gene that whether you realize it or not, most of your tomatoes have.” However, this same trait reduces sugars and nutrients in the fruit.

Naturally, tomatoes have uneven ripening, showing darker green patches when unripe and variable redness when ripe — traits that still show up in garden-variety and heirloom breeds. However, in the late 1920s, commercial breeders stumbled across a natural mutation that caused tomatoes to ripen uniformly—from an even shade of light green to an even shade of red. This mutation, known by plant biologists as ‘uniform ripening’, has become indispensable to the $2 billion a year US commercial tomato market, showing up in almost all tomatoes produced for grocery stores. The uniform redness makes it ideal for the grocery sector, which has to appeal to customer expectations of evenly collared, red fruit.

See The Tomato Genome Revealed video

Mr Nguyen conducted positional cloning and, with access to solgenomics.net, an online, public database hosted at BTI, he determined that the uniform ripening gene was located at a specific location on chromosome 10. With this location now known, the team could decipher the gene coding for thNike