CORVALLIS – Researchers at Oregon State University have created purple-fruited tomatoes that include anthocyanins – the same class of health-promoting pigments in red wine that function as antioxidants and are believed to prevent heart disease.
Their research is featured as the cover story in the latest issue of the Journal of Heredity.
Domestic tomato varieties grown and consumed in the United States do not normally produce fruit containing any anthocyanin, explained Jim Myers, OSU's Baggett Frazier professor of vegetable breeding. The success in producing anthocyanin-containing tomatoes – through traditional breeding techniques – could help researchers develop even more new varieties of tomatoes with other nutrients, both for home gardeners and for the food industry, he added.
"Tomatoes are second only to the potato in terms of the top vegetable consumed in the world," Myers said. "Per capita use in the U.S. in 2003 was 89 pounds of tomatoes per person. If we could boost the nutritional value of tomatoes, a large part of the population would benefit from that."
The OSU researchers accomplished the feat through the characterization of the inheritance pattern of a little studied gene in tomatoes called "anthocyanin fruit," or Aft. Myers and his OSU graduate students crossed a domestic tomato plant with a genetic stock of tomato that included a gene incorporated from a wild relative with anthocyanin-containing fruit and the Aft gene. The result: a domestic-type tomato fruit containing the purple pigment and the Aft gene, thereby opening the door towards developing anthocyanin-rich tomatoes.
Assisting Myers were graduate students Carl M. Jones, now at the University of California-Davis, and Peter Mes.
The OSU researchers grew the seeds of their new cross of anthocyanin tomato fruit in the OSU research greenhouse for two generations, backcrossing them with the original parent types. This work led them to confirm that anthocyanin fruits are transmitted in tomatoes by a single dominant gene, Aft.
"We are learning about how anthocyanin genes are expressed in tomatoes, and how we might cross tomatoes to get more nutritional value," explained Myers.
Comparing chemical analyses of the tomatoes with the Aft gene to those without the gene, the OSU plant breeders determined the pigment composition of anthocyanin fruit gene, explained Myers. They also verified that indeed, having fruits containing anthocyanin could be inherited through a single gene, Aft.
Anthocyanins are the source of the blue, purple and red in berries, grapes and some other fruits and vegetables. These pigments also function as antioxidants, believed to protect the human body from oxidative damage that may lead to heart disease, cancer and aging, explained Mes.
Working with Myers on his doctoral research, Mes is breeding new crosses of tomatoes and analyzing the antioxidant activity of not only anthocyanins in the fruits, but also carotenoids, another class of beneficial phytonutrients. He is also conducting preliminary nutrition studies on humans that have consumed different types of his tomatoes as juice, to see how the various carotenoids are metabolized and which carotenoids prevent oxidation in human plasma.
Industry is interested in their work with higher nutrient tomatoes, say Mes and Myers.
"The medical, the nutritional and the food research industries all are keenly interested in the health benefits of phytochemicals in all sorts of fruits and vegetables," said Myers. "We are happy to find out we can accomplish this in tomatoes using traditional, classical plant breeding techniques."
For more than 40 years, OSU vegetable breeders W.A. Frazier, James Baggett and now Myers, the current OSU Baggett-Frazier Professor of Vegetable Breeding, have developed more than a dozen tomato varieties for commercial and home growers around the world.
NOTE TO EDITORS: Downloadable photos of the anthocyanin-containined tomatoes are available at: http://osu.orst.edu/dept/ncs/photos/index.html