Genes improve tomato firmness by 40%.

Looking to develop delicious, firmer tomatoes that can survive a week of shipping and handling and still remain firm on the kitchen counter for another week or longer? Then you should consider licensing USDA-ARS technology that uses a family of tomato genes to produce tomatoes that are 40% firmer than normal. This research could help fill consumer needs for tastier, vine-ripened, fresh-market tomatoes. In addition, these genes may be useful for preparing vegetable products, such as ketchup, pastes, sauces and soups, clear fruit juices and biofilms.

ARS researchers have given us a clear picture of some of the genes involved in turning a firm tomato into mush. Tomato plants were engineered with a reversed gene that blocks removal of galactose from the cell walls of the plant. Galactose appears to play a key role in the loss of cell wall structure, which is necessary for tomato firmness. The enzymes encoded by these genes remove a galactose residue from plant cell walls and other plant components, including galactolipids in membranes.

The scientists have produced vine-ripened tomatoes that are 40% firmer than unmodified siblings and that stay firmer for at least two weeks. Those firm tomatoes support the researchers' theory that the loss of galactose plays a key role in the loss of cell wall structural integrity. And structurally sound cell walls are essential to a tomato's firmness. The researchers focused on galactose because it's the sugar that changes the most as fruit develops.

The investigators identified and sequenced seven different genes that code for the galactose-removing enzyme--beta galactosidase. They inserted five of those genes into the tomato genome and have tested tomatoes with only one of the reversed, or antisense, genes.

Tomatoes containing genetically engineered copies of the novel genes are a significant improvement over previously marketed genetically-modified tomatoes in that they are firmer, and they can be vine-ripened. The technology is covered under patent application SN 09/701,868, "Genes Coding for Tomato Beta-Galactosidase Polypeptides," which was filed on Dec. 5, 2000.

Further information. June Blalock, USDA-ARS Office of Technology Transfer, Room 4-1174, 5601 Sunnyside Ave., GWCC-BLTSVL, Beltsville, MD 20705; phone: [phone]; fax: [phone]; email: [e-mail].