A Genetic Cure for Tomato Rot Gardeners are all too familiar with the experience. You plant a handful of shriveled sand-colored tomato seeds, urge them out of the ground with diligent tending, and then smile with self-satisfaction as the first plump fruits ripen, flush on their furry stalks. But then, the bottoms collapse. The lower halves of your tomatoes turn brown and squishy, and your fruits have been ruined - victims of a common disease called blossom end rot. It's as if your time and effort were all for nought. Blossom end rot has long been a serious problem for both recreational and commercial tomato growers. But the problem may eventually wane, at least for commercial growers who are interested in genetically modified, or transgenic, plants. A study published online this week in The Plant Journal details how tweaking the genes of experimental tomatoes significantly reduced the number of fruits with blossom end rot. "This study showed an 80 percent reduction" in rotting tomatoes, said Avtar Handa, a horticulturist at Purdue University and one of the study's authors. Dr. Handa engineered the transgenic tomato plant used in the study in the early 1990s while trying to create one that would be ideal for commercial production of tomato paste. He changed the chemistry of a carbohydrate called pectin that adds structure and texture to tomatoes and other fruits. Different varieties of tomatoes are suited to different purposes. "A salad tomato is juicer and best to bite," Dr. Handa said, but tomatoes grown for turning into tomato paste are firmer, "like hard rocks." He said these variations in the softness of structure and the tightness of skin depend largely on pectin. The type of pectin Dr. Handa engineered into his transgenic tomatoes "led to very good quality paste," he said. What he didn't realize at the time, though, is how the pectin in his transgenic tomatoes could also stave off blossom end rot. Horticulturists at the University of California-Davis recently came across Dr. Handa's original research and thought the chemistry in his tomatoes might lessen their vulnerability to the disorder. They approached him and asked for permission to use his seeds. Blossom end rot results from a calcium deficiency in the fruit, said Beth Mitcham, a horticulturalist at the University of California at Davis who is also an author of the study. She said that calcium in fruits with the disoder becomes trapped by the fruits" cell walls rather than reaching the cell membranes, the sacs inside cell walls that hold the cells together. Cells with insufficient calcium in their membranes die. Dr. Handa's genetically modified tomatoes sequester less calcium in the cell walls and more calcium supporting the cell membranes, Dr. Mitcham said. Peaches, apples, pears, and other fruits are affected by blossom end rot, too, Dr. Handa said. He suggests that the new results regarding pectin and health about could serve as a model for the development of other genetically modified fruit types. But Dr. Mitcham said that people who breed tomato varieties conventionally can also benefit from the results. "Breeders might be able to select for plants resistant to blossom end rot without needing to get transgenic," she said. Attitudes toward genetically modified organisms vary. While Dr.. Handa and Dr. Mitcham are confident in the safety of modern G.M.O.s, many people are less so. Among them is Gary Ibsen, an expert heirloom tomato farmer and executive director of the Carmel TomatoFest in California. Genetic modification of tomato plants is "very unfortunate," he said. "I know it makes good business sense for some people," he said. But Mr. Ibsen said he didn't want to "mess with" the qualities that have been passed down through his tomato plants for generations. "Blossom end rot can be prevented just by good farming process," he said. He said that taking care to aerate and properly drain garden soil will help tomato plants absorb the calcium they need to be healthy. Despite anti-G.M.O. viewpoints, Dr. Handa expects that his transgenic tomato will soon be used by the commercial tomato industry to produce tomato paste - almost two decades after he originally engineered it. Though commercial growers in the 1990s were very interested in his genetically engineered tomatoes, Dr. Handa said, "they didn't know at that time that Europe would have such a problem with transgenic crops." In the late 1990s, many European countries began fervently opposing genetic modification. Yet official policies on genetically modified crops have been softening. "It's only a matter of time until genetically modified crops will be accepted by most of the population," Dr. Handa said.