Genetics Firm Tries to Fool Mother Nature, Blocking Enzyme to Slow Aging--but Don’t Check the Store Yet : Science vs. the Mushy Tomato
Build a better mousetrap and the world will beat a path to your doorstep. But in the high stakes world of produce, serve a soft tomato, and you may soon be history.
In the latest step in the increasingly scientific battle to improve crop yields and the quality of the foods we eat, a Davis, Calif., genetic engineering firm announced this week that it has found a way to suppress the enzyme that makes tomatoes go mushy.
And while some scientists think that the tampering might make tomatoes taste even worse--one of the myriad complaints plaguing the household staple--scientists at Calgene Inc. say the trait can be introduced into tomato strains that, apart from aging too fast, already have desirable taste, color and shape.
Vine-ripened tomatoes, as any back yard gardener knows, are generally much tastier than store-bought, and Calgene’s process would allow growers to leave tomatoes on the vine longer without risking spoilage.
“While it’s on the vine it’s picking up sucrose,” said microbiologist William Hiatt, Calgene’s managing scientist on the tomato project. “If you pick something that’s immature, you may be able to turn that tomato red by treating it with ethylene, but it simply hasn’t had the time to develop all the components for flavor.”
Consumers tend to look for nice color and firmness, and shippers use ethylene gas to darken the skins of fruit that hasn’t had the chance to soften--or to fully ripen.
‘Tomatoes Don’t Taste Good’
“Right now everything you buy in the store was picked green. That’s so they could pick it when it was a nice hard green baseball” and resistant to rough handling and the long trip to the processing plant or the grocery store, said Alan Bennett, a UC Davis plant geneticist.
“The No. 1 produce complaint today is that tomatoes don’t taste good,” said Dan Wagster, Calgene’s chief financial officer. “Tomato breeders select varieties for their firmness and hardiness to minimize spoilage, but those selections are at the expense of taste, so taste has effectively been bred out of the tomato.”
Growers sold about $1.26 billion worth of tomatoes for market and processing in 1987. About 80% of the $450 million a year worth of tomatoes for processing were grown in California, according to statistics from the state Department of Food and Agriculture.
The Calgene process is actually fairly simple by genetic engineering standards. “What we’ve done in a sense is a mutant experiment,” said Hiatt, explaining that about 20 years ago, scientists determined which one of the 100,000 of so tomato genes was responsible for softening. The gene produces a messenger RNA, which in turn produces the enzyme that breaks down pectin within the fruit.
Using techniques successfully used in genetic engineering of bacteria and animals, a team of nine scientists working under Hiatt has created a mirror image of the gene that, when reinserted into tomato plants, produces a second messenger RNA, preventing the first from producing the enzyme.
According to Hiatt, the new plants may not even need approval under federal standards. “The genetic change is very minute, so hypothetically any changes that result should be minimal, and we’re in the process of proving that,” he said. Company officials don’t expect consumers to see their new and improved tomatoes until at least 1992.
But plant breeders at UC Davis caution that other genes may play roles in the softening process, and that the gene in question may affect not only softening but other characteristics.
“It may keep the tomato from getting mushy, but it may taste terrible, too,” said John Yoder, a molecular geneticist at UC Davis. And no one knows how long the mutant tomatoes will take to soften or if the process works too well, keeping the fruit hard until it rots. “If they never got soft, you couldn’t really eat a tomato that tastes like an apple,” Yoder said.
Said Bennett, one of the first to clone the gene used in the Calgene experiment: “At this point we don’t know that by turning off this single gene you’re going to dramatically alter the characteristics of the fruit.”
Processors such as Campbell Soup Co., which funded most of the $6 million Calgene research, stand to save considerable sums using firmer tomatoes because presently they must heat the fruit to prevent the enzyme from making it runny.
And since “heating to some extent destroys flavor,” catsups made from firmer tomatoes that were left on the vine longer would be thicker and tastier, as would sauces, pastes, and juices, according to David Zollinger of the California Tomato Growers’ Assn., representing growers of processing tomatoes.
Finding ways to reducing spoilage and improve yield would mean greater abundance of all sorts of produce, lower costs for producers and lower prices for consumers.
“Close to 50% of what’s harvested is never eaten by the consumer. It’s lost. It may rot, it may ripen too quickly--a number of factors that reduce its shelf life--and it’s thrown away,” said Rick Jones, an associate professor of genetics and plant breeder at UC Davis who uses more traditional methods to improve tomatoes and other crops.
“In the last decade that we’ve seen an enormous proliferation in scientific research into all the crops,” he said.
Calgene officials say genetic engineering is a shortcut to traditional breeding methods and could eventually be used on other crops, but few expect the result to revolutionize the tomato.
“They may be a year or two ahead,” said Ted Batkin of the California Fresh Market Tomato Advisory Board, a growers group. But, he said, “there’s a lot of seed companies out there trying to find the perfect tomato, or the perfect cauliflower.”
