By Brad Buck, UF/IFAS
Harry Klee, an eminent scholar and professor in the UF/IFAS horticultural sciences department, is pictured in the greenhouse with hybrid tomatoes derived from heirlooms. The tomatoes are part of a tomato flavor improvement project that is looking at producing hybrids that have great taste like heirlooms but better performance. The project is also looking at transferring the enjoyable taste of heirlooms into supermarket tomatoes.
Some consumers crave tastier tomatoes than those they buy at the supermarket, so a University of Florida Institute of Food and Agricultural Sciences researcher led a global team of scientists that found chemical combinations for better flavor.
In a study published in the journal Science, Harry Klee, a UF/IFAS professor of horticultural sciences, led an international research team that included scientists from China, Israel and Spain. Researchers identified chemicals that contribute to tomato flavor.
Step one was to find out which of the hundreds of chemicals in a tomato contribute the most to taste.
Then, Klee said, they asked, “what’s wrong with the modern tomatoes?” They lack sufficient sugars and volatile chemicals critical to better flavor. Those traits have been lost during the past 50 years because breeders have not had the tools to routinely screen for flavor, Klee said.
To help, researchers studied what they call “alleles,” the versions of DNA in a tomato gene that give it its specific traits. Klee likened the concept to the genetic makeup of humans. Everyone has the same number of genes in their DNA, but a particular version of each gene determines traits such as height, weight and hair color.
“We wanted to identify why modern tomato varieties are deficient in those flavor chemicals,” Klee said. “It’s because they have lost the more desirable alleles of a number of genes.”
Scientists then identified the locations of the good alleles in the tomato genome, he said. That required what’s called a genome-wide association study. There, scientists mapped genes that control synthesis of all the important chemicals. Once they found them, they use genetic analysis to replace bad alleles in modern tomato varieties with the good alleles, Klee said.
“We identified the important factors that have been lost and showed how to move them back into the modern types of tomatoes,” he said, stressing that this technique involves classical genetics, not genetic modification. “We’re just fixing what has been damaged over the last half century to push them back to where they were a century ago, taste-wise. We can make the supermarket tomato taste noticeably better.”
The U.S. is second only to China in worldwide tomato production, according to the U.S. Department of Agriculture. Florida and California account for two-thirds to three-fourths of all commercially produced fresh-market tomatoes in the U.S. Florida growers produce 33,000 acres of tomatoes worth $437 million annually as of 2014, according to UF/IFAS economic research.
Because breeding takes time, and the scientists are replacing five or more genes, Klee said the genetic traits from his latest study may take about three or four years to produce new tomato varieties.
“Around the world, the tomato is one of the most popular foods,” said Gert de Couet, director of the National Science Foundation Division of Integrative Organismal Systems, which funded the research. “This state-of-the-art analysis sets the stage to return it to the taste of decades ago by directed breeding informed by molecular genetics.”