Growers are to blame for the awful taste of today’s supermarket tomatoes and its all because they wanted them to be uniformly the same color at harvest. A new study has revealed that over the last several decades the fruit was bred for uniform color which in turn robbed them of a gene that boosts their sugar content and gives them better tasting results.
Alisdair Fernie of the Max Planck Institute of Molecular Plant Physiology in Potsdam, Germany calls the discovery a “massive advance” in the understanding of tomato fruit development and ripening.
Originating in South America tomatoes now ship more than 15 million tons in the United States alone. For years farmers mutated the tomatoes so they would be uniformly light green on the vine at the time of picking, thus allowing them to more easily spot tomatoes that were ripe for the picking. Tomatoes are picked green so they have just the right amount of time to ripen as they reach store shelves. Varieties in the wild on the other hand are ready to harvest when they turn dark green.
To determine the gene change that led to a different color the research team cross cultivated varieties of wild tomatoes with commercial tomatoes. Plants with dark green shoulders were crossed back to cultivated varieties and eventually they narrowed down the culprit on chromosome 10. The group then used the recently completed tomato genome sequence to identify the gene as SlGLK2, a transcriptor factor which controls when and where other genes are turned on and off.
According to ScienceMag.com”
“In wild tomatoes, SlGLK2 increases the formation of chloroplasts, the compartments in plant cells that carry out photosynthesis. Chloroplasts use a green pigment, chlorophyll, to capture the sunlight plants need to grow. A higher number of chloroplasts gives wild tomatoes their darker green color. Even though chloroplast formation and chlorophyll synthesis are among the most important developmental processes in biology, little is known about them, says David Francis, a tomato geneticist at Ohio State University, Wooster, who was not involved in the work. This is a “significant and important” finding, he says. “The authors have described a gene that helps regulate the process.”
The group found that most tomatoes on store shelves have a deactivated SlGLK2 sequence.
Researchers are not sure where or when the sequence turned off but they acknowledge that errors can occur when repeated cross-breeding occur.
There is some good news, researchers were able to inject an intact copy of the gene into tomatoes which in turn increased the amount of glucose and fructose in tomatoes by up to 40%. The injection also increased lycopene, an antioxidant that has many health benefits.