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    UMass Amherst research team tracks evolution of modern-day tomato

    Plump, savory tomatoes fresh off the vine are the stuff of summer memories and a versatile heart of myriad dishes. But have you ever wondered how the modern-day tomato came to be?

    In a new paper, UMass Amherst professors and researchers say they have identified missing links in the tomato’s evolution from a wild blueberry-sized fruit to the version that graces our kitchen tables today. They suggest the fruit evolved genetically via intermediate steps, and that the modern tomato is more closely related to weed-like fruit in Mexico than to semi-domesticated versions in South America, as commonly thought.

    The work could have broader implications, as tomatoes are an important model organism for researching other fruits.

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    “Unlike other major crops, the domestication history of tomato has long been somewhat of a mystery, because all wild tomato species are native to the western coast of South America, but the modern domesticated tomato is known from Mexico," said Professor Ana Caicedo, an associate professor of biology at Mass Amherst and the paper’s senior author.

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    The study, which appears in Molecular Biology and Evolution, is part of a larger research effort supported by the National Science Foundation and led by Esther van der Knaap of the University of Georgia.

    The National Science Foundation had posited that there was an oversimplification of tomato domestication, involving only two major transitions: the first of these transitions is from small and wild version to the semi-domesticated and intermediate one; the second is the transition from intermediate to a fully domesticated, cultivated tomato.

    This new research fleshes out that story, bringing new information to light.

    Hamid Razifard, a UMass postdoctoral research and first author of the research paper, helped to generate new whole-genome sequences for 166 tomato samples. The team created a data-set of public genomic variants. These new samples were created with a special attention to under-represented statistics.

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    “We found that the intermediate group may have originated in Ecuador around 80,000 years ago as a wild species rather than a domesticate. We also found that two subgroups from the intermediate group may have spread northward to Central America and Mexico, possibly as a weedy companion to other crops,” Razifard said.

    He also said Mexico should also be considered as a site for tomato domestication, as those weedy tomatoes seem to have been domesticated 7,000 years ago in Mexico.

    So what’s next for the research? Caicedo said the DNA trait characterization used during the study can be used by breeders for the improvement of tomatoes and other crops.

    Razifard, meanwhile, highlighted another component of the research: the female-majority list of authors.

    "I hope this paper services as a model for gender equity in STEM fields,” Razifard said.