This week, an international team of researchers, led by the Chinese Academy of Agricultural Sciences in Beijing, is publishing a brief genomic history of tomato breeding, based on the sequencing of 360 varieties of the tomato plant.

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Scientists at the University of California Davis also worked on the gene sequencing project, providing seed from both cultivated tomatoes varieties and related wild species (wild crop relatives).

The work builds on the first tomato gene sequence, which was completed two years ago. UC Davis scientists said it has given researchers and crop breeders a detailed insight into the domestication of the tomato plant, which belongs to the 'nightshade' family. The family also includes potatoes and aubergines. A number of plants in tomatoes' family have become staple crops for a variety of cultures around the world.

Researchers discovered how early domestication and modern breeding influenced the genetic makeup of cultivated tomatoes. Looking at domestic tomatoes' genes alongside the plants' wild relatives led to discoveries including that selection of certain two independent genes during the domestication process, which led modern tomatoes to become 100 times larger than their wild ancestors.  

The international research also laid bare the value of preserving crops' wild relatives; expert scientists have warned that, as crop plants' breeding stock narrows and biodiversity declines, we risk losing important traits in wild or older commercial strains plants, which could hold the key to dealing with threats posed by climate change, pests or disease.  

The investigation into tomatoes and their relatives revealed that specific areas of the tomato genome were unintentionally depleted in the process of creating the modern tomato. DNA around genes conferring larger fruit size and others governing disease resistance were both affected.

UC Davis' Roger Chetelat said, "These stretches of genetic uniformity illustrate the need to increase overall genetic diversity in modern varieties and highlight the important role that the Rick Tomato Genetics Resource Center and similar collections play in housing much of the genetic variability that will be critical for future breeding and research on tomato."