Evolution of fruit size in tomato( Domesticated tomatoes can be up to 100...)

Domesticated tomatoes can be up to 1000 times larger than their wild relatives. How did they get so big? In general, domesticated food plants have larger fruits, heads of grain, tubers, etc, because this is one of the characteristics that early hunter-gatherers chose when foraging for food. In addition to size, tomatoes have been bred for shape, texture, flavor, shelf-life, and nutrient composition, but it has been difficult to study these traits in tomatoes, because many of them are the result of many genes acting together. These genes are often located in close proximity on chromosomal regions called loci, and regions with groups of genes that influence a particular trait are called quantitative trait loci (QTLs). When a trait is influenced by one gene, it is much simpler to study, but quantitative traits, like skin and eye color in humans or fruit size in tomatoes, cannot be easily defined just by crossing different individuals. Now, with genome sequencing and genomics tools, chromosomal regions with QTLs can be mapped and cloned more easily than in the past. These genomic maps can also be compared across plant genomes to identify similar genes in other species. With this knowledge, breeders can improve tomato varieties as well as other less well known food plants in the family Solanaceae.

Dr. Steven D. Tanksley and his colleagues, Bin Cong and Luz S. Barrero, are studying QTLs that influence fruit size. Dr. Barrero, of the Corporacin Colombiana de Investigacin Agropecuaria (CORPOICA), Colombia, will be presenting this work at a symposium on the Biology of Solanaceous Species at the annual meeting of the American Society of Plant Biologists in Mrida, Mexico (June 29, 8:30 AM).

Tomato (Solanum lycopersicum) is a member of the Solanaceae or nightshade family, which also includes potato, eggplant, tobacco, and chili peppers. The center of origin and diversity of tomato and other solanaceous species is in the northern Andes
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