The Constant Evolution of the Humble Tomato

tomatoes are favorites of gardeners and advocates of locally grown foods. The tomato enthusiast might conclude that, given the immense varieties, heirlooms must have a more diverse and superior set of genes than the tomatoes available in grocery stores, those ordinary hybrid varieties such as cherry and plum. However, their seeming diversity is only skin-deep: heirlooms are actually feeble and inbred—the defective product of breeding experiments that began hundreds of years ago, and exploded thanks to enthusiastic backyard gardeners. The irony of all this," says Steven Tanksley, a geneticist at Cornell University, is all that diversity of heirlooms can be accounted for by a handful of genes. There're probably no more than 10 mutant genes that create the diversity of heirlooms you see. But rather than simply proving that the myth about the heirloom's diversity is wrong, Tanksley's deconstruction of the tomato genome, along with work by others, is showing how a small berry-like fruit from the Andes became one of the world's top crops. B The cultivated tomato is a member of the nightshade family that includes New World crops such as the potato, which spread around the globe after Christopher Columbus brought them back to…