Geneticists improve on 10,000 years of tomato domestication

From their giant fruits to compact plant size, today’s tomatoes have been sculpted by thousands of years of breeding. But mutations linked to prized traits—including one that made them easier to harvest—yield an undesirable plant when combined, geneticists have found.

It is a rare example of a gene harnessed during domestication that later hampered crop improvement efforts, says geneticist Zachary Lippman of Cold Spring Harbor Laboratory in New York. After identifying the mutations, he and his colleagues used CRISPR gene editing to engineer more productive plants—a strategy that plant breeders are eager to adopt.

“It’s pretty exciting,” says Rod Wing, a plant geneticist at the University of Arizona in Tucson. “The approach can be applied to crop improvement, not just in tomato, but in all crops.”

The geneticists had previously screened a collection of 4,193 varieties of tomato, looking for those with unusual branching patterns. From that collection, they tracked down variants of two genes that, together, caused extreme branching similar to what plant breeders had seen. One of the two genes, the team reports in a paper published online in Cell on 18 May, is responsible for the jointless trait.

The other gene favours the formation of a large green cap of leaf-like structures on top of the fruit—a trait that was selected for thousands of years ago, in the early days of tomato domestication. The benefits of this trait are unclear, Lippman says, but it may have helped to support heavier fruits.

With these genes uncovered, his team used CRISPR–Cas9 editing to eliminate their activity, as well as that of a third gene that also affects flower number, in various combinations. This generated a range of plant architectures, from long, spindly flower-bearing branches to bushy, cauliflower-like bunches of flowers—including some with improved yields.

Read more at Scientific American