How tweaking 'hybrid vigor' gene generates higher tomato crop yields

Researchers have determined a way to produce more tomato fruit without sacrificing that unique and necessary bushy plant shape.

The study by CSHL researchers has revealed one genetic mechanism for hybrid vigor, a property of plant breeding that has been exploited to boost yield since the early 20th century. Teasing out the hidden subtleties of a type of hybrid vigor involving just one gene has provided the scientists with means to tweak the length of time that bushy tomato varieties can produce flowers. In these plants, longer flowering time substantially raises fruit yield.

First identified at CSHL by George Shull in 1908, hybrid vigor - or heterosis, as biologists call it - involves interbreeding genetically distinct plants to generate offspring more robust than either inbred parent.

In his previous work, CSHL Associate Professor Zach Lippman and Israeli colleagues identified a rare example of hybrid vigor involving a genetic defect in the gene that makes florigen, a hormone that controls the process of flowering and flower production.

The mutation dramatically increases tomato yields in bush tomatoes, and Lippman and his team, led by postdoctoral researcher Ke Jiang, set out to understand the mechanism behind this remarkable result.

They found that bushy plants with a mutation in one of the two copies of the florigen gene, producing half as much florigen as plants without the mutation do, postpone the moment when they stop producing flowers.

This, in turn, leads to many more fruits overall. "This is because," Lippman explains, "bushy tomato varieties are highly sensitive to the amount, or dosage, of the florigen hormone, which alters plant architecture - that is, how many flowers can form before growth ends. These discoveries lead to an exciting prediction: that it may be possible to tweak florigen levels to increase yields even further.