In plants such as tomatoes, flowering (and therefore yield) is controlled by a delicate balance between the florigen protein, which promotes flowering, and another related protein, that delays flowering. A mutation in only one copy of the florigen gene causes the hybrid to produce more flowers in less time - the key to improved yield.

"It's the Goldilocks concept," explains Lippman. "What we find is that to maximize yield, you can't have too much or too little florigen. A mutation in one copy of the gene results in the exact dose of florigen required to cause heterosis."

The scientists have observed the gene's heterosis effect in different varieties of tomatoes and in plants grown in different climate and soil conditions, both in Israel and locally in New York at CSHL and the Cornell Horticultural Experiment Station at Riverhead, NY.

In addition to superior yield, the hybrids also display another, perhaps equally important quality - taste. Tomato plants only produce a finite amount of sugar, which they distribute equally among their fruits. So higher yields usually result in each fruit having less sugar. But, remarkably, the florigen gene also boosted the sugar and sweetness of individual fruits.

The researchers are already planning to explore if genes related to florigen in other crops can cause heterosis and improve yield. The concept that a mutation in only one copy of a single gene can improve yield has broad implications for plant breeding. "Mutant plants are usually thrown away because of the notion that mutations would have negative effects on growth," says Lippman. "Our results indicate that breeding with hybrid mutations could prove to be a powerful new way to increase yields, not only in tomato, but all crops."

Source: Cold Spring Harbor Laboratory