Tomatoes to be tastier after experts discover a mutant gene

The mutant gene increases yields and also produces sweeter fruit. Researchers believe cousins of the gene in other crops might have a similar effect.

Hybrid vigour, also known as 'heterosis', is the phenomenon where two genetically different parents produce fitter, stronger offspring.

Researchers investigating hybrid vigour in tomatoes turned to a vast "mutant library" of 5,000 plants, each with a single gene mutation that affects growth.

The team picked a diverse set of mutants and set about crossing each one with its "normal" counterpart, keeping an eye out for hybrids with improved yield.

They hit on one which increased yield by 60 per cent. This hybrid had one normal copy and one mutated copy of a single gene that produces a protein called florigen.

Study leader Dr Zach Lippman, from Cold Spring Harbor Laboratory in New York, said: "What we find is that to maximise yield, you can't have too much or too little florigen. A mutation in one copy results in the exact dose of florigen required to cause heterosis."

Florigen was discovered in 2005 and instructs plants when to stop making leaves and start making flowers. Scientists also discovered that having one copy of the mutant florigen gene boosted the sugar content of the tomatoes, making them sweeter.

Usually, increasing yield "dilutes" the amount of sugar available so that each fruit carries less. The findings were reported in the journal Nature Genetics.

Dr Lippman's team is now planning to explore if genes related to florigen in other crops also cause hybrid vigour and improve yield.

"Our results indicate that breeding with hybrid mutations could prove to be a powerful new ways to increase yields, not only in tomato, but all crops," said Dr Lippman.