Don’t like the seeds in tomatoes? You might be pleased to know that seedless ones have been created by gene editing.
The technique will make it possible to make a much wider range of seedless fruits than is currently available – and also means farmers might not have to rely on declining bee populations. Whether we ever see such fruits on supermarket shelves, however, may depend on how regulators decide to treat gene-edited crops.
Several types of seedless fruits, from bananas to cucumbers to grapes, are already widely available, but many have come about by luck rather than design. Seedless bananas are the result of accidental crosses between subspecies, for instance, while other seedless fruits stem from spontaneous mutations. There are a few seedless varieties of tomato, but they have taken breeders many years to create.
Now Keishi Osakabe at Tokushima University in Japan and his colleagues have used the CRISPR gene-editing technique to deliberately introduce a mutation that makes tomatoes seedless. The mutation increases levels of a hormone called auxin, which stimulates fruits to develop even though no seeds have begun to form.
The precise nature of the CRISPR technique meant that no mutations were introduced into other parts of the plant genome. The only obvious difference is that the mutant plant’s leaves had simpler, less intricate shapes than normal, because higher auxin levels also affect the formation of leaves.
“We haven’t tasted them yet, but in theory they should taste the same,” says Osakabe.
Freed from seeds
A few attempts have been made at creating seedless tomatoes using earlier genetic-engineering techniques. But these methods were clunky and time-consuming, whereas CRISPR is quick, easy and accurate.
Some “seedless” fruits just have very small seeds, and still require pollination. But completely seedless – or parthenocarpic – fruit like this tomato do not require pollination at all. They could therefore improve food security by reducing our reliance on declining numbers of bees, says Saul Cunningham at the Australian National University.
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| Development of a fetus of the usual (top) and edited tomato |
The downside for farmers is that seedless plants have to be grown from cuttings, which may be more labour-intenstive. Tomatoes are usually grown from seed, but they can also be propagated by cuttings.
Some people also like the flavour that tomato seeds add. Seedless versions would, however, be ideal for processing into sauces and pastes.
And CRISPR could be used to develop other types of fruit crop that don’t require pollination, as well as introduce beneficial mutations that improve traits such as stress tolerance, says Osakabe.
Whether these seedless varieties make it to shop shelves may depend on whether gene-edited plants have to meet the same criteria for approval as genetically modified plants, which would greatly increase costs. Some argue that where gene-editing is used to introduce mutations already found in some of the plant we eat, it should not require such strict regulation.