For a brief moment in the 1990s, the UK dared to dream of a better tomato. In February 1996 the shelves of Sainsbury and Safeway were crammed with newly-launched cans of tomato paste made from a fruit that, thanks to a tweak to its genome, was more flavourful and cheaper to process. On the can, a yellow label proudly proclaimed the paste’s genetically modified origins.
The paste – the first genetically modified food sold in the UK – was a hit, selling 1.8 million cans in three years. Stacked next to its unmodified doppelgänger, the cheaper paste often outsold paste made with normal tomato varieties. “My prediction is that in ten to 15 years, almost all plant foods will be genetically modified in some way,” Don Grierson, the biologist who created the edited tomato, prophesied at the time.
And then all at once the genetically-modified house of cards came tumbling down. In June 1998, the investigative current affairs show World in Action aired an episode, based on preliminary and insufficient scientific data, implying that genetically modified food was harmful to human health. In the ensuing media storm, the public turned their backs on the genetically modified tomato paste and with it, the dream of a more flavourful tomato.
But now the hunt for a less bland tomato is underway again. Armed with new genetic insights and breeding methods, researchers are returning us to the sweet, tart, tangy tomatoes of yore. After half a century of blandness, a tastier tomato might finally be on the horizon.
Since the Second World War, the fresh tomatoes sold in UK supermarkets have steadily become rounder, more uniform and less flavourful. “In the last five or six decades producers have focussed on high yield, introducing resistance to diseases and ship-ability – being able to grow them far away and ship vast distances,” says Harry Klee, a specialist in the genetics and biochemistry of tomato flavour at the University of Florida.
As the tomato industry grew, it became more centralised. Italy and Spain together account for just under two-thirds of the EU’s entire tomato production. Tomato growers, driven by the demand for year-round availability of fresh fruit, started focusing their breeding efforts towards plants that produced fruit that was round, plump and bright red, and lots of it. Since the 1950s, the average yield of a tomato plant has gone up by 300 per cent – at the cost of flavour.
“Flavour is just so complicated and involves so many different genes that breeders really haven't had the tools to accurately follow it, measure it and select for it, so they’ve basically ignored it,” Klee says. Although modern tomatoes are plumper than their antecedents, they’re filled out with water instead of the sugars that form the basis for most of the fruit’s flavour compounds.
What these plumper tomatoes lack in flavour, they make up in shelf life. Starting in the 1980s, breeders started cultivating tomato plants with a naturally-occurring genetic mutation that slowed the ripening process. Plants armed with a single copy of the of the ripening inhibitor gene produced fruit that ripened more slowly, meaning that growers could harvest the fruits while they were still firm and able to withstand the bump and tumbling of long journeys by lorry and cargo ship. The longer the fruits stay firm, the less susceptible they are to funguses and other pathogens that could infect the plants when their cell walls break down.
This ripening inhibitor – which is now present in most of the widely-sold commercial varieties – meant that the growing could become ever more centralised while tomatoes reached supermarkets even further afield. In the US, where almost two-thirds of tomatoes are produced in Florida and California, the total value of fresh tomatoes topped $1.22 billion (£940 million) in 2015.
But all of this optimisation has had a disastrous impact on the fruit’s flavour. “The downside is that they’re not really fully ripe. They just don’t taste as good,” says Jim Giovannoni, a plant molecular biologist at the Boyce Thompson Institute in Ithaca, New York. “They're just kind of tasteless because they haven't developed the sugars, they haven't developed the acids.”
Left to ripen on the vine, a truly ripe tomato – when it is at its most flavourful – is much softer to the touch than the taut, fit-to-burst tomatoes we’re used to. But to consumers, softness is a sign of a tomato whose best days are well behind it. “In theory, the perfect tomato is one that is fully ripe, but just more firm,” says Giovannoni. “This has long been the holy grail for tomato breeders.”
For a better tomato, plant biologists like Klee and Giovannoni are digging back into the fruit’s flavourful past to uncover the genetic basis for their superior flavour. In June 2019, Klee co-authored a paper detailing the genes that determine tomato flavour, narrowing the field down to a set of 20 or so genes that have the strongest influence on taste.
Like humans, tomato plants contain two copies of every gene, including those that determine flavour. Klee and his colleagues worked out which version of each gene was responsible for better flavour, and which was associated with worse flavour. When it comes to their flavour-determining genes, most modern tomatoes have inherited slightly more bad versions of genes than good ones.
Now they know what’s missing from modern tomatoes, they’re starting to work out how to re-introduce flavour to commercially-grown tomatoes. To do that, Klee is returning to some of the oldest tomato varieties in the US and crossing those tomatoes with existing commercial varieties. The three varieties Klee has picked as his starting point – Brandywine, Maglia Rosa and Peacevine Cherry – were chosen because they each have a handful of the eight genetic variations that Klee pinpointed as being linked to good flavour.
Breeding tomato plants is a painstaking business. Pollination has to be done by hand, and it takes between five and six months for the cross-bred tomatoes to grow. Although Klee and his colleagues use molecular breeding techniques to discard cross-bred tomatoes that didn’t pick up the desired genes without needing to grow them, the process is still slow. “If we were doing GMOs we could engineer a tomato today that would taste vastly better,” says Klee, who expects to test the first crop of improved tomatoes by next spring. But these plants will only have two or three of the eight genetic variations linked to good flavour. The question is whether this is enough to impart a truly superior taste.
And even if Klee is able to improve the flavour of his tomatoes, there’s another challenge looming. Today’s commercial varieties have been bred for reliability and yield – but introducing better flavour might come at the cost of yield. “We've made varieties that taste fabulous, and don't make that high yield,” says Klee. And although a small number of growers have taken up these varieties, tomatoes that sacrifice yield for taste will always be a niche market.
Ultimately, we might have to settle for a compromise tomato. “I think we can make vast improvements in these commercial tomatoes. Will they ever taste like a 100-year-old heirloom? Maybe not. But I’m sure that we can make a tomato that will give that 100 per cent yield and give you vastly better flavour.”
But will anyone buy it? “There is a subset of consumers who are willing to pay a premium for flavour.” says Giovannoni. In the UK, it’s becoming much more common to see tomatoes sold in supermarkets under their variety names. The San Marzano, one of only two tomato varieties designated by the True Neapolitan Pizza Association as the proper topping for a Neapolitan pizza, is now a familiar sight in high-end supermarkets.
And there are signs that even lower-end commercial tomatoes are starting to recover some of their lost flavour. In 2019, Giovannoni published a paper detailing the genetic variety between 725 different cultivated and wild tomatoes. In the process, they came across a gene involved in the production of volatiles – compounds that evaporate easily, contributing to the aroma and flavour of tomatoes.
While the rare version of this gene is abundant in wild tomato varieties, it was almost completely lost in commercially cultivated tomatoes, existing in just two per cent of older varieties. But now the proportion of cultivated tomatoes with the gene is starting to creep up to around seven or eight per cent. “If you look back ten years there has been a lot of improvement,” Giovannoni says.
While the wait for improved tomatoes continues, there are a few rules that buyers can follow to try and avoid bland fruit. Smaller tomatoes are more likely to be more flavourful than their larger cousins. “Size actually runs runs counter to flavour. the bigger the tomato is, in general, the less flavour it has.” And although some modern tomatoes have been bred to resemble older varieties without sharing in their flavour, on the whole oddly shaped tomatoes are more likely to be from a more flavourful variety. “If you see something that looks weird, there's a decent chance that it's a better tomato than what you're seeing in the supermarket.”
This article was originally published by WIRED UK
