Tasty tomatoes will be back on the shelves

Tasty tomatoes could soon be put back on the supermarket shelves without resorting to '˜Frankenstein food' genetic modification.

Friday, 27th January 2017, 10:07 am
Updated Friday, 27th January 2017, 11:03 am

Consumers constantly complain the commercial varieties on sale lack the flavour of older varieties.

Most breeders have focused on yield, disease resistance, and firmness which are essential for shipping, long-term storage, and external appearance at the expense of flavour.

Now scientists from the University of Florida have identified the chemical combinations and genes to make them taste great again.

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But it will still be at least four years before they start appearing in the aisles.

To get the best tasting ones, the study advised consumers to pick smaller tomatoes which retain their taste compared to larger varieties.

Professor of horticultural sciences Harry Klee also stressed his technique involves classical breeding, not genetic modification

Prof Klee said: ‘The tomato is the highest-value fruit and vegetable crop worldwide and an important source of micronutrients in the human diet.

‘Nonetheless, deterioration in flavour quality of the modern commercial tomato relative to heirloom varieties is a major cause of consumer complaint.

‘To address this problem, we performed a comprehensive study of the chemistry and genetics of tomato flavour

‘We’re just fixing what has been damaged over the last half century to push them back to where they were a century ago, taste-wise.

‘We can make the supermarket tomato taste noticeably better.’

The study, in the journal Science, first quantified flavour associated chemicals in 398 modern, heritage and wild accession.

Then 160 tomato samples representing 101 varieties were evaluated by a consumer panel that rated the samples on qualities such as ‘overall liking’ and ‘flavour intensity.’

This identified 13 chemical compounds associated with flavour that were significantly reduced in modern varieties relative to heirloom varieties.

Genetic sequencing identified the corresponding lost genes.

He added: ‘The flavour of any food is the sum of interactions between taste and olfaction.

‘For the tomato, sugars and acids activate taste receptors, while a diverse set of volatile compounds activate olfactory receptors.

‘Volatiles, in particular, are essential for good flavour.

But he noted removing specific carotenoid-derived volatiles or refrigeration which selectively alters the volatile content of fruit without altering sugars and acids results in consumers disliking the end product.

The modern tomato lacked sufficient sugars and volatile chemicals critical to better flavour and these traits were lost because breeders lacked the tools to routinely screen for flavour.

The study looked at ‘alleles,’ the versions of DNA in a tomato gene that give it its specific traits.

Prof Klee likened the concept to human DNA - everyone has the same number but a particular version of each gene determines traits such as height, weight and hair colour.

He said: ‘We wanted to identify why modern tomato varieties are deficient in those flavour chemicals

‘It’s because they have lost the more desirable alleles of a number of genes.’

The locations of the good alleles in the tomato genome were identified and the genes that control synthesis of all the important chemicals were mapped.

Once these were found genetic analysis was used to replace bad alleles in modern tomato varieties with the good alleles.

But because breeding takes time and they are studying five or more genes the genetic traits may take three to four years to produce in new tomato varieties.

He concluded: ‘Modern commercial tomatoes do not have the flavour of older varieties.

‘Although post harvest practices, such as refrigeration, can irreversibly damage

flavor, making improvements in flavour-associated chemicals is the first step to restoring the potential of widely grown commercial varieties.

‘Our results provide a roadmap for improvement of flavour.

‘The genes and pathways identified here in the tomato almost certainly point to pathways worth investigating for improvement of flavour quality in other fruit crops.’