Breeding for high yield tomatoes has engineered out resistance to pests study finds

Wild tomatoes are better able to protect themselves against the destructive whitefly than modern, commercial varieties, new research led by Newcastle University has shown.

Image: Pixabay
Image: Pixabay

The research showed that in our quest for larger, redder, longer-lasting tomatoes we have inadvertently bred out key characteristics that help the plant defend itself against glasshouse whitefly (Trialeurodes vaporariorum) – one of the most problematic pests in the UK’s commercial tomato crops.

The project also revealed that wild tomatoes have a dual line of defence against these voracious insects. They have an initial mechanism, which discourages the whitefly from settling on the plant in the first place and a second line of defence, which happens inside the plant where a chemical reaction causes the plant sap to "gum up" and block the whitefly's feeding tube.

Thomas McDaniel, the PhD student who led the research, said: "By selecting for certain characteristics we have inadvertently lost some really useful ones. Our research suggests that if we can breed the whitefly resistant genes back into our commercial varieties then we can produce a super tomato that not only has all the characteristics that we have selected for but is also naturally resistant to the whitefly."

Whitefly damages the plant in three ways – by extracting sap and therefore vital nutrients, by creating a sticky 'honeydew' on the surface of the plant which attracts mould, and by transmitting damaging plant viruses through their saliva.

In the study, funded by the Biotechnology and Biological Sciences Research Council (BBSRC), the team also found that when given free choice, the whitefly were 80 per cent more likely to settle and feed on commercial tomato plants – in this case Solanum lycopersicum or 'Elegance' – over the wild variety – Lycopersicon pimpinellifolium.

"One option would be to revert back to growing more of the older, wild varieties, and certainly we are already seeing a trend towards this, particularly on allotments and among smaller growers," said McDaniel.

"However, lower yields means the wild varieties are unlikely to be a viable option on a large scale.

"Our findings suggest that if we can breed the wild, whitefly resistant genes back into our tomatoes – either through a selective breeding programme or genetic engineering – then it offers a real solution for the commercial tomato industry."

Project supervisor Dr Barry Brogan, also from Newcastle University, said the findings highlighted the importance of maintaining biodiversity.

"There has been growing interest in traditional and wild varieties of fruit and veg, driven mainly by people wanting to re-capture the tastes of their childhood," explains Dr Brogan.

"But actually it's playing a vital role in protecting these older varieties and maintaining biodiversity. If we allow our wild species to be lost then we risk losing potentially useful traits that we might need at a later date."

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