Researchers from Newcastle University have said that breeders, in their quest for larger, redder, longer-lasting tomatoes, have inadvertently bred out key characteristics that help the plant defend itself against predators.
In recent years, there have been calls to protect biodiversity, not only to improve the health and resilience of natural ecosystems, but also because ‘wild relatives’ of key crops on which humans rely can carry traits that will prove vital in combating new crop pests or diseases, improving the nutritional value of crops and helping adapt them to a changing climate.
Newcastle researchers said wild tomatoes have a dual line of defence against glasshouse whitefly - the main insect pest for tomato growers. These defences include 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" blocking the whitefly's feeding tube.
Thomas McDaniel, who described these mechanisms, said breeders need to rediscover some of the natural traits that have been lost over generations of plant breeding; speaking about the natural resistance of wild plant varieties Thomas said it that in many cases it would be better to "breed some of that wildness back in" to crop varieties instead of continuously looking for new methods of pest control.
"By selecting for certain characteristics we have inadvertently lost some really useful ones.”The tomatoes we buy in the supermarket may have a long shelf life and be twice as big as the wild varieties but the trade-off is an intensive and costly pest control regime -- both biological and in the form of chemical pesticides.
"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."
The team led by McDaniel found that when given free choice, whitefly were 80% more likely to settle and feed on the commercial tomato plants - in this case Solanum lycopersicum or 'Elegance' - over a wild variety - Lycopersicon pimpinellifolium. By fitting gold wires to the back of individual whitefly and measuring the electro-chemical signals as they fed on the plant sap, the team found the insects spent more time 'roaming' and less time feeding on the wild varieties than those which settled on the commercial plants.