Grafted Tomatoes Grow Best With One Stressed Parent And One Chill One

For the first time, a agriculturally useful crop has been grown by grafting epigenetically modified tomatoes to commercially available shoots. Penn State

In a world struggling to feed more people without consuming additional land or resources, any boost to crop growth is worth celebrating. By grafting epigenetically modified rootstock to unmodified shoots, scientists have produced seeds that dramatically outperform either parent, creating what may be the biggest advance in crop productivity for a long time.

Just as people are changed by stressful situations, plants pushed to the limit of survival grow differently thereafter. Crops denied water at a crucial development stage become more thrifty, an exceptionally important attribute where irrigation water is scarce.

Rather than risking plants' lives by drying them out, Penn State researchers have modified them epigenetically to mimic the effects of surviving a drought. No genes are added or replaced, but by altering the methylation of the MSH1 gene that helps control plant responses to many stressors, the team changed the extent to which 1,380 genes were expressed in tomato plants.

It's hoped plants produced in this way will arouse less public alarm than transgenic crops, while achieving similar boosts in production. Although such epigenetic modifications have been done before, previous studies have not looked at the subsequent generations. To change this, the team grafted modified tomato plants to commercial shoots that had enjoyed an abundance of water and other nutrients in peace.

In Nature Communications, the team report seeds from the grafted plants were 35 percent more productive than their off-the-shelf counterparts, while also apparently being more resilient. Tomatoes grown from these seeds survived a flood that killed most neighbors, invaluable in an increasingly volatile climate. "When a plant experiences a stress such as drought or prolonged extreme heat, it has the ability to adjust quickly to its environment to become phenotypically 'plastic' – or flexible," senior author Professor Sally Mackenzie said in a statement. "And, it turns out, it 'remembers.'"

At the height of the Green Revolution, it was common for hybrids to be produced that doubled or tripled output from a given area. That work helped overcome predictions of global famines caused by population growth, but in recent years progress in crop yields has slowed dramatically. Today, advances edge, rather than bound, forward, and usually only apply to a single type of crop at a time.

That makes Mackenzie's work particularly significant. "Although we did this with tomato, it can be done with any plant,” she said. Mackenzie's team got similar results with the model organism Arabidopsis, although they admit things may be different for longer-lived plants like fruit trees, and didn't see the same benefits when grafting distantly related tomato plants together.

Most scientific advances take a long time to reach the market, but Mackenzie described this one as “ready to go”, with any plant breeder who wants to apply the research welcome to copy their work.

Mackenzie helped discover the MSH1 gene and has already used its epigenetics to boost production 13 to 14 percent in soybeans. Nevertheless, getting more than double that benefit from having only one parent undergo the process was a pleasant surprise.

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