Humans have been grafting plants onto other plants for thousands of years, but only in the last few generations have we understood the genetic implications of the technique. Researchers from Penn State and the University of Florida partnered with a Nebraska startup to combine genetically “stressed” roots with regular tomato plants to study the effects on crop yields. The team found that stressed roots boosted production dramatically, even several generations down the line. This could have applications far beyond bigger, better tomatoes.
Grafting allows you to combine the properties of two different plants. Usually, this takes the form of a “rootstock” that grows from the ground and a “scion” above ground. The rootstock is usually selected for heartiness or adaptability, and the scion contains the genes you wish to produce fruit, flowers, or seeds.
Many of the techniques currently used to boost crop yields rely on adding or removing genes, which comes with a whole set of concerns and controversies. However, neither the rootstock nor the scions in this study have any new genetic material. Instead, they have been modified “epigenetically.” That simply means the researchers have altered the expression of genes to change how the plant behaves rather than changing the genes.
The team targeted a gene in tomato plants known as MSH1, which controls stress responses in many plants. MSH1 is a DNA repair protein that slows the rate of mutation, which is usually what you want. However, plants can suppress MSH1 when stressed by extreme temperatures or lack of water, allowing them to become more adaptable. The rootstocks used in this study had been modified in just such a way, and grafting scions onto them caused a whopping 35 percent increase in growing productivity. This boosted growth even persisted over five generations when those seeds were cultivated without further grafts. Growing that first generation on genetically stressed rootstocks essentially turned them into a line of super-growers.
An unexpected weather system also revealed the offspring of the grafted plants were hardier than your average tomato plant. In 2018, storms dropped more than seven inches of rain at Penn State’s agricultural research center. Many of the unmodified control plants were wiped out, but the offspring of grafted plants largely survived and thrived.
The team notes that the same techniques could work on a wide variety of plants, and this could become vitally important as climate change affects crops. It might be possible to create stressed rootstocks to induce quick, effective genetic changes in scions that go on to produce more food in harsher conditions for generations to come.
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