Photo/Illutration The images show both good and bad examples of different plants being combined by digesting cell walls with cellulase. Chrysanthemum on top of chrysanthemum, left, and tobacco on top of chrysanthemum, right, were successfully grafted, but linking soybean on top of chrysanthemum, center, proved a failure. (Provided by Michitaka Notaguchi, an associate professor of plant science at Nagoya University)

NAGOYA--Researchers say they have figured out a grafting mechanism that can overcome the “impossible” process of combining widely different plant species.

The grafting technique takes advantage of the strong points of both plants, and has been used to connect a tobacco plant with two distant species, according to the team of scientists from Nagoya University and elsewhere.

The researchers expect their discovery to lead to a much more efficient grafting method, denying the traditional saying that “eggplants do not emerge from a gourd vine,” which means talented children are never born from ordinary parents.

After the team discovered that tobacco plants can be grafted with pea family species, cabbage family variants, such as broccoli, and other varieties, it confirmed successful grafting in 73 species from 38 families.

Of 79 genes actively working in the process, the scientists focused on genes that produce an enzyme known as cellulase that digests cell walls around the grafted sections. The results showed cellulase’s inability makes it difficult to graft trees, likely because the enzyme melts cell walls so that they are glued together.

Grafting techniques have long been used for preventing plant diseases and increasing yields.
Improved grafting technologies are expected to help not only cover more species but also create new plants that can grow in dry zones, salt-damaged lands and other harsh environments.

“The latest achievement reveals how trees are glued,” said Michitaka Notaguchi, an associate professor of plant science at Nagoya University. “Other key genes must also work to play an important role in grafting. We will survey such topics as how the tissues of different plants are connected.”

The team’s findings have been published in the U.S. scientific journal Science at (https://science.sciencemag.org/content/369/6504/698).