Plants Don't Need Sex to Create Entirely New Species: Asexual Grafting is Key

It turns out that new species can be created asexually in nature. Scientists have found that plants have the unique ability to create an entirely new species by reproducing asexually.

Occasionally, two different plant species will interbreed with each other in nature. While this usually causes problems since the genetic information of both parents doesn't match, sometimes nature uses a trick; instead of passing on only half of each parent's genetic material, both plants transmit the complete information to the next generation. The chromosomes are able to find their suitable partner in meiosis, and a new species is created. This, however, is sexual reproduction; asexual reproduction is another matter entirely.

Grafting is a process that can enable plants to grow together at their contact zones. For example, researchers can graft pest-sensitive grape cultivars onto pest-resistant wild rootstocks. It's this grafting that may generate a new species.

"In our previous work we were able to prove that, contrary to the generally accepted dogma, there is horizontal gene transfer of chloroplast genes at the contact zone between grafted plants," said Ralph Bock, one of the researchers, in a news release. "Now we wanted to investigate if there is a transfer of genetic information between the nuclei as well."

The researchers introduced resistance genes against two different antibiotics into the nuclear genomes of two tobacco species, which usually can't be crossed. Afterward, one of the species was grafted onto the other. After fusion occurred, the scientists then excised tissue at the contact zone and cultivated it on a growth medium containing both antibiotics so that only cells containing both the resistance genes and, thus, DNA from both species would survive. In the end, the researchers succeeded in growing resistant plantlets.

"Indeed, we found 72 chromosomes in the resistant plants," said Bock in a news release. "Seventy-two is the sum of the 24 N. glauca chromosomes and the 48 N. tabacum chromosomes." In other words, the researchers successfully produced allopolyploid plants without sexual reproduction.

The findings reveal that it's possible to create an entirely new species through grafting rather than through sexual reproduction. This could have enormous implications for plant breeding in the future as researchers attempt to create plants with more desirable traits.

The findings are published in the journal Nature.