Toronto: Using gene-editing tools to create virus-resistant plants may have an unintended consequence of propagating of mutated viruses, according to scientists including one of Indian origin. Researchers at the University of Alberta in Canada and University of Liege in Belgium attempted to genetically engineer cassava plants to fight off viruses.
“Because this technology creates a selection pressure on the viruses to evolve more quickly, and also provides the viruses a means to evolve, it resulted in a virus mutant that is resistant to our interventions,” said Devang Mehta, from University of Alberta. For the study, published in the journal Genome Biology, the researchers used a new gene-editing technology called CRISPR-Cas9 in an attempt to design cassava plants that could cut the DNA of the mosaic virus and make the plants resistant to its damaging effects.
They were not successful and decided to sequence hundreds of viral genomes found in each plant to understand exactly what happened. “We discovered that the pressure that CRISPR-Cas9 applied to the virus probably encouraged it to evolve in a way that increased resistance to intervention,” said Mehta, who noted CRISPR-Cas9 has many other applications in food and agriculture that do not pose the same risks.
CRISPR-Cas9 is found in nature, where bacteria use it to defend against viruses. However, the researchers found the 
technology results in different outcomes in plants — and researchers are stressing the importance of screening against these sorts of unintended results in the future. The cassava plant is a starchy root vegetable that is consumed for food throughout the tropics. Cassava is a primary staple crop grown in South America, Africa and Asia, from which a billion people get most of their calories each day.
Each year, cassava crops are plagued by cassava mosaic disease, which causes 20 per cent crop loss. It is the mosaic disease that researchers endeavoured to engineer against. The research team is encouraging other scientists who are using CRISPR-Cas9 technology to engineer virus-resistant plants, to test their plants to detect similar viral mutations. “We need to do more research on these types of applications of CRISPR-Cas9 technology before we proceed with field testing,” said Mehta.