The banana streak virus can not only be spread from plant to plant by insects like most plant viruses. It also integrates its DNA into the banana’s genome. In places like west Africa, where bananas are a staple food, most bananas have now the virus lurking inside them.
When these plants are stressed by heat or drought, the virus emerges from dormancy and causes outbreaks that can destroy plantations. And there’s nothing farmers can do.
Destroying the virus
But Leena Tripathi at the International Institute of Tropical Agriculture in Kenya has now used the CRISPR genome editing method to target and destroy the viral DNA inside the genome of a banana variety called Gonja Manjaya.
The plan is to use these plants to breed virus-free plants for farmers. Her team is also using CRISPR to make the bananas resistant to the virus, so they are not simply re-infected.
But the legal status of genome-edited plants in the west African countries where Gonja Manjaya is grown remains uncertain. “I think right now they are in discussions about whether it requires legislation,” says Tripathi.
The banana streak virus does not infect the popular Cavendish banana. But a fungal strain called Tropical Race 4 is devastating Cavendish plantations as it spreads around the world. Before the 1960s the most popular banana was the reportedly more delicious Gros Michel, which farmers had to stop growing because of the spread of another fungal strain called Tropical Race 1.
Because the Cavendish is a sterile mutant that can only be propagated by cloning, there is no way to breed resistant varieties. Instead, several teams worldwide are trying to use CRISPR to make it resistant to Tropical Race 4.
An Australian team has already genetically engineered the Cavendish to make it resistant by adding a gene from a wild banana. But because of the opposition to GM food worldwide, this variety may never be grown commercially. Using CRISPR is seen as preferable because some countries including the US do not regard genome edited plants as transgenic, depending on what has been done.
