Scientists have warned that nearly half of the world’s bananas are at risk of extinction due to a fungal infection. Cavendish bananas, which account for 47% of global banana production, have been targeted by a soil-born fungus. Crops in Asia, Africa, Australia and Central America have been impacted by the disease, which causes bananas to wilt and go brown. Cavendish replaced Gros Michel, which was the main banana until the 1950s after the Panama disease wiped the Big Mike type out. Cavendish was immune, which allowed it to dominate the market until scientists discovered a new strain called TR4 in 1997. "Since then, it has spread to India and China, the world’s largest producers of bananas. It has also spread to the Middle East and Africa and very recently was found in South America," James Dale, professor of banana biotechnology at Queensland University of Technology, told Insider. Scientists at QUT are working on a TR4-resistant banana using CRISPR-Cas9, a technique that allows DNA to be altered. A genetically modified version of the Cavendish banana, called QCAV-4, is under development.