Nature – Declan Butler, The disease is caused by strains of a soil fungus called Fusarium oxysporum f. sp.cubense (Foc). A strain of Foc previously wiped out the Gros Michel cultivar, which was the main exported banana variety from the nineteenth century until the 1950s. In response, the industry replaced Gros Michel plants with the Cavendish variety, which is resistant to that Foc strain. But Cavendish is susceptible to the new Foc Tropical Race 4 (Foc-TR4) strain, and could meet the same fate as Gros Michel if the fungus reaches Latin America, the world’s leading banana exporter, says Rony Swennen of the Catholic University of Leuven in Belgium, and a banana breeder at the International Institute of Tropical Agriculture in Dar es Salaam. “It’s a gigantic problem,” he adds. Although Foc strains spread slowly, they are almost impossible to eliminate from soil.”