Fusarium wilt Tropical Race 4 is a devastating fungal disease that destroys banana crops worldwide, particularly the commercially important Cavendish variety. Researchers discovered that this fungus carries a special accessory chromosome that is not essential for basic fungal survival but is critical for its ability to infect and damage banana plants. By removing this chromosome in laboratory studies, scientists found that infected bananas suffered significantly less damage, suggesting that understanding this chromosome could lead to better strategies for protecting banana crops from this destructive disease.