The pathogen that caused the Irish Potato Famine is secretly building a massive genetic reservoir across five South American countries.

Genetic monitoring of the potato blight across Ecuador, Colombia, Peru, Bolivia, and Uruguay reveals a complex and shifting population structure. This fungus remains the single most dangerous threat to global potato production today. By mapping how the pathogen moves and evolves in its native South American range, new strains can be identified before they jump to other continents. These findings show that the famine pathogen is far from extinct and is actively adapting to modern fungicides and climate conditions. Safeguarding the fourth most important food crop in the world depends entirely on tracking these hidden genetic shifts.