Irrigation can create new green bridges that promote rapid intercontinental spread of the wheat stem rust pathogen

Abstract Wheat stem rust epidemics caused by the obligate pathogenic fungus Puccinia graminis f.sp. tritici have historically driven severe yield losses on all wheat growing continents and, after many decades of control, is re-emerging as a disease concern. In 1998, highly virulent race able to overcome 90% world cultivars, Ug99, was identified in Uganda. Since initial detection, pathogen has evolved new variants and spread countries. The original variant from East Africa Middle with three years between detection Ethiopia subsequent Yemen. 2014, another Ug99 (TTKTT), one most complex virulence profiles, detected Kenya. This also East, but only year Iraq. Here we investigate potential airborne migration routes account for rapid TTKTT beyond using an integrated model combining outputs meteorology-driven fungal spore dispersion epidemiological models seasonal availability susceptible crops conditions release infectivity. We find viable pathways 2018/19 season that incorporate critical stepping-stone locations Yemen or Saudi Arabia, presence newly irrigated regions Ethiopia. Our results indicate increasing importance areas Ethiopia, Arabia inter-regional movements. Future movement races out considered likely expand. Targeted surveillance use mitigation strategies including durable resistant varieties irrigation are required reduce risks enhanced dispersal other regions.