Translating Ethiopian potato seed networks: Identifying strategic intervention points for managing bacterial wilt and other diseases

Informal seed trade can exacerbate crop disease epidemics. Potato production across Ethiopia is threatened by the spread of seedborne pests and pathogens, particularly by bacterial wilt, caused by the Ralstonia solanacearum species complex (RSSC). The RSSC is commonly dispersed through informal trade of seed potato, with the potential to move long distances across Ethiopia and among trading countries. Efficient disease testing programs and formal seed systems can reduce the risk of disease expansion in national potato cropping systems. We characterized networks of potato value chain actors. We also identified candidate locations for disease surveillance and management interventions for improved seed systems, and locations at high risk for bacterial wilt establishment. We propose strategies to reduce the spread of bacterial wilt via infected seed. We analyzed seed potato stakeholders' perceptions, characterizing interaction networks of potato value chain actors, focusing on stakeholders engaged in seed potato quality assurance. We collected data regarding Ethiopia's potato seed systems using expert knowledge elicitation and analyzed the risk of national spread of the RSSC and other pathogens. Network metrics were used to characterize the informal seed system in Ethiopia, along with simulations of pathogen spread across an epidemic network in social-ecological scenario analyses. We characterized potato exports and imports, evaluating the risk of pathogen movement through Ethiopia's trading partners and neighboring countries where bacterial wilt has not yet been reported. Ware potato farmers and traders were reported to have weak communication with other stakeholders in the potato value chain. In network analyses and simulated epidemics, locations in Agew Awi, Gamo, Gofa, Kembata and Tembaro zones were identified as candidate priorities for national surveillance of pathogen invasion and important for management interventions and formal seed system development. Ethiopia has potato commodity trade with countries where bacterial wilt has not been reported, and Ethiopia may be at risk of reintroduction of the RSSC from countries where it is present. Improving seed systems to manage the RSSC and other seedborne pathogens is important for supporting food security and the livelihoods of smallholder farmers in Ethiopia. This analysis provides a baseline for prioritization for implementing surveillance systems and management programs targeting the locations identified, which can be built on as more data and model components become available. Improving communication between ware potato traders and other stakeholders can also help to strengthen informal trade of seed potato and mitigate pathogen spread in infected seed. • Seedborne diseases like bacterial wilt threaten potato seed systems in Ethiopia. • We integrate across data types to evaluate priorities for this system. • We report candidate locations for formal seed systems and seed potato surveillance. • Stakeholder interactions with farmers and seed traders could be strengthened. • Ethiopia trades with countries reporting bacterial wilt, a risk for reintroduction.