Current and future potential distribution of maize chlorotic mottle virus and risk of maize lethal necrosis disease in Africa

Abstract

Maize Lethal Necrosis (MLN), caused by the synergistic effect of maize chlorotic mottle virus (MCMV; Tombusviridae: Machlomovirus) and any potyvirus, has the potential to devastate maize production across Africa. Since the first report in Kenya in 2011, MLN has spread to Tanzania, Uganda, Rwanda, and probably other surrounding countries. To understand the spatiotemporal distribution of MCMV and MLN risk in Africa, we developed ecological niche models using a genetic algorithm (GARP). Model inputs included climatic data (temperature and rainfall) and known detections of MCMV and MLN across Africa. Model performances were more statistically significant (p < 0.05) than random expectations, with Receivership Operating Curves (ROC) / Area Under Curve (AUC) scores above 86% and Kappa values above 0.936. Field observations generally confirmed model predictions. MCMV and MLN-positive incidences across the region corresponded to a variety of temperature and precipitation regimes in the semi-arid and sub- humid tropical sectors of central and eastern Africa. Ethiopia, Tanzania, and Democratic Republic of Congo have the potential to lose 662,974, 625,690 and 615,940 km 2 potential maize landmass, respectively. In terms of proportional loss of national maize production area, Rwanda, Burundi, and Swaziland have the potential to lose each 100%, and Uganda 88.1%. Future projections indicate smaller potential areas (-18% and -24% by 2020 and 2050, respectively) but climates consistent with current MCMV distributions and MLN risk are predicted even into the future. In conclusion, MLN risk in Africa is high, hence the need for better allocation of resources in management of MLN, with special emphasis on eastern and central Africa, which are and will remain hotspots for these problems in the future.