Transmission and Persistence of Maize Lethal Necrosis in Infested Soil and Infected Maize Residue

Maize lethal necrosis (MLN) is a viral disease caused by a co-infection of maize chlorotic mottle virus (MCMV) and any one of cereal viruses including sugarcane mosaic virus (SCMV), maize dwarf mosaic virus, wheat streak mosaic virus or Johnsongrass mosaic virus. MLN has been identified as the most devastating maize disease that causes the highest yield loss in major maize growing areas in Eastern Africa including Ethiopia. In this study, field assessment, laboratory, and greenhouse experiments were conducted using MCMV and SCMV infected maize residue and infested soil to: (1) assess the role of MLN infected maize residue and infested soil in the transmission of MLN causing viruses, and (2) determine the longevity of the viruses both in the infected maize residue and in the infested soils. Serological detection and back-inoculation test results showed that MCMV was detected and confirmed to be transmitted from infested soil to newly germinated maize seedlings. However, SCMV was neither detected in soil samples from infected fields nor transmitted to maize seedlings. The present study confirmed that MLN infested soil is an essential medium for the survival and spread of MCMV under natural conditions. Under experimental condition, MCMV remained persistent and transmissible up to 6 months to maize planted on MLN infested soil mixed with MLN infected maize residues. Proper management or clearing of crop residues in the field after harvest is necessary to minimize adverse effects of MLN on maize production. Crop rotation is also one of the ways of freeing the soil from MLN disease.