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Maize lethal necrosis (MLN) is becoming a great challenge to maize production that threatens food security for most households in East Africa since 2011. MLN in East Africa, including Ethiopia, is caused by co-infection of maize chlorotic mottle virus (MCMV) and any other potyvirus, often sugarcane mosaic virus (SCMV). A greenhouse study was conducted at Ambo Agricultural Research Center to determine the reactions of various maize genotypes to MLN to identify resistant genotypes that can be either utilized in breeding programs or recommended for commercial production. A total of 306 maize genotypes (275 inbred lines and 31 commercial varieties) collected from various research centers and seed companies were evaluated in the greenhouse under artificial MLN inoculation. Weekly MLN severity score, pooled mean of weekly severity score, area under disease progress curve (AUDPC), final disease severity, and disease incidence were used to assess reactions of the maize genotypes to MLN. Double antibody sandwich enzyme-linked immunosorbent assay test showed that only 2% of the highland maize inbred lines were resistant to MLN, whereas none of the lowland and mid-altitude inbred lines were resistant to the disease. Roughly 7%, 16.7%, and 5.5% of the inbred lines from highland, mid-altitude, and lowland maize breeding programs, respectively, showed moderately resistant reactions to MLN. However, higher proportion of the inbred lines from all the breeding programs revealed susceptible to highly susceptible reactions. Most of the maize varieties evaluated were infected by MLN with different levels of reactions that ranged from moderately susceptible to highly susceptible. Only two highland varieties (Wenchi and Kolba) showed moderately resistant reaction. In general, while most of the maize genotypes evaluated were infected by the viruses, considerable number of inbred lines and varieties showed resistant/tolerant reactions to MLN. Inbred lines that showed good level of resistance to the disease can be used as sources of desirable genes in maize breeding programs, while MLN resistant or tolerant varieties could be recommended for extensive commercial production.

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