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POSTERS: New and emerging diseases

Distribution and population of viruses in maize (Zea mays) in the United Republic of Tanzania
Deogracious Massawe - The Ohio State University. Lucy Stewart- USDA ARS

Maize chlorotic mottle virus (MCMV) coinfection with any of several viruses in the family Potyviridae, causes maize lethal necrosis (MLN), characterized by severe necrosis and yield loss. The Potyviridae viruses are endemic to Tanzania, while MCMV was first reported in 2012 in northern Tanzania. Little information is available regarding the distribution of MCMV in Tanzania. Therefore, a survey was conducted in 2016/2017 to test the prevalence and distribution of viruses in maize across the country. Sampling for symptomatic maize and a second unbiased sampling at regular intervals across field transects was used to collect 1100 samples from 110 fields representing 11 regions. Next generation sequencing (NGS) and serological assays were used for virus discovery and diagnosis. Sequences mapped to important maize viruses, including sugarcane mosaic virus, MCMV and maize streak virus. MCMV distribution varied widely by region. Of all the reads that mapped to MCMV, 70.3% mapped to Northern region samples but only 0.22% mapped to Southern regions samples.Sequences with top hits to maize yellow dwarf virus (MYDV-RMV2), Johnsongrass mosaic virus, maize associated totiviruses, maize associated pteridoviruses and taro vein chlorosis virus were found. Analysis of transect samples showed that the incidences of potyviruses were similar across regions, whereas; MCMV was found across the country but incidences were highest in the Northern regions