Characterising maize viruses associated with maize lethal necrosis symptoms in sub Saharan Africa

Abstract

Maize lethal necrosis disease (MLN) is an emerging disease in East Africa caused by the introduction of Maize chlorotic mottle virus (MCMV). Recent activity seeking to limit spread of the disease is reliant on effective diagnostics. Traditional diagnostics applied on samples with typical field symptoms of MLN have often given negative results using ELISA or PCR for MCMV and Sugarcane mosaic virus (SCMV). Samples collected in the field with typical MLN symptoms were examined using next generation sequencing (NGS). SCMV was found to be more prevalent than suggested by targeted diagnostics. Additionally, the panel of samples were found to be infected with a range of other viruses, seven of which are described here for the first time. Although not previously identified in the region, Maize yellow mosaic virus (MYMV) was the most prevalent virus after MCMV. The development of targeted diagnostics for emerging viruses is complicated when the extent of field variation is unknown, something that can be negated by using NGS methods. As a result we explored MinION technology which may be more readily deployable in resource poor settings. The results show that this sequencer can diagnose known viruses and future iterations have the potential to identify novel viruses.

Aphid transmission of maize yellow mosaic virus: an emerging polerovirus

“…1c) that coalesced and became necrotic after the tasseling stage (data not shown). A kind of synergism in maize involving a potyvirus and MCMV, intensifying symptoms, and increasing damage to the host is known as maize lethal necrosis (Niblett and Claflin 1978), and the involvement of poleroviruses in the disease has been the subject of recent reports (Wamaitha et al 2018;Adams et al 2017). However, here, we did not detect MCMV in any sample, and the synergism was exclusively due to the co-infection of SCMV and MaYMV, as experimentally shown by our studies.…”

“…R. maidis is a known vector of other poleroviruses, such as barley yellow dwarf virus-RMV (BYDV-RMV) (Rochow 1961) and sugarcane yellow leaf virus (Schenck and Lehrer 2000). Originally described as a luteovirus, BYDV-RMV was later assigned to the genus Polerovirus based on genome sequence analysis and renamed as Maize yellow dwarf virus-RMV (Miller et al 2013;Krueger et al 2016). Luteovirids have a persistent circulative relationship with their vectors (Gray and Gildow 2003), explaining the retention of MaYMV by R. maidis for relatively long periods in the present study.…”

Occurrence, genetic diversity, and recombination of maize lethal necrosis disease-causing viruses in Kenya

“…They were 99.4 % similar to MH205607 ( Wamaitha et al, 2018 ) hereby described as MYDMV-RMV from Kenya and MF684367, MaYMV from Ethiopia. They were also 99 % similar to MF974579, a Kenyan isolate ( Massawe et al, 2018 ) and MF425856 Ethiopian isolate ( Adams et al, 2017 ).…”

“…The paired-end sequencing yielded 102,169,109 reads (35–151 bp) but 53,297,590 good quality reads were obtained (17–122 bp) after performing quality control. Following contigs assembly and BLASTN identification, most samples strongly showed the presence of MCMV and SCMV while a few samples showed the presence of Maize Yellow Mosaic virus (MaYMV), a recently described polerovirus ( Adams et al, 2017 and Massawe et al, 2018 ). It was also demonstrated that there were no artefactual sequences that were generated in this study for the MCMV, SCMV and MaYMV had significant genome coverage by de novo and reference assemblies.…”

“…MaYMV has been detected in maize samples from recent MLN survey studies in eastern Africa and other MLN endemic countries worldwide ( Asiimwe et al, 2019 ). In eastern Africa, MaYMV has been found present in all recent MLN related studies though some publications have described it as Maize yellow dwarf mosaic virus (MYDMV) ( Adams et al, 2017 : Massawe et al, 2018 : Wamaitha et al, 2018 ; Read et al, 2019 ; Asiimwe et al, 2019 ; Kiruwa et al, 2019: Stewart et al, 2020). The recent study of maize infecting viruses in South Korea ( Lim et al, 2018 ) identified MaYMV prevalence but no link to MLN related symptoms.…”