Maize Lethal Necrosis (MLN) disease is caused by synergistic interaction between Maize chlorotic mottle virus (MCMV) and Sugarcane mosaic virus (SCMV). However, some East African countries have detected maize infecting Polerovirus named Maize yellow mosaic virus (MaYMV) also known as Maize yellow dwarf virus (MYDV-RMV) co-infecting maize with MLN viruses. Maize yellow dwarf virus occurrence and distribution in different parts of Kenya are not yet elucidated. This study aimed to establish the occurrence of MaYMV in maize and sorghum in Bomet County, MLN hotspot region in Kenya. Maize (n=90) and sorghum (n=19) samples were collected from East and Central sub-counties of Bomet County in 2019/2020. Reverse transcription-polymerase chain reaction (RT-PCR) protocol was developed and optimized for screening the samples using specific primers. Amplicons of 600 bp, 250 bp and 169 bp were generated for MaYMV, MCMV and SCMV, respectively. The analysis revealed 56% (62/109) of the samples tested positive for MaYMV co-infecting maize with MLN viruses. Sanger Sequencing of representative samples confirmed the presence of MaYMV. BLASTN analysis showed 95-100% sequence identity to MaYMV/MYDV-RMV hence confirmed the occurrence of MaYMV infecting maize and sorghum in Bomet County whose impacts is a potential threat to food security.

Keywords: Occurrence, co-infection, Maize lethal necrosis, Maize yellow mosaic virus, Maize chlorotic mottle virus, Sugarcane mosaic virus