Status of maize lethal necrosis disease in seed production system in Kenya

Maize production in Kenya is now under threat from the devastating maize lethal necrosis (MLN) disease in the field. This study was conducted to assess status of MLN in maize seed production fields from both small- and large-scale producers in Kenya. The survey was conducted in five Agro-ecological Zones (AEZ)s in 13 counties in 2015, 2017, 2018, and 2019. Sampling for asymptomatic and non-symptomatic was done using standardized protocol. On-site maize chlorotic mottle virus (MCMV) testing was performed by immunostrips followed by laboratory qRT-PCR test. A total of 2,550 ha was surveyed with 21% having MLN disease and varying levels of severity. The MLN incidence and severity was not significantly different (P > 0.05) in the various Kenyan sampled agro-ecological zones, counties, maize varieties, and maize growth stages. Elevated MLN incidences and severities were observed in sub-humid AEZs comprising Embu, Uasin Gishu, Nakuru, and Elegeyo Marakwet counties that form the hotspots for MLN disease. The main MLN-causing viruses detected using q-RT-PCR were MCMV and sugarcane mosaic virus (SCMV). Out of the total samples analyzed using qRT-PCR, 38% were found to have MCMV, 14% with SCMV, and 18% with both MCMV and SCMV. From the 185 sample analyzed with immunostrip from 2017 to 2019, 29 (16%) were positive for MCMV. Phytosanitary programs should be included in seed legislation for legal adoption and strategies to control the spread of MLN disease should focus on high-risk hotspots agro-ecological zones and counties.