Effect of Sequence of Infection of Maize with Viruses Causing Maize Lethal Necrosis on Disease Development

Maize is the main staple food crop in Kenya. However, its production is constrained by maize lethal necrosis (MLN) disease, a result of dual infection of maize plants with Maize chlorotic mottle virus (MCMV) and a potyvirus Sugarcane mosaic virus (SCMV). In the field, infection by the two viruses is independent rather than occurring simultaneously since MCMV and SCMV are transmitted by different vectors. This study aimed at evaluating the effect of sequence of infection of maize by the two viruses causing MLN disease in the greenhouse. Two susceptible maize hybrids (DUMA 43 and H614D) were each infected with either of the two viruses first and later inoculated with the second virus. The plants were assessed for disease development weekly over a period of 2 months. Symptoms were significantly (p=0.05) more severe in maize plants initially infected with MCMV followed by SCMV, resulting in rapid death of plants compared to plants infected with SCMV followed by MCMV. The results indicate that severity of symptoms is influenced by the sequence of infection of maize plants with the causal agents of MLN disease. More remarkable was the synergism observed in maize plants pre-inoculated with SCMV followed by MCMV that had a slow manifestation of MLN disease symptoms. The results suggest that initial infection by SCMV may result in maize plants developing some levels of resistance resulting in initial suppression of MCMV infection. This study contributes to the understanding of resistance mechanisms exhibited by the plants during MLN disease development. Keywords: Maize, MCMV, SCMV, Synergism, Sequence of infection DOI: 10.7176/JNSR/9-8-06 Publication date: April 30th 201