Abstract
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 30 th 2019
Highlights
Maize (Zea mays) is the backbone of food security in Kenya
At 40 dpi, maize plants initially inoculated with Maize chlorotic mottle virus (MCMV) followed by Sugarcane mosaic virus (SCMV) had more severe symptoms leading to a ‘dead heart’ (Fig. 5) compared to maize plants inoculated initially www.iiste.org with SCMV followed by MCMV but less than for those inoculated with Maize lethal necrosis (MLN) (Fig. 1 and Fig. 2)
In this study, maize seedlings at the fourth leaf stage were initially inoculated with SCMV or MCMV followed with MCMV or SCMV after seven days to have a sequence combination of SCMV + MCMV and MCMV + SCMV
Summary
Maize (Zea mays) is the backbone of food security in Kenya. Large as well as small-scale farmers produce the crop and a large percentage of the population depends on maize farming for income generation (Manje et al 2015). Single infections with either MCMV or SCMV especially at early stages of infection are often inconspicuous and resemble physiological disorders Such infections cause only mild mosaic or mottling symptoms and a moderate reduction in plant growth. Infection of plants with only MCMV results in various symptoms, including moderate fine chlorotic spots, which appear first on the youngest leaves, which coalesce and develop into broad chlorotic stripes along the veins. These chlorotic stripes contrast with dark green tissue when observed against the light (Lommel et al 1991). Plants affected with MLN disease appear stunted and show a general chlorosis, leaf bleaching and necrosis
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