Distribution, Incidence and Severity of Maize Lethal Necrosis Disease in Major Maize Growing Agro-ecological Zones of Uganda

Dora C Kilalo,Godfrey Asea,Daniel K Bomet,John Adriko,Andrew Kiggundu,Douglas Watuku Miano,Florence M’Mogi Olubayo,Barnabas Mudde

doi:10.5539/jas.v10n6p72

Abstract

The distribution, incidence and severity of maize lethal necrosis (MLN) disease in major maize growing agro-ecological zones (AEZ) of Uganda was determined following field surveys carried out in 16 major maize growing districts from 5 AEZ over three consecutive seasons. A total of 604 maize fields were visited and MLN disease status visually assessed and 3,624 maize leaf samples collected for identification and confirmation of the MLN causal viruses by Double antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) and Reverse Transcription Polymerase Chain Reaction (RT-PCR). MLN disease was not widely distributed at an epidemic proportion, with only 36 (5%) of the 604 farms surveyed over three seasons confirmed to have the disease. The MLN incidence and severity was significantly (P < 0.05) higher in the Eastern AEZ during the three seasons. The main MLN-causing viruses detected using DAS-ELISA were Maize chlorotic mottle virus (MCMV) and Sugarcane mosaic virus (SCMV). MCMV was the most prevalent MLN causing virus driving the epidemic in Uganda. The three major districts where MLN disease has been found in all three seasons surveyed are Bulambuli, Tororo and Busia which are hotspots for MLN disease. Strategies to control spread of MLN disease should focus on high risk AEZs and hotspot districts.

Highlights

Maize (Zea mays L.) is a dietary staple and significant cash crop throughout the tropical world; serving as a food security crop for more than 70 million people in Sub Saharan Africa (Melinda et al, 2013)
maize lethal necrosis disease (MLN) disease symptom incidence and severity was highest in Eastern Agro-ecological zone (14% and 1.48) followed by Eastern Highland Agro-ecological zone (12.07% and 1.42), South Eastern Agro-ecological zone (6.17% and 1.2)
Incidence and severity of MLN disease symptoms recorded during second season 2014 was highest in Eastern Agro-ecological zone (9.4% and 1.33); followed by Eastern Highland Agro-ecological zone (4.08% and 1.14) and South Eastern Agro-ecological zone (4.05% and 1.13)

Summary

Introduction

Maize (Zea mays L.) is a dietary staple and significant cash crop throughout the tropical world; serving as a food security crop for more than 70 million people in Sub Saharan Africa (Melinda et al, 2013). Uganda is the eighth largest maize producing country in Africa with 2,748,000 tonnes produced in 2013 (FAOSTAT, 2015). Since 2012, the major threat to maize production in Uganda is the maize lethal necrosis disease (MLN) disease (Asea, 2013). The MLN-causing viruses are known to be transmitted from plant to plant by several insect vectors (Jiang et al, 1992; Cabanas, 2013; Ford et al, 2004) with alternative host plants in maize fields acting as sources of the MLN-causing viruses spread to maize (Nelson et al, 2011)

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