1. DISTRIBUTION OF MAIZE LETHAL NECROSIS, ITS VECTORS AND HOST PLANTS IN MAJOR MAIZE GROWING AREAS OF UGANDA
PhD proposed research in Uganda by
Mudde Barnabas PhD student, University of Nairobi
Presented During The Workshop To Develop Strategic Plan For Maize Lethal Necrosis Disease For Eastern And Central Africa, Jacaranda Hotel, Nairobi, Kenya 21st -23rd August, 2013
Supervisors
1. Prof . Olubayo Florence, Faculty of Agriculture, University of Nairobi
2. Dr. Miano Douglas, Faculty of Agriculture, University of Nairobi
3. Dr. Asea Godfrey, National Agricultural Research Organisation (NARO)

2. Background
Maize Zea mays (L.) is one of the chief starchy cereal crops in East Africa
It is the vital staple for over 70 million people
Uganda ranked 10th in Africa
Annual production estimate at 1,373,000 tonnes
Annual yield is 1.5 tons per hectare
Low yields majorly attributed to biotic constraints
Major biotic constraints include diseases caused by
Fungi
Bacteria
Viruses
Most important viruses are
Maize streak virus, Maize rough dwarf virus
And the new Maize lethal necrosis

3. Maize lethal necrosis disease
Maize Lethal Necrosis disease (MLN) first identified in USA in 1976; In East Africa from Kenya and Tanzania (2011); In Uganda (2012).
Symptoms include; drying of leaves, premature plant death; failure to tassel / sterility in male plants; malformed /no ears; premature drying or rotting of cobs
Potential yield losses %. (Wangai et al., 2012)
MLN caused by double infection with Maize chlorotic mottle virus (MCMV) and any of cereal viruses in Potyviridae group; Sugarcane mosaic virus (SCMV), Maize dwarf mosaic virus (MDMV) or Wheat streak mosaic virus (WSMV).
MLN-causing viruses are transmitted by several insect vectors. MCMV (thrips and beetles) MDMV and SCMV (aphids).
Alternate hosts of MLN causing viruses include; Maize, sugarcane, grasses of family poaceae, sorghum, millet and johnson grass.

4. Symptoms
Fine chlorotic streaks
Dead heart symptoms
Complete necrosis

5. Problem statement
Maize Lethal Necrosis disease (MLN) stands out as greatest threat to African food security crop (maize).
In 2012, this MLN disease outbreak was first reported in Busia district in eastern Uganda, it is not known to what extent this disease is now prevalent and distributed in Uganda.
It is not known which maize viruses of the Potyviridae group in Uganda could be combining with MCMV to cause the MLN symptoms observed in maize fields so far.
Apart from maize, the maize lethal necrosis causing viruses are haboured by alternate plant hosts. The potential plant hosts for MLN causing viruses in Uganda not known.
The vectors of the MLN-causing viruses in Uganda are not known and their virus transmission efficiency.
Plant virus epidemics are multi-component systems resulting from interactions between the virus (es), vectors and host plant (s).
A full understanding of the epidemiology of MLN disease is critical for development of sustainable management strategies

6. Objectives General Objective
To provide a better understanding of the epidemiology, host plants, vector range of MLN disease for improved control
Specific objectives of the study
1. To establish the distribution and incidence of MLN in Uganda
2. To determine alternate hosts of MLN causing viruses in Uganda
3. To identify potential insect vectors of MLN causing viruses in Uganda
4. To determine transmission efficiencies of vectors of MLN causing viruses in Uganda

7. Survey in 13 districts of Uganda
Methodology
Survey in 13 districts of Uganda
Maize
Alternate hosts
ELISA and PCR
Objective 1
Objective 2
Collection of potential vectors of MLN causing viruses
Species identification
ELISA and PCR and transmission
Objective 3
Conduct studies to determine efficiency of transmission of different species of confirmed vectors of MLN viruses
Objective 4

8. Methodology
Objective. 1 . Distribution, incidence and severity of MLN in major maize growing districts of Uganda
Data from 13 major maize-growing districts of Uganda
Disease incidence: Estimate of percentage of maize plants infested
Severity assessed using a 1 to 5 scale by Biswanath et al. 2013
GPS coordinates recorded

9. Methodology cont’d
Activity 1.1. Serological and molecular detection of MLN in maize samples
Lab studies at National Crop Resources Research Institute, Namulonge in Uganda.
ELISA against MLN causing viruses (MCMV, SCMV, MDMV, WSMV) as well as antibodies against the entire Potyvirus genus (AGDIA, Elkhart,IN).
Confirmation with reverse transcription-polymerase chain reaction (RT-PCR) using specific primers (Wangai et al., 2012)

10. Methodology cont’d
Objective 2: Identification of alternate plant hosts of MLN in Uganda
Alternate MLN host plants collected from confirmed hotspots of MLN in Uganda.
Identified to species level in collaboration with Botany and Zoology department of Makerere University Institute of Environment and Natural Resources
ELISA against MLN causing viruses (MCMV, SCMV, MDMV, WSMV) as well as antibodies against the entire Potyvirus genus (AGDIA, Elkhart,IN).

11. Methodology cont’d
Objective 3: Identification of potential insect vectors in Uganda
Activity 3.1. Vector collection
Sampling vectors from confirmed hotspots of MLN in Uganda.
Potential vectors colonizing maize will be identified to species level in collaboration with ICIPE.
Insect vector viral content MLN causing viruses will be determined using Enzyme Linked Immunosorbent Assay as previously described by Chu and Francki, (1982).
Real time PCR will be also be used to quantify viral load in potential vectors

12. Methodology cont’d
Objective 4: Determine transmission efficiencies of potential vectors in Uganda to transmit MLN
Vectors transferred to MLN-infected 3 week old maize
For each insect vector, 3 species selected for transmission studies
MCMV symptoms noted in seedlings at 5, 10, 15, 20, after feeding
Viral content will be measured at each of these stages using ELISA
Percent transmission rates based on number of infected plants out of total observed

13. Expected budget and output
Budget : USD 90,000
Outputs
1. Incidence and distribution of MLN in Uganda established.
Knowledge of alternative hosts and vectors of MLN causing viruses prevalent in Uganda
3. At least 4 scientific papers and PhD thesis published.

14. Acknowledgements NARO Government of Uganda Development Partners
University of Nairobi

15. THANK YOU FOR LISTENING