Presented by Bright Jumbo, Lava Kumar, Dan Makumbi, George Mahuku and Yangole Luhenda at the Africa RISING East and Southern Africa Review and Planning Meeting, Malawi, 14-16 July 2015

1. Management of Maize Lethal Necrosis
(MLN) in Tanzania
Bright Jumbo1, Lava Kumar2, Dan Makumbi1, George Mahuku2 and
Yangole Luhenda3
1International Maize and Wheat Improvement Centre (CIMMYT)
2International Institute of Tropical Agriculture (IITA)
3Selian Agricultural Research Institute
Africa RISING East and Southern Africa Review and Planning Meeting, Malawi, 14-16 July 2015

2. MLN-Background
 Kansas & Nebraska, USA, 1976
 MLN was first reported in
Kenya in 2011 (Wangai et al.,
2012)
 MLN has rapidly spread in EA
with confirmed reports in
Tanzania, Uganda, Rwanda,
Ethiopia, South Sudan
 In Tanzania, MLN is aggressive
in Mwanza, Arusha regions

3. What causes MLN
 Cocktail of two viruses;
 Maize Chlorotic Mottle Virus (MCMV) in combination with any of the
cereal viruses of family pottyviridea
 Sugarcane Mosaic Virus (SCMV)
 Wheat Streak Mosaic Virus (WSMV)
 Maize Dwarf Mosaic Virus (MDMV)
 Surveys show that most commonly it is MCMV and SCMV causing MLN
in East Africa.
 MLN is spread by insect vectors (Thrips, Aphids)
 Seed transmission is said to be very low, 0.04%, however, this seems to
be the major source of disease introduction to places where there is no
MLN
 MLN was first known in Kansas, USA, in around 70s
 But samples from surveys show that strains present in Africa are similar
to those in ASIA

4. What is the magnitude of yield loss associated
with MLN
MLN causes serious yield losses
where the disease pressure is
high – 100%
 Drying of leaves, reduced
photosynthesis
 Sterility of tassels-no pollen
production
 Poor seed set
 Premature drying of cobs
 Secondary infection-rotting

6. Table1. Maize Yield Losses Associated with MLN-Babati
Pedigree
Grain Yield
(tha-1)
Grain Yield
(tha-1)
MLN
Ear
Rot
(%)
Ear
Rot
(%)
MLN
Number of
Plants plot-
1
Number of
Plants
plot-1
MLN
Ear
Aspect
(1-5)
Ear
Aspect
(1-5)
MLN
SYN(B)F2-5-8/CML539/CML442 7.6 2 4.8 45 22 18 2.8 2.8
SYN(B)F2-17-1/CML539/CML442 7.2 2.2 4.8 20 22 14 2.8 3
SYN(B)F2-14-3/CML539/CML442 7.1 1.8 5.0 19 22 15 2.7 3
SYN(B)F2-17-4/CML539/CML442 7.1 2.2 4.6 24 22 16 2.7 2.8
SYN(B)F2-19-4/CML539/CML442 7.1 1.6 4.6 20 22 18 2.8 3
SYN(B)F2-11-11/CML539/CML442 7.1 2.2 4.8 31 22 18 2.8 2.4
SYN(B)F2-5-5/CML539/CML442 7.0 2.9 4.7 11 22 18 2.8 3.4
SYN(B)F2-23-5/CML539/CML442 7.0 2.1 4.7 35 22 15 2.8 3
SYN(B)F2-22-3/CML539/CML442 7.0 1.4 4.8 45 21 13 2.8 3.3
SYN(B)F2-5-1/CML539/CML442 7.0 1.5 5.0 31 22 12 2.7 3.6
SYN(B)F2-5-4/CML539/CML442 7.0 1.1 4.8 14 22 12 2.8 3.5
SYN(B)F2-14-13/CML539/CML442 7.0 1.3 5.1 57 22 17 2.6 4
SYN(B)F2-9-1/CML539/CML442 6.9 1.5 4.9 47 22 17 2.7 3.6
SYN(B)F2-6-6/CML539/CML442 6.9 2.5 4.7 39 22 18 2.8 3.2
SYN(B)F2-12-2/CML539/CML442 6.9 1.1 4.7 46 22 8 2.6 4.1
SYN(B)F2-12-3/CML539/CML442 6.9 1.3 4.7 45 22 11 2.6 3.5
SYN(B)F2-17-3/CML539/CML442 6.9 2 4.6 32 22 18 2.7 3.1
SYN(B)F2-14-14/CML539/CML442 6.8 1.7 4.9 43 21 17 2.9 3.6
SYN(B)F2-7-1/CML539/CML442 6.8 2.2 5.0 28 22 17 2.7 3.1
SYN(B)F2-7-3/CML539/CML442 6.8 1.7 5.1 35 22 12 2.8 3.3
SYN(B)F2-11-8/CML539/CML442 6.8 0.4 5.3 60 22 16 2.8 4
Comercial Check 6.0 0.9 5.3 49 21 13 3.0 4.2
Experiment Mean 6.4 1.60 4.9 36.2 22 14 2.9 3.5
LSD (0.05) 2.3 1.33* 10.4 34.8* 3 8 0.8 1.1*
CV 18.8 41.85 107.8 48.6 8 30 13.6 16.0

7. Management and Control of MLN
Late planting in March
at MARA farm in Babati
attacked by MLN
Early planting
in January ,
2014, clean
Integrated management
approach is needed
 Host resistance
 Use of resistant varieties is key
 Cultural practices
 Crop rotation
 Use of certified seed
 Timely planting (some how tricky)
 Rogueing of sick plants
 Application of good agronomic practices
 Vector management
 Chemical application (sprays and seed
dressing)?

8. Host Resistance
Several hybrids and inbred lines have
been screened under natural and
artificial inoculation
 A regional MLN screening facility was set
up in Naivasha, Kenya
 To date, over 25,000 hybrids and maize
inbred lines have been screed
 Some new hybrids are showing better
response
 We have identified inbred lines with some
moderate resistance
 Fast track Marker Assisted Backcrossing
program is in place for introgression of
MLN resistance in key susceptible lines at
CIMMYT -Kenya

9. Africa Research in
Sustainable
Intensification for
the Next
Generation (Africa
RISING), is
supporting on-farm
research work on
MLN in Babati,
Tanzania

10. Focus areas
 To identify MLN resistant varieties from available commercial,
farmers and experimental maize varieties grown under high
disease pressure.
 Assess the effectiveness of different disease management options
(cultural practices) in reducing the incidence of MLN for
recommendation in target maize growing areas
 Establish the prevalence of MLN and identify causative virus
strains sampled from diseased maize plants in Africa RISING
research sites in Babati.
 Determine key biophysical factors of MLN epidemiology
 Develop capacity for diagnosis of MLN viruses (equipping
diagnostic lab and training course for relevant staff)

11. MLN TRIALS 2014 in Babati

12. Table2. MeanGrain yield andother important agronomictraits for the top performing
hybrids among the 47 experimental 3way-hybrids (3WHYB-2014-14AFR) and 3
commercial hybrids evaluated atMatufa in Babati under natural MLN infestation.
Pedigree
Grain
Yield
(t ha-1)
Plant
Height
(cm)
Ear
Height
(cm)
Ear
Position
Ears
Per
Plant
Ear Rot
(%)
Grain
Moisture
(%)
Number
of Plants
CKH122206 8.1 205 111 0.5 2.0 20.5 17.1 12
CKH122255 7.2 218 121 0.6 1.4 28.2 20.6 11
CKH122251 7.1 189 108 0.6 1.5 15.0 16.8 12
CKH123730 7.1 216 111 0.5 1.1 5.9 18.3 14
CKH122157 6.8 198 111 0.6 1.2 10.9 17.3 12
CKH122244 6.6 201 113 0.6 1.3 29.7 16.4 14
CKH123995 6.5 220 123 0.6 1.2 41.2 18.5 13
CKH122159 6.4 203 125 0.6 1.6 19.0 17.0 9
CKH121957 6.3 194 103 0.5 1.0 15.9 19.8 15
CKH122253 6.2 221 122 0.6 1.7 24.0 17.7 11
CKH123729 6.0 224 118 0.5 1.1 14.0 16.3 14
SC 627 5.5 206 118 0.6 1.0 24.1 19.6 9
WH509 4.0 208 117 0.6 1.5 22.1 20.0 7
WH403 2.6 195 114 0.6 0.9 28.2 18.0 7
WH505 2.3 196 104 0.5 1.4 47.0 18.6 8
Experiment Mean 4.9 206 112 0.5 1.2 26.3 18.2 12
LSD (0.05) 3.0* 29 26 0.1 0.3* 26.9* 3.6* 4*
MSe 2.2 199 167 0.0 0.0 174.3 3.1 4
CV 30.1 7 12 8.7 13.5 50.3 9.6 18
Number of reps 2 2 2 2 2 2 2 2

13. Table 3. Preliminary results among new maize hybrids evaluated in 33 trials in
Babati
Name of hybrid GY PH (cm) EH (cm) EP EPP ER GM % NP
CKH124960 6.35 197.35 105.09 0.53 1.56 30.50 18.90 11.02
CKH124718 6.05 198.66 107.47 0.53 1.67 15.76 19.45 10.71
CKH124713 6.04 196.92 100.17 0.52 1.30 13.32 21.35 11.14
CKH124783 6.02 206.37 115.82 0.58 1.31 25.03 17.95 10.03
CKH124727 6.02 195.90 95.90 0.51 1.27 7.27 19.10 13.38
CKH124776 5.75 196.51 120.19 0.57 1.34 19.28 20.70 10.62
CKH124742 5.71 187.09 98.09 0.51 1.41 18.05 21.00 10.09
CKH124712 5.70 190.61 96.35 0.51 1.26 29.78 20.05 11.48
CKH124730 5.68 194.67 96.11 0.52 1.26 22.28 18.35 12.15
CKH124743 5.63 185.44 95.54 0.51 1.23 8.85 20.30 13.46
CKH124775 5.60 213.84 110.66 0.54 1.20 20.54 19.20 10.41
CKH124715 5.50 176.08 97.92 0.56 1.25 -0.27 20.40 8.24
CKH124710 5.46 181.65 109.20 0.60 1.20 39.55 19.20 14.54
CKH124781 5.39 195.97 106.69 0.54 1.40 20.00 19.70 12.57
WH403 3.73 182.20 96.46 0.54 1.16 21.67 24.05 6.48
WH505 3.44 187.86 104.02 0.58 1.19 37.96 19.35 12.91
H520 2.75 223.29 126.32 0.59 1.47 44.05 19.20 11.42
Experiment Mean 4.14 191.50 104.77 0.55 1.33 26.96 20.42 10.26
LSD (0.05) 3.13 23.12 17.59 0.09 0.52 30.44 4.46 5.69
MSe 2.44 133.33 77.19 0.00 0.07 231.03 4.95 8.08
CV 37.8 6.03 8.39 8.24 19.52 56.38 10.90 27.70
p 0.61 0.00 0.00 0.27 0.15 0.23 0.41 0.42
p ns ** ** ns ns ns ns ns
NumSignificantSites 0.00 1.00 1.00 0.00 0.00 0.00 0.00 0.00
NumReps 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00

14. Geographic coverage
Sub-Humid District
(1610 to 2178 mts)
Semi-Arid Districts
(1261- 1527 mts)
Medium elevation
Assessment of maize lethal necrosis in AfricaRISING target areas

15. MLN prevalence in 2015 crop season
Widespread and expanding; incidence between 5 to >70%

16. 67.2
43.1
23.3
0
20
40
60
80
Maize lethal
necrosis (MLN)
Maize streak
(MSV)
None
PercentPrevalence of maize lethal necrosis and maize
streak in 2015 crop season (N = 116)

17. 0.0
20.0
40.0
60.0
80.0
100.0
120.0
1
4
7
10
13
16
19
22
25
28
31
34
37
40
43
46
49
52
55
58
61
64
67
70
73
76
79
82
85
88
91
94
97
100
103
106
109
112
115
118
121
124
127
Manyara Dodoma Arusha
Babati
Percentincidence
Prevalence and incidence of maize lethal
necrosis in 2015 crop season (N = 116)

18. MLN Surveys in Tanzania
Table 4. Prevalence, incidence and severity of maize virus diseases during minor maize season (2015)
Region District
No. of
fields
Virus
incidence
(%)
virus
disease
severity
MLN
prevalence
MLN
severity
(%)
MLN
Incidence
(%)
MSV
prevalen
ce
MSV
severit
y
MSV
Incidence
(%)
Arusha Meru 8 60.4 2.7 100 2.5 35 7.5 2.8 29
Manyara Babati 10 20 2.1 90 2 17 30 2.8 10
Manyara Mbulu 5 23 2.3 80 2.2 17 40 2.5 13
Dodoma Kongwa 6 6 2.4 66.6 2.4 4 33.3 2.5 3
Dodoma
Mpwap
wa 7 10 2.3 57.1 2.1 6 42.8 3 4
Total 36 23.8 2.3 78.7 2.2 15.8 30.8 2.7 11.8
Note: In each field 30 plants were assessed; MSV = maize streak virus; MLN = maize lethal necrosis; incidence is
expressed as % infected plants of the total plants assessed; and symptom severity is assessed based on 1 to 5 rating
scale, where 1 = no symptoms and 5 = most severe symptoms

19. Table 5. Incidence and severity of maize viruses on various cultivars observed during minor maize season
surveys (2015)
Variety
Total fields
observed
Virus
incidence
(%)
Mean
severity
MLN Incidence
(%)
MLN
severi
ty
MSV Incidence
(%)
MSV
severity
Local 12 14 2 11 2 3 1
SC627 5 15 2 12 2 3 1
STAHA 3 8 2 6 2 2 2
Stuka 3 33 3 10 2 23 2
TMV-1 3 2 1 1 1 1 1
unknown
3 68 3 40 3 27 3
DK8031 3 22 2 12 2 10 2
Kaspino 1 60 2.6 53 2.4 7 3.5
Kiboseed
5013
1 73
2.7
40
3.1
33
2.2
Pannar
1 10
2.3
3
2
7
2.5
SC719
1 37
2.6
37
2.6
0
0
Note: In each field 30 plants were assessed; MSV = maize streak virus; MLN = maize lethal necrosis; incidence
is expressed as % infected plants of the total plants assessed; and symptom severity is assessed based on 1 to
5 rating scale, where 1 = no symptoms and 5 = most severe symptoms

20. Capacity building
 MLN training was organized in Arusha by IITA, CIMMYT and CIAT
which drew participation from extension, researchers and students
 26 participants
 Key areas covered were MLN diagonistics, vector identification and
MLN lab establishment at SELIAN Agricultural Research Institute in
Arusha, Tanzania

21. Scaling of new diagnostic tools developed in
AfricaRISING
•New diagnostics for new viruses
developed in 2013-14
•Recombinant polyclonal
antibodies against MCMV

22. •Established a MLN diagnostic Lab at Selian Agricultural
Research Institute (SARI), Arusha
•Pathology lab refurbished with essential equipment
•Training to staff

23. •22 persons trained from Tanzania and Kenya (Kenyan
participants supported by CRP-Maize)
•Field and lab diagnosis | Insect vector identification
•Disease control

24. Work in progress
Work presented here continues
 We have MLN trials in Babati to
validate hybrids identified in
2014 season
 Hybrids confirmed in
validation trials will be
recommended for fast track
release for scaling in
subsequent phase
 Capacity building work will
continue
 More MLN surveys will be
done

25. Summary
 MLN is a complex issue that requires integrated efforts involving
researchers, maize producers, seed suppliers, policy makers, crop
regulatory authorities to work together for measures to be effective
 We need an integrated and comprehensive approach that includes
use of host resistance, strong sensitization on importance of using
certified seed, applying good agricultural management practices,
good pest management, inspection of fields to remove diseased
plants at early stages, encouraging crop rotation and timely planting

26. Lets all joins hands and work together to
defeat MLN and keep maize healthy!