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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
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
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
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
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
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)?
Host ResistanceSeveral 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
Africa Research in
Sustainable
Intensification for
the Next
Generation (Africa
RISING), is
supporting on-farm
research work on
MLN in Babati,
Tanzania
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)
MLN TRIALS 2014 in Babati
Table 2. Mean Grain yield and other important agronomic traits for the top performing
hybrids among the 47 experimental 3way-hybrids (3WHYB-2014-14AFR) and 3
commercial hybrids evaluated at Matufa 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
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
Geographic coverageSub-Humid District
(1610 to 2178 mts)
Semi-Arid Districts
(1261- 1527 mts)Medium elevation
Assessment of maize lethal necrosis in AfricaRISING target areas
MLN prevalence in 2015 crop season
Widespread and expanding; incidence between 5 to >70%
67.2
43.1
23.3
0
20
40
60
80
Maize lethalnecrosis (MLN)
Maize streak(MSV)
None
Perc
ent
Prevalence of maize lethal necrosis and maize
streak in 2015 crop season (N = 116)
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
10
0
10
3
10
6
10
9
11
2
11
5
11
8
12
1
12
4
12
7
Manyara Dodoma Arusha
Babati
Perc
ent
incid
ence
Prevalence and incidence of maize lethal
necrosis in 2015 crop season (N = 116)
MLN Surveys in Tanzania
Table 4. Prevalence, incidence and severity of maize virus diseases during minor maize season (2015)
Region DistrictNo. 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
DodomaMpwapwa 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
Table 5. Incidence and severity of maize viruses on various cultivars observed during minor maize season surveys (2015)
VarietyTotal fields observed
Virus incidence
(%)Mean
severityMLN Incidence
(%)
MLN severi
tyMSV 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 1unknown
3 68 3 40 3 27 3
DK8031 3 22 2 12 2 10 2Kaspino 1 60 2.6 53 2.4 7 3.5
Kiboseed 5013
1 73
2.7
40
3.1
33
2.2
Pannar1 10
2.33
27
2.5
SC7191 37
2.637
2.60
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
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
Scaling of new diagnostic tools developed in
AfricaRISING
•New diagnostics for new viruses
developed in 2013-14
•Recombinant polyclonal
antibodies against MCMV
•Established a MLN diagnostic Lab at Selian Agricultural
Research Institute (SARI), Arusha
•Pathology lab refurbished with essential equipment
•Training to staff
•22 persons trained from Tanzania and Kenya (Kenyan
participants supported by CRP-Maize)
•Field and lab diagnosis | Insect vector identification
•Disease control
Work in progressWork 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
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
Lets all joins hands and work together to defeat MLN and keep maize healthy!