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!