The document discusses research on the cassava virus known as cassava brown streak virus (CBSV). CBSV poses a major threat to cassava production in Africa by reducing yields by up to one third. The research aims to "tame" or control CBSV through various strategies including mitigation, co-existence, and eradication. The research is conducted by the International Institute of Tropical Agriculture (IITA) and involves developing diagnostic tools, understanding CBSV epidemiology through field experiments, assessing virus diversity, and promoting tolerant cassava varieties. The goal is to reduce the negative impacts of CBSV on smallholder farmers in Africa.

1. Taming the Cassava Virus Monster:
A Research for Development Case Study
James Legg: Review Seminar – IITA-Ibadan, March 22, 2011

2. CLARFIYING DEFINITIONS

4. Merriam-Webster Definition
1. A creature of abnormal form or
structure
2. One who deviates from normal or
acceptable behaviour or character
3. A threatening force
4. One that is highly successful

5. How do you tame it?
1. Stab it through the heart with a knife
 Outcome. DEATH (unless it’s a vampire, in which
case you need a wooden stake)
2. Put some fresh cassava leaves in its supper
 Outcome. DEATH
3. Infect it with a nasty chronic disease
(preferably a virus)
 Outcome. WEAKNESS
4. Be extra nice to it (and hope it reciprocates
the favour)
 Outcome. UNAFFECTED

6. Effect of Taming Strategies on Outcomes
for Monsters and Humans
Taming Strategy Also Called Who Wins?
1 (Murder) Eradication Humans
2 (Infection) Mitigation Mainly humans
3 (Friendship) Co-existence Mainly monsters
4 (Chasing) Chasing Monsters Humans

8. …….but they can look pretty scary…

9. And together ‘attack’ humans indirectly through
removing ca. 1/3 of all production of one of their
food staples in Africa: Cassava
4.5
4
3.5
3
Kg/plant
2.5
2
1.5
1
0.5
0
V
g
y
-U
lth
M
V
AC
ea
M
H
g+
C
EA
-U
V
M
C
EA

10. Human Defense Strategy Against this Attack ?
Primarily Strategy 2
Mitigation
Adequate ?

12. CBSD
incidence
2010
(GLCI)
Map: Hein Bouwmeester

13. CBSD
incidence
change
2009-10
Map: Hein Bouwmeester

14. How Good has our Taming
been so far?
Cassava Mosaic Geminiviruses (CMGs)
Conventional HPR – virtual immunity
Cassava Brown Streak Viruses (CBSVs)
Limited effort
Promotion of ‘tolerant’ varieties
Cassava Whiteflies
Largely ignored. Virus management perceived
to be more straightforward

15. Problems in Taming CBSVs
Knowledge. Almost none prior to 2008
Symptoms. Cryptic. Field diagnosis hard
Awareness. Little before late 2000s
One-dimensional. Existing mitigation work

16. Status of CBSD Knowledge
Element Pre-2008 Post-2008 IITA
1. Partial sequencing S
2. Whole genome sequencing X
3. Confirmation of aetiology X
4. Symptom relationship characterization L
5. Crop loss assessment L
6. Determination of vector X
7. Characterization of transmission L
8. Field-based epidemiology L
9. Regional epidemiology L
10. Development of diagnostics S
11. Molecular markers L
12. Conventional HP tolerance L
13. Transgenic resistance X

17. Framework for CBSV
Research at IITA
Foundation of support through CORE
GLCI Project (IITA-Ibadan, IITA-Tanzania)
Biotechnology Project (IITA-Kenya)
Malawi CBSV Project (IITA: Tanzania, Ibadan
and Malawi)

20. 795
Diversity of CBSVs in Malawi
780
SPF
(Slide from Lava Kumar)
MV
-ug
280 R3)1
279
)2
3/r3)4
)4
CBSV
3)4
208(f3/r3)4
178 /r3)4
217(F3R3
167 (f3/r3)4
(10
35 (10-1 1)3
)4
(10
f3/r3
FJ
18 3(f3 /r3)4 )1
17 0 (f R3)1
35 (10/ 1)2
292 (F3
/r3
(f3/r
82
3(F
17 7(f3 3R3
35
- 11
- 11
17
2
168(f
(f3
(f3
FJ
229(
Karonga & Rhumpi 95
27
3
3R
(f3
82
170
)2
)2
231
/r3 )4
CB
8( 0- 1
27
17
A SV 35
3)2
6( /r3
21
94
10 1
)4
)4
6(
28
1)2
1
CB F31 3(K 8(15 /r3
1
-1 )2
AY SV 10 6BH 0-
f3
008 (K 52(101) 11 f3 3)4
442 BH C -1 C )2 0.1 7( /r )4
CB 1P
2) BS )2 20 3(f3 3/r3 )4
S
AF V f /r3 3)1
FN4
FN4
234 31(typ CPV 29 18( (f3 3R
2341 1 10 e 3 6 (F 3
7 CB 7 CBS 53 A)
CBCP 32 24 /R3)
SV-C V N 3 (F3
P (N am-M SV 5 )2
A Y 00
8440 am - oz 33 (F3R3 )2
Moz 1
CBSV
(type ) 275 3(10-1 1)3
C) CP 24 3(10/1 3
17 0/ 11)
A Y 007
597 C B 335(1
/1 1)3
SV CP 209(10
357(F3R3 273 (10/11)3
)2
354(F3R3)2 332(f3/r3)4
355(F3R3)2
354 (10/11-)3 -Tz UCBSV 181(f3/r3)4
273(F3R3)
271(F3R3) 2
10 -2 N
9(ele-11)2zz 173(F3/R 2
l35ed(10 T 1)3
ie 7 1 ( 1 T z
a3eln -ele-/1(T)3
(N
-CP nd 5nd e-211
BSV -Nalie alie 55(l10
3
/ All areas 241
138 (F3R3
3)3
243 (F3/R3)1
18 C BSVCP (N iende
234 6 C V -
P
FN4 341 BS l )C 26 (F3 )3
V-N
a
eB 25 1(F /R3)
2
FN4 3416
C BS (ty
p
3)4 24 0EU3R3)2 3
(F9
E
8C SV 3/r 2 7( U31 9R 8
N42 2341 4(f 2548(FF3/R63)1
EE E E
F CB 9( 3R 1683 1
UU U U9
4 31 33
F 3 3 ) 29 C
91 91 1
FN 41 )4
91
84 /r3 3)2 4
68 68 3
R3 )2 C BS
(f33R /r3)
68
00
28 7 32 0 C
9 )2 BS V
AY
2
28 5(F (f3 V (BS
)3
C C CB BS
BS S S V
1
25 294
68
(L A
/1
B
W 2)
29 ( f 3/ 3
V V V (B (IG
0
2228(
(1
R2 CP
(H(N S A8
96 5(F
5(f f3/r r3/) 3
EU9EU9
9
80
)C
M TG A 4 ) C
3/r 3)4R )3
A9 1 ) C P
FJ039
P
80(F
242 (F
1682 6826 C
3)4
)C)C P
8
9 3
0
26 (F3/R )1
P P
209 (F3R3)1
(
3R 3
F3 R3)
13 (F3
43
1
328(F3/R3)3
4
9(
520 C
5 CB BSV (ML
321(F3/R3)3
R3 1
7 R3
81 (F3/R
F3 3)3
13
337(f3/r3)4
)2
)1
R3
8(1
SV (
BSV-M
)1
0- 1
14
274 -11)2
23(1
M LB
1)2
3)3
(F3R3
(10-
0
LB T z
3) C P
11)2
70 isolates were analyzed from six districts
281
B9) CP
)1
Based on 3’ coat protein gene sequence
(10
-11
Neighbor-Joining method; 1000 bootstraps
)2
Reference sequences from GenBank are with accession numbers

21. CBSV Diagnostics
at IITA-Tanzania

22. CBSV Diagnostics Validation
Tanzania CBSVs detected by primers combination
CBSV 10/11 with CBSV UG F/R detect > 99% real-time +ves
Working with IITA-Ibadan/NRI to add F3/R3, new primers
CBSV CBSV Real CBSV UG CBSUV
10/11 F/R Real
CBSV + + - -
UCBSV-1 - - + +
UCBSV-2 + - + +
CBSV+UCBSV-1/2 + + + +

25. Putting PCR into practise
PCR underway: ISABU,
Bujumbura, Burundi
PCR results: ISAR,
Ruhengeri, Rwanda

26. New Understanding of Epidemiology
Epidemiology Questions
Can it spread through plant parts ?
Can it spread via other plants ?
Is there a vector ?
If so, how good is it?
How important is plant vs. vector spread ?
What are the effects of environment ? (crop
intensity, crop management, variety, temperature)
Are all these things the same or different for
different viruses ?

27. What are the conditions for doing
epidemiology experiments ?
Guaranteed CBSV-free planting material
TC introductions through NRI partnership
Establishment of isolated nuclear multiplication sites
Usambara Mountains – eastern Tanzania
Sensitive, reliable and robust diagnostics
Developed with IITA-Ibadan, NRI and FERA
Routine RT-PCR and real-time RT-PCR in Tanzania
Extensive experimental programme
Field and screenhouse experimental sites set up

30. Whitefly Control – CBSV Epidemiology

31. TC Epidemiology Trial – Kibaha,
Tanzania

32. TC Epidemiology Trial – Kibaha,
Tanzania
Second Planting, cv. Kiroba – 4 sites

33. CBSD Epidemic Simulation - Kibaha
Materials: CBSD-infected spreader, CBSD-free test plants,
whiteflies introduced
Treatments: Drought and fertilization
Replicates: 1 (next to spreader) to 4 (far from spreader)

34. CBSD Epidemic Simulation Results

35. Inoculum Pressure Assessment Study
Tertiary Multiplication Sites
Question? How does the location of a tertiary site
affect CBSD infection
Plan: Assess inoculum pressure for 20 tertiary
sites in Lake Zone, Tz
Measured: CBSD in multiplication sites as well as
surrounding farmers’ fields
Factors Compared: District, Source of planting
material, Inoculum pressure, Virus species
Virus Diagnostics: Used to confirm virus
presence and identity

36. CBSD incidence in multiplication sites vs.
surrounding farmers’ fields

37. Effect of distance from surrounding farmers’ fields
on CBSD incidence in multiplication sites

38. 21 CBSV 10-11
CBSVs in Inoculum
138 CBSV 10-11
120 CBSV 10-11
57 CBSV 10-11
108 CBSV 10-11
Pressure Study
121 CBSV 10-11
116 CBSV 10-11
101 CBSV 10-11
94 CBSV 10-11
(IITA-Tanzania)
92 CBSV 10-11
43
141 CBSV 10-11
12 CBSV 10-11
135 CBSV 10-11
26 CBSV 10-11
50
80 CBSV 10-11
102 CBSV 10-11
CBSV
18 CBSV 10-11
106 CBSV 10-11
131 CBSV 10-11
145 CBSV 10-11
Farmers’ Fields:
137 CBSV 10-11
AY008440 short
30
62
AY008442 short
AY008441 short
Both UCBSV and CBSV
32 AF311052 short
65 AF311053 short
25
65
141 CBSV UG
142 CBSV UG
123 CBSV UG
Tertiary Sites:
65
CBSV MLB9 short
90 129 CBSV UG
36 45
96 CBSV UG
54 CBSV UG
Mainly CBSV
37 62 CBSV UG
DQ837303 short
75 DQ837302 short
43 DQ837304 short
98
22 CBSV UG
72 CBSV UG UCBSV
98 CBSV UG
10
72 121 CBSV UG
105 CBSV UG
122 CBSV UG
57
35 CBSV UG
25 CBSV UG
49
37 25 CBSV 10-11
19
35 CBSV 10-11
50 98 CBSV 10-11
72 CBSV 10-11
48
14 52 CBSV 10-11
18 93 CBSV 10-11
CVYV short
0.02

39. Inoculum Pressure Assessment Study
Outcomes
Key Factors in CBSD infection?
Source of planting material: No
District location: No
Virus species prevalent: No
Proximity to neighbouring fields: YES
QMP outcomes: 8 out of 22 fields failed. All
isolated fields passed
Control implications: Isolation critical.

40. Vector Transmission
IITA partnering with NRI, UK (Maruthi)
CBSV/UCBSV: Summary of NRI/IITA PhD
results
Irrefutable confirmation of B. tabaci as vector
Min. acquisition period – 5 mins
Min. Inoculation period – 30 mins
Max. retention time – 1 hour
Results suggest semi-persistent transmission

42. Regional Epidemiology
Tanzania Lake Zone Surveys 2000-2009
(Jeremiah and Ndyetabula)
Wf Pk 1 Wf Pk 2 Wf Pk 3 CBSD>10 CMD >50
Bukoba 2000 2004 2007 2008 2000
Muleba 2000 2004 2007 2007 2001
Biharamulo 2000 2004 2007 2007 2001
Karagwe 2002 2004 2009 2008 2005
Ngara 2002 2007 2009 2008 2005
Ukerewe 2000 2002 2009 2007 2001
Geita 2002 2009 2008 2001
Sengerema 2004 2009 2008 2005
Mwanza 2004 2009 2009 2003
Magu 2004 0 2009 2005
Kwimba 0 0 0 2007
Misungwi 2004 0 0 2007
Kibondo 2004 2007 0 2003
Kasulu 2004 2007 2008 2003
Kigoma 2004 2007 2009 0 2007
Bukombe 2004 2007 2009 2008 2005
Kahama 0 0 0 2009 0
Bunda 2004 2007 2007 2007
Musoma 2004 2007 2009 2007 2005
Tarime 2004 2007 2009 2007 2005
Serengeti 2007 2009 2008 2005

43. Whitefly Population Peaks vs.
Disease Outbreaks
12
10
8
A v e r a g e D if f e r e n c e in Y e a r s 6
4
2
0
W h it e ly a b u n d a n c e p e a k s

44. Proposed Model for Epidemiology
of CMD and CBSD Pandemics

47. Monster Taming Strategies
The Case of CBSD
Taming Strategy Also Called Who Wins?
1 (Murder) Eradication Humans
2 (Infection) Mitigation Mainly humans
3 (Friendship) Co-existence Mainly monsters
4 (Chasing) Chasing Monsters Humans

48. Monster Taming Strategies
The Case of CBSD
Taming Strategy Also Called Who Wins?
1 (Murder) Eradication Humans
2 (Infection) Mitigation Mainly humans
3 (Friendship) Co-existence Mainly monsters
4 (Chasing) Chasing Monsters Humans

49. Strengthen Mitigation
Resistance breeding for CBSV
Tolerance and resistance. Continue
existing search
Wild relatives. Identify new sources of
resistance
Biotech approaches. Molecular markers
and GM
Resistance breeding for whiteflies
Existing germplasm

50. Application to Introduce Eretmocerus
hayati for the control of Bemisia whiteflies in
Tanzania
Presented at the 16th Biological Control Agents sub-Committee
(BCAS) Meeting
SRI, Kibaha – February 25, 2011

52. Virus-free Cassava Seed Systems
Strategic Laboratory Network
Virus testing and indexing. Standard
protocols
NARS facilities. Regional support from IITA
Virus-free propagation material. In TC
Virus-free Strategic Propagation Sites
‘Holding site’, ‘Clean seed site’
Regional sites for decentralized

56. Community Phytosanitation
Collective Action to Eradicate Viruses
Primary
Recipient
Community
> 200m
Secondary
Recipient
Community