This document summarizes the status of banana bunchy top virus (BBTV) in sub-Saharan Africa. BBTV is widespread and found in 39.4% of surveyed sites. It is transmitted by the banana aphid and causes significant damage by reducing plant growth. The virus in sub-Saharan Africa is most similar to isolates from the South Pacific. Spread is primarily through infected planting material and future efforts should focus on producing and distributing clean planting material, controlling the vector, and cultivating tolerant varieties.

1. BBTV in sub-Saharan Africa
Status and Needs
Lava Kumar & Rachid Hanna
B Mwemenamda M Soko (Malawi)
F Beed R Londa (Angola)
J Lorenzen J Ngeve (Cameroon)
K Fiaboe MP Mutunda (Angola)
O Opyami D Kiala (Angola)
P van Asten RA Naidu (USA)
S Hauser
S Akinbade
TT Oben
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2. Banana bunchy top virus
•Type species in the genus, Babuvirus (family,
Nanoviridae)
•Transmitted by the banana aphid, Pentalonia
nigronervosa, persistent circulative manner.
•Occurs in Africa, South and Southeast Asia, Australia
and South Pacific
•Virus in Southeast Asia is different from South Asia
Banana aphid
BBTV-South pacific group
BBTV-Asian group
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3. •BBTV is amongst the list
of top 100 of invasive
species.
•Difficult to control and
eradicate.
2010: UN Year of Biodiversity
Scope for exploiting threats to
biodiveristy – eg. BBTV on
plantain diversity
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4. Banana aphid
Direct damage – reduced plant growth
Vector banana bunchy top virus
(+ other viruses)
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5. BBTV - not a new foe in SSA
•Severe BBTV outbreaks in
Malawi, Mozambique and
Zambia.
•What are the causes for the
recent surge of BBTV in SSA?
•Variation in the virus or Reproduced from “Foure and Manser (1982) Fruits Vol 37, 410.
vector, introduction/evolution
of a more virulent forms?
•BBTV occurrence in Kisangani (DRC) and
Gabon known since mid-1950s.
•Changes in cultural practices
or the environment, including
climate change effect, causing
this spread?
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6. BBTV in SSA
Present
Before 1960s
Since 1980s
Since 1990s
Since 2004
Present 2009
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7. BBTV Survey
•Roving survey in major
and minor banana growing
areas.
•Focus of BBTV and banana
aphids.
•Leaf samples collected
from symptomatic and
asymptomatic plants for
virus analysis.
•Interviews with farmers
•Surveys were also conducted in Nigeria, Benin and Ghana, but There
is no evidence of BBTV in these countries.
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8. BBTV Detection
Multiplex PCR with internal control primer
Internal Control
[BRep-1] (400 bp)
BBTV specific
(240 bp)
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9. Number of surveyed sites with BBTV
Sites surveyed Sites with BBTV
80
68
Number of sites
•Survey conducted 70 62
in 198 sites in 5 60
countries. 50
40 34 31
30 27
•BBTV detected in 18 20
20 10
39.4% sites 10 3 3
surveyed 0
Angola Cameroon Gabon DRC Malawi
Percent samples positive to BBTV
50
N=7 N=295
45
Percent infection
40 43% 44%
35 N=224
30 33%
•BBTV detected in
25 N=1159 22.7% of the
20 N=107 22.7% samples tested.
15 19%
10 N=520
5
6%
0
Angola Cameroon Gabon DRC Malawi Total
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10. •BBTV is widespread in Central and Southern Africa. Widespread occurrence
since 1994
•Severe disease expression in Cavendish, but local varieties, despite
infection can tolerate (suppressed symptoms) the disease.
•Human movement of planting material seems to be the main
reason for widespread distribution.
•Role of aphid transmission is significant in most places.
•Infected plants are the potential sources for new spread.
•Risk of spread is high in the routes of traditional exchange of planting
material.
•Important to protect the source sites.
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11. •Nkumba village
•Symptoms are not apparent, but BBTV positive;
•Original source brought in 1997 www.iita.org

12. •Nkunga
•Symptoms are not apparent, BBTV not detected
•No new planting material for over 50 years. www.iita.org

13. •Mampakasa (Inside Luki reserve, Boma, DRC)
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14. www.iita.org

15. BBTV spread mainly through infected suckers
Banana rich
Banana rich
First outbreak
Movement of
planting material
Banana rich
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16. BBTV Geneology in SSA
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17. Geneology of BBTV
• Coat protein (DNA-S) and replicase (DNA-R) gene
sequences of 10 BBTV isolates from Cameroon,
Gabon, DRC, Malawi and Angola determined.
DNA-R(1) •Pair-wise comparisons of coat protein sequences
1111 nts
(nucleotides / amino acids)
286aa
DNA-S(3)
1075 nts
175aa
•Very high sequence similarities 98-100% sequence identity
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18. Coat protein-based geneology
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19. Replicase-gene based geneology
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20. •BBTV in SSA aligns with BBTV isolates from South Pacific group.
•High sequence similarity between the BBTV isolates suggest a common origin.
•There is no evidence of any unusual features in virus.
•Severe incidence and spread seems to be due to
-Increase in cultivation of most susceptible varieties, such as Cavendish
-Planting of infected suckers
-Aphids vector contributing to the secondary spread.
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21. •Basic knowledge and technologies available to tackle
the problem.
•Tolerant (or less susceptible) varieties available, which
could avert economic losses .
•Awareness creation, training in virus monitoring and
production of clean planting material is necessary.
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22. Future Needs
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23. BBTV control in SSA
Curative Preventive
1. Reduce sources of inoculum- Exclusion & Prevention
Eliminate crop refuges Control of material movement
Awareness campaigns
Increased vigilance
2. Reduce spread
Routine surveillance
Vector control
Field isolations
Physical barriers
Seed testing
3. Reduce impact
Replace infected mats
Cultivate tolerant varieties
4. Avoidance by cultural methods
Field isolation (buffer zone)
Plant spacing
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24. BBTV Control in SSA
•Production and distribution of clean planting material is the key
•Protect new planting material from new infection
•Prevent further spread and protect source sites from BBTV infestation
Immediate
•Awareness creation [Share information]
•Strengthen monitoring capacity [Diagnostics]
•Clearly delineate affected areas to contain the spread [intensive surveillance]
Shot to Medium-term
•Promote production and distribution of clean planting material
Medium to long term
•Vector control and genetic enhancement
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25. Thank you
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26. R4D issues
Etiology, Epidemiology and vector control
• virus diversity;
• virus-vector interactions, its survival and spread;
• ecology of aphids and means of its involvement in long and short-
distance spread of virus.
• Develop sensitive diagnostic tools for on-site virus detection.
• Explore biocontrol approaches for virus (biopriming with
endophytes) and banana aphid (natural enemies and biopriming
with endophytes))
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27. R4D issues
Genetic enhancement
• Evaluate African Musa germplasm for selection of farmer-preferred
varieties with partial resistance/tolerance to the virus and/or vector
to slow the epidemic.
• Explore novel conventional and non-conventional approaches
against BBTV or banana aphid or both
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28. R4D issues
Extension
• Create awareness about the disease and control options, including
importance of planting disease-free suckers, among farmers and officials
associated with agricultural sector in SSA.
• Train farmers in the production of clean planting material (lessons from on-
going IITA activities).
• Train national partners in virus indexing and producing virus-free planting
material.
• Pest risk analysis in SSA.
Impact on livelihoods and crop diversity
• Socio-economic studies to determine the implications and feasibility of
phytosanitary approaches under subsistence farming conditions.
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