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Lava Kumar & Rachid Hanna

B Mwemenamda

F Beed

J Lorenzen

K Fiaboe

O Opyami

P van Asten

S Hauser

S Akinbade

TT Oben

M Soko (Malawi)

R Londa (Angola)

J Ngeve (Cameroon)

MP Mutunda (Angola)

D Kiala (Angola)

RA Naidu (USA)

Status and Needs

BBTV in sub-Saharan Africa

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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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•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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Banana aphid

Vector banana bunchy top virus

(+ other viruses)

Direct damage – reduced plant growth

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•Severe BBTV outbreaks in

Malawi, Mozambique and

Zambia.

•What are the causes for the

recent surge of BBTV in SSA?

BBTV - not a new foe in SSA

•Variation in the virus or

vector, introduction/evolution

of a more virulent forms?

•Changes in cultural practices

or the environment, including

climate change effect, causing

this spread?

Reproduced from “Foure and Manser (1982) Fruits Vol 37, 410.

•BBTV occurrence in Kisangani (DRC) and

Gabon known since mid-1950s.

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Before 1960s

Since 1980s

Since 1990s

Since 2004

BBTV in SSAPresent

Present 2009

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•Surveys were also conducted in Nigeria, Benin and Ghana, but There

is no evidence of BBTV in these countries.

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

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BBTV Detection

BBTV specific

(240 bp)

Internal Control

[BRep-1] (400 bp)

Multiplex PCR with internal control primer

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3

62

34 31

68

310

18 2027

0

10

20

30

40

50

60

70

80Sites surveyed Sites with BBTV

Angola Cameroon Gabon DRC MalawiN

um

ber

of

sit

es

Number of surveyed sites with BBTV

•Survey conducted

in 198 sites in 5

countries.

•BBTV detected in

39.4% sites

surveyed

N=7

6%

33%

44%

19%

0

5

10

15

20

25

30

35

40

45

50

Angola Cameroon Gabon DRC Malawi

43%

N=520

N=224

N=295

N=107 22.7%

N=1159

Perc

en

t in

fecti

on

Percent samples positive to BBTV

Total

•BBTV detected in

22.7% of the

samples tested.

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•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.

•Role of aphid transmission is significant in most places.

•Human movement of planting material seems to be the main

reason for widespread distribution.

•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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•Nkumba village

•Symptoms are not apparent, but BBTV positive;

•Original source brought in 1997

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•Nkunga

•Symptoms are not apparent, BBTV not detected

•No new planting material for over 50 years.

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•Mampakasa (Inside Luki reserve, Boma, DRC)

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Movement of

planting material

First outbreak

Banana rich

Banana rich

Banana rich

BBTV spread mainly through infected suckers

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BBTV Geneology in SSA

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• 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)1111 nts

Geneology of BBTV

•Pair-wise comparisons of coat protein sequences

(nucleotides / amino acids)

DNA-S(3)

1075 nts

286aa

175aa•Very high sequence similarities 98-100% sequence identity

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Coat protein-based geneology

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Replicase-gene based geneology

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•High sequence similarity between the BBTV isolates suggest a common origin.

•BBTV in SSA aligns with BBTV isolates from South Pacific group.

•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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•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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Future Needs

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Exclusion & Prevention

Control of material movement

Awareness campaigns

Increased vigilance

Routine surveillance

Field isolations

1. Reduce sources of inoculum-

Eliminate crop refuges

3. Reduce impact

Replace infected mats

Cultivate tolerant varieties

2. Reduce spread

Vector control

Physical barriers

Seed testing

4. Avoidance by cultural methods

Field isolation (buffer zone)

Plant spacing

BBTV control in SSA

Curative Preventive

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BBTV Control in SSA

•Production and distribution of clean planting material is the key

•Protect new planting material from new infection

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

•Prevent further spread and protect source sites from BBTV infestation

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Thank you

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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))

R4D issues

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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

R4D issues

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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.

R4D issues