BBTV in sub-Saharan Africa: Status and Needs


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Banana bunchy top virus,BBTV Survey and Detection,BBTV Geneology in SSA,BBTV control in SSA

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BBTV in sub-Saharan Africa: Status and Needs

  1. 1. BBTV in sub-Saharan AfricaStatus and NeedsLava Kumar & Rachid HannaB 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 HauserS AkinbadeTT Oben
  2. 2. Banana bunchy top virus•Type species in the genus, Babuvirus (family,Nanoviridae)•Transmitted by the banana aphid, Pentalonianigronervosa, persistent circulative manner.•Occurs in Africa, South and Southeast Asia, Australiaand South Pacific•Virus in Southeast Asia is different from South Asia Banana aphid BBTV-South pacific group BBTV-Asian group
  3. 3. •BBTV is amongst the list of top 100 of invasive species. •Difficult to control and eradicate.2010: UN Year of BiodiversityScope for exploiting threats tobiodiveristy – eg. BBTV onplantain diversity
  4. 4. Banana aphid Direct damage – reduced plant growthVector banana bunchy top virus(+ other viruses)
  5. 5. BBTV - not a new foe in SSA•Severe BBTV outbreaks inMalawi, Mozambique andZambia.•What are the causes for therecent surge of BBTV in SSA?•Variation in the virus or Reproduced from “Foure and Manser (1982) Fruits Vol 37, 410.vector, introduction/evolutionof a more virulent forms? •BBTV occurrence in Kisangani (DRC) and Gabon known since mid-1950s.•Changes in cultural practicesor the environment, includingclimate change effect, causingthis spread?
  6. 6. BBTV in SSA Present Before 1960s Since 1980s Since 1990s Since 2004 Present 2009
  7. 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 Thereis no evidence of BBTV in these countries.
  8. 8. BBTV Detection Multiplex PCR with internal control primer Internal Control[BRep-1] (400 bp) BBTV specific (240 bp)
  9. 9. Number of surveyed sites with BBTV Sites surveyed Sites with BBTV 80 68 Number of sites•Survey conducted 70 62in 198 sites in 5 60countries. 50 40 34 31 30 27•BBTV detected in 18 20 20 1039.4% sites 10 3 3surveyed 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
  10. 10. •BBTV is widespread in Central and Southern Africa. Widespread occurrencesince 1994•Severe disease expression in Cavendish, but local varieties, despiteinfection can tolerate (suppressed symptoms) the disease.•Human movement of planting material seems to be the mainreason 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 plantingmaterial.•Important to protect the source sites.
  11. 11. •Nkumba village•Symptoms are not apparent, but BBTV positive;•Original source brought in 1997
  12. 12. •Nkunga•Symptoms are not apparent, BBTV not detected•No new planting material for over 50 years.
  13. 13. •Mampakasa (Inside Luki reserve, Boma, DRC)
  14. 14.
  15. 15. BBTV spread mainly through infected suckers Banana rich Banana richFirst outbreak Movement of planting material Banana rich
  16. 16. BBTV Geneology in SSA
  17. 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) 286aaDNA-S(3)1075 nts 175aa •Very high sequence similarities 98-100% sequence identity
  18. 18. Coat protein-based geneology
  19. 19. Replicase-gene based geneology
  20. 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.
  21. 21. •Basic knowledge and technologies available to tacklethe problem.•Tolerant (or less susceptible) varieties available, whichcould avert economic losses .•Awareness creation, training in virus monitoring andproduction of clean planting material is necessary.
  22. 22. Future Needs
  23. 23. BBTV control in SSA Curative Preventive1. Reduce sources of inoculum- Exclusion & PreventionEliminate crop refuges Control of material movement Awareness campaigns Increased vigilance2. Reduce spread Routine surveillanceVector control Field isolationsPhysical barriersSeed testing3. Reduce impactReplace infected matsCultivate tolerant varieties4. Avoidance by cultural methodsField isolation (buffer zone)Plant spacing
  24. 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 infestationImmediate•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 materialMedium to long term•Vector control and genetic enhancement
  25. 25. Thank you
  26. 26. R4D issuesEtiology, 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))
  27. 27. R4D issuesGenetic 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
  28. 28. R4D issuesExtension• 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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