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Taming the Cassava Virus Monster: A Research for Development Case Study
 

Taming the Cassava Virus Monster: A Research for Development Case Study

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Human Defense Strategy Against this Attack,Problems in Taming CBSVs(Cassava Brown Streak Viruses),New Understanding of Epidemiology,Virus-free Cassava Seed Systems

Human Defense Strategy Against this Attack,Problems in Taming CBSVs(Cassava Brown Streak Viruses),New Understanding of Epidemiology,Virus-free Cassava Seed Systems

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    Taming the Cassava Virus Monster: A Research for Development Case Study Taming the Cassava Virus Monster: A Research for Development Case Study Presentation Transcript

    • Taming the Cassava Virus Monster: A Research for Development Case StudyJames Legg: Review Seminar – IITA-Ibadan, March 22, 2011
    • CLARFIYING DEFINITIONS
    • Merriam-Webster Definition1. A creature of abnormal form or structure2. One who deviates from normal or acceptable behaviour or character3. A threatening force4. One that is highly successful
    • 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. DEATH3. Infect it with a nasty chronic disease (preferably a virus)  Outcome. WEAKNESS4. Be extra nice to it (and hope it reciprocates the favour)  Outcome. UNAFFECTED
    • Effect of Taming Strategies on Outcomes for Monsters and HumansTaming 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
    • …….but they can look pretty scary…
    • And together ‘attack’ humans indirectly throughremoving 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
    • Human Defense Strategy Against this Attack ? Primarily Strategy 2 Mitigation Adequate ?
    • CBSDincidence 2010 (GLCI) Map: Hein Bouwmeester
    • CBSDincidence change 2009-10 Map: Hein Bouwmeester
    • How Good has our Taming been so far?Cassava Mosaic Geminiviruses (CMGs)Conventional HPR – virtual immunityCassava Brown Streak Viruses (CBSVs)Limited effortPromotion of ‘tolerant’ varietiesCassava WhitefliesLargely ignored. Virus management perceivedto be more straightforward
    • Problems in Taming CBSVsKnowledge. Almost none prior to 2008Symptoms. Cryptic. Field diagnosis hardAwareness. Little before late 2000sOne-dimensional. Existing mitigation work
    • Status of CBSD KnowledgeElement Pre-2008 Post-2008 IITA1. Partial sequencing S2. Whole genome sequencing X3. Confirmation of aetiology X4. Symptom relationship characterization L5. Crop loss assessment L6. Determination of vector X7. Characterization of transmission L8. Field-based epidemiology L9. Regional epidemiology L10. Development of diagnostics S11. Molecular markers L12. Conventional HP tolerance L13. Transgenic resistance X
    • Framework for CBSV Research at IITAFoundation of support through COREGLCI Project (IITA-Ibadan, IITA-Tanzania)Biotechnology Project (IITA-Kenya)Malawi CBSV Project (IITA: Tanzania, Ibadanand Malawi)
    • 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)270 isolates were analyzed from six districts 281 B9) CP )1Based on 3’ coat protein gene sequence (10 -11Neighbor-Joining method; 1000 bootstraps )2Reference sequences from GenBank are with accession numbers
    • CBSV Diagnostics at IITA-Tanzania
    • CBSV Diagnostics ValidationTanzania CBSVs detected by primers combinationCBSV 10/11 with CBSV UG F/R detect > 99% real-time +vesWorking with IITA-Ibadan/NRI to add F3/R3, new primers CBSV CBSV Real CBSV UG CBSUV 10/11 F/R RealCBSV + + - -UCBSV-1 - - + +UCBSV-2 + - + +CBSV+UCBSV-1/2 + + + +
    • Putting PCR into practise PCR underway: ISABU, Bujumbura, BurundiPCR results: ISAR,Ruhengeri, Rwanda
    • New Understanding of Epidemiology Epidemiology QuestionsCan 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 ? (cropintensity, crop management, variety, temperature)Are all these things the same or different fordifferent viruses ?
    • What are the conditions for doing epidemiology experiments ?Guaranteed CBSV-free planting materialTC introductions through NRI partnershipEstablishment of isolated nuclear multiplication sitesUsambara Mountains – eastern TanzaniaSensitive, reliable and robust diagnosticsDeveloped with IITA-Ibadan, NRI and FERARoutine RT-PCR and real-time RT-PCR in TanzaniaExtensive experimental programmeField and screenhouse experimental sites set up
    • Whitefly Control – CBSV Epidemiology
    • TC Epidemiology Trial – Kibaha, Tanzania
    • TC Epidemiology Trial – Kibaha, TanzaniaSecond Planting, cv. Kiroba – 4 sites
    • CBSD Epidemic Simulation - KibahaMaterials: CBSD-infected spreader, CBSD-free test plants,whiteflies introducedTreatments: Drought and fertilizationReplicates: 1 (next to spreader) to 4 (far from spreader)
    • CBSD Epidemic Simulation Results
    • Inoculum Pressure Assessment Study Tertiary Multiplication SitesQuestion? How does the location of a tertiary siteaffect CBSD infectionPlan: Assess inoculum pressure for 20 tertiarysites in Lake Zone, TzMeasured: CBSD in multiplication sites as well assurrounding farmers’ fieldsFactors Compared: District, Source of plantingmaterial, Inoculum pressure, Virus speciesVirus Diagnostics: Used to confirm viruspresence and identity
    • CBSD incidence in multiplication sites vs. surrounding farmers’ fields
    • Effect of distance from surrounding farmers’ fields on CBSD incidence in multiplication sites
    • 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 short0.02
    • Inoculum Pressure Assessment Study OutcomesKey Factors in CBSD infection?Source of planting material: NoDistrict location: NoVirus species prevalent: NoProximity to neighbouring fields: YESQMP outcomes: 8 out of 22 fields failed. Allisolated fields passedControl implications: Isolation critical.
    • Vector Transmission IITA partnering with NRI, UK (Maruthi)CBSV/UCBSV: Summary of NRI/IITA PhDresultsIrrefutable confirmation of B. tabaci as vectorMin. acquisition period – 5 minsMin. Inoculation period – 30 minsMax. retention time – 1 hourResults suggest semi-persistent transmission
    • Regional Epidemiology Tanzania Lake Zone Surveys 2000-2009 (Jeremiah and Ndyetabula) Wf Pk 1 Wf Pk 2 Wf Pk 3 CBSD>10 CMD >50Bukoba 2000 2004 2007 2008 2000Muleba 2000 2004 2007 2007 2001Biharamulo 2000 2004 2007 2007 2001Karagwe 2002 2004 2009 2008 2005Ngara 2002 2007 2009 2008 2005Ukerewe 2000 2002 2009 2007 2001Geita 2002 2009 2008 2001Sengerema 2004 2009 2008 2005Mwanza 2004 2009 2009 2003Magu 2004 0 2009 2005Kwimba 0 0 0 2007Misungwi 2004 0 0 2007Kibondo 2004 2007 0 2003Kasulu 2004 2007 2008 2003Kigoma 2004 2007 2009 0 2007Bukombe 2004 2007 2009 2008 2005Kahama 0 0 0 2009 0Bunda 2004 2007 2007 2007Musoma 2004 2007 2009 2007 2005Tarime 2004 2007 2009 2007 2005Serengeti 2007 2009 2008 2005
    • Whitefly Population Peaks vs. Disease Outbreaks 12 10 8A 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
    • Proposed Model for Epidemiology of CMD and CBSD Pandemics
    • Monster Taming Strategies The Case of CBSDTaming 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
    • Monster Taming Strategies The Case of CBSDTaming 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
    • Strengthen MitigationResistance breeding for CBSVTolerance and resistance. Continueexisting searchWild relatives. Identify new sources ofresistanceBiotech approaches. Molecular markersand GMResistance breeding for whitefliesExisting germplasm
    • Application to Introduce Eretmocerus hayati for the control of Bemisia whiteflies in TanzaniaPresented at the 16th Biological Control Agents sub-Committee (BCAS) Meeting SRI, Kibaha – February 25, 2011
    • Virus-free Cassava Seed SystemsStrategic Laboratory NetworkVirus testing and indexing. StandardprotocolsNARS facilities. Regional support from IITAVirus-free propagation material. In TCVirus-free Strategic Propagation Sites‘Holding site’, ‘Clean seed site’Regional sites for decentralized
    • Community Phytosanitation Collective Action to Eradicate Viruses Primary Recipient Community > 200mSecondary RecipientCommunity