Progress in developing cassava varieties with resistance to CMD and CBSD in eastern Africa

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Major causes for low yields of crops,Cassava Mosaic disease,Cassava Brown Streak Disease

Major causes for low yields of crops,Cassava Mosaic disease,Cassava Brown Streak Disease

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  • 1. Progress in developing cassavavarieties with resistance to CMD and CBSD in eastern Africa Edward Kanju Contract review seminar, 11th October 2010, Ibadan, Nigeria International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
  • 2. Introduction• Cassava is an important food crop in Tanzania: – Tanzania is the fifth cassava producer in Africa – Production is estimated at 7 million MT (fresh weight) – Is the second important staple after maize• It is produced mainly through subsistence farming with use of low inputs, rudimentary technology, large post-harvest losses and minimal processing• Yields are lower than world’s average of 10.5 MT/ha International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
  • 3. International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
  • 4. Introduction contd.• Major causes for low yields: – Pests and diseases – Poor agronomic practices – Poor soil fertility – Use of cultivars with poor genetic potential – Drought International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
  • 5. Introduction contd.• Major pests: • Major diseases: – Cassava green mites (CGM) – Cassava mosaic – Termites disease (CMD) – Cassava mealybugs (CM) - • EACMV at some pockets • ACMV – Variegated grasshoppers – • EACMV-UG sporadic – Cassava brown – White cassava scales - streak disease sporadic (CBSD) – Cassava bacterial blight (CBB) International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
  • 6. Cassava Mosaic disease (CMD) International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
  • 7. Evolution of the CMD Pandemic 2005 2001 1997 > 2,700,000 sq. km0 400 800 km International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
  • 8. Super-abundant whiteflies transmitviruses and cause up to 50% lossthrough physical damage CBSV damages International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
  • 9. EACMV-UG resistant germplasm developed and released in all affected countries International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
  • 10. Severe CMD symptoms at Kibaha, Tanzania where no ACMV nor EACMV-UG has been detected International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
  • 11. Cassava Brown Streak Disease (CBSD) International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
  • 12. • Causal agent: Equatorial Guinea Uganda – Genus: Ipomovirus ROC Kenya – Family: Potyviridae DRC Tanzania• Vector: Bemisia tabaci (Maruthi et al., 2005) Malawi Zambia• Losses: Mozambique – Economic loss (SSA): >USD 75 CBSD devastating CBSD damaging million/annum from 1.6 million CBSD reported tons (Manyong et al., 2010) Source: James Legg Affected countries: Malawi, Mozambique, Kenya, Uganda, Tanzania, Rwanda International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
  • 13. CBSD leaf symptoms International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
  • 14. CBSD stem symptoms on young plants International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
  • 15. CBSD Stem Symptoms on older plants International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
  • 16. The many faces of CBSD root necrosis International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
  • 17. Severely affected roots are unmarketable! International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
  • 18. • CBSD has increased the labour requirement in trial evaluation International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
  • 19. Breeding for resistance: History– Host plant resistance is the most effective and realistic approach to reducing losses– Started at Amani in 1930s (for both CMD and CBSD)– Very few varieties possessed resistance to CBSD e.g. Aipin valenca and Aipin Macaxeira– Interspecific hybrids were developed and backcrossed to cassava three times: • Manihot melanobasis – Amani 5543/156 (also had M. glaziovii) • M. glaziovii – Amani 46106/27 was developed; resistant to CBSD; still grown in Kenya (Kaleso) – resistance has persisted to date. International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
  • 20. Resistant/Tolerant Varieties• Tanzania: Kigoma Mafia, Kiroba, Nanchinyaya, Namikonga, Kalulu, Kitumbua, Mfaransa, Gezaulole, Muzege, Kikombe, Kibangameno, Mwari , UKG 91/041, NDL 90/34 and IR 40-6 (from CIAT).• Kenya: Kaleso, Guzo, Gushe, Kahoteli, Ambari and Kibiriti Mweusi• Uganda: MM 96/4271??? Too early to be sureSome of the present day so-called local cultivars are former Amani hybrids International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
  • 21. Resistance: Definition• Virus resistance terminology is a contentious issue on which there is no general agreement (Thresh et al., 1998)• Any inhibition of virus multiplication or of its pathogenic effects on the plant (used in the general sense of Fraser, 1986).• Breeders emphasize the effect on yield and quality in contrast to pathologists who consider the fate of the virus in the plant (Lapidot and Friedmann, 2002).• Most of the CBSD resistant cultivars are better described as “tolerant” in that they readily show foliar symptoms but root necrosis is delayed or absent (Hillocks and Jennings, 2003). International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
  • 22. Challenges• Disease assessment: – Screening for resistance is based on phenotypic expression of symptom severity in the field relying upon natural infection – Grafting is a very severe challenge (unless we are looking for immunity) International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
  • 23. Inheritance of CBSD resistance: Update• Both additive and non-additive genetic effects reported (Munga, 2009; Mtunda, 2010) – Additive effects were more important than non-additive• The best parents to use for improvement of CBSD resistance was Kaleso and Namikonga. – Using >500 SNP markers we have proved that the two clones are genetically identical. International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
  • 24. Progress of a Breeding Program (Lozano, 1980)– Genetics of the desired trait– Number of traits that have to be incorporated • Biotech can help– Effectiveness of the evaluation techniques • Revisit?– Number of progeny evaluated yearly International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
  • 25. Promising clones evaluated at ARI Naliendele, UYT 2010 S/N Accession Pedigree1. NDL 2003/031 NACHINYAYA X KIROBA2. NDL 2003/111 NAMIKONGA X KALULU3. NDL 2005/492 NAMIKONGA - HS4. NDL 2005/201 NDL 90/034 X NAMIKONGA5. NDL 2005/1472 NACHINYAYA - HS6. NDL 2005/1471 NACHINYAYA - HS7. NDL 2006/283 NDL 90/034 - HS8. NDL 2006/035 84/00353 X 080/00519. NDL 2006/241 I 92/0057 X 84/0035310. NDL 2006/013 I 90/0099 X I 92/005711. NDL 2006/349 KIROBA X KIGOMA RED12. NDL 2006/034 NAMIKONGA X KIROBA13. NDL 2006/155 I 90/0099 X I 92/005714. NDL 2006/018 NACHINYAYA X KIROBA International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
  • 26. Promising clones evaluated on-farm, Eastern Zone, 2010 S/N Accession Pedigree1. KBH 02/66 96/1613 HS (IITA Ibadan)2. KBH 02/1203. KBH 02/135 TME 130 HS (IITA Ibadan)4. KBH 02/363 I 96/1632 (IITA Ibadan)5. I 92B/00073 ? (IITA Ibadan)6. KBH 06/26 LML 2000/2174 HS7. KBH 06/74 LML 91/0119 HS8. KBH 06/189. NDL 06/74 Nachinyaya x Kitumbua10. ZNZ 05/31 TMS 4(2)1425 HS11. ZNZ 06/30 Kitumbua HS12. ZNZ 06/06 Kigoma Red HS13. ZNZ 06/63 TMS 30001 HS14. International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
  • 27. Performance of 14 clones selected from the AYT at Mukono, 2008/09 Clone Pedigree Fresh Root Yield DMC (%) (T/ha)MM 2006/0013 Kitumbua-OP 11.2 47.7MM 2006/0090 Kibaha-OP 18.0 47.4MM 2006/0130 Kitumbua-OP 8.3 46.0MM 2006/0143 Kibaha-OP 5.7 43.2MM 2006/0139 Kibaha-OP 20.1 43.1MM 2006/0082** Kibaha-OP 9.8 43.1MM 2006/0128** Kigoma Red-OP 6.9 41.5MM 2006/0123** Kibaha-OP 13.8 37.9MM 2006/0083 Kibaha-OP 3.8 37.9MM 2006/0046 Kigoma Red-OP 5.0 37.6MM 2006/0112 Kibaha-OP 25.2 34.7MM 2006/0074 Kigoma Red-OP 5.2 34.5MM 2006/0005 SS4-OP 17.3 29.4MM 2006/0138 Kibaha-OP 22.5 40.7TME 204 (Check) 4.8Trial Mean 10.2Lsd (0.05%) 10.7 International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
  • 28. MM 06/0013 wasone of the eightclones that hadno visible CBSDsymptoms up toAugust 2009. Ithas succumbedto CBSD at allthe threeevaluation sitesin Uganda International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
  • 29. MM 06/0090: very low incidence (class 3) at Serere (leftphoto); high incidence (class 4) at Mukono (right photo). Mukono had the highest incidence of severe root necrosis; Serere the lowest International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
  • 30. TME 204International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
  • 31. GLCI Participatory Variety Selection (PVS) Trials International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
  • 32. Participatory Variety Selection (PVS)• Enables farmers to test and select improved varieties that best meet their diverse needs within their socio-economic and agro-ecological context• Is a key to providing a steady stream of new material which is essential to address changing farmer requirements and to create a suitable multiplication system• Is an effective means of achieving rapid adoption of newly developed varieties. – Directly through farmers using material from on-farm trials – Indirectly because the participatory approach ensures that the varieties are more suited to farmers’ diverse needs and the on-farm trials serve as demonstrations (awareness/promotion) of the best variteies International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
  • 33. The three promising clones clones (MM 96/3567,MM 96/3972 and MM 96/2335) have succumbed to CBSD in 2010 International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
  • 34. Way Forward• Work very closely with virologists to elucidate mechanism of resistance and genotype x virus x environment• Inter-se mating of elite clones to generate new source population to capitalize on the additive gene variation (identify parents with high GCA values)• Development of inbred/semi-inbred lines to exploit hybrid vigour (identify heterotic groups)• Incorporate new sources of CMD (CIAT and IITA-Ibadan) and CBSD (from IITA-Ibadan) to broaden genetic base of the local germplasm• Deploy CBSD tolerant germplasm (TC and true seeds) to recently affected and threatened regions• Interspecific crosses International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
  • 35. Acknowledgements• All the other Scientists and Technical staff supporting our work• All the farmers who actively participate in germplasm evaluation• All the donors who fund our activities International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
  • 36. Thank you for the attention! Asanteni sana! International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org