Root and Tuber Systems Program                            Output 2Description of biotic and abiotic processes and         ...
Major Cassava Pests and Diseases in Africa   Cassava green mite                                    African root and tuber ...
Major Cassava Pests and Diseases in AfricaWhiteflies                                        Cassava bacterial blight Root ...
Bitoic processes and interactions   Purpose Improve knowledge on the diversity and biology of  target pests/diseases and ...
Description of biotic processes and interactions                      (example output targets) Biotic processes    Profi...
Description of biotic processes and interactions                     (example output targets) Biotic processes    Profil...
Profiling sources of resistance to CMD and                        pyramiding resistance genesDixon et al.               In...
Biological control of cassava green mite in Africa      1st release     1993, Benin              International Institute o...
Plant characteristics affecting predator abundance                       and biocontrol of cassava green miteHanna et al. ...
Sensitivity of T. aripo to UVB radiation (282-320 nm)Hanna et al.               Apex provides considerable protection from...
Prey location behavior on hairy and glabrous plantsHanna et al.     Predators show greater ability to locate prey on hairy...
Plant characteristics affecting predator abundance and                                      biocontrolHanna et al.     Vu...
How does soil fertility affect pest and disease                                  incidence?Fermont et al.         Complet...
300           Cassava Bacterial Blight                                              300             Cassava Green Mites   ...
Activities/output targets in R&TS – Output 2     Description of biotic and abiotic processes and interactions Biotic proc...
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Root and Tuber Systems Program

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Major Cassava Pests and Diseases in Africa,Bitoic processes and interactions,Biological control of cassava green mite in Africa,Plant characteristics affecting predator abundance and biocontrol of cassava green mite,Prey location behavior on hairy and glabrous plants,Plant characteristics affecting predator abundance and
biocontrol,How does soil fertility affect pest and disease incidence?

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Root and Tuber Systems Program

  1. 1. Root and Tuber Systems Program Output 2Description of biotic and abiotic processes and interactionsRachid Hanna, Denis Cornet, Stefan Hauser, Pheneas Ntawuruhunga, Nzola-Meso Mahungu, Jelle Duindam, Caroline Herron, Anneke Fermont, Alfred Dixon, SarahHearne, Ranajit Bandyopadhyay, Maria Ayodele, Robert Asiedu, Robert Abaidoo, Busie Maziya-Dixon, James Legg,Kerstin Hell, Lava Kumar International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
  2. 2. Major Cassava Pests and Diseases in Africa Cassava green mite African root and tuber scaleCassava mosaic disease Cassava brown streak disease International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
  3. 3. Major Cassava Pests and Diseases in AfricaWhiteflies Cassava bacterial blight Root rots Nematodes International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
  4. 4. Bitoic processes and interactions Purpose Improve knowledge on the diversity and biology of target pests/diseases and factors affecting their abundance and severity with the intent to use this knowledge, along with information on distribution and impact of these pests and diseases to develop environmentally-sound and cost-effective management strategies to minimize crop losses. International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
  5. 5. Description of biotic processes and interactions (example output targets) Biotic processes  Profiling CMD resistance and gene pyramiding  Monocolonal antibodies for CBSD  Cassava root rots complex  Mechanism of cassava clone preference by predatory mites  Ants associated with Africa root and tuber scale  Entomopathogenic fungi for ARTS and ant control Interactions between biotic and abiotic processes  Soil fertility and cassava pest and disease severity  Effects of AMF and nematodes on yam yield International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
  6. 6. Description of biotic processes and interactions (example output targets) Biotic processes  Profiling CMD resistance and gene pyramiding  Monocolonal antibodies for CBSD  Cassava root rots complex  Mechanism of cassava clone preference by predatory mites  Ants associated with Africa root and tuber scale  Entomopathogenic fungi for ARTS and ant control Interactions between biotic and abiotic processes  Soil fertility and cassava pest and disease severity  Effects of AMF and nematodes on yam yield International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
  7. 7. Profiling sources of resistance to CMD and pyramiding resistance genesDixon et al. In collaboration with Plant Virus Division Braunschweig, GermanySix distinct virus species causing CMD Africa; 2 in India; greatest diversity in East Africa;Worst is EACMV-UG; cause of present pandemic;Strong evolutionary pushing the devel. new strains/variants;Response of parental clones from seven groups of sources of resistance to CMD;Three varieties – TME 4, 96/1089A, 96/0529A are resistant to all single or combination of viruses causing CMD;Multiple crossing schemes are being used to pyramid CMD resistance genes. International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
  8. 8. Biological control of cassava green mite in Africa 1st release 1993, Benin International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
  9. 9. Plant characteristics affecting predator abundance and biocontrol of cassava green miteHanna et al.  Unusual behavior of living in the apex during the day and foraging on leaves at night  Predators more abundant on plants with hairy apex  Biological control of cassava green mite is T. aripo more likely on varieties with hairy apex  Understand the reasons for the unusual diurnal behavior and the preference for hair apices  Genetic control of apex hairiness to incorporate it in breeding programs International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
  10. 10. Sensitivity of T. aripo to UVB radiation (282-320 nm)Hanna et al. Apex provides considerable protection from UVB 96% 25% Direct Apex International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
  11. 11. Prey location behavior on hairy and glabrous plantsHanna et al. Predators show greater ability to locate prey on hairy apex from a distance compared with prey on glabrous apex Glabrous apex 27 63 Hairy apex % T. aripo to either olfactometer arm International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
  12. 12. Plant characteristics affecting predator abundance and biocontrolHanna et al.  Vulnerable to predation form other predators and T. aripo uses the apex as a refuge from other predators  T. aripo is sensitive to low relative humidity – presently investigating the hypothesis that the apex (and particularly hairy apex) moderates humidity and improve survival and improves predator fitness – in progress  Genetic control of hairiness to incorporate it in breeding programs – in progress International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
  13. 13. How does soil fertility affect pest and disease incidence?Fermont et al.  Completed 2-yr trials in Uganda and Kenya  50 trials; in 8 sites: 6 on-farm and 2 on-station  4 improved cassava varieties  NPK and control  Severity of cassava mosaic disease, cassava bacterial blight, cassava anthracnose, cassava green mite International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
  14. 14. 300 Cassava Bacterial Blight 300 Cassava Green Mites AUSiPC in fertilized plots AUSiPC in fertilized plots 250 250 200 200Fermont et al. 150 150 100 MM96/5280 100 I92/0067Area Under Severity 50 Nase 3 50 MM96/4884Index Progress 0 0 0 50 100 150 200 250 300 0 50 100 150 200 250 300Curve (AUSiPC) AUSiPC in non-fertilized plots AUSiPC in non-fertilized plotsUnfertilzed (x-axis) 150 Cassava Anthracnose Disease 400 Cassava Mosaic DiseaseFertilized (y-axis) AUSiPC in fertilized plots AUSiPC in fertilized plots 300 100 200 50 100 0 0 0 50 100 150 0 100 200 300 400 AUSiPC in non-fertilized plots AUSiPC in non-fertilized plots  CMD > tolerant but not affected by fertilizer in resistant variety  CAD and CBB only slight increased; CGM decreased with fertilizer  Yield > up to 12 T by 2nd yr  Cost-benefit analysis: fertilizer cost effective only if yields > 9 T/ha International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
  15. 15. Activities/output targets in R&TS – Output 2 Description of biotic and abiotic processes and interactions Biotic processes  Cassava root rots complex  55% F. oxysporum in cleared forest (what does this mean)  63% Botrydiplodia theobromae (humid forest)  77% F. solani (derived savanna)  TMS 4(2) 1425 least rot incidence (<27%)  Effect of habitat characteristics on ARTS & A. tenella  206 morphospecies (35 genera); A. tenella dominant where ARTS present; 5 other species dominant where ARTS absent; A. tenella < with higher soil & air temp.  Entomopathogenic fungi for ARTS and ant control  M. anisopliae (2) & B. bassiana (2) virulent against ARTS and A. tenella International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org

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