Root and Tuber Systems Program

International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org

Root and Tuber Systems Program

Output 2

Description of biotic and abiotic processes and

interactions

Rachid Hanna, Denis Cornet, Stefan Hauser, Pheneas

Ntawuruhunga, Nzola-Meso Mahungu, Jelle Duindam,

Caroline Herron, Anneke Fermont, Alfred Dixon, Sarah

Hearne, Ranajit Bandyopadhyay, Maria Ayodele, Robert

Asiedu, Robert Abaidoo, Busie Maziya-Dixon, James

Legg,Kerstin Hell, Lava Kumar


Cassava brown streak disease

Major Cassava Pests and Diseases in Africa

Cassava green mite

Cassava mosaic disease

African root and tuber scale


Major Cassava Pests and Diseases in Africa

Cassava bacterial blight

NematodesRoot rots

Whiteflies


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.

Bitoic processes and interactions

Purpose


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


Description of biotic processes and interactions

(example output targets)

Biotic processes

Profiling CMD resistance and gene pyramiding

Monocolonal antibodies for CBSD


Mechanism of cassava clone preference by predatory

mites

Ants associated with Africa root and tuber scale


Interactions between biotic and abiotic processes

Soil fertility and cassava pest and disease severity

Effects of AMF and nematodes on yam yield


Profiling sources of resistance to CMD and

pyramiding resistance genes

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.

Dixon et al.


Biological control of cassava green mite in Africa

1st release

1993, Benin


Plant characteristics affecting predator abundance

and biocontrol of cassava green mite

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

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

T. aripo

Hanna et al.


Sensitivity of T. aripo to UVB radiation (282-320 nm)

Hanna et al.

Apex provides considerable protection from UVB

96%

25%

Direct Apex


Glabrous apex Hairy apex27 63

% T. aripo to either olfactometer arm

Prey location behavior on hairy and glabrous plants

Predators show greater ability to locate prey on hairy apex

from a distance compared with prey on glabrous apex

Hanna et al.


Plant characteristics affecting predator abundance and

biocontrol

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

Hanna et al.


How does soil fertility affect pest and disease

incidence?

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

Fermont et al.


Cassava Mosaic Disease

0

100

200

300

400

0 100 200 300 400AUSiPC in non-fertilized plots

AU

SiP

C in

fer

tilize

d p

lots

Cassava Anthracnose Disease

0

50

100

150

0 50 100 150AUSiPC in non-fertilized plots

AU

SiP

C in

fer

tilize

d p

lots

Cassava Green Mites

0

50

100

150

200

250

300

0 50 100 150 200 250 300AUSiPC in non-fertilized plots

AU

SiP

C in

fer

tilize

d p

lots

Cassava Bacterial Blight

0

50

100

150

200

250

300

0 50 100 150 200 250 300AUSiPC in non-fertilized plots

AU

SiP

C in

fer

tilize

d p

lots

MM96/5280

I92/0067

Nase 3

MM96/4884

Area Under Severity

Index Progress

Curve (AUSiPC)

Unfertilzed (x-axis)

Fertilized (y-axis)

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

Fermont et al.


Activities/output targets in R&TS – Output 2

Description of biotic and abiotic processes and interactions

Biotic processes


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.


M. anisopliae (2) & B. bassiana (2) virulent against ARTS and

A. tenella

Root and Tuber Systems Program

Technology

Transcript of Root and Tuber Systems Program