Visual inspection to manage bacterial wilt in Sub-Saharan Africa:
Improving seed quality and impacting smallholder farmers
Parker, ML, Mugo, J, Gutarra, L, Orrego, R and Schulte-Geldermann, E.
European Association of Potato Research Triennial Conference, Brussels July 7-11, 2014
Bacterial Wilt (BW) major (principal) constraint to potato production
BW = Ralstonia solanacearum
Massive host range (> 200 plant species)
Survivor
Impact of bacterial wilt on smallholder farmers
Major cause of poor seed quality and consequently, low yields
(8-12 t/ha)
Spread seed tubers contaminants irrigation/water run-off
NO host resistance
NO chemical control
Management relies on: clean seed sound crop rotation
Management
Unavailable
Quality (formal) seed difficult to access
Expensive
Informal seed system dominates in SSA farmer-saved seed unmarketable tubers
Main culprit = SEED
Prevalence
Wide spread in SSA from low to high altitudes
Region Incidence(%)
1500 -2200 m
> 2201 m Region Incidence(%)
1500 -2200 m
> 2201 m
Aberdares 0 6 5 Mau 0 1 4
1-9 1 4 complex 1-9 5 3
10-20 2 5 10-20 2 2
above 20 0 6 above 20 1 1
Elgon 0 4 6 Mt Kenya 0 6 3
1-9 2 2 1-9 2 0
10-20 3 4 10-20 3 1
above 20 1 7 above 20 4 1
BW was observed on 121 farms of a total 156 farms (78%)
Improving access to quality seed
Certification regulations exist, practice is minimal In Kenya
quantities of certified (formal) seed supply approximately 2% of demand
available at a few locations across the country Costly
certify seed lots purchase
tissue culture/minitubers/first field generations
onward, localised multiplication
decentralised multipliers
Improving access to quality seed
Formal certification
Quality Declared Planting Material
QDPM
VISUAL INSPECTION by recognised committees
Removing infected plants from seed multiplication plots (negative selection)
GAP - particularly crop rotation, alternative host management and field hygiene
QDPM is promoted among decentralised multipliers
Thereby increasing geographic and economic accessibility to quality seed
Local trade only
QDPM: an alternative approach to assess seed health
Yie
ld t
/ha
35.0
25.0
8.0
05
10
1520
25
30
Improvedon-station
Improvedon-farm
National Average
QDPM
Ethiopia
QDPM: an alternative approach to assess seed health
VISUAL INSPECTION
Farm-saved seed
Marking and saving tubers from the healthiest plants in a crop for the following season’s seed
Positive selection
BW
in
cid
ence
(%
) 45
20
FSS PSS CS
Kakuhenzire et al., 2013
Positive selection
Another main culprit = poor rotation
Potato key (only!) cash and food security crop for farmers in mid to highland regions
Season after season, farmers plant potato on same site
Lower altitudes, farmers crop numerous solanaceous crops
Improving crop rotation
Region CropCFU / g soil
Before planting After planting
Huanucalla Potato 188 11248
Onion 836 401
Chinchinga Potato 50 426
Onion 38 17
In each region, onion reduced CFU by ~ 50%
Genotype Biovar1 Biovar 2A Biovar 2T Biovar 3204 364
Wilt Latent Wilt Latent Wilt Latent Wilt Latent Wilt Latent
391919.3 0 0 67 0 7 0 0 0 0 13 391930.1 0 27 47 0 20 7 0 0 0 7 392278.19 0 33 73 0 20 0 0 20 0 0 394895.7 0 0 7 0 0 0 0 0 0 7 394903.5 0 7 20 33 13 7 0 0 0 0 394904.2 0 0 27 27 13 20 0 0 0 7 394904.9 0 0 47 0 20 0 0 20 0 0 394905.8 0 0 13 33 0 7 0 0 0 7 393909.2 0 20 87 0 60 0 0 13 0 0 395438.1 0 7 33 0 13 13 0 0 0 011049.0 7 7 33 0 0 0 0 0 0 60Revolución 0 27 87 13 60 0 0 60 0 27
No visible wilt and no latent infection = NO THREAT
Can latent infection threaten effectiveness of QDPM?
Can latent infection threaten effectiveness of QDPM?
Genotype Biovar1 Biovar 2A Biovar 2T Biovar 3
204 364
Wilt Latent Wilt Latent Wilt Latent Wilt Latent Wilt Latent
391919.3 0 0 67 0 7 0 0 0 0 13 391930.1 0 27 47 0 20 7 0 0 0 7 392278.19 0 33 73 0 20 0 0 20 0 0 394895.7 0 0 7 0 0 0 0 0 0 7 394903.5 0 7 20 33 13 7 0 0 0 0 394904.2 0 0 27 27 13 20 0 0 0 7 394904.9 0 0 47 0 20 0 0 20 0 0 394905.8 0 0 13 33 0 7 0 0 0 7 393909.2 0 20 87 0 60 0 0 13 0 0 395438.1 0 7 33 0 13 13 0 0 0 011049.0 7 7 33 0 0 0 0 0 0 60Revolución 0 27 87 13 60 0 0 60 0 27
Very visible wilt and no latent infection = NO THREAT
Can latent infection threaten effectiveness of QDPM? Genotype Biovar1 Biovar 2A Biovar 2T Biovar 3
204 364
Wilt Latent Wilt Latent Wilt Latent Wilt Latent Wilt Latent
391919.3 0 0 67 0 7 0 0 0 0 13 391930.1 0 27 47 0 20 7 0 0 0 7 392278.19 0 33 73 0 20 0 0 20 0 0 394895.7 0 0 7 0 0 0 0 0 0 7 394903.5 0 7 20 33 13 7 0 0 0 0 394904.2 0 0 27 27 13 20 0 0 0 7 394904.9 0 0 47 0 20 0 0 20 0 0 394905.8 0 0 13 33 0 7 0 0 0 7 393909.2 0 20 87 0 60 0 0 13 0 0 395438.1 0 7 33 0 13 13 0 0 0 011049.0 7 7 33 0 0 0 0 0 0 60Revolución 0 27 87 13 60 0 0 60 0 27
No visible wilt and latent infection = THREAT
Can latent infection threaten effectiveness of QDPM?
Genotype Biovar1 Biovar 2A Biovar 2T Biovar 3
204 364
Wilt Latent Wilt Latent Wilt Latent Wilt Latent Wilt Latent
391919.3 0 0 67 0 7 0 0 0 0 13 391930.1 0 27 47 0 20 7 0 0 0 7 392278.19 0 33 73 0 20 0 0 20 0 0 394895.7 0 0 7 0 0 0 0 0 0 7 394903.5 0 7 20 33 13 7 0 0 0 0 394904.2 0 0 27 27 13 20 0 0 0 7 394904.9 0 0 47 0 20 0 0 20 0 0 394905.8 0 0 13 33 0 7 0 0 0 7 393909.2 0 20 87 0 60 0 0 13 0 0 395438.1 0 7 33 0 13 13 0 0 0 011049.0 7 7 33 0 0 0 0 0 0 60Revolución 0 27 87 13 60 0 0 60 0 27
Visible wilt and latent infection = THREAT
Improving effectiveness of visible inspection
Knowledge on Rs isolates
Simple tools for field based diagnostics
Further validation of rotation (onion) to reduce Rs populations in soil
Understand infection gradient from an infected source
Asante Merci
Murakoze Thank you
Gracias Obrigado
አመሰግናለ
ሁ
Zikomo
Dank u wel
Summary
QDPM is an effective and accessible approach for small-scale seed multipliers to maintain seed quality
Positive selection provides farmers a way to save seed on farm while maintaining quality
Although promising, crop rotation patterns require further validation to assess effect on BW
Attention to Rs isolates and latent infection
CS
20
40Tu
ber
yie
ld (
t h
a-1)
FSPSSQDPMBasic
Kakuhenzire et al., 2013
QDPM: an alternative approach to assess seed health
CS
20
40Tu
ber
yie
ld (
t h
a-1)
FSPSSQDPMBasic
Kakuhenzire et al., 2013
QDPM: an alternative approach to assess seed health
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