Presentation at the EAPR 2014 Conference

1. 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

2.  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)

3.  Spread
 seed tubers
 contaminants
 irrigation/water run-off
 NO host resistance
 NO chemical control
 Management relies on:
 clean seed
 sound crop rotation
Management

4. Unavailable
Quality (formal) seed difficult to access
Expensive
Informal seed system dominates in SSA
 farmer-saved seed
 unmarketable tubers
Main culprit = SEED

5. 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%)

6. 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

7. tissue culture/minitubers/first field generations
onward, localised multiplication
decentralised multipliers
Improving access to quality seed
Formal certification
Quality Declared
Planting Material
QDPM

8.  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

9. 35.0
25.0
8.0
0
5
10
15
20
25
30
Improved
on-station
Improved
on-farm
National
Average
QDPM
Ethiopia
QDPM: an alternative approach to assess seed
health

10.  VISUAL INSPECTION
 Farm-saved seed
 Marking and saving tubers from
the healthiest plants in a crop
for the following season’s seed
Positive selection

11. BWincidence(%) 45
20
FSS PSS CS
Kakuhenzire et al., 2013
Positive selection

12. 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

13. Improving crop rotation
Region Crop
CFU / 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%

14. 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 0
11049.0 7 7 33 0 0 0 0 0 0 60
Revolución 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?

15. 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 0
11049.0 7 7 33 0 0 0 0 0 0 60
Revolución 0 27 87 13 60 0 0 60 0 27
Very visible wilt and no latent infection = NO THREAT

16. 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 0
11049.0 7 7 33 0 0 0 0 0 0 60
Revolución 0 27 87 13 60 0 0 60 0 27
No visible wilt and latent infection = THREAT

17. 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 0
11049.0 7 7 33 0 0 0 0 0 0 60
Revolución 0 27 87 13 60 0 0 60 0 27
Visible wilt and latent infection = THREAT

18. 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

20. 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

21. CS
20
40Tuberyield(tha-1)
FSPSSQDPMBasic
Kakuhenzire et al., 2013
QDPM: an alternative approach to assess seed health

22. CS
20
40Tuberyield(tha-1)
FSPSSQDPMBasic
Kakuhenzire et al., 2013
QDPM: an alternative approach to assess seed health