Soil microorganisms and organic

fertilization history in relationship to

Striga hermonthica (Del.) Benth. seed

bank density

S. Bökle, T.A. van Mourik, M. Cotter, J. Sauerborn

seboekle@uni-hohenheim.de

Garbenstr. 13, 70599 Stuttgart, Germany

Striga and organic matter

Striga appearance

2/15

Village

~2kmSauerborn et al. 2003

Introduction Objective Material&Methods Results Outlook

Objective

Which soil parameter induces lower Striga infestation

under high organic fertilization practice?

Investigation of:

• Microbial communities via PLFA- Analysis

(Phospholipid fatty acids)

• Soil characteristics

• Field history

Introduction Objective Material&Methods Results Outlook 3/15

Material and methods

• Sindala, Mali (40km SW from

Bamako, near Siby)

• Guinean agro-ecological zone

with 1043mm annual rainfall

• Sandy silty to sandy loamy

Leptosols

• Highly infested area

Introduction Objective Material&Methods Results Outlook4/15

Material and methods

• Mapping the territory

• Interviews with farmers

• Field history

• Crops

• Fertilization

• Striga development

Introduction Objective Material&Methods Results Outlook5/15

Material and methods

Field selection:

• At least 5 out of 10 years sown with host crops

• Organic fertilization

• high ( > 6 out of 10 years)

• low ( < 2 out of 10 years)

• 28 fields

• 2- 6 samples/ field

• 100 soil samples in total

Introduction Objective Material&Methods Results Outlook6/15

Material and methods

Data collection:

• Emerged Striga and seed bank density

• Soil parameters (Corg, Mic C, -N & -P,

N, P, K, CEC, pH, texture)

PLFA Analysis

• PLFAs: components of microbial

membranes

• Peak patterns indicate microbial

community composition.

8/15Introduction Objective Material&Methods Results Outlook7/15

Material and methods

PLFA Analysis :

• Phospholipid fatty acids as bioindicators for microbial

communities (Kandeler et al. 2008)

9/168/15

Introduction Objective Material&Methods Results Outlook

Preliminary resultsNo clear gradients in any directions from the village

9/15Introduction Objective Material&Methods Results Outlook9/15

Preliminary results

10/15

Negative relation of Striga and Gram- bacteria bioindicator

p= 0.0151

R²= 0.0596

Introduction Objective Material&Methods Results Outlook10/15

0.0 0.1 0.2 0.3 0.4 0.5

Preliminary results

11/15

Negative relation of Striga and bacterial bioindicator

p= 0.0457

R²= 0.0389

Introduction Objective Material&Methods Results Outlook11/15

0.0 0.2 0.4 0.6 0.8

Field

Preliminary results

13/15

3 fields with high spacial variability :

• high and low Striga emergence in close vicinity

~20m

Introduction Objective Material&Methods Results Outlook12/15

Preliminary results

13/15

Gra

m+

Fun

giGra

m-

Gra

m-G

ram

+

Gra

m+

Gra

m+

bac

teri

al

bac

teri

al

Bacteria dominate in low Striga spots

Introduction Objective Material&Methods Results Outlook13/15

2

1.5

1

0.5

0

Conclusions & outlook• Statistical analysis show that Striga seed bank density

and bacterial abundance (especially Gram-) are negatively

related.

Examples: Azospirillum brasilense, Pseudomonas putida

(Hassan, M.M. 2009)

• Soil chemical analysis are on-going and will be

integrated in the database and in further statistical

analyses

• Future investigations on soil born Striga control should

focus on bacterial strains especially Gram- ones.

Introduction Objective Material&Methods Results Outlook 14/1514/15

Thanks for your attention!

Acknowledgements: To all my supervisors and the EWRS for the scholarship

15/1515/15