1. Using fungi to improve phosphorus
uptake in barley
Jaleh Bahri-Esfahani
12th
April 2013
Tim George (JHI) and Geoff Gadd (UoD)

2. Food security
• 9 billion people by 2030
• Limited by available land mass
• Current methods inefficient – we need changes!
• All agricultural systems need nutrient input

3. Phosphorus
• Phosphorus (P) is an essential nutrient
• Majority of P occurs in terrestrial soils, crustal rocks,
in biomass and in marine sediments
• Deficiencies in available soil P are a global concern
• Lack of auxin production, slower growth, delayed
maturation and lower yield
• Commonly used in fertilizers, often in the form of
rock phosphate (RP)

4. Rock Phosphate (RP)
Cordell, D. et al (2009)
The Story of Phosphorus: Global food security and food for
thought.
Global Environmental Change Journal.
• Heterogeneous form of phosphate-
rich rock
• Used to produce inorganic
fertilizers
• Expensive, inefficient and finite
• Expected to “peak” around 2030
• No single replacement for
phosphorus production

5. What can be done?
• Improve phosphorus recovery from current waste
systems
• Use additional alternative sources (human excreta,
guano)
• Select for crop species most suited to phosphorus
deficiencies
• Improve plant acquisition of phosphorus from soils
• Improve availability of phosphorus to plants within soils

6. Fungal intervention
• “Mining” strategy
• Enhancing solubilization or mobilisation
of P from sparingly-soluble P sources
• Fungi play key roles in soil
• Soil structure
• Nutrient cycles
• Organic acid production
• Use natural fungal processes to enhance
availability of P in the rhizosphere,
increasing P available to plants
Gadd, G. M. 2004. Mycotransformation of organic and
inorganic substrates. Mycologist, 18, 60-70.

7. Phosphorus cycle
Output: P export
Input: fertilizer added
Soil solution P
Inorganic P Organic P
Residues
Microbial P
organic acids
Weight in kg P ha-1
year-1
0.5 - 10
5 - 10
10 - 20
10 - 25
0.01
100 - 40050 - 200
10 - 30

8. Aims
1. Analyse overall properties of RP
2. Characterize fungal interactions with RP
and P minerals
3. Evaluate validity of downstream theory:
could the fungal inoculant be used as a
biofertilizer?

9. Fungal interactions with P minerals
• 3 fungi used; Serpula himantioides, Trametes
versicolor, Aspergillus niger
• Minerals included RP, tri-calcium phosphate
(TCP), and plant-available KH2PO4(Pi)
• Most effective fungus chosen

10. Fungal interactions with RP
Control With A. niger
Fungal exudates – SEM Fungal hyphae – cryogenic SEM
With A. nigerApatite + Whewellite
CaC2O4∙H2OCa5(PO4)2X

11. Method of solubilization
• High Performance Liquid
Chromoatography with
Transgenomic Coregel
64H Column at 55°C
• Samples ran for 92 hours at
0.6 ml/min 4 mM H2SO4
• Gluconic acid produced in
time with P release

12. Summary so far
• Aspergillus niger is able to:
• break down P minerals
• release P in a plant-available form
• alter the chemical makeup of RP
• alter the morphology of RP
• Chemical interaction due to production of gluconic acid
• Physical interaction due to hyphal burrowing and
thigmotropism

13. Aims
1. Analyse overall properties of RP
2. Characterize fungal interactions with RP
and P minerals
3. Evaluate validity of downstream theory:
could the fungal inoculant be used as a
biofertilizer?

14. Barley and A. niger
• Barley (Hordeum vulgare) as model organism
• Theory: presence of fungal inoculant will increase solubilization of
sparingly-soluble phosphate sources, enhancing proportion of
readily-available phosphate to plants
• Overall biomass and P content analysed
Control :
No P
+ TCP + Pi + RP
(850-500
µm)
+ RP
(250-120
µm)
+ 100 µL 1x104
spores mL-1
in 10% glycerol
+ 100 µL 10% glycerol

15. Effect of P source and A. niger inoculum on relative P accumulation in barley shoots
P source
No P TCP Pi RP1 RP2
µgP/mgDWbiomass
0
2
4
6
8
10
Plant only
With fungal inoculum
Sterile seed experiment
Effect of P source and A. niger inoculum on leaf biomass in barley shoots
P source
No P TCP Pi RP1 RP2
Dryweight(mg)
0
50
100
150
200
Plant only
With fungal inoculum
• Biomass data indicates that fungal presence reduces total biomass
of barley shoots
• However, plants grown with a fungal inoculant showed an increase
in P accumulation from sparingly-soluble sources

16. Summary
• We know and understand how A. niger could be used to improve P
uptake by plants
• In a uniform gel medium, A. niger has a negative impact on biomass
of barley under short term growth conditions
• Presence of fungal inoculum in gel media allowed for increased
P to be acquired from insoluble P sources

17. Future work
• Study effects of inoculant in more complex growth
conditions (soil, field trials)
• Adapt to application systems for commercial use
• Analyse the “wider” effects: microbial community in the
soil, other nutrients the inoculant may interact with

18. Acknowledgments
Geoff Gadd
Tim George
Lawrie Brown (JHI Dundee)
Rob Hancock (JHI Dundee)
Steven Hillier (JHI Aberdeen)
Martin Kierans (CHIPS, UoD)