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