Add arrow for P taken up by soil microorganisms. No link to P uptake from plants
1. Using fungi to improve phosphorusuptake in barleyJaleh Bahri-Esfahani12thApril 2013Tim 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, delayedmaturation and lower yield• Commonly used in fertilizers, often in the form ofrock phosphate (RP)
4. Rock Phosphate (RP)Cordell, D. et al (2009)The Story of Phosphorus: Global food security and food forthought.Global Environmental Change Journal.• Heterogeneous form of phosphate-rich rock• Used to produce inorganicfertilizers• Expensive, inefficient and finite• Expected to “peak” around 2030• No single replacement forphosphorus production
5. What can be done?• Improve phosphorus recovery from current wastesystems• Use additional alternative sources (human excreta,guano)• Select for crop species most suited to phosphorusdeficiencies• Improve plant acquisition of phosphorus from soils• Improve availability of phosphorus to plants within soils
6. Fungal intervention• “Mining” strategy• Enhancing solubilization or mobilisationof P from sparingly-soluble P sources• Fungi play key roles in soil• Soil structure• Nutrient cycles• Organic acid production• Use natural fungal processes to enhanceavailability of P in the rhizosphere,increasing P available to plantsGadd, G. M. 2004. Mycotransformation of organic andinorganic substrates. Mycologist, 18, 60-70.
7. Phosphorus cycleOutput: P exportInput: fertilizer addedSoil solution PInorganic P Organic PResiduesMicrobial Porganic acidsWeight in kg P ha-1year-10.5 - 105 - 1010 - 2010 - 250.01100 - 40050 - 20010 - 30
8. Aims1. Analyse overall properties of RP2. Characterize fungal interactions with RPand P minerals3. Evaluate validity of downstream theory:could the fungal inoculant be used as abiofertilizer?
9. Fungal interactions with P minerals• 3 fungi used; Serpula himantioides, Trametesversicolor, Aspergillus niger• Minerals included RP, tri-calcium phosphate(TCP), and plant-available KH2PO4(Pi)• Most effective fungus chosen
10. Fungal interactions with RPControl With A. nigerFungal exudates – SEM Fungal hyphae – cryogenic SEMWith A. nigerApatite + WhewelliteCaC2O4∙H2OCa5(PO4)2X
11. Method of solubilization• High Performance LiquidChromoatography withTransgenomic Coregel64H Column at 55°C• Samples ran for 92 hours at0.6 ml/min 4 mM H2SO4• Gluconic acid produced intime 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 andthigmotropism
13. Aims1. Analyse overall properties of RP2. Characterize fungal interactions with RPand P minerals3. Evaluate validity of downstream theory:could the fungal inoculant be used as abiofertilizer?
14. Barley and A. niger• Barley (Hordeum vulgare) as model organism• Theory: presence of fungal inoculant will increase solubilization ofsparingly-soluble phosphate sources, enhancing proportion ofreadily-available phosphate to plants• Overall biomass and P content analysedControl :No P+ TCP + Pi + RP(850-500µm)+ RP(250-120µm)+ 100 µL 1x104spores mL-1in 10% glycerol+ 100 µL 10% glycerol
15. Effect of P source and A. niger inoculum on relative P accumulation in barley shootsP sourceNo P TCP Pi RP1 RP2µgP/mgDWbiomass0246810Plant onlyWith fungal inoculumSterile seed experimentEffect of P source and A. niger inoculum on leaf biomass in barley shootsP sourceNo P TCP Pi RP1 RP2Dryweight(mg)050100150200Plant onlyWith fungal inoculum• Biomass data indicates that fungal presence reduces total biomassof barley shoots• However, plants grown with a fungal inoculant showed an increasein P accumulation from sparingly-soluble sources
16. Summary• We know and understand how A. niger could be used to improve Puptake by plants• In a uniform gel medium, A. niger has a negative impact on biomassof barley under short term growth conditions• Presence of fungal inoculum in gel media allowed for increasedP to be acquired from insoluble P sources
17. Future work• Study effects of inoculant in more complex growthconditions (soil, field trials)• Adapt to application systems for commercial use• Analyse the “wider” effects: microbial community in thesoil, other nutrients the inoculant may interact with