microbial biofertilizers and their potential in ... · microbial biofertilizers and their potential...
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Microbial Biofertilizers and theirMicrobial Biofertilizers and theirPotential in sustainable
Agriculture
Dr. Heike Bücking
Outline
1. Overview – Plant Microbe Interactions
2. Mycorrhizal interactions
ff f h l
4 I t ti b t h
3. Effect of mycorrhizal interactions on nutrient uptake and pathogen resistance
4. Interactions between exchange processes
5. Nitrogen flux in the symbiosis
6. Mycorrhizal fungi and their application
Ectomycorrhiza Fagus
Overview – Plant-Microbe Interactions
BacteriaNitrogen (N2) Fixation
Symbiotic bacteria (Rhizobia, Frankia)Associated bacteria (Acetobacter - sugarcane)Free living bacteria (Frankia rhizosphere)Free-living bacteria (Frankia – rhizosphere)
Plant Growth promoting Bacteria
F i
Abrosimov 2007
FungiMycorrhizal associations
Arbuscular mycorrhizal fungiy gEctomycorrhizal fungiOther root colonizing fungi
Smith and Read 1997Smith and Read 1997
Plant-Growth Promoting Bacteria
Enhanced N supply to the host by N2pp y y 2
fixationEnhanced supply of other plant nutrients ( b l S d h l )(P mobilization, S oxidation, Fe chelation)Phytochrome production leading to increases in root surface area (IAA,
Siberian soy beans, 1 – control, 2 - nodule bacteria; 3 - nodule bacteria and pseudomonads (Dashkevish 2007)
c eases oot su ace a ea ( ,cytokinin, gibberllin)Enhancement of other beneficical bacterial or fungal symbioses
The significance of mycorrhizal interactions
80-90% of all known plant species
bryophytes, pteridophytes, gymnosperms and most of the angiospermsangiospermssimultaneous colonization by various mycorrhizal types and fungal species,
essential for achlorophyllous plants
dependent on environmental conditions
Increasing attention for their role as biofertilizers, bioprotectors and bioregulatorsbioregulators
Smith and Read 1997
The benefits for both partners
Carbohydrates
Nutrients
Stress resistance
modified Egli, Brunner 2002
The life cycle and morphology of anasexual coenocytic obligate symbiont
Germinatingspore
Spores
Appressorium
Spores
Sporulation
H h l b h
Arbuscule
Hyphal branches
Structure of an arbuscular mycorrhizal root
Mycorrhizal root (light microscope) Arbuscule (electron microscope)
How does the fungus-plant interaction work ?
Increase in the nutrient absorbing surface area beyond the depletion zone of the root
Highly efficient nutrientHighly efficient nutrientuptake systems
Better P storage capabilities
Utilization of organic nutrient resources
How does the fungus-plant interaction work ?
Increased nutrient supply
Competition among the microorganisms for limited nutrient resources
Effect on the quantity and quality of root exudatesroot exudates
Selective pressure on the microbial populations in the rhizosphere leading topopulations in the rhizosphere leading toan increase in the number of microorganisms with antagonistic p ope tiesproperties
Activation of defense mechanisms by the mutualistic fungus
Mycorrhizal and nonmycorrhizal barley plants after colonisation with Cochliobolus sativus (Kogel, Giessen)
mutualistic fungus
Nutrient exchange always includes an apoplastic step
Arbuscular interfaceIntercellular interfaceArbuscular interface
Plant plasma membrane
Intercellular interface
Plant plasma membrane
Interfacial matrix
Plant cell wall
Interfacial matrixInterfacial matrix
Fungal cell wall
Interfacial matrix
Fungal cell wall
Fungal plasma membrane Fungal plasma membrane arbuscular mycorrhizaarbuscular mycorrhiza
Nutrient exchange includes passive and active steps
SoilSoil FungusFungus InterfacialInterfacialApoplastApoplast
PlantPlant
Pi
H+H+
Pi Pi Pi
ATPH+H+
ATP
ADPH+ H+
Hexoseacid
H+H+
Hexose
SucroseSucroseInvertase
H+
ATPH+ H+
ADP ADP
The C availability affects P uptake and P transfer by arbuscular mycorrhizas
Sucrose Phosphate
CC CC C
PP Growth
Extraradical mycelium (ERM)Daucus root system
PolyP LP, DNA-PPolyP LP, DNA-PPi Cytopl.
Bücking, Shachar-Hill, 2005
P uptake and P transfer is stimulated by the carbohydrate availability
SoilSoil FungusFungus InterfacialInterfacialApoplastApoplast
PlantPlant
Pi
H+H+
Pi Pi Pi
ATPH+H+
Pi
H+H+
Pi Pi Pi
ATPH+H+
Pi
H+H+
Pi Pi SinksPi
ATPH+H+
ATP
ADPH+ H+
ATP
ADPH+ H+
FungalCarbohyd.
Growth
ATP
ADPH+ H+
polyP
Hexoseacid
H+H+
HexoseH+H+
Hexose HexoseH+H+
Hexose
Hexose-P
Hexoseacid
SucroseSucroseInvertase
H+
ATPH+H+
ATPH+ H+H+H+ H+
ATP Photo-synthesisSucroseSucrose
Invertase
ADP ADPADP ADPADP ADP
Nitrogen flux in the arbuscular mycorrhizal symbiosis
Sucrose
SucroseNO3 NH4Hexose
NO3 NH4
Hexose
Protein
C
Pool
C
Pool
ERM
Amino
acidsAAAA
IRM ERM
INTERFACIAL
APOPLAST
SOILHOST
Nitrogen flux in the arbuscular mycorrhizal symbiosis
Sucrose
SucroseNO3 NH4HexoseNO3 NH4
NO3 NH4
Hexose
ProteinNO3 NH4
Protein
C
Pool
C
Pool
GS
ERM
Amino
acidsAAAA AAAA Amino
acids
IRM ERM
INTERFACIAL
APOPLAST
SOILHOST
Nitrogen flux in the arbuscular mycorrhizal symbiosis
Sucrose
SucroseNO3 NH4Hexose
NO3 NH4
Hexose
ProteinProtein
C
Pool
C
Pool
ERM
Amino
acidsAAAA AAAA Amino
acids
IRM ERM
INTERFACIAL
APOPLAST Arg-N
SOILHOST
Nitrogen flux in the arbuscular mycorrhizal symbiosis
Sucrose
SucroseNO3 NH4Hexose
NO3 NH4
Hexose
Protein
C
Pool
C
PoolC
Pool
ERM
Amino
acidsAAAA AA Amino
acids
IRM ERM
INTERFACIAL
APOPLAST Arg-C
SOILHOST
Nitrogen flux in the arbuscular mycorrhizal symbiosis
Sucrose
SucroseNO3 NH4Hexose
NO3 NH4
Hexose
Glu
Arg
Gln
C
Pool
NH4NH4 Orn
Urea
NH4
Arg
C
Pool
ERM
PolyP
P
PolyP
Pi PiPi
Arg
IRM ERM
INTERFACIAL
APOPLAST
Pii ii
SOILPiHOST
The dependency of various crop species on mycorrhiza
Mycorrhiza Potential yield loss Cropsdependency without mycorrhizaVery high Greater than 90 % LinseedHigh 60 – 80 % Sunflower, mungbean,g , g ,
pigeon pea, maize, chickpea
Medium 40 – 60 % Sorghum, soybeanLow 10 – 30 % Wheat, barley, triticaleVery low 0 – 10 % Panicum, canaryNil 0 Canola lupins
The State of Queensland (Department of Primary Industries and Fisheries)
Nil 0 Canola, lupins
Application of mycorrhizal fungi
Arbuscular mycorrhizal fungi can account for 5 – 50 % of theArbuscular mycorrhizal fungi can account for 5 50 % of themicrobial biomass in the soil (Ryan and Graham, 2002)
Efficient mycorrhizal symbiosis can substitute 222 kg P2O5 ha-12 5
(Kelly et al., 2001)
In field studies, the growth yield of linseed could be correlated to the mycorrhizal colonization rate (Thompson et al 1991)to the mycorrhizal colonization rate (Thompson et al., 1991)High P levels in the soil reduce significantly the colonization rate.
Why do we need mycorrhizal research?
We need to better understand:
Regulation of transport processes (beneficial nutrient transportRegulation of transport processes (beneficial nutrient transportin relation to the carbon costs for the plant)
Complex role of arbuscular mycorrhizal fungi in resource allocation
Partner choice in mycorrhizal systems
Effects of mycorrhizal colonization on the nutritional valueEffects of mycorrhizal colonization on the nutritional value
Interactions between arbuscular mycorrhizal fungi and root pathogen under field conditionsp g
P management
Studying metabolism and transport in arbuscular and ectomycorrhizal associations
Soilculture
In vivo Sampleanalysis
0
1
10
2 4 8 24 48 96
Moleculartools
Localizationand regulation
Monoxenic culture
ERM ERMAc Plant Ac
AutoradiographyGC/MS
LSM and analyticalMonoxenic culture
Data analysis
LSM and analyticalelectron microscopy
Invitro
Axenic culture
Data analysis
vitroLabelingLabeling with stable with stable or radioactive or radioactive
isotopesisotopesSustainableagriculture
RevegetationRemediation
Research QuestionsNitrogen metabolism and transport in the symbiosis
Sucrose
SucroseNO3 NH4
Hexose
3 33
Gln
C
NO3 NH4
Hexose
NH4NH4 Orn
Urea
NH4
Glu
C1
1
3
PolyP
ArgC
Pool
P PP
Urea
Arg
C
Pool
PolyP
1 2
2
IRM ERM
INTERFACIAL
APOPLAST
Pi
P
Pi PiPi
SOILPiHOST
Activity and regulation of the urea cycle in the IRM1
Interactions between the N and P flux in the symbiosis2
Gene expression, in situ hybridization, labeling studies, GC/MS, microautoradiography,
enzymatic assays, Western blots, EDXS
Regulation of plant and fungal N transporters and interactions of C and N flux3
The application of mycorrhizal fungi in sustainable agriculture
Maximal benefit of mycorrhizal fungi by:
Inoculation with efficient mycorrhizal fungi Increase of activity by proper cultural y y p ppractices
Cultural practices that increase theCultural practices that increase theactivityReduced tillageCrop rotationsCover cropsPhosphorus managementp g
Collaborators
Yair Shachar- Hill, Michigan State University
Philip E. Pfeffer, USDA – Wyndmoor
Peter Lammers, New Mexico State University
Toby Kiers, University Amsterdam
Arbuscule
Thanks for your attention