Disease Suppressive Soils: Fact or Fiction

1
Disease Suppressive Soils Fact or Fiction?

• Hida Manns
• March 26, 2007

2
OUTLINE

• Definition
• Natural controls on plant pathogens
• General Suppression
• Organic Matter
• Microbial Biomass
• Actinomycetes
• Specific Suppression
• SAR/ISR
• Antagonism
• Example Systems
• Potato Common scab
• Fusarium in France
• Take-all of Wheat
• Sugar beet cyst nematode in California
• Steps to building suppressive soils
• Composted Bark
• Ecological Equilibrium

3
DEFINITION

• Disease suppressive soils
• Pathogen is added to soil but does not persist
• Pathogen exists in soil but does not establish in
  plants or does not produce disease
• There is a decline in disease severity over time
• (Lyda, 1982, Weller et al., 2002).

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Disease Suppression

• General Disease Suppression
• Controls levels of most plant pathogens
• Increased microbial activity
• Greater microbial diversity
• Exists over time, regardless of crop
• Fungistasis
• Inhibition of germination or growth of fungi
• Lyda, 1982

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General Suppression

• Abiotic
• pH
• N, C, Mg, K
• Sand/clay
• CEC (Cation Exchange Capacity)
• Organic matter
• Biotic
• Microbial biomass
• Actinomycetes

6
Management

• When chemicals are substituted for organic matter
  in agriculture, plant diseases soon develop
• Bailey Lazarovits, 2003
• Biologic Vacuum
• Reduce disease in crops from
• cover crops
• compost
• tillage
• crop rotation
• Garbeva et al., 2004

7
Organic Matter

• Organic matter associated with higher
• Cation exchange (CEC)
• Soil moisture
• Available nutrients (e.g. nitrogen)
• Activity and diversity of soil microorganisms
• Bailey Lazarovits, 2003

8
Biological stresses

• Diversity of organisms
• Degradation of plant residues and also resting
  propagules
• Releasing different products into soil solution
• Antibiotics
• Fungistatic/biostatic compounds (2nd metabolites)
• Competition for nutrients
• Competition for space
• Predation

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Fungi

• Celluloytic activity of Fungi (enzymes)
• ß glucosidase and Cellobiohydrolase
• Correlated with carbon and CEC
• Seedling blight of barley
• Ratio of oligotrophic/copiotrophic species
• Mycorrhiza
• Diversity
• Janvier et al. 2007

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Mycorrhiza

• Mycorrhiza reduced the negative effect of
  take-all on plant growth of wheat at 5 weeks.
• (Khaosaad 2007)
• AMF was found to actively reduce pathogen
  infections in plant roots
• Only with high level of Mycorrhiza colonization
• Substitution of P fertilizer for mycorrhiza did
  not exhibit disease resistance
• (Fritz, 2006)

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Actinomycetes

• Large, diverse group, active residue decomposers
• Streptomyces produce anti-fungal compounds
• Mazzola, 2002
• Non-Streptomyces
• Endophytes
• Rhizosphere competent
• Slower growing in culture
• Cell wall-degrading enzymes
• El-Tarabily Sivasithamparam, 2006

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Specific Disease Suppression

• Individual, rather than most pathogens do not
  produce disease
• Often, antagonism by a certain species of
  organisms is the reason
• These can be tested and utilized by inoculation
• eg. Flourescent Pseudomonads (Mazzola, 2002)
• Does not exist without specific crop host
• Agrawal et al., 1999

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Specific Suppression

• Antagonistic bacteria
• Non-pathogens the same species as pathogen
• SAR Systematic Acquired Resistance
• Activated by biotic and abiotic agents
• Signal molecule salicylic acid or
• Jasmonic acid or ethylene
• Pathogen itself
• ISR Induced Systemic Resistance
• Hypersensitivity response
• Requires salicylic acid in process
• Agrawal et al., 1999

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Fo47 Experiment

• F. oxysporum strain Fo47 isolated from
  Chateaurenard by Alabouvette antagonist
• F. oxysporum f.sp. Lycopersici Fo18 pathogenic
• Tomato plants (Bonny Best)
• susceptible to Fusarium
• Tested with hydroponic, potting mix, sterile soil
• One side subjected to pathogen, other to
  antagonist
• Fuchs et al., 1997

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Split-root system

• Split root system
• Roots grown in 2 parts
• 1 side inoculated with Fo47
• 10 days later, plant exposed to Fo18

Fucks et al., 1997
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ISR

• Results
• Inoculation with Fo47 reduced Fusarium wilt from
  37-54 at 4 weeks
• Fo47 was not found
• Protective effect disappeared after 2 weeks
• Fucks et al., 1997
• Plant responded to both stimulus on both sides.
• Antagonist Pathogen
• ISR small volume
  large response (1000 x)
• Competition large volume (10-100x)
  small response
• Fravel et al., 2003

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Examples

• Potato Wheat
  Sugar Beets
• Common scab Fusarium
  Take-all Cyst Nematode
• General
• Suppression
• Abiotic
• Biotic
• Specific
• Suppression
• Antagonist
• SAR
• ISR

18
Potato Common Scab
Cornell University Vegetable MD Online Potato
Common Scab http//vegetabledonline.ppath.edu/phot
opages/impt_Diseases/potato/pot_scab.htm
19
Common Scab

• Potato scab (Streptomyces scabies)
• 1950 old potato fields scab free
• new potato fields, scab existed
• Tested old and virgin soil
• Scab developed in all soils in the first year
• Increased in virgin soil suppressed in old
  fields
• Weller et al., 2002
• Actinomycetes (Non-streptomycetes) produce
  antibiotics
• Present in scab free soil, and form inoculation
  at 1
• Weller et al., 2002
• Soybean cover crop incorporation prevented scab
  in virgin soil
  
  Weinhold, 1970
• OM additives dung, wheat straw, saw dust,
  soybean
• Mishra Srivastava, 2004

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Fusarium Wilt
Fusarium http//ecoport.org/ep?SearchTypepdbPdb
ID3593
Hwang, S.C., Ko,W.H., Plant Disease cover Images.
http//www.apsnet.org/online/Archive/PDCoverImage
s/2004V88/jun_I.asp
21
Fusarium

• Chateaurenard Valley in France
• Soils suppressive to Fusarium (1800s)
• Melons grown for centuries
• 2 km away, no effect of soil
• Only vegetables grown there
• Cook, 1982

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Soil suppressive to Fusarium

• Fusarium live saprophytically, and persists as
  chlamydospores
• Exudates from plant roots overcome fungistasis
• Interaction of species exerts control (Alabouvett
  e, 1986)
• Chateaurenard soils
• high populations of F. oxysporum and F. solani
• especially non-pathogenic strains (Fravel et
  al., 2003)
• Soils tested for Non-pathogenic Fusarium using
  Kochs Postulates
• Heat destroyed suppressive effect
  (microbiological)
• Restored with inoculation (Fravel et al., 2003)

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F. oxysporum

• Series of elimination tests
• soils inhibit all formae speciales of F.
  oxysporum, but allow other soil-borne disease
• Competition between the pathogenic and
  non-pathogenic strains did not limit
  establishment
• independent of the ability of the soil to support
  populations
• colonization on the root surface was not
  inhibited by non-pathogenic Fusarium
• Alabouvette, 1986

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Mechanism

• Intrageneric competition
• Occurs in the soil
• In the immediate vicinity of the roots
• During saprophytic development that
• Precedes the establishment of F. oxysporum
• at the root surface
• (Alabouvette, 1986)

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Take-all of Wheat
Take-all of Wheat http//scarab.msu.montana.edu/Di
sease/DiseaseGuidewebpics/Petewebpics61-70Img0065.
jpg Also 0066 and 0067
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Take-all (Ggt)

• (Gaeumannomyces graminis var. tritici) (pathogen
  of wheat)
• Take-all decline only in presence of pathogen
• Transferrable suppression with 1 soil
• Affected by biotic and abiotic factors in the
  environment
• Flourescent Pseudomonads (Siderophores)
• Trichoderma koningii
• Simon Sivasithamparam, 1989

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Antagonist Cause of Disease Decline
Weller et al., 2002
28
Pseudomonas fluoresens and Ggt
Weller Cook, 1983
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Trichoderma koningii

• T. koningii vs Ggt
• Seeds grown in tubes
• 8 different soils
• 2 replications
• 2 trials
• Measured degree of color on roots by PCF
• T. koningii reduced disease suppression
• Affect varied with soils
• Supportiveness of soil to T. koningii
• Principal components analysis
• Soil factors -pH, -Phosphorous, NO3,
  Fe
• Chemical effects Copper, magnesium
• Clay effects Boron, clay

Duffy et al.,1997
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Principal Components Analysis
Influence of soil factors on disease reduction by
T. koningii
Duffy et al., 1997
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Specific effects of soil

• NH4 decreases pH
• Increases antagonistic bacteria
• Trichoderma koningii
• Production of antibiotics
• Pseudomonads
• Production of antibiotics Duffy et al., 1997
• Phl (DAPG) 2,4-diacetylphloroglucinol
• PH1C phenazine-1-carboxylate
• Fe chelated by Siderophores
• Used in production of H2O2 by bacteria
• Zn used for production of antibiotics
• High diversity is suppressive soil, Increased by
  clay
• Raaijmakers et al., 1999

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Heterodera schachtii
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Sugar Beet cyst nematode

• The sugar beet cyst nematode (Heterodera
  schachtii) was first identified in Utah and
  California in 1907 in areas of intensive
  cultivation of sugar beets
• In the Imperial Valley, sugar beets were first
  grown in 1938, and the nematode detected in 1957
• Within 3 years, the nematode was widespread, as
  it can complete up to 5 generations per year
• As of 1983, 11 of the total cultivated acreage
  in the valley was infested
• Caswell Thomason, 1985

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Geographic distribution of H. schachtii
Cumulative geographic distribution of sugar beet
fields in the Imperial Valley of California that
have not been found to be infested with the sugar
beet cyst nematode during 1961-1983. Major
cities and railroad lines are indicated. Caswell
Thomason, 1985
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Defense

• Efforts sought to quarantine the disease
• The number of fields infected slowly spread to
  the function of planted fields infested
• 13.12 (0.583 x number of years)
• Solution cleanliness
• isolate specific antidote
• Caswell Thomason, 1985

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Fungal parasitism

• Acremonium strictum Gams and
• F. oxysporum Schlecht were tested for
• active parasitic activity on H. schachtii eggs
• activity of the fungus in females
• relative plant parasitic activity
• Nigh et al., 1980

37
Fusarium on H. schachtii eggs
Nigh et al., 1980
38
Effects of soil on H. schachtii egg survival
Greenhouse Experiment Suppressive and conducive
soils With swiss chard
Westphal Becker, 1999
39
Creating suppressive soil

• Composted Bark
• Peat /Composted Bark
• suppresses disease in seedling
• extensively used in greenhouse/nursery
• Replaced Peat
• Sterilization, fungicides, isolation
• Aeration, antagonists, phagous fugicidal
  properties of composted Bark gave suppressiveness
• Hoitink, 1980

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Microbial Diversity

• Pythium
• Rests in low volume in soil
• Increased disease only with high moisture and
  carbon
• Pythium in soil with peat alone (conducive) and
  mature compost mix (suppressive)
• Increased OM decomposition and microflora
  sustained disease suppression
• Conducive peat Composted peat
• Bacteria species that
• induced suppression 1 23
• Pseudomonads 0 25-45
• Arthrobacter 30 3-15
• Anaerobic bacteria predominant Yes No

Boehm et al., 1993
41
Change in colonization species with decomposition

Hoitink Boehm, 1999
42
Soil Food Web

• Trophic levels
• Microorganism (Producers)
• Nematodes (Consumers)
• Predaceous Nematodes (Predators)

43
Trophic Forces

• Bottom-up control (restricted by resource
  limitscarrying capacity)
• organic matter
• nutrients
• microbial processes
• Top-down control (restriction by consumers)
• predation

44
Trophic levels

• Microcosms 3 trophic levels
• 10 species bacteria 10 species fungi
• Microbes bacterial and fungal nematode
• Microbes microbivores predatory nematode
• Results
• 3rd trophic level decreased 2nd trophic level
• gt Top down control
• Abundance of bacteria, not affected by food chain
• Abundance of fungi increased with predation
• Mikola Satala, 1998

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Trophic Cascades vs Bottom up control

• No evidence of trophic cascades (top-down
  control) that interactions between trophic levels
  regulates microbial biomass and productivity in
  soil food webs
• Microbial community adjusts growth rate and
  turnover rate
• Microbial community growth not differentiated by
  trophic level
• Competition between species with environmental
  conditions and plant exudates determines species
  composition (bottom-up control)
• Mikola Satala, 1998

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Summary of factors

• General Suppression
• Species number and diversity
• Abiotic factors
• Soil moisture
• H2O2
• Specific factors
• Cultivar specific
• Antibiotics (Phl)
• SAR/ISR

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Biological control

• Attributes for Biocontrol
• Non-Streptomycete actinomycetes
• Antibiosis
• Hyperparasitic
• Cell-wall degrading enzymes
• Plant growth promotant
• El-Tarabily Sivasithamparam, 2006
• General Biocontrol agents
• Active suppression
• Population density
• Transferable (inoculation)
• Functional activity
• Weller,et al., 2002

48
Barriers to development of suppressive soil

• Host-pathogen specificity
• Soil variables
• Climate variables
• Nutrient inputs
• Crop rotations

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Conclusions

• Multiple methods of control by suppressive soil
• Biological Interaction between control and
  pathogen
• Competition for nutrients (Fe)
• Competition for colonization
• Production of specific inhibitors (H2O2,
  Antibiotics)
• SAR/ISR
• Driven by cultivar exudates and response
• Species specific
• Modified by environment
• Organic matter
• pH
• Nitrogen form (NH4)
• Sand/clay

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• References
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  from the Chateaurrenard region review of 10
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• Boehm, M.J., Madden, L.V., Hoitink, H.A.J., 1993.
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51

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