This document discusses mycorrhizal induced resistance (MIR) and plant innate immunity. It describes the different types of mycorrhizal associations including arbuscular mycorrhizae. MIR occurs in four phases and involves modulation of the plant immune system through changes in hormones like jasmonic acid and salicylic acid. Arbuscular mycorrhizal fungi can prime the jasmonic acid pathway in plants to induce a stronger defense response against pathogens. Gene expression is also altered in mycorrhizal plants to produce antifungal proteins that enhance resistance.

1. Mycorrhizal induced resistance and
plant innate immunity
Presented by-
Nongthombam Olivia Devi
PhD 1st Year 2nd sem
CAU/CPGS/PATHO/P16/03
School of Crop Protection, Plant Pathology
CPGS, Umiam ,Barapani
CREDIT SEMINAR
ON

2. CONTENT
Introduction
Types of mycorrhiza
MIR phases
Mycorrhizosphere effect
Strigolactones: multipurpose rhizosphere signals
Modulation of host immunity
Signal transduction between AMF and plant upon pathogen
attack
Priming of JA-dependent Defenses in Mycorrhiza- Induced
Resistance
Mycorrhiza Interactions with phytopathogens
Case Studies

3. INTRODUCTION
 Mycorrhizas are mutualistic associations
between the roots of 80 % of terrestrial plant
species and fungi (Schüßler et al., 2001).
 Greek “mycos” and “rhiza” meaning “fungus-
root,” oldest and most widespread plant
symbiosis.
 Plants develop enhanced defensive capacity due
to infection by arbuscular mycorrhizal fungi
(AMF) (Cameron et al.2013).
 ‘Mycorrhiza-induced resistance’ (MIR) provides
systemic protection against a wide range of
attackers.
Coined the term
mycorrhiza (1885)

4. The mycorrhizal fungi germinate make way to root.
Roots colonized by fungi, penetrate root create internal
fungal network structure, exchange nutrients and sugar.
Hyphae develop outside roots to explore soil.
Nutrients
Sugar
How does symbiosis take
place?
P,N,K

5. TYPES OF MYCORRHIZA
Mycorrhizae
Endomycorrhizae
Arbuscular
Mycorrhiza(AM)
Ericoid
endomycorrhiza
Arbutoid
endomycorrhiza
Monotropoid
endomycorrhiza
Orchidaceaous
endomycorrhiza
Ectomycorrhizae

6. • The fungal structure entirely within the host root, common with
herbaceous plants also associated with some woody plants.
• Associations where Glomeromycete
fungi produce arbuscules, hyphae, and
vesicles within root cortex cells.
• Defined by the presence of arbuscules.
• Obligate biotrophs, endotrophic.
• Act as bioprotectors of plants(Xavier
and Boyetchko, 2004)
ENDOMYCORRHIZA
ARBUSCULAR
ENDOMYCORRHIZA
Fig 2.Arbuscule of a Glomus species
in a root cortex cell
Fig 1:Vesicles of a Glomus species in
a root cortex.
(Fig. Source-Brunett,2008)

7.  Most advanced symbiotic
association.
 Basidiomycota and include
common woodland
mushrooms, such
as Amanita spp., Boletus spp.
and Tricholoma spp(David et
al. 2011).
 Form a mantle around roots
and a Hartig net between root
cells (Brunett,2008).
ECTOMYCORRHIZAE
Fig 3-Suillus sibiricus ectomycorrhizae on
inoculated Pinus albicaulis seedling in the
nursery
Fig 4-Cortical hartig net of ECM root
(Fig. Source-Brunett,2008)

8. Ericoid Arbutoid Monotropoid Orchidaceous
Coils of hyphae
within very thin
roots(root hairs) of
the ericaceae.
Found in certain
plants in the
Arbutoideae and
Pyrolaceae
characterized by
hyphal coils in
epidermal cells.
Mycorrhizal
association
formed by the
achlorophyllous
plants of the
Montropaceae.
Association where
coils of hyphae
penetrate within
cells in a root or
stem in the plant
family
orchidaceae.
Fig 6-Arbutus
unedo root with Hartig
net (arrows), coils (C)
and mantle (M) of
hyphae.
Fig 8-Orchid
mycorrhizas with
hyphae in trichomes
and hyphal coils in stem
of Pterostylis vittata
Fig 7-Monotropa root
with epidermal Hartig
net (H) and mantle
(M) in a cross-section
viewed with UV light.
Fig 5- Ericoid
mycorrhizas with hyphal
coils in hair roots
of Leucopogon
verticillatus

9. Fig 9-The principle structural features of the five main types of mycorrhiza.
(David et al. 2011)

10. SOME OF THE COMMERCIALLY IMPORTANT PLANT GROUPS THAT BENEFIT FROM -
MYCORRHIZAL FUNGI:

11. What is induced resistance and innate
immunity?
INDUCED RESISTANCE - enhanced
defensive capacity of plant when
appropriately stimulated.
Systemic Acquired Resistance (SAR)
Induced Systemic Resistance (ISR)
Plant defenses preconditioned by
prior infection results in resistance
against subsequent challenge by a
pathogen (Choudhary et al. 2007).

12. Plants are invaded by an array of pathogens of which only a
few succeed in causing disease. The attack by others is
countered by a sophisticated immune system possessed by
the plants (Muthamilarasan and Prasad, 2003).
The plant immune system is broadly divided into two-
Microbial-associated molecular-patterns-triggered
immunity (MTI)
 Effector-triggered immunity (ETI).
INNATE IMMUNITY OF PLANTS

13. PATHOGEN
SAR/IRPLANTAMF
Fig 10. Interaction of AMF induced plant defense responses (SAR/IR)
with the pathogen

14. Mycorrhizal induced resistance has four phases-
Source-Duncan et al.(2013),Trends plant Science

16. Mycorrhizosphere effect
Mycorrhizal hyphae exude chemical
compounds , have selective effect on
the microbial communities.
(mycorrhizosphere) (Duponnois et
al. 2008).
Enhanced microbial activity
surrounding mycorrhizal roots
(mycorrhizosphere effect.)
Mycorrhizosphere-inhabiting bacteria,
called ‘ mycorrhiza helper bacteria’
(MHB), stimulate mycorrhizal
symbioses ,deliver ISR-eliciting
signals. (Duncan et al.2014).
Multitrophic interactions.
Fig source-Audet,2012
Fig 11-Defining the
mycorrhizosphere and its
zone of influence

17. Fig 12-Mycorhizosphere tailoring-microbial interactions involving selected
AM fungi and PGPR

18. Fig 13-Schematic summary of the mechanisms by which the endobacterium affects
G. margarita metabolism Source-Salvioli et al.201

19. Strigolactones: multipurpose rhizosphere signals
• Early phase of colonization
strigolactone (SL) production high.
• Later AMF perceived as an alien
organism,salicylic acid (SA) levels
increased.
• well-established mycorrhiza both SL
and SA production repressed while
biosynthesis of jasmonates (JA)
increases.
• Plant sesquiterpenes that are exuded from roots.
• Role for seed germination of parasitic weeds
(Orobanche and Striga) (Garrido et al.2009).
• Stimulates branching of hyphae during germination of the spores
of AM fungi(Besserer et al.2006).
Fig. 14 Model for hormonal changes in the roots
associated to thearbuscular mycorrhizal symbiosis
Source-Jung et al. (2012). J.Chem Ecol

20. Strigolactones Stimulate Arbuscular Mycorrhizal Fungi by
Activating Mitochondria
• Branching Factor of a monocotyledonous
plant Sorghum strigolactone.
• Strigolactones strongly and rapidly
stimulated cell proliferation of Gigaspora
rosea at conc. 10-13 M.
• Within 1 h treatment, density of
mitochondria in fungal cells increased, their
shape and movement changed .
• Strigolactones stimulated spore
germination Glomus intraradices and Gl.
claroideum.
Besserer et al., 2006, PLoS Biol
Fig15

21. Fig.16

23. The plant immune system responding to AMF infection
..
AMF initiate
infection of the
root cortex
Microbe-
associated
molecular
patterns
(MAMPs) from
the fungus
recognised by
the plant innate
immune
system
transient
expression of
MAMP-
triggered
immunity (red
cells) and
generation of
long-distance
signals in the
vascular
tissues
induce long-
lasting priming
of salicylic acid
(SA)-
dependent
defences and
systemic
acquired
resistance
(SAR).
Long distance signal
MAMP
triggered
immunuty

24. Fig. 17 Model for the modulation of host immunity in the ecto- and
endomycorrhizal symbioses
B
Source-Zamioudis et al .(2012) The American Phytopathological
Society

25. Symbiotic mycorrhizal
fungi reduce stimulation
of the host’s immune
system.
Mycorrhizal fungi initially
elicit an MTI response,
which is subsequently
suppressed
Insights into the genome
of mycorrhizal fungi:
secretion of effector-like
molecules.
Mycorrhizal fungi
suppress SA-mediated
defense responses by
utilizing the Myc
signaling pathway
MODULATION OF HOST IMMUNITY

26. Modulation of plant defense response
Mycorhiza
establish
ment
Change in
Jasmonic
acid
Change in
Salicylic
acid
Change in
Ehtylene
Stimulate
abscisic
acid
(ABA)
Transported
through the
xylem to the
shoot, prime cell
wall defences.
combined impact of plant immune
modulation, enhanced sugar allocation,
increased nutrient uptake, and fungal
modification of root exudates leads to
changes in root exudation chemistry and
selection of specific mycorrhizosphere
bacteria

27. Fig 18-Hypothetical model representating the regulatory mechanism involved in
plant defense response during establishment of AM fungi
Garrido et al. (2002). Journal of experimental biology

28. Signal transduction between AMF and plant upon pathogen attack
Fig 19- Schematic representation of AMF-induced defence signaling in plant cell
Defense gene induction
Defense related proteins
Ellicitors inducing defense related genes
Hypersensitivity
Ca
JA
Biosynthesis
Source-Khan et al., 2010,J.Phytol.

29. Priming of JA-dependent Defenses in Mycorrhiza- Induced
Resistance
• In non-mycorrhizal plants (−
AMF) the initial wound signal
activates the JA-dependent
pathway that leads to the
activation of defense genes (DG).
• In mycorrhizal plants (+ AMF) the
response to the wound signal is
amplified leading to a primed
defense response.
Fig. 3 Priming of jasmonate-dependent
wound signaling in the shoots.
“This priming is common upon interaction
with beneficial microorganisms, and has
important fitness benefits compared to direct
activation of defenses’’

30. PathogenPathogen
JASA
Defense gene
expression
Mycorrhiza
JA
Defense gene
expression
Fig 20-Model illustrating priming of JA-dependent responses in
mycorrhizal plants.

31. Table 2 -Defense mechanisms associated with ISR by AMF
Source-(Cameron et al.2013).

32. Table 3. List of genes induced after AMF colonization in host plant and are responsible for
the plant’s defense against phytopathogen
Sl.No
.
Genes Products Function Source Reference
1 TC104515 Cysteine rich
protein
Antifungal property M. truncatula Liu et al.,
2007
2. TC101060 Cysteine rich
protein
Antifungal property M. truncatula Liu et al.,
2007
3 PR-1a PR-1a protein Pathogenesis-related
(Antimicrobial
Tomato Conrath et
al., 2006
4 BLG β-1,3 Glucanase
(PR protein family)
Antifungal property Tomato tomato Conrath et
al., 2006
5 VCH3 Chitinase protein
(PR protein family)
Antifungal property against
Meloidogyne incognita
Vitis
amurensis
Rupr.
(Grapevine)
Li et al., 2006
6. Pal Phenylalanine
ammonia lyase
(PAL)
enzyme
leads to production of
phytoalexins and phenolic
substances
Rice Blilou et al.,
2000b.
7. Ltp Lipid transfer
protein
Antimicrobial Rice Blilou et al.,
2000b.
Source-khan et al.2010

33. (Source-Trouvelot et al.2015, Agron. Sustain. Dev)
Increase plant resistance against
biotic stresses while reducing
phytochemical inputs
Increase plant/soil adherence
Improve soil water retention
Improve soil structure and
stability
Increase plant resistance to abiotic
stresses (Drought,salinity,metals
and mineral nutrient depletion)
Promote plant growth
Bioregulation of plant development
and increase in plant quality for
human health
Reduce fertilizer requirement

34. Mycorrhiza Interactions with phytopathogens
• Mycorrhiza fungi make roots more resistant to
invasion by pathogen like Fusarium, Rhizoctonia,
Macrophomina, or Verticillium, bacteria such as
Erwinia carotovora; or oomycetes like
Phytophthora, Pythium, and Aphanomyces and
soil inhabiting nematodes (Whips, 2004).
• AMF have impact on root-feeding insects, mostly
members of the genus Otiorhynchus, or weevils
(Koricheva et al., 2009).

35. Pathogen Host Effect in Mycorrhizal
plants
Olpidium brassicae Tobacco,lettuce Reduction of infection
Pythium ultimum soybean none
Pythium ultimum poinsettia Reduced stunting
Phytophthora megasperma soybean Fewer plants killed
P.palmivora papaya none
P.parasitica Citrus Reduction of damage
Rhizoctonia solani poinsettia Reduction of damage
Thielaviopsis basicola Tobacco,alfalfa,cotton Less stunting,inhibition of
chlamydospore
Cylindrocarpon destructans Strawberry Less stunting,reduction of
infection
Cylindrocladium scoparium Yellow poplar Less stunting,reduction of
infection
Fusarium oxysporium tomato Less stunting,reduction of
infection
Fusarium oxysprium cucumber Less stunting,reduction of
infection
Phoma terrestris onion Less stunting,reduction of
infection
Table 4 -Effect of AM on soil borne diseases caused by Fungi
Source-Declerck et al, (2010) in vitro culture of mycorrhizae,pp-131

36. Bacterial species AMF species Interaction type Reference
Azospirillum
brasilence
Glomus intraradices Neutral Hildebrandt et al
.(2002)
Bacillus
chitinosporus,B.pabuli
and other spore-
associated bacteria
G.clarum Positive,neutral or
negative
Xavier and
Germida(2003)
Clavibacter
michiganensis
ssp.michiganensis
G.intraradices Neutral Filion et al.(1999)
Corynebacterium sp. G.versiforme Positive Mayo et al. (1986)
Escherichia coli G.inraradices neutral Hildebrandt et al(2002)
Paenibacillus validus G.intraradices positive Hildebrandt et al(2002)
Pseudomonas sp. Endogone sp. positive Mosse(1962)
P.aeruginosa G.intraradices positive Villegas and
Fortin(2001,2002)
P.fluorescens Gigaspora margarita positive Bianciotto et al.(1996)
P.putida G.intraradices Positive or neutral Villegas and
Frotin(2001,2002)
Table 5-INTERACTION BETWEEN AM FUNGI AND BACTERIA IN VITRO
Source-Declerck et al, (2010) in vitro culture of mycorrhizae,pp-219

37. CROP NEMATODES FUNGUS EFFECT REFERENCE
Pepper R.Similis and
M.incognita
Glomus mosseae 60% population
reduction
Sivasprasad and
Sheela,1998
Cardamon M.incognita G.fasciculatum Nematode population
reduction
Sivaprasad et
al.,2001
Ginger M.incognita G.fasiculatum Nematode population
reduction
Joseph et al.,2001
Brinjal M.incogita G.fasiculatum Nematode population
reduction
Trivedi,2003
Coconut R.similis Glomus sp. Reduced lesion
no.and improved
plant gowth
Koshy et al,1998
Banana M.Incognita and
R.similis
G.mosseae Nematode population
reduction and
improved plant
growth
Trivedi,2003
Tomato M.incognita G.fasiculatum Smaller galls and less
no.of giant
cells.Reduction in
no.of galls,egg
masses,eggs and
juvenile
Suresh et al,1985 and
Sharma et al.,1994
Table 6-AMF INTERACTION WITH NEMATODES
Source-Nehru (2005),Plant disease biocontrol management,pp-199-200

38. MYCORRHIZA AND VIRUS INTERACTION
THE GENERAL RESPONSE OF MYCORRHIZAL PLANTS TO THE
PRESENCE OF VIRAL PATHOGENS IS AS FOLLOWS-
Mycorrhizal plants apparently enhanced the
rate of multiplication of viruses in some plants
More leaf lesions were found on mycorrhizal
plants than on non mycorrhizal plants.
The number of AMF spores in the
rhizosphere was reduced considerably
Source-Xavier and Boyetchko (2004),Fungal biotech.in Agril.,Food and
Environmental appl.

39. Systemic Resistance in Arabidopsis Conferred by the Mycorrhizal
Fungus Piriformospora indica Requires Jasmonic Acid Signaling and
the Cytoplasmic Function of NPR1
• Analyzed specific defense pathways for powdery mildew
(Golovinomyces orontii) resistance induced by Piriformospora
indica in Arabidopsis.
• Piriformospora indica root colonization reduced G. orontii conidia in
wild-type (Col-0), npr1-3 (non expressor of PR genes 1-3) and NahG
plants, but not in the npr1-1 null mutant.
• Two jasmonate signaling mutants non-responsive to P. indica, and
jasmonic acid-responsive vegetative storage protein expression
primed and elevated in response to powdery mildew.
Source-Stein et al.2008, Plant
cell Physiol

40. Enhanced tomato disease resistance primed
by arbuscular mycorrhizal fungus
• Tomato plants (S. lycopersicum ) inoculated with mycorrhizal
fungus Funneliformis mosseae and A. solani (ACCC36110) tomato
early blight disease.
• AMF pre-inoculation increases activities of β-1,3-glucanase,
chitinase, phenylalanine ammonia-lyase (PAL) and lipoxygenase
(LOX) in tomato leaves upon pathogen inoculation.
• provoked defense responses of three genes encoding
pathogenesis-related proteins, PR1, PR2, and PR3, as well as
defense-related genes LOX, AOC, and PAL, in tomato leaves.
Source-Song et al. (2015) Front. Plant Sci.,

41. TABLE 7. Mycorrhizal colonization rates, disease incidences, and indices of tomato
plants inoculated with either Funneliformis mosseae, Alternaria solani, or both.
FIGURE 21. Disease symptoms of early blight in leaves of tomato plants
with or without mycorrhizal colonization by Funneliformis mosseae.
Source-Song et al. (2015) Front. Plant Sci.,

42. Induction of defense responses in common bean
plants by arbuscular mycorrhizal fungi
• Interaction between AM fungi and Rhizoctonia ( root rot
disease of common bean) investigated in pot experiment.
• Mixture of Egyptian formulated AM (Multi- VAM) suspension
form (1×106 unit L−1 in concentration) used at dilution of 5ml
L−1 water.
• colonization of bean plants with AM fungi increased
1. growth parameters,
2. yield parameters and
3. mineral nutrient concentrations and reduced disease
severity and disease incidence.
Fattah et al.,2010,Microbiological Researc

43. • Different physical and biochemical mechanisms play a role in
enhancement of plant resistance against Rhizoctonia solani, -
1. improved plant nutrition,
2. improved plant growth,
3. increase in cell wall thickening,
4. cytoplasmic granulation, and
5. accumulation of some antimicrobial substances (phenolic
compounds and defense related enzymes).

44. Fig 22-Pot experiment, effect of different treatments on the growth of the common
bean plants

45. Figure 23. Effect of mycorrhizal colonization with different treatments on defense related
enzyme activities in the root of common bean plants infected with Rhizoctonia root rot disease.
C, control; F, fungicide; P, pathogen.

46. • PAbs separately raised against F. solani, T. hamatum and G. mosseae
purified and packaged into serological formats (PTA-ELISA, DIBA,
western blot and immunofluorescence).
• Successful root colonization with G. mosseae confirmed by cellular
localization in mandarin root tissues (FITC labeled immunofluorescence
assay).
• Enhanced growth of the saplings in AMF inoculated plants.
• suppressed root rot of mandarin.
• Induction of major defense enzymes such as chitinase, β 1-3 glucanase
and peroxidase by treatment with AMF and T. hamatum.
Activation of defense Response of Mandarin plants Against Fusarium
Rot disease using Glomus mosseae and Trichoderma hamatum
Source-Allay and Chakraborty (2010),. J.Mycol.Pl.Pathol.

47. Antigen Source Pab chitinase Pab of beta 1,3-glucanase
A 405
ELISA
Colour intensity
Dot-Blot
A 405 ELISA Colour intensity
Dot-Blot
Control 0.034 Light pink 0.049 Light pink
Fusarium solani
inoculated
0.036 Light pink 0.052 Light pink
F.solani+G.mosseae
treated
0.520 Deep purplish 0.368 Dark pink
F.solani+T.hamatum
treated
0.768 Dark pink 0.445 Dark pink
F.solani+G.mosseae+T.h
amatum
0.982 Deep purplish 0.865 Deep purplish
Table 8-ELISA and Dot-blot values of reactions between Pabs of defense
Enzymes and enzyme extracts from treated mandarin plants-

48. 0
2
4
6
8
Rootrotindex
Effect of application of T.hamatum and G.mosseae
on root rot caused by F.solani on mandarin
15days
30days
45 days
Fig 24:Mandarin plants inoculated
With G.mosseae
and T.hamatum

49. Mycorrhizal symbioses have an important impact on
plant interactions with pathogens and insects.
Fungal stimulation of the plant immune system is solely
responsible for MIR.
MIR in aboveground tissues seems effective against
necrotrophic pathogens and generalist chewing insects
but not against biotrophs.
Mycorrhiza increases the susceptibility to viral disease.
CONCLUSION

50. MIR is partially determined by resistance-inducing
bacteria in the mycorrhizosphere .
Priming of plant immunity and jasmonate signaling plays
a major role in MIR.
 In the future, mycorrhizosphere management must
become one of the viable and ecosystem friendly
solutions to managing plant diseases.