Systemic Acquired Resistance (SAR) and it’s Significance in Plant Disease Management

Welcome
To seminar
Series
2017-18

Reg. No. 1010116006
Doctor of Philosophy
Department of Plant Pathology
N.M.C.A, N.A.U, Navsari
Major Advisor
Dr. K. B. Rakholiya
Associate Professor
Department of Plant Pathology
N. M. College of Agriculture
Navsari Agricultural University
Navsari – 396 450
Co-Advisor
Dr. A. G. Shukla
Senior Acarologist
Department of Agril. Entomology
N. M. College of Agriculture
Navsari Agricultural University
Navsari – 396 450
2

Content
IntroductionIntroduction
Basics of Systemic Acquired Resistance (SAR)Basics of Systemic Acquired Resistance (SAR)
History of SARHistory of SAR
Importance of SAR in plant diseases managementImportance of SAR in plant diseases management
Mechanisms of SARMechanisms of SAR
ReviewsReviews
ConclusionConclusion
3

I n t ro d u c t i o n
Systemic Acquired Resistance (SAR) is plant defense a mechanism of induced defense
that confers long-lasting protection against a broad spectrum of microorganisms & pest.
Presently disease control is largely based on the use of hazardous chemicals viz.,
fungicides, bactericides and insecticides for either direct or indirect disease
management.
The hazardous natures of the products on the environment, human and animal health
strongly necessitates to search for new safer means of disease control.
SAR have high potential to diminish the use of toxic chemicals in the agriculture and
has emerged as an alternative, non-conventional, non-biocidal and eco-friendly
approach for plant protection and hence for sustainable agriculture.
SAR requires the signal molecule salicylic acid (SA) and is associated with
accumulation of pathogenesis-related proteins, which are thought to contribute to
resistance (Dube, 2017).
5

Plant Defense
Passive defensesPassive defenses Active defensesActive defenses
Physical
barriers
Chemical
barriers
Rapid
defense
Delayed
defense
 Wax
 Cuticle
 Cell wall
 Stomata
 Lenticels
 pH
 Phytoanticipins
 Membrane
permeability loss
 Oxidative burst
 Fortification cell wall
 HR
 Phytoalexin –
production
PR- Proteins
Induced Systemic
Resistance (ISR)
 Systemic Acquired
Resistance (SAR)
6 (Choi & Hwang, 2011)

Basic events in an incompatible host–pathogen interaction 7

What is induced resistance ???What is induced resistance ???
The induced resistance can be defined as an increased
expression of natural defense mechanisms of plants against
different pathogens.
8
LAR ISR SAR

o A distinct signal transduction pathway that plays an important role in the
ability of plants to defend themselves against pathogens…..
o Significant phenomenon recognized by Chester in 1933.
o Concept of SAR proposed by Ronald Ross in 1961.
o Infection of plants with necrotizing pathogens (causing HR) often results in
enhanced resistance to subsequent infections by a variety of bio-tropic
pathogens.
o SAR requires the signal molecule salicylic acid (SA) and is associated with
accumulation of Pathogenesis Related proteins, which are thought to
contribute to resistance.
o Resistance triggered in the plant during its life time is Acquired Resistance.
 Local (LAR) confined to few cells or tissues
 Systemic (SAR) having been moved through out the plant
SAR (Systemic AcquiredResistance)
9

10
SAR
Characteristics
Broad-
spectrum
Expression
of PR-
protein
Involvement
SA
signaling
Necrotic
lesions (pp)
as inducing
agent
SAR depend
on plant &
inducing
factor
10
Establishment

Year Name Contribution
1901 Ray & Beauverie
The natural phenomenon of resistant in response to pathogen infection or plant
immunity
1932
Carbonne &
Kalaljev
Showed that acquired resistant also depends on the general fitness of the host
1933 Chester Documented the idea of Physiological Acquired Immunity
1961 A. F. Ross
Published the first systemic study of SAR
He coined the term “Systemic acquired resistance”
1970 Van et al.
Showed that viral infection of tobacco induced the accumulation of a distinct
set of proteins, called pathogenesis-related proteins (PR proteins)
1979 Ray White
observed that PR protein accumulation and resistance to TMV could be
induced by treatment of tobacco with salicylic acid (SA), aspirin (acetyl SA), or
benzoic acid
1991 Ward et al.
Studied steady-state mRNA levels from at least nine families of genes were
shown to be coordinately induced in uninfected leaves of inoculated plants;
these gene families are now known as SAR genes
1993 Gaffney et al
A requirement for SA as an endogenous signal for SAR was proven with using
a bacterial gene, nahG, encoding salicylate hydroxylase, which removes SA by
conversion tocatechol
History of SAR
11

o SA dependent
o Necrosis reaction
present
o Signaling molecules SA
o Less elastic
o Against biotrophs
o Continuous irritation is
not required
o PR-proteins involved
o SA independent
o Necrosis reaction
absent
o Signaling molecules
JA, Ethylene
o More elastic
o Against necrotrophs
and insects
o Continuous irritation
is required
o Defense genes
involved
12
SAR ISR

Importance of SAR in plant diseases management
o SAR can also be transmitted to the next generation progeny.
o Its provides a broad-range resistance against fungal, bacterial and viral
pathogens.
o Leads to pathogenesis-related (PR) gene expression.
o Its ability to immunize susceptible plants implies that genetic potential
for resistance is in all types of plants.
o The significant practical aspects of SAR is the discovery of chemical inducers of
plant defense.
o New generation fungicides act as a plant defense system. (rather than killing
pathogen.) ICGA-245704, a benzothiadiazole (BTH) (Alfa-Aesar) & Dichloro-
isonicotinic acid (DCINA) compound (plant-activator) switches SAR in plant.
13

Signal generation and transmission In SAR
Ideal Charactristics of Transported Signal:
o Induce a defensive response
o Produced or released at the site of attack
o Translocated from the attacked to the systemic tissue
o Accumulate in the systemic tissue before resistance expression takes place
(Choi & Hwang, 2011)14

Pathogenesis related proteins (PRs) are assigned an important role in
plant defense against pathogenic constraints and in general adaptation
to stressful environment.
These proteins are accumulated 7-10 days after infection and indicate
the attainment of SAR.
It is accumulated in the intercellular spaces (first line of defence) and
vacuole (second line of defence by lytic enzyme).
Pathogenesis-Related (PR) Proteins in SAR
17

Accumulation of PR Proteins in SAR
18 (Pieterse and Van Loon, 2004)
Cytoplasma

19
Low-molecular
proteins
(5-75 kDa)
Stable at low
pH (< 3)
Thermostable &
Highly resistant
to proteases
Contains four α-
helices and β-
strands
arranged
antiparallel
between
helices
Established in
all plant organs
– leaves, stems,
roots, flowers
Feature:
Antifungal,
Antibacterial,
Insecticidal &
Antiviral action
Biochemical
and structural
characteristics
of PR Proteins

Family Type member Properties Targeted Pathogen Site
PR-1 Tobacco PR-1a Antifungal Active against Oomycetes
PR-2 Tobacco PR-2 β-1,3-Glucanase Cell wall Glucan of fungi
PR-3 Tobacco P, Q
Chitinase
(class I,II, IV,V,VI,VI)
Cell wall Chitin of fungi
PR-4 Tobacco ‘R’ Chitinase class I,II Cell wall Chitin of fungi
PR-5 Tobacco S Thaumatin-like, Active against Oomycetes
PR-6 Tomato Inhibitor I Proteinase-inhibitor Active on Nematodes + Insect
PR-7 Tomato P69 Endoproteinase Microbial cell wall dissolution
PR-8 Cucumber chitinase Chitinase class III
Cell wall Chitin of fungi +
Mucopeptide wall of bacteria
PR-9
Tobacco ‘lignin-
forming peroxidase’ 35
Peroxidase
Antimicrobial activity by
catalyzing oxidative cross-linking
protein and phenolic in cell wall
leading to physical barrier
Classification and Properties of families of PR proteins
20

Family Type member Properties Targeted Pathogen Site
PR-10 Parsley ‘PR1’ ‘Ribonuclease-like’ Viral-RNA
PR-11 Tobacco ‘class V’ chitinase Chitinase class I Cell wall chitin of fungi
PR-12 Radish Rs-AFP3 Defensin Antifungal and Antibacterial
PR-13 Arabidopsis THI2.1 Thionin Antifungal and Antibacterial
PR-14 Barley LTP4 Lipid-transfer protein Antifungal and Antibacterial
PR-15 Barley OxOa (germin) Oxalate oxidase
Produce H2O2 that inhibite
microbes and also stimulates
host defense
PR-16 Barley OxOLP ‘Oxalate oxidase-like’
Produce H2O2 that inhibite
microbes and also stimulates
host defense
PR-17 Tobacco PRp27 Unknown -
(Dube, 2017)Conti… 21

NPR1: non-expresser of PR genes
22
NPR1 is key & positive regulator of SAR
Downstream of SA, upstream of PR genes
npr1 mutants are susceptible to various pathogens
The non-expresser of PR genes (NPR1) has emerged as a good candidate
to provide broad-spectrum resistance.
NPR1 is a regulatory protein that activates & expression of PR genes.
npr1 mutants are impaired in their ability to induce PR gene expression and
mount a SAR response, even after treatment with SA & INA.
It also participates in the jasmonate and ethylene regulation, SA-
independent induced systemic resistance (ISR).

How NPR1 work ?
(Pieterse and Van Loon, 2004)23
Inactive oligomeric of NPR1
Active monomeric of NPR1
Translocated monomeric of
NPR1 & bind with TGATGA2
Activation of PR gene
Accumulation antioxidants

Plant Inducer organism SAR Systemic protection against SAR gene
Arabidopsis
Turnip crinkle virus
Pseudomonas syringae
Fusarium oxysporum
+
+
+
+
Turnip crinkle virus
Peronospora parasitica
PR-1, PR-2
Sugarcane Colletotrichum falcatum + Colletotrichum falcatum
PAL,
Peroxidase,
Polyphenol
oxidase
Rice Pseudomonas syringae + Magnaporthe grisea Lip oxygenase
Tobacco
Tobacco mosaic virus
Tobacco necrosis virus
Thielaviopsis basicola
Pseudomonas fluorescens
+
+
+
+
Thielaviopsis basicola
Phytophthora parasitica
Peronospora tabacina
Pseudomonas tabaci
PR-1, PR-2,
PR-3, PR-4,
PR-5, PR-1g
PR-8,
Potato
Phytophthora infestans
Phytophthora cryptogea
+ Phytophthora infestans β- 1,3-glucanase
Tomato Phytophthora infestans + Phytophthora infestans Chitinase
Plants exhibiting SAR
24 (Sticher, 1997)

Major pathways of secondary-metabolite biosynthesis
25
SA

SIGNALS FOR SYSTEMIC ACQUIRED RESISTANCE
Electrical
Signals
Reactive
Oxygen Species
Lipid-Based Signal
Molecule
Natural Organic
Compounds
Inorganic
Compounds
o Salicylic Acid (SA)
o Jasmonic Acid (JA)
o Methyl ester JA (MeJA)
o Methyl ester SA (MeSA)
o Ethylene
o Systemin
o Riboflavin
o Phosphate salts
o Silicon
o Synthetic compounds
BABA (β-aminobutyric acid)
INA (2,6 – dichloroisonicotinic acid )
BTH/ ASM (Benzo-(1, 2, 3)-thiadiazole-7-
carbothioic acid S-methyl ester )
o H2 O2
o DPI (Diphenylene iodonium)
o dir 1
o LTPs
o eds 1
o pad 4
o SABP 2
o Pin2 mRNA
26
(Sticher, 1997)

 SA/ orthohydroxy benzoic acid group of phenolics.
 SAR- endogenous signal produced by infected leaf and translocate in the phloem
to other plant parts. Vascular mobile signal that moves throughout the plant after
initial infection.
 It is reported in several plant species i.e., Tomato, Potato, Rice, Sugarcane, Okra,
Wheat, Carrot, Tobacco, Bean and Papaya.
 Salicylate regulated defenses more active against biotropic pathogens.
 Salicylic acid is part of signaling pathway involved in transmission
 of the defense response throughout the plant to produce SAR.
 SA reported as the endogenously as well as exogenously signal of SAR.
 SA play role in elicitation of Pathogenesis-Related proteins.
 Analogs: INA or BTH
Salicylic Acid (SA)
27

28
Chorismic AcidChorismic Acid
IsoChorismic AcidIsoChorismic Acid
Salicylic Acid (SA)Salicylic Acid (SA)
SA-2-glucosideSA-2-glucosideMethyl Salicylate
(MeSA)
Methyl Salicylate
(MeSA)
IsoChorismate Synthase (ICS)
IsoChorismate Pyruvate lyase
Salicylic Acid (SA) Biosynthesis Pathway
28

Fig. 1: Effect of BTH (1.2 mM) on tobacco against Tobacco mosaic virus (TMV)
 Upper, uninoculated leaves from control (left) and 1.2 mM BTH 7 days prior to TMV infection
(right).
 Each bar in the histograms represents the average disease level of six plants
USA Friedrich et al. (1996)30

Fig. 2: Effects of AABA, BABA and GABA (10 mM) applied as a foliar spray to
three-leaf cauliflower plants on sporulation of Peronospora parasitica
• Plants were inoculated 1 day after spray and spore counts in leaf discs were taken 7 days after.
• Bars represent standard deviations. Treatments with the same letter are not significantly different at the 5%
probability level.
• DL- a-(AABA), DL-b -(BABA) and g-(GABA) (ABA-aminon –butanoic acid)
• Plants were inoculated 1 day after spray and spore counts in leaf discs were taken 7 days after.
• Bars represent standard deviations. Treatments with the same letter are not significantly different at the 5%
probability level.
• DL- a-(AABA), DL-b -(BABA) and g-(GABA) (ABA-aminon –butanoic acid)
Israel Silue et al. (2002)31
Untreated

Table-1: The effect of BTH treatment on Phytophthora root rot symptoms and
growth in papaya plants
Table-1: The effect of BTH treatment on Phytophthora root rot symptoms and
growth in papaya plants
Treatment Disease rating
Plant heights
(cm)
Stem diameter
(mm)
Untreated (H2O) 3.40a 85.2b 14.5b
BTH at 1.0 µM 3.25a 85.3b 14.7b
BTH at 5.0 µM 0.95b 86.0b 15.0b
BTH at 25.0 µM 0.64c 88.4a 16.4a
BTH at 100 µM 0.60c 85.2b 14.5b
a Disease rating was assessed 6-weeks after P. palmivora inoculation, scored on a scale of 0 (healthy) to 5
(dead plants).
b The growth data were collected six weeks after treatment without P. palmivora inoculation. Letters a–c
are class measures of the Waller- Duncan K-ratio T test. Means with the same letter are not significantly.
• CD at p=0.05.
USA Zhu et al. (2003)32

Treatmentx y z
Incidence (%)
BHN 466 Neptune Equinox
Actigard (3 μg/ml) 5 0 95
Untreated 30 20 95
Chi-Squre 21.64** NA 7.14NS
Table-2: Effect of acibenzolar-S-methyl (ASM) on per cent bacterial wilt (Ralstonia
solanacearum) incidence in moderately resistant and susceptible tomato
cultivars under greenhouse conditions
• For foliar sprays, a volume of 10 ml of ASM solution (3 μg/ml=0.003 g/l)
• x Acibenzolar-S-methyl (Actigard 50 WG) was applied twice before transplanting and four times
after transplanting at weekly intervals.
• y BHN 466 and Neptune are moderately resistant to bacterial wilt, and Equinox is susceptible to the
disease.
• z Mean of five replications.
• Values followed by ** indicate significant difference between Actigard treated and untreated plants for
the corresponding cultivar at P = 0.01 based on χ2 test. NS indicates not significant, and NA indicates
chi-square test not applicable.
Florida Pradhanang et al. (2005)33

Fig. 3: Effect of BTH (50 ppm) on control of faba bean rust
Australia Huang and Deverall (2006)
 BTH (50 ppm) = sprayed 4 days before inoculation of Uromyces viciae-fabae spores
34

• Disease symptoms were characterized 7 d after inoculation. (GC=growth chamber & GH=greenhouse)
• The bars represent the number of susceptible-type lesions in the 10-cm central region of the sixth leaves of
Japan Shimono et al. (2007)
Fig. 4: Effect of BTH (0.5 mM) on blast (Magnaporthe grisea) resistance of
WRKY45-ox (TF-gene) of rice
35
Untreated
Untreated Untreated

Table-3: Responses of seedlings and older tobacco plants treated with acibenzolar-S-
methyl (ASM) to Tomato spotted wilt virusy
Age of Plant
(DAS)
Local infection Systemic infection
% plant % plant
No. of
lesion/plant
symptomatic symptomatic
75 Treated 3.0 63.3 0.0
No treated 20.3 100.0 0.0
45 Treated 0.2 10.0 3.3
No treated 87.6 100.0 50.0
• Plants treated with 2 g of ASM/7,000 plants at 40 to 45 DAS.
• Mechanically inoculated at 7 days post treatment (DPI). Local lesions were counted at 6 DPI and systemic at 30 DPI.
• ASM treatment significantly reduced local and systemic infections compared with nontreated control plants only in plant
age 45 days after seeding (DAS) but not in 75 DAS.
• least significant difference test at P = 0.05. Values in columns marked with same letter are not significantly different at P
= 0.05. z Plants were transplanted to pots 35 DAS.
New Delhi (IARI) Mandal et al. (2008)36

Protection of tobacco plants of cv. K326 by
acibenzolar-S-methyl (ASM) from infection by
Tomato spotted wilt virus at 5 days post-treatment
Fig. 5: Relationship of quantity of
acibenzolar-S-methyl(ASM) used
to treat tobacco plants of cv.
K326 and the development of
number of local lesions caused
by Tomato spotted wilt virus
A B
New Delhi (IARI) Mandal et al. (2008)
A- ASM at the rate of 4 g a.i./7,000 plants
B- water (Control)
• Plants were treated with ASM at the rate of 0, 0.25, 0.5, 1.0, 2.0, and 4.0 g/7,000 plants.
• Local lesions were counted at 6 days post inoculation.
Ob= Observed
Pr = Predicted
37

Iran Esmailzadeh et al. (2008)
Fig. 6: Protection of tomato leaves against Alternaria alternata by a foliar spray with (a) 400
µM SA & (b) distilled water 4 day after inoculation with Alternaria conidial
suspension (1X 105 cfu)
38

Fig. 7: Effect of BTH application on Agrobacterium infectivity in tomato plant
South Korea Anand et al. (2008)
• Three days post-treatment, shoots were inoculated with the strain Agrobacterium tumefaciens A348
and were photographed 6 weeks post-infection.
• These experiments were repeated at least three times with a minimum of 100 leaf discs for each plant and the data
presented are the mean with SE values. Letters indicate significant difference using Fisher’s LSD test at p=0.05.
39
Untreated BTH treated plants

Treatment
(250 μM)
Disease rating (0-9)
CoC 671 CoC 92061
Days after pre-treatment
30 60 30 60
Control 8.7b 9.0a 9.0a 9.0a
BTH 2.0c 2.3c 3.0c 5.5b
SA 3.6b 3.7c 3.6c 5.7b
Table-4: Effect of BTH and SA treatment on sugarcane cvs CoC 671 and CoC 92061 on
red rot incidence due to challenge inoculation with Colletotrichum falcatum
Mean of three replications (10 canes per replication);
Significantly different at the 5 per cent level by DMRT
Coimbatore (TN) Sundar et al. (2009)40
CoC 671 CoC 92061

Fig. 8: Effects of 200 µM salicylic acid (SA) treatments and inoculation of Fusarium
oxysporum f. sp. lycopersici (Fol) by root feeding (Vascular browning) [a] and
foliar spray (Leaf yellowing wilting) [b] on hydroponically grown tomato
Kharagpur (WB) Mandal et al. (2009)
(1)= No symptoms (2)= 1-25% (3)= 26 -50 % (4)= 51-75 % (5)= ≥ 75 %
41
Untreated
Untreated

Fig. 9: Effect of SA (100 µM ) resistance to black rot (Alternaria radicina) of
AtNPR1 (Arabidopsis thaliana Non-Expressor-PR gene) transgenic carrot
plants
Canada Wally (2010)
A. A. radicina resistance was measured as the mean of the area of individual root lesions infected by the fungus
B. Typical black rot symptoms on taproots of AtNPR1 expressing transgenic (right) and non-transformed (left) carrot
10 days after inoculation
42

Fig. 10: Effect of INA (500 µM ) on powdery mildew (Erysiphe heraclei) (D) and bacterial
blight (Xanthomonas hortorum pv. carotae) (E) of AtNPR1 transgenic carrot plants
1: 0% 2: 1–10% 3: 11–25% 4: 26–40% 5: 41–55% 6: ≥56%
Canada Wally (2010)43

Treatment Conc. (mM) % Charcoal rot % Protection
Riboflavin
0.1 55.3 12.5
0.25 47.0 25.6
0.5 35.0 44.6
1.0 28.9 54.3
2.5 22.7 64.1
5 22.7 64.1
10 22.7 64.1
Thiamine
0.1 50.2 20.6
0.25 41.9 33.7
0.5 35.7 43.5
1.0 25.3 60.0
2.5 18.4 70.9
5 13.3 79.0
10 13.3 79.0
Control 63.2 -
LSD at 0.05 5.07 -
Table-5: Effect of soybean seedling treatment with different concentrations of
inducers resistance riboflavin and thiamine on charcoal rot diseases
(Macrophomina phaseolina) under greenhouse conditions
Table-5: Effect of soybean seedling treatment with different concentrations of
inducers resistance riboflavin and thiamine on charcoal rot diseases
(Macrophomina phaseolina) under greenhouse conditions
Egypt Montaser (2011)44

Treatments % Damping-off (1) % Root rot/charcoal
rot (2) % Survival plants
Summer season 2009
Riboflavin 6.45 9.25 84.30
Thiamine 3.23 5.25 91.52
Control 14.33 26.59 59.08
LSD at 0.05 1.72 2.95 7.85
Summer season 2010
Riboflavin 6.96 12.74 80.3
Thiamine 4.12 6.05 89.83
Control 16.41 28.24 55.35
LSD at 0.05 0.86 1.48 8.27
1Damping-off were recorded after 30 days from planting:
2charcoal rot was recorded based on 0 to 5 scale according to percentage of foliage yellowing/necrosis (0=0%, 1=1-25%, 2=26-50%, 3=51-75%, 4=>76%, 5=dead plants)
• Damping-off (%) = (Pre-emergence+ post emergence / No. of planted seeds) x100;
Table-6: Effect of soybean seed soaking in riboflavin (2.5 mM) and thiamine (5 mM) on
damping-off and charcoal rot diseases during summer seasons (2009 and 2010)
under field conditions
Table-6: Effect of soybean seed soaking in riboflavin (2.5 mM) and thiamine (5 mM) on
damping-off and charcoal rot diseases during summer seasons (2009 and 2010)
under field conditions
Egypt Montaser (2011)45

a- Uninoculated control
b- BTH @ 250 µM priming showing restricted lesion (6 % infection)
c- SA @ 250 µM (20 % infection)
d- C. falcatum elicitor (17 % infection)
e- Untreated inoculated control showing extended and progressive lesion throughout the stalk of the
cane (100 % infection)
Coimbatore (TN) Selvaraj et al. (2014)
Fig. 11: Evaluation of efficacy of SAR priming on 20 days post inoculation in
sugarcane cv. CoC 671 against red rot (Colletotrichum falcatum)
46

SAR activators
Concentration
(ppm)
Per cent
Disease Intensity
Per cent
Disease control
60 DAS 90 DAS 60 DAS 90 DAS
Salicylic acid 100
5.90
(14.06)
17.80
(24.95)
22.37 29.95
Isonicotinic acid 100
6.60
(14.89)
20.80
(27.13)
13.16 18.14
Hydrogen peroxide 100
7.10
(15.45)
23.10
(28.73)
6.58 9.09
Indole acetic acid 100
7.30
(15.68)
23.90
(29.27)
3.95 5.94
Azoxystrobin 1000
6.40
(14.65)
19.90
(26.49)
15.79 21.68
Control -
7.60
(16.00)
25.41
(30.27)
- -
SEm+ 0.16 0.22
CD (p=0.05) 0.49 0.65
Table-7: Efficacy of systemic acquired resistance (SAR) activators against Alternaria
leaf spot (Alternaria alternata (Fr.) Keissler) of okra (Seed soaking method)
* Average of four replications, seed soaking for 30 min Figures given in parentheses are angular transformed values
Jobner (RJ) Yadav (2018)Jobner (RJ) Yadav (2018)47

SAR activators
Concentration
(ppm)
Per cent
Disease intensity
Per cent
Disease control
Salicylic acid 100
3.50
(10.78)
10.70
(19.09)
55.13 57.89
5.00
(12.92)
15.24
(22.98)
35.89 40.02
5.50
(13.56)
15.33
(23.05)
29.49 39.67
6.20
(14.42)
18.26
(25.30)
20.51 28.14
Azoxystrobin 1000
4.40
(12.11)
13.12
(21.24)
43.59 48.37
Control -
7.80
(16.25)
26.40
(30.92)
- -
SEm+ 0.13 0.18
CD (p=0.05) 0.38 0.54
leaf spot (Alternaria alternata (Fr.) Keissler) of okra (Foliar spray method)
Jobner (RJ) Yadav (2018)Jobner (RJ) Yadav (2018)
* Average of four replications, foliar spray = 40 DAS Figures given in parentheses are angular transformed values
48

SAR activators
Concentration
(ppm)
Per cent
Disease intensity
Per cent
Disease control
Salicylic acid 100
2.90
(9.80)
8.40
(16.85)
62.44 66.94
4.40
(12.11)
12.14
(20.39)
43.01 52.22
4.90
(12.79)
13.36
(21.44)
36.53 47.42
5.50
(13.56)
17.61
(24.81)
28.76 30.70
Azoxystrobin 1000
3.60
(10.94)
10.65
(19.05)
53.37 58.09
Control -
7.72
(16.20)
26.40
(30.92)
- -
SEm+ 0.10 0.22
CD (p=0.05) 0.29 0.65
leaf spot (Alternaria alternata (Fr.) Keissler) of okra (Seed-cum-foliar spray)
Jobner (RJ) Yadav (2018)Jobner (RJ) Yadav (2018)
* Average of four replications, seed soaking for 30 min., foliar spray = 40 DAS Figures given in parentheses are angular transformed values
49

Conclusion
SAR is effective against a broad range of pathogens and parasites,
including fungi, bacteria and viruses.
Salicylic acid is not a translocated signal responsible for inducing SAR
but is required in signal transduction.
Methyl salicylate, lipid signaling, peptide signaling, Green-leaf volatiles
are the transported signals in SAR.
SA, MeSA, JA, BTH/ASM, INA, BABA and H2O2 plays important role in
building broad-spectrum disease resistance against many plant diseases.
Over expression of an essential regulatory gene (NPR 1) leads to the
generation of broad-spectrum disease resistance in plant which is also
known as systemic acquired resistance.
50

REVIEW OF LITERATUE
Friedrich et al. (1996) reported that application of 1.2mM BTH on tobacco plant provide protection against Tobacco mosaic virus (TMV). Pathogens inoculation along
with BTH treatment decreased the lesion size and also induced resistance against TMV.
Silue et al. (2002) recorded effects of AABA, BABA and GABA (10 mM) applied as a foliar spray to cauliflower plants on sporulation of Peronospora parasitica. From the results
obtained after 1 day sporulation of P. parasitica was almost completely suppressed in plants treated with BABA but less in plants treated with AABA. However, no suppression of
sporulation was observed with GABA.
Zhu et al. (2003) studied the effect of BTH treatment on Phytophthora root rot symptoms and growth in papaya plants. Plants pre-treated with 25 and 100 µM BTH expressed very minor
root rot disease symptoms consisting of minor leaf yellowing (12.00 %) as compared to water (68.00%).
Pradhanang et al. (2005) observed the effect of acibenzolar-S-methyl (ASM) on bacterial wilt incidence and yield of moderately resistant (BHN 466 & Neptune) and susceptible (Equinox)
tomato cultivars under greenhouse and field conditions. ASM application on tomato moderately resistant cv. Neptune recorded no wilt incidence (0.0%) as compared to untreated (20.0%),
while, cv. Equinox did not showed effective control against bacterial wilt (95.00 %) under greenhouse condition.
Huang and Deverall (2006) reported that application of BTH (50 ppm) significantly reduced the severity (12.00 %) of faba bean rust as compared to untreated control (42.00 %).
Shimono et al. (2007) observed that the rice plants treated with 0.5 mM BTH, showed expression of WRKY transcription factor (TF) gene and developed resistance against rice blast
(Magnaporthe grisea). The results showed that no symptoms of lesions of blast on treated rice plants after 15, 21 and 24hr after treatment under growth chamber as well as greenhouse
condition.
Mandal et al. (2008) studied responses of seedlings and older plants treated with acibenzolar-S-methyl (ASM) to Tomato spotted wilt virusy. They reported that ASM treatment had
significantly reduced the number of lesions in local (10 & 63.3 %) 45 & 75 DAS, respectively and systemic infections (3.3 %) as compared to untreated control plants only at plant age of
45 days after seeding (DAS) but not in 75 DAS. However, relationship of quantity of ASM used to treat tobacco plants of cv. K326 showed that at 0.25 g a.i. of ASM, only 10.6 lesions per
plant were developed, which was a significant reduction as compared to untreated control. The mean number of local lesions declined further to 1.8 to 0.2 at 1 to 4 g a.i. of ASM. The
majority of the plants were free from local lesions when treated with ≥2 g a.i. of ASM.
Esmailzadeh et al. (2008) depicted protection of tomato leaves against Alternaria alternata by a foliar spray with 400 µM SA. They recorded fewer necrosis lesions per leaf and reduction
of blighted (87.5%) leaf area (mm2) as compared to control.
Anand et al. (2008) conducted stable and transient transformation assays to characterize the effect of BTH application on Agrobacterium infectivity. They supplied BTH exogenously at
different concentrations, 0.1 to 0.33 mM on tomato plants. The averaged tumours 6.86 & 1.0 mm (0.1 mM) to 4.06 & 0.7 mm (0.3 mM) in the BTH-treated plants as compared to larger
tumours (23.56 & 6.9 mm) on the mock-treated plants, respectively.
Sundar et al. (2009) examined the effect of BTH and SA treatment (250 μM) on sugarcane cvs. CoC 671 and CoC 92061 against red rot incidence due to challenge inoculation with
Colletotrichum falcatum. A significant inhibition of pathogen growth inside the pre-treated cane tissues in both the highly susceptible cultivars was recorded. The disease severity ranged
between 22 and 63 per cent in plant activator treated cane tissues as compared to untreated (100 %) control.
Mandal et al. (2009) recorded the effects of 200 µM salicylic acid (SA) treatments (2 day after SA application) and inoculation of Fusarium oxysporum f. sp. lycopersici (Fol) by root
feeding (a) and foliar spray (b) on hydroponically grown tomato. Tomato plants inoculated with Fol conidia, but not receiving 200 µM SA treatment through roots and foliar application,
exhibited typical vascular browning and leaf yellowing wilting, while the SA-treated plants showed less than 25 per cent vascular browning and leaf yellowing wilting after 4 weeks of the
experiment.
Wally (2010) studied resistance to black rot, powdery mildew and bacterial blight of AtNPR1 transgenic carrot plants and harvested taproots. Lesions for both lines I and XI were reduced in
diameter by more than 50 per cent at 10 dai. Both lines I and XI had a reduced number of necrotic lesions on the leaf tissue, with greater than 33 per cent reduction in DSI for both lines.
AtNPRl expressing lines also exhibited a high level of resistance to powdery mildew and bacterial leaf blight. Lines I and XI were tested for their resistance to powdery mildew infection,
the number of newly formed sporulating colonies was significantly reduced by 90 per cent in both lines at 7 and 10 dai. Line I exhibited 80 per cent reduction of bacterial leaf blight in DSI
towards X. hortorum as compared to the control at 10 dai.
Montaser (2011) observed that soybean seedlings treated with different concentrations of riboflavin and thiamine acts as inducers of resistance on charcoal rot disease under greenhouse
conditions. The dose effect of riboflavin and thiamine showed that the concentration of 2.5 and 5 mM, respectively were found most effective and sufficient for induction of resistance
against charcoal rot disease (64.1 and 79.0 % protection). While, In this regard, thiamine was the highest effective in the reduction of damping-off and charcoal rot severity than riboflavin
treatment; thiamine recorded 3.23 and 4.12 per cent damping-off and 5.25 and 6.05 per cent charcoal rot in both seasons.
Selvaraj et al. (2014) depicted evaluation of efficacy of different SAR priming (i.e., BTH, SA, C. falcatum) on 20 days post inoculation in sugarcane cv. CoC 671. Among them, BTH
priming showing restricted lesion and lower infection (6 %) of red rot of sugarcane followed by SAR (20 %).
Yadav (2018) studied efficacy of systemic acquired resistance activators viz., SA, isonicotinic acid, H2O2, IAA & azoxystrobin at different concentration at against alternaria leaf spot
(Alternaria alternata (Fr.) Keissler) of okra seed soaking, foliar spray and seed-cum-foliar spray. They recorded lower per cent disease intensity (5.90 & 17.80) and higher per cent disease
control (22.37 & 29.95) at 60 & 90 DAS, respectively in seed soaking with SA at 100 ppm. Further, same results were observed in foliar spray and seed-cum-foliar spray.

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