Basic HTML Version
Molecular Microbiology Research (Online) 2013, Vol.3 No.3 20-29
ISSN 1027-5595
http://mmr.sophiapublisher.com
25
pathogens and their expressions were prominent when
compared to untreated control. Similarly Thaler et al.
(1996) observed that induction of PPO in tomato plant
by caterpillar feeding. Radjacommare et al. (2000)
reported that Pf1 strain induced PPO isozymes in rice
against sheath blight and leaf folder. Harish (2005)
reported the higher induction of PPO enzymes in
PGPR treated banana plants challenge inoculated with
viruliferous aphids carrying
Banana bunchy top virus.
Mathiyazhagan et al. (2009) reported that application
of
Pseudomonas
strains BSCBE4, PA23 and ENPF1
increased the defense related enzymes such as
peroxidase, polyphenol oxidase, chitinase and β -1, 3
glucanase in
P. amaranthus
up to ten days after
challenge inoculation with
C. cassicola.
Native gel
electrophoretic analysis revealed that challenge
inoculation of pathogen with PA23 induced both
peroxidase and polyphnol oxidase isoforms.
2.1.4. β-1, 3 glucanase
The current results are in agreement with several
workers pathogenesis related (PR) proteins are host
coded proteins induced by different pathogens and
abiotic stresses (Van Loon, 1997). Synthesis and
accumulation of PR proteins have been reported to
play important role in plant defense. β-1, 3
glucanase are classified under PR-2 group of PR
proteins have been reported to be associated with plant
resistance against fungal pathogens (Maurhofer et al.,
1994). In Tobacco induction of β-1, 3 glucanase was
noticed due to application of
P. fluorescens
isolate
CHAO in response to infection by
Tobacco necrosis
virus
(TNV) (Maurhofer et al., 1994). Induction of
hydrolytic enzymes was also reported in pea against
P.
ultimum
and
F. oxisporum
f. sp
pisi
(Benhamou et al.,
1996). Govindappa et al. (2010) reported that the
higher activity of peroxidase, phenylalanine
ammonia-lyase, chitinase, polyphenol oxidase and β-1,
3-glucanase in
P. fluorescens
and
T. harzianum
treated
safflower plants after challenge inoculation with
M.
phaseolina
.
2.1.6. Super oxide dismutase (SOD)
In this study SOD activities were more in the Physic
nut plants treated with Pf1 than the uninoculated
control. Plants produce active oxygen species (AOS)
such as superoxide anion (O
-
2
), hydrogen peroxide
(H
2
O
2
) and hydroxyl radical (OH) as one of the
earliest responses to attempted infection pathogens
(Grant and Loake, 2000). Scavengers of AOS like
catalase (which catalyzes the decomposition of H
2
O
2
)
(Scandalios, 1994), SOD (which scavenges O
-
2
)
suppresses the oxidative burst and inhibit tissue
necrotization. Peroxidase are of particular interest
because of their role in binding salicylic acid which
plays an important role in induced resistance.
Production of reactive oxygen species (ROS)
particularly H
2
O
2
has repeatedly been associated with
diverse plant pathogen. Systemic H
2
O
2
production has
been observed in response to wounding in several
plant species. H
2
O
2
accumulates in inter cellular
spaces near vascular bundles and can move in the
plant tissues by diffusion. It functions as the second
messenger to activate the membrane bound NADPH
complex which leads to defence genes induction
(Orozco- Cardens et al., 2001).
2.1.4. Phenol
The present study revealed that the phenolic activity
gradually increased in physic nut leaves and following
treatments with
P. fluorescens
,
Bacillus
EPCO16,
Copper sulphate and Lemon grass oil reached
maximum level at 5
th
day after treatment when
compared to control. The enzyme activity
subsequently declined.
Similar findings were reported
in sugarcane against
C. falcatum
(Viswanathan and
Samiyappan, 1999), groundnut against
C. personata
(Meena et al., 2000), rice against
R. solani
(Radjacommare et al., 2004), and turmeric against
P.
aphanidermatum
. Cherif et al. (2007) reported that
phenolics compounds were shown to accumulate both
in roots and shoots in response to various fungal
infection and elicitors, and their levels significantly
increase in plants pre- treated with antagonistic
microorganisms.
3. Materials and Methods
3.1. Isolation of pathogen and maintenance of bio
control agents
The leaf blight pathogen
Curvularia clavata
was
isolated from coleus plants showing typical root rot
symptoms and pure cultures of the pathogen were
obtained by the single hyphal tip method
(Rangaswami 1972). The bio control agents