Role of hydrogen peroxide in management of root rot and wilt disease of thyme plant

Abstract

Thyme (Thymus vulgaris) is an aromatic medicinal plant cultivated in many countries, including Egypt. The plant has many medicinal benefits that make it an important medical crop. In 2017, root rot and wilt symptoms were detected on thyme plants at different locations of Giza governorate and samples were collected from the infected plants. Seven fungi were isolated from the infected plants (Pythium sp., Fusarium solani, Rhizoctonia solani, Macrophomina phaseolina, F. oxysporum, Botryodiplodia sp., Alternaria tennis). Pathogenicity tests of the isolated fungi proved that all of them were pathogenic to thyme. The effect of hydrogen peroxide at different concentrations (0.25 %, 0.50 %, 1 % and 2 %) on linear growth of Botryodiplodia sp., F. oxysporum, F. solani, M. phaseolina, Pythium sp. and R. solani was evaluated in vitro. All concentrations significantly reduced the fungal liner growth of all the tested fungi. However, the concentration of 2% was completely inhibited the fungal growth of R. solani, Pythium sp. and F. solani. Evaluation of hydrogen peroxide application as seed treatment and soil drenching for controlling root rot and wilt diseases of thyme was also performed under greenhouse conditions. A remarkable reduction in pre- and post- emergence damping off as a response to hydrogen peroxide was detected with all the tested fungi. Furthermore, the treatment of hydrogen peroxide yielded serious increasing in plant survival with all tested fungi compared with untreated plants.

Full text

Journal of Phytopathology
and Pest Management
pISSN: 2356-8577
eISSN: 2356-6507
Volume (5), Issue (3)
2018

Journal of Phytopathology and Pest Management 5(3): 1-13, 2018
pISSN:2356-8577 eISSN: 2356-6507
Journal homepage: http://ppmj.net/
∗
Corresponding author:
A.A.M. Ali,
E-mail: abdallahali461@gmail.com
1
Copyright © 2018
Role of hydrogen peroxide in management
of root rot and wilt disease of thyme plant
A.A.M. Ali*
Plant Pathology Department, Faculty of Agriculture and Natural Resources, Aswan University,
Aswan, Egypt
Abstract
Keywords: Thymus vulgaris, root rot, wilt, hydrogen peroxide, damping-off.
Thyme (Thymus vulgaris) is an aromatic medicinal plant cultivated in many
countries, including Egypt. The plant has many medicinal benefits that make it an
important medical crop. In 2017, root rot and wilt symptoms were detected on
thyme plants at different locations of Giza governorate and samples were collected
from the infected plants. Seven fungi were isolated from the infected plants
(Pythium sp., Fusarium solani, Rhizoctonia solani, Macrophomina phaseolina, F.
oxysporum, Botryodiplodia sp., Alternaria tennis). Pathogenicity tests of the isolated
fungi proved that all of them were pathogenic to thyme. The effect of hydrogen
peroxide at different concentrations (0.25%, 0.50%, 1 % and 2%) on linear growth
of Botryodiplodia sp., F. oxysporum, F. solani, M. phaseolina, Pythium sp. and R.
solani was evaluated in vitro. All concentrations significantly reduced the fungal
linear growth of all the tested fungi. However, the concentration of 2% was
completely inhibited the fungal growth of R. solani, Pythium sp. and F. solani.
Evaluation of hydrogen peroxide application as seed treatment and soil drenching
for controlling root rot and wilt disease of thyme was also performed under
greenhouse conditions. A remarkable reduction in pre- and post- emergence
damping off as a response to hydrogen peroxide was detected with all the tested
fungi. Furthermore, the treatment of hydrogen peroxide yielded serious increasing
in plant survival with all tested fungi compared with untreated plants.

Ali, 2018
2
Introduction
Thymus vulgaris
is an aromatic medicinal
plant belonging to the family Lamiaceae;
it is spread entirely over the world
(Hosseinzadeh et al., 2015). The plant has
been cultivated in several countries,
including Egypt, for medicinal and
culinary uses (Stahl-Biskup &
Venskutonis, 2012; Stahl-Biskup & Sáez,
2002). It is considered an important
export crop in Egypt, the average dry
material yield of thyme is about 800 kg/
acre which produce about 16 kg essential
oil. Its medical uses include therapy for
chest infections, sore throat, cough, it has
antifungal, antiseptic, and antibiotic
properties (Ekoh et al., 2014).
Additionally; it has other properties,
include appetite stimulant effect;
improvement of liver function; therapy of
urinary and bronchial infections (Reddy
et al., 2014).
T. vulgaris
is attacked by
certain soil borne fungi causing root rot
disease (Carr, 1987). Many studies
reported that
Rhizoctonia solani
,
Fusarium
spp.,
Macrophomina
phaseolina, Alternaria
spp.,
Colletotrichum
spp.,
Botrytis cinerea
,
Stemphylium botryosum
,
Cladosporium
cladosporioides
and
Phoma multirostrata
var. macrospora
are the most important
plant pathogens in thyme plant , causing
root, stem and foliage diseases
(Palacioğlu et al., 2017). Machowicz-
Stefaniak et al. (2002) reported that the
bases of roots and stems of thyme were
colonized by many pathogenic fungi
include;
R. solani
,
Fusarium
spp.,
Alternaria
spp.,
Colletotrichum
spp. and
Thielaviopsis basicola
. Root rots disease
caused by many soil borne fungi,
however, the poor conditions of the soil,
such as the high proportion of the ground
water and poor drainage is considered an
important factor for disease infection.
Alternative control methods are being
considered because of the high costs for
continues production of new chemicals to
overcome the development of pathogen
resistance to fungicides (Kotan et al.,
2009; Laitila et al., 2002). Additionally,
fungicides are harmful to human, living
organisms and the environment (Jarvis,
1988). Reactive oxygen species (ROS)
are considered the toxic side effects of
O
2
,
used for respiration and energy
supply in aerobic organisms. These
chemical compounds include hydrogen
peroxide (H
2
O
2
), hydroxyl radical (OH),
singlet oxygen (
1
O
2
), superoxide anion
(O
2-
) and alpha-oxygen. ROS have
harmful effects on DNA, lipids and
proteins; it is also related to plant defense
due to their antimicrobial activity (Daub
et al., 2013; Fridovich, 1998). Hydrogen
peroxide is a reactive oxygen species that
occurs in all aerobic organisms as a
metabolite. It is considered a cytotoxic at
high concentrations, due to conversion to
the stronger oxidant, hydroxyl radical
OH (Apel & Hirt, 2004). It inhibits, with
other reactive oxygen species, the
development of microbes and contributes
in various protection responses (Garcia-
Brugger et al., 2006; Baker & Orlandi,
1995). Hydrogen peroxide also has
multiple models of oxidative structural
and different stages of oxidation to amino
acids and proteins, and variations in its
activity against a microbial enzyme
(Finnegan et al., 2010). The present work
aimed to evaluate hydrogen peroxide, as
a reactive oxygen species, against the
mycelial growth of root rot and wilt fungi
isolated from infected
T. vulgaris
.
Moreover, hydrogen peroxide
application
in controlling root rots and wilt disease of
T. vulgaris
under greenhouse conditions
was also evaluated.

Ali, 2018
3
Materials and methods
Isolation and identification of the
causal fungi:
Thyme plants showing root
rot and wilt disease symptoms (include
yellowing, dryness and wilt) were
collected from different locations of Giza
governorate during 2017. The infected
roots were thoroughly washed under
running tap water then cut into small
pieces with sterilized scalpel, and surface
sterilized in 1% sodium hypochlorite for
2 minutes, then rinsed several times in
sterilized distilled water. The sterilized
pieces were then dried between folds of
sterilized filter papers and placed on
potato dextrose agar. The inoculated
plates were incubated at 27
o
C for seven
days and checked daily for fungal
development. The developing fungi were
purified using the hyphal tip or single
spore technique. Identification of the
isolated fungi was carried out at the
department of mycology and plant
disease survey research, Plant Pathology
Research Institute., ARC, Giza, Egypt,
according to description given by Gilman
(1957), Barnett and Hunter (1972) and
Nelson et al. (1983). Isolation frequency
of the developing colonies of each fungus
was calculated as percentage of the total
developing colonies.
Preparation of inoculum:
Inoculum of
obtained fungi (
Botryodiplodia
sp.,
Fusarium oxysporum, F. solani,
Macrophomina phaseolina, Pythium
sp
.
and
Rhizoctonia solani
) was separately
grown on corn sand meal medium in 500
ml glass bottles. Bottles were incubated
at 27°C for 20 days (Ahmed et al., 2016).
Pathogenicity tests:
This experiment
was carried out under greenhouse
conditions. Sterilized clay sand soil (1:1
w/w) was individually infested with the
tested fungi at the rate of 2% (w/w) in
formalin sterilized pots (20 cm diam.).
The pots were watered for one week to
enhance growth and distribution of the
fungal inoculum. Then, twenty seeds/ pot
were planted and three replicates were
used for each fungi treatment.
Percentages of pre- and post-emergence
damping-off were recorded after 15 and
30 days from planting date, respectively.
Pathogenicity of isolated fungi to 30 and
60 days-old thyme plants was also tested
in infested pots. Each pot was planted
with four unrooted stem tip cuttings.
Four replicates were used for each
treatment. Percentages of wilted thyme
plants were recorded after 30 and 60
days from planting date as follows:
Disease incidence (%) =
No. of infected plants
×100
Total No. of plants
Effect of different hydrogen peroxide
concentrations on linear growth of the
tested fungi:
The effect of hydrogen
peroxide (El Nasr Company for
Intermediate Chemicals, Alexandria
Desert Road km 28, Industrial Area,
Abou-Rawash, Giza, Egypt) on linear
growth of the tested fungi was carried
out
in vitro
. Potato dextrose agar (PDA)
medium was autoclaved at 121°C for 15
min. Hydrogen peroxide (50) was added
to PDA with different concentrations
(0.25%, 0.50%, 1% and 2%) directly
before poured into 9 cm diameter
sterilized Petri dishes. Three replicates
for each concentration were used and
plates containing only PDA medium
were used as control. All plates were
then inoculated individually by the tested

Ali, 2018
4
fungi using 5 mm fungal growth discs
taken from 14 days old cultures and
incubated at 27°C. The plates were
checked daily and the experiment was
terminated when the mycelial growth of
control covered the medium surface. The
fungal growth diameter of all treatments
and control was measured and percentage
of reduction in mycelial growth was
calculated using the formula suggested
by Ahmed (2005) as following:
Reduction in linear growth (%) =
G1- G2
×100
G1
Where, G1 = Linear growth of fungal
control. G2 = Linear growth of fungal
treatment.
Effect of hydrogen peroxide as seed
treatment and soil drenching on pre-
and post- emergence damping-off
under greenhouse conditions:
Hydrogen peroxide was tested for
controlling root rot and wilt disease
caused by
Botryodiplodia
sp.,
F.
oxysporum
,
F. solani
,
M. phaseolina
,
Pythium
sp.,
R. solani
in pot experiment.
Sterilized clay sand soils (1:1 w/w) were
mixed separately with each fungal
inoculum at 2% (w/w). Formalin
sterilized pots (20 cm diam.) were packed
with sterilized soils and watered for 7
days to enhance growth and distribution
of the fungal inoculum. Twenty seeds/
pot were soaked in hydrogen peroxide
with concentration of 2 % for 20 min
before planting. Three replicates were
used for each fungi treatment. After 15
days, the pots were irrigated with
hydrogen peroxide (with concentration of
2%). Control pots were left without
addition of hydrogen peroxide.
Statistical analysis:
The present study
was carried out with three replicates as
designed factorial experiment in a
complete randomized design (Snedecor
& Cochran, 1980). MSTAT-C statistical
package version (4) was used for
analysis using Least Significant
Difference (L.S.D) test at 0.05.
Results
Isolation and identification of the
causal fungi:
Data in Table (1) showed
that seven fungi (
Alternaria tennis
,
Botryodiplodia
sp.,
Fusarium
oxysporum
,
F. solani
,
Macrophomina
phaseolina
,
Pythium
sp.,
Rhizoctonia
solani
) were isolated from plants
collected from Giza governorate.
Pythium
sp. was the most frequently
isolated fungi (31.25%) followed by
F.
solani
(22.32%),
R. solani
(16.96%) and
M. phaseolina
(11.61%), while
A. tennis
(3.57%),
Botryodiplodia
sp. (5.36%) and
F. oxysporum
(8.93) showed the lowest
isolation frequency.
Pathogenicity tests:
Data in Table (2)
showed the pathogenicity of six fungi as
percentages of pre- and post-emergence
damping-off as well as those of survival
seedlings. All the tested fungi were able
to infect the plants and cause pre- and
post-emergence damping-off. However,
Pythium sp.
followed by
M. phaseolina
recorded the highest percentages of pre-
emergence damping-off (45% and 41.7,
respectively). Moreover,
F. solani
followed by
M. phaseolina
recorded the
highest percentages of post- emergence
damping-off (55% and 36.7%,
respectively). Subsequently, they
recorded the highest percentages of

Ali, 2018
5
reduction in survivals which recorded 85
% and 78.4 %, respectively (Figure 1). In
contrast,
Botryodiplodia
sp. recorded the
lowest percentages of pre- and post-
emergence dumping-off (30% and
18.3%, respectively). Subsequently, it
recorded the lowest percentage of
reduction in survivals (48.3 %).
Table 1: Frequency percentages of the isolated fungi from diseased thyme plants collected
from Giza governorate, Egypt.
Fungi
Number of isolates
Frequency (%)
Symptoms
Alternaria tennis
4
3.57
Root rot
Botryodiplodia sp.
6
5.36
Root rot
Fusarium oxysporum
10
8.93
Wilt/root rot
F. solani
25
22.32
Root rot
Macrophomina phaseolina
13
11.61
Root rot
Pythium sp.
35
31.25
Root rot
Rhizoctonia solani
19
16.96
Root rot
Total
112
100
Root rot
Figure 1: Reduction percentages in survivals of thyme plants in response to the infection with the tested fungi.
Table (3) showed that all the tested fungi
were significantly pathogenic to thyme
plants causing root rot or wilt disease in
different degrees compared with the
control treatment. Moreover, percentages
of disease incidence positively correlated
by the time elapse from 30 to 60 days
after planting date.
R. solani
was the
most virulent fungus as it recorded the
highest percentage of disease incidence,
30 after planting date (62.5%), followed
by
F. solani
(50%),
F. oxysporum
and
Botryodiplodia
sp. (25%). Furthermore,
F. solani
,
F. oxysporum
and
R.
solani
recorded the highest percentages of
disease incidence, 60 after planting date
(75%). In contrast,
Pythium
sp. was the
lowest pathogenic fungi resulting in 25%
disease incidence after 60 days from
planting date.

Ali, 2018
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Table 2: Percentages of pre- and post- emergence damping-off infection caused by the tested fungi, 15
and 30 days after planting date, respectively.
Fungi
Pre- emergence damping
off after 15 days (%)
Post- emergence damping
off after 30 days (%)
Survivals
(%)
Botryodiplodia sp.
30.0
18.3
51.7
Fusarium oxysporum
40.0
31.7
28.3
F. solani
30.0
55.0
15.0
Macrophomina phaseolina
41.7
36.7
21.6
Pythium sp.
45.0
26.7
28.3
Rhizoctonia solani
38.3
20.0
41.7
Control
0.0
0.0
100.0
L.S.D at 5%
3.9
5.1
-
Table 3: Percentages of wilted thyme plants, 30 and 60 days after planting date in infested soil with the tested
fungi under greenhouse conditions.
Fungi
Disease incidence after 30 days (%)
Disease incidence after 60 days (%)
Botryodiplodia sp.
25.0
37.5
Fusarium oxysporum
25.0
75.0
F. solani
50.0
75.0
Macrophomina phaseolina
18.8
62.5
Pythium sp.
12.5
25.0
Rhizoctonia solani
62.5
75.0
Control
0.0
0.0
L.S.D at 5%
8.05
13.80
Effect of hydrogen peroxide on root rot
and wilt disease of thyme plants
in
vitro
:
The mycelium linear growth of the
tested fungi was significantly affected (P
≤ 0.5) with hydrogen peroxide treatments
compared to the control (Table 4). A
positive correlation between hydrogen
peroxide concentration and reduction of
fungal liner growth was detected. The
tested fungi were varied in their response
to hydrogen peroxide.
R. solani
was the
most sensitive to hydrogen peroxide at all
concentrations except the concentration
of 1%.
In contrast,
M. phaseolina
was the
lowest sensitive to hydrogen peroxide at
all concentrations. The concentration of
2% was completely inhibited the fungal
growth of
R. solani
,
Pythium
sp. and
F.
solani
.
Effect of hydrogen peroxide on root rot
and wilt disease of thyme plants under
greenhouse conditions:
This experiment
was performed to test the efficiency of
hydrogen peroxide as seed treatment and
soil drenching for controlling root rot
and wilt disease caused by the tested
fungi shown in table 5. The experiment
was carried out in pots (20-cm diam.)
under greenhouse conditions. Hydrogen
peroxide treatment yielded a remarkable
reduction in pre- and post- emergence
damping off with all the tested fungi.
The percentages of reduction were varied
depending on the response of each
fungus to hydrogen peroxide. Regarding
the reduction in pre- emergence damping
off,
Pythium
sp. followed by
F.
oxysporum
were the most sensitive to
hydrogen peroxide, 92.7% and 92.1%,
respectively, while,
R. solani
recorded
the lowest percent, 54% (Figure 2).

Ali, 2018
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Table 4: The in-vitro effect of different hydrogen peroxide concentrations on linear growth of the tested
fungi.
Fungi
Concentrations of hydrogen peroxide
Control (%)
0.25 %
0.50 %
1 %
2 %
Botryodiplodia sp.
(9.0) a
(4.3) a
(52.2%) b
(3.7) a
(58.9%) b
(2.7) a
(70%) b
(1.6) a
(82.2%) b
Fusarium oxysporum
(9.0) a
(5.6) a
(37.8%) b
(6.6) a
(26.7%) b
(2.5) a
(72.2%) b
(1.0) a
(88.9%) b
F. solani
(9.0) a
(6.5) a
(27.8%) b
(5.1) a
(43.3) b
(3.6) a
(60%) b
(0.0) a
(100%) b
Macrophomina phaseolina
(9.0) a
(8.2) a
(8.9%) b
(7.8) a
(13.3%) b
(6.7) a
(25.6%) b
(5.6) a
(37.8%) b
Pythium sp.
(9.0) a
(4.7) a
(47.8%) b
(3.3) a
(63.3%) b
(1.3) a
(85.6%) b
(0.0) a
(100%) b
Rhizoctonia solani
(9.0) a
(4.0) a
(55.6%) b
(2.0) a
(77.8%) b
(1.5) a
(83.3%) b
(0.0) a
(100%) b
L.S.D 5 %: Fungi (F) = 0.5, Concentration (C) = 0.3, Interaction (F) x (C) = 0.7. a mean of linear growth
(cm) of three replicates. b Reduction percentage of fungal growth compared to the control.
Figure 2: Reduction percentages in pre- emergence damping off in response to hydrogen peroxide treatment.
Furthermore,
F. solani
followed by
Pythium
sp. recorded the highest
reduction percentages in post- emergence
damping off as a response to hydrogen
peroxide treatment (88.3%, 87.6%,
respectively), while,
M. phaseolina
recorded the lowest percent, 53% (Figure
3). Overall, the treatment of hydrogen
peroxide has yielded serious increasing
in plant survivals with all tested fungi
compared with untreated plants. The
percentages of survival increasing were
varied according to the applicable fungus
and its response to hydrogen peroxide.
The highest percent of survival
increasing was recorded on the plants

Ali, 2018
8
infected with
M. phaseolina,
81.3%,
followed by the plants infected with
F.
oxysporum
, 73% (Figure 4). However,
the plants infected with
Botryodiplodia
sp. was recorded the lowest percentage
of survival increasing (37.9%).
Table 5: Effect of hydrogen peroxide as seed treatment on pre- and post- emergence damping-off, 15
and 30 days after planting date in soil infested with the tested fungi, respectively, under greenhouse
conditions.
Fungi
Treatment
Pre- emergence
damping off (%)
Post- emergence
damping off (%)
Survivals (%)
Botryodiplodia sp.
H2O2
10.0
6.7
83.3
Control
30.0
18.3
51.7
F. oxysporum
H2O2
3.3
16.7
80.0
Control
41.7
36.7
21.6
F. solani
H2O2
6.7
3.3
90.0
Control
36.7
28.3
35.0
M. phaseolina
H2O2
13.3
13.3
73.4
Control
40.0
28.3
13.7
Pythium sp.
H2O2
3.3
3.3
93.4
Control
45.0
26.7
28.3
R. solani
H2O2
16.7
13.3
70.0
Control
36.3
38.3
25.4
L.S.D at 5%
6.9
6.6
-
Figure 3: Reduction percentages in post- emergence damping off in response to hydrogen peroxide treatment.

Ali, 2018
9
Figure 4: Increasing percentages in survivals of thyme plants in response to hydrogen peroxide treatment.
Discussion
Thyme (
Thymus vulgaris
) is an aromatic
plant cultivated for medicinal and
culinary uses. Many studies reported that
thyme is attacked by some soil borne
fungi, causing root rot infections. Seven
fungi;
Alternaria tennis
,
Botryodiplodia
sp.,
Fusarium oxysporum
,
F. solani
,
Macrophomina phaseolina
,
Pythium
sp.,
Rhizoctonia solani
were isolated from the
collected thyme plants. The isolated
causal agents of root rot and wilt disease
are similar to those reported by several
studies (Palacioğlu et al., 2017;
Machowicz-Stefaniak & Zalewska 2004;
Machowicz-Stefaniak et al., 2002). The
pathogenicity tests proved that all
isolated fungi from the naturally infected
samples were able to infect the plants and
cause pre- and post-emergence damping-
off. However,
F. solani
was the most
pathogenic fungi as it recorded the
highest percentages of post- emergence
damping-off and reduction in survivals.
Also, all the tested fungi were
significantly pathogenic to thyme plants
causing root rot or wilt disease in
different degrees,
R. solani
was the most
virulent one followed by
F. solani
and
F.
oxysporum
, respectively. Similar results
reported that
R. solani
,
F. solani
and
F.
oxysporum
were the most virulent fungi
infect
Coleus forskohlii
, belonging to the
family Lamiaceae (Pulla et al., 2013;
Singh et al., 2009; Shivkumar et al.,
2006). Fungicide treatments are the main
control method for these diseases.
However, fungicides are harmful to
human, living organisms and the
environment (Guzzo et al., 1993; Jarvis,
1988). Using of abiotic-agents to give
plant acquired resistance against
pathogens is considered alternative
control methods to fungicide
applications. The current study presented
a trial to investigate the possibility of
minimizing the infection with root rot
and wilt disease of thyme using
hydrogen peroxide. The effect of
hydrogen peroxide at different
concentrations on linear growth of the

Ali, 2018
10
tested fungi was evaluated
in vitro
. The
reduction of fungal liner growth was
positively correlated with hydrogen
peroxide concentration. The
concentration of 2% was completely
inhibited the fungal growth of
R. solani
,
Pythium
sp. and
F. solani
. These results
are in agreement somewhat with
Angelova et al. (2005) who reported that
exposure of fungal mycelia or spores of
12 fungal species to hydrogen peroxide
promoted oxidative stress, as evidenced
by inhibition of biomass production and
spore germination; accumulation of
oxidative modified proteins. Under
greenhouse conditions, a remarkable
reduction in pre- and post- emergence
damping off as a response to hydrogen
peroxide treatment was detected with all
the tested fungi. However, the
percentages of reduction were varied
depending on the response of each
fungus to hydrogen peroxide treatment.
Pythium
sp.,
F. oxysporum
and
F. solani
recorded the highest percentages of
reduction in pre- and post- emergence
damping off as a response to hydrogen
peroxide treatment. Abdel-Monaim et al.
(2012) demonstrated that plant resistance,
in various plant species, can be induced
with elicitors such as salicylic acid and
hydrogen peroxide against a wide range
of pathogens. Such chemical elicitors
activate a wide range of protective
mechanisms against pathogen; include
the fast production of reactive oxygen
species; accumulation of phytoalexins;
synthesis of defense proteins and
peptides (De Gara et al., 2003; Agrios,
2005; Castro & Fontes, 2005). Previous
studies also demonstrated the role of
hydrogen peroxide in activation of host
defense mechanisms, including stimulate
activity of enzymes as chitinase and
peroxidase followed by a significant
increase in the suberin and lignin content
(Quiroga et al., 2000). Additionally,
Copes (2009) reported that hydrogen
peroxide plays an essential role in
lignifications, and a strengthening of cell
walls at the site of pathogen attack. The
results of the present study revealed
serious increasing in plant survival as a
response to hydrogen peroxide treatment
with all tested fungi compared with
untreated plants. This finding is in
agreement with Abdel-Monaim (2013)
who found that the treatment of
hydrogen peroxide as seed soaking under
green house and field conditions
significantly reduced damping-off and
root rot/wilt severity in faba bean.
Additionally, the treatment with
hydrogen peroxide
resulted in an increase
of survival plants and fresh/dry weights
of the survival plants in pots compared
with control. Regarding the effect on
seed germination, Wojtyla et al. (2016)
reported that the application of hydrogen
peroxide as seed soaking lead to improve
the seed quality, resulting in better
germination performance. Moreover,
Lariguet et al. (2013) suggested that
hydrogen peroxide considered a gene
expression regulator of the gene
encoding enzyme hydrolyzing the
endosperm, which encourage
Arabidopsis
germination. Also, Barba-
Espín et al. (2012) found that treatment
of pea seeds with hydrogen peroxide as
seed soaking resulting in an increase of
seed germination as well as the seedling
growth. The authors also proposed that
hydrogen peroxide has an important role
at the beginning of seed germination,
since it could act as a signaling molecule.
In conclusion, the present study proved
that hydrogen peroxide treatment as seed

Ali, 2018
11
soaking and soil drenching significantly
reduced damping-off disease in
T.
vulgaris
, in addition to an increase of
survival plants compared with control.
These results may help to use hydrogen
peroxide for controlling damping-off and
root rot/wilt disease in
T. vulgaris
.
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