Journal of Phytopathology and Pest Management 5(2): 25-47, 2018
pISSN:2356-8577 eISSN: 2356-6507
Journal homepage: http://ppmj.net/
∗
Corresponding author:
Noher A. Mahmoud,
E-mail: hadir1998@yahoo.com
25
Copyright © 2018
Integration between soil solarization and
four biofungicides for controlling garlic
white rot disease
Noher A. Mahmoud
*
Plant Pathology Research Institute, Agricultural Research Center, Dokki, Giza, Egypt
Abstract
Keywords: garlic, white rot disease, bulb yield, solarization, biofungicides, soil microbial counts.
Impact of soil solarization and different biofungicides and/or Folicur fungicide
as dipping treatment on the incidence of white rot and bulb yield of garlic was
investigated. Results revealed that solarization treatment reduced percentage of
white rot (WR) of garlic plants and increased garlic bulb yield compared to un-
solarized infested soil under greenhouse and filed conditions. On the other hand,
dipping garlic cloves before planting in four biofungicides i.e. Bio Arc, Bio Zeid,
Bio Nagi and Bio-4 and/or Folicur fungicide significantly reduced WR disease
incidence compared with untreated cloves. Dipping treatment with Folicur
fungicide (tebuconazole) gave the highest reduction of WR % followed by the
biofungicides i.e. Bio Nagi and Bio Zeid, respectively under greenhouse and field
experiments during the two growing seasons (2015/16 and 2016/17), meanwhile,
Bio-4 followed by Bio Arc resulted the least effective ones in this respect.
Integration between solarization and dipping treatments increased the efficacy
of WR reduction with high significant differences compared to un-solarized
infested soil under greenhouse and filed conditions. Soil solarized plus Folicur
fungicide followed by Bio Nagi and Bio Zeid, respectively were most superior
integrated treatments for suppressive garlic white rot disease under greenhouse
and filed conditions. Bio Nagi achieved closer results to Folicur fungicide for
controlling WR incidence at the two successive seasons. However, the most
superior integration treatment for increasing garlic yield was solarization
treatment combined with each of Bio Nagi, Bio Zeid and Bio Arc, respectively.
Population densities of total fungi, bacteria and actinomycetes in artificially
infested soil were greatly reduced directly after solarization than before
solarization. Solarization treatment alone or in combined with different dipping
treatments were greatly decreased the total fungi, bacteria and actinomycetes
population counts as compared with un-solarized infested soil one during the
three timing intervals (30, 60 and 90 days after planting). The suppressive effect
of solarization and dipping treatments was more effective in reducing soil
microbial counts during the first 30 days of planting, then was decreased
gradually from 60 to 90 days after planting. However, the total counts of
bacteria and actinomycetes were slightly increased in solarized soil after 60 days
then it rapidly increased at the 90 days interval.
Mahmoud Noher, 2018
26
Introduction
Garlic (
Allium sativaum
L.) is an
important vegetable crop which
cultivated for fresh and dry consumption.
Garlic has been used as a flavoring agent
and a traditional medicine since antiquity,
and is now cultivated worldwide
including Egypt (Satyal, et al., 2017).
Nowadays Egypt occupies the fourth
country in the world for garlic production
(Abou El-Magd et al., 2014) In Egyptian
market, garlic is one of the most highest-
value cash crops. Garlic has multifarious
use in local consumption, food,
processing and exportation. Value of this
crop in Egypt, reaches about 2.889
million dollars, representing 0.14% of the
total value of Egyptian agricultural
exports in the period of 2007-2009
(Eleshmawiy et al., 2010). The annual
cultivated area by garlic in Egypt was
12688.51 hectares (ha) (equal 31354 fed)
in 2015/16 season this area produced
around 272769
Megagrams (Mg) or tons
(1 Megagram is exactly 1000 kilograms)
as mentioned by the yearly book 2016 of
Economics and Statistics of the Economic
Affairs Sectors, Agriculture Ministry in
Egypt. White rot disease caused by
Sclerotium cepivorum
is one of the major
fungal diseases reducing yield of garlic
throughout the world, including Egypt.
White rot is a significant threat to garlic
and onion in Egypt. The pathogen
produces a great number of poppy seed-
sized sclerotia, which can survive in soil
for many years. Once the land has been
infested, it is generally considered not
suitable for garlic or onion production for
up to 40 or more years (Bo Ming et al.,
2010). The use of chemical fungicides is
the most common control method for the
disease at the present time. This control
measure is costly, contaminates the
environment, and harms non-target
organisms (Mahdizadehnaraghi et al.,
2015).
Soil solarization is a method for
soil disinfestation, implemented by
increasing soil temperatures under
transparent polyethylene sheets during
the hot season. Early studies indicated
that solarization may control
S.
cepivorum
(white rot pathogen) in onions
(Satour et al., 1989). In
Egypt,
S
.
cepivorum
was completely
controlled by solarization, even in
heavily infested soils (Satour et al.,
1989). Solarization was consistently
found to reduce the viable inoculum
density in the soil and provided good
control of white rot of garlic in Spain and
Mexico
(Ulacio-Osorio et al., 2006;
Melero-Vara et al., 2000). Biological
control using microbial antagonists has
been shown to be a suitable ecologically-
friendly candidate who could replace
chemical pesticides (Cook & Baker,
1988). Different fungal and bacterial
antagonists have proved to be potential
biocontrol agents for controlling many
plant pathogenic fungi (Blaszczyk et al.,
2014; Kakvan et al., 2013).
Biocides or
bioformulations of antagonistic fungi and
bacteria can be used for controlling white
rot pathogen,(
S. cepivorum
)
in onion
(Khalifa et al., 2013; Mohamed, 2012;
Ouf et al
.
, 2008) and garlic
(Mahdizadehnaraghi et al., 2015). It has
been reported that remediation of highly
infested soils and sustainable
management of Allium white rot not only
be achieved by single treatment but also
through a combination of strategies
which might continuously several years
(1 to 3, or more depending on the degree
of soil infestation) before planting garlic
or onion (Ulacio-Osorio et al., 2006).
Therefore, the objective of this study was
to evaluate the impact of combination of
solarization, and different biofungicides
on the incidence of white rot disease and
the garlic yield, as well as soil microbial
counts under artificially and naturally
infestation in greenhouse and filed
Mahmoud Noher, 2018
27
conditions, respectively during the two
growing seasons 2015/16 and 2016/17.
Materials and methods
An experiment consisted of two main
treatments namely, solarized (mulched
with 35 μm VIF (virtually impermeable
films) plastic and unmulched (exposed to
direct sun-light) was conducted in
artificially infested soil with
S.
cepivorum
at greenhouse conditions at
Agriculture Research Center, Giza and in
natural soil heavily infested with
S.
cepivorum
at field in Agricultural
Research farm, El Khatatba location,
Menofia governorate, Egypt.
Greenhouse experiment:
Pot
experiment was carried out in a
randomized complete block design under
greenhouse conditions at Agriculture
Research Center, Giza.
Preparation of fungal inoculum and
soil infestation:
Reference isolate of
Sclerotium cepivourum obtained from
Onion, Garlic and Oil Crops Diseases
Research Department, Plant Pathology
Research Institute, Agriculture Research
Centre, Giza, Egypt, for used in this
study. Fungal inoculation of S.
cepivorum was prepared using sorghum-
coarse sand water (2:1:2 v/v) medium.
The ingredients were mixed, bottled and
autoclaved for one hour at 1.5 air
pressure. The autoclaved media in glass
bottles were inoculated separately using
agar discs obtained from the periphery of
five days old colony of the tested fungi
and incubated at (20±2°C) for two weeks
and used for soil infestation. Fungal
propagules of S. cepivorum were added
to the natural clay loam soil (around 200
kg soil) at the rate of 10.0 g/kg soil
(w/w), mixed thoroughly with the soil.
Infested soil was divided into two beds
each one was (2.0 x 2.0 m2) in
greenhouse then irrigated with water and
left for one week for the inoculum
establishment.
Soil solarization:
Soil preparation that
leads to a smooth soil surface facilitates
plastic mulching and prevents tearing
was done in this experiment. Infested soil
with
S. cepivorum
in one of the two beds
was thoroughly irrigated to reach field
capacity in the upper 20 cm layer 1–2
days before being covered with 35 μm
VIF (virtually impermeable films)
plastic. Another bed was left without
covering with 35 μm VIF plastic
(exposed to direct sun light only). Soil
solarization was accomplished by
covering moist soil with VIF plastic on
15
th
July for 45 day. Covering soil with
VIF plastic was provided every week
with water for 30 min. through the drip
irrigation system that located under the
VIF plastic mulch to improve heat
conduction for the more efficient
eradication of the
S. cepivorum
in deeper
soil (Satour et al., 1989). VIF plastic
mulch was removed after 45 day.
Biological treatments:
Four
biofungicides, Bio Arc, Bio Zeid, Bio
Nagi and Bio-4 as well as Folicur
fungicide, were used in this investigation
as dipping treatments and applied in
combination with or without soil
solarization for controlling garlic white
rot disease. The two biofungicides Bio-
Arc 6% WP and Bio-Zeid 25% WP are
commercial biofungicides labeled on
different crops in Egypt
.
However, the
Mahmoud Noher, 2018
28
other two biofungicides
i.e.
Bio Nagi and
Bio-4 are still under registration and
obtained from Identification of
Microorganisms, Biological Control of
Plant Diseases and Evaluation of
Biofungicides Unit,
Plant Path. Res. Inst.,
Agric. Res. Center, Giza, Egypt. Bio Arc
is consist of (
Bacillus megaterium
2.5x10
7
cfu/g), Bio Zeid (
Tricoderma
album
10
7
spore/g), Bio Nagi
(
Tricoderma
asperellum
10
7
spore/g) and
Bio-4 (mixture of
four
Bacillus
spp
. i.e.
B. megaterium
,
B. subtilis, B. lechnifrmes
and
B. pumolis
2.5x10
7
cfu/g), as well as
Folicur 25% EC fungicide
(Tebuconazole).
Biological and soil solarization
treatments:
Plastic pots (30 cm-diam)
were sterilized by dipped in 5.0%
formalin solution for 15 minutes, left to
dry for two days to get rid of formalin
residues, then filled with infested soil
(3kg/pot) previously solarized or
unsolarized as mentioned before. The
pots were containing either solarized or
unsolarized infested soil were divided
into equal two partitions and arranged in
randomized complete block design with
three replicates. Each partition was
containing 18 pots (6 treatments x 3
replicates). Healthy garlic bulbs of Sids-
40 cultivar (obtained from Onion, Garlic
and Oil Crops Diseases Research
Department, Plant Pathology Research
Institute, Agriculture Research Centre,
Giza, Egypt) were split into the
individual cloves. The cloves were
chosen for size homogenate and free
from all defects and then soaked in water
over-night. Apparently healthy garlic
cloves were dipped in each particular
biofungicide as mentioned above
(5g/liter) and/or Folicur fungicide (25
ml/liter) mixed with 1% Arabic gum
solution as sticker for 15 min. for
biofungicide and 3 min. for fungicide,
then raised and left to air dried before
planting then planted at the first week of
September 2015/162015/16 season in
solarized or unsolarized infested potted
soil at the rate of 5 cloves per pot. Three
replicates (pots) for each particular
treatment were used and garlic cloves
were dipped before planting in 1%
Arabic gum solution only as control. The
number of garlic plants having specific
white rot disease symptoms (yellowing,
leaf dieback, and wilting) was counted
after two and four month from planting
and their percentage were calculated
according to Hovius and Goldman
(2004)
as follows:
Disease incidence (%)=
No. of garlic plants
infected with white rot
×100
Total No. of garlic plants
Also, garlic plants from each pot of
different treatments were collected after
harvest and weighed as g/pot.
Microbial populations:
Soil samples
were collected at four different sampling
periods with a sampling tube 2 cm inside
diameter from the upper 10 cm of soil
rhizosphere. Soil samples were taken pre
and post solarization process in solarized
or unsolarized infested soil as well as 30
and 60 days from planting. Three soil
samples were collected from each
treatment. The soil of each tube was
bulked for each treatment and kept in
plastic bags to form composite samples
at 4
o
C to stabilize the microbiological
activity distributed during soil sampling
and handling according to the method of
Johnson et al. (1959). For total microbial
count determination at four different
Mahmoud Noher, 2018
29
sampling periods as mentioned above,
plate count technique was applied using
potato dextrose agar medium (PDA) and
nutrient agar medium (Difco, 1985) to
determinate total fungal and bacterial
count, respectively. Total actinomycetes
were estimated by the standard procedure
of Rolf and Bakken (1987).
Field experiment:
Field experiment was
carried out during the two successive
growing seasons 2015/16 and 2016/17 in
natural soil heavily infested with
S.
cepivorum
at Agricultural Research farm,
El Khatatba location, Menofia
governorate. The soil texture was sandy
loam having the following
characteristics, sand 60.5%, silt 24.2%,
loam 15.5% and pH 7.6, EC 1. 36 ds/m,
Organic matter 0.85% (Khalifa et al.,
2017). The present study included 12
treatments (2 solarizaition treatments × 6
dipping treatments) that were laid out in a
randomized complete block with three
replicates. The two solarizaition
treatments
i.e.
solarized soil treatment
(mulched with 35 μm VIF plastic and
unmulched soil treatment (exposed to
direct sun-light). The size of the each plot
was 10.5 m
2
(1/400fed.), each plot
consisted of 6 rows, 50 cm wide and 3.5
m long. The soil was ploughed twice,
listed to form raised beds and flood
irrigated the day before VIF plastic
sheets were placed on soil. Soil of plots
to be solarized was thoroughly rotovated
and irrigated to reach field capacity in the
upper 30–40 cm layer 1–2 days before
being covered with 35 μm VIF plastic.
Soil solarization was accomplished by
covering moist soil with 35 μm VIF
plastic on 1st July 2015, and plots of the
unmulched soil were left exposed to
direct sun light. Edges of the VIF tarps
were buried in furrows between beds.
Special care was taken to minimize the
distance between the tarps and soil to
prevent the formation of air pockets that
retard the soil heating process. All plots
were supplemental irrigated with 10-15
cm flood irrigation every two weeks until
the VIF plastic mulch were removed
after 45day. Prior to planting, the field
was irrigated (2-3 days) in order to
provide good clove-soil- water contact.
Healthy garlic bulbs were split into the
individual cloves. The cloves were
chosen for size homogenate and free
from all defects, and then soaked in
water over-night. Apparently healthy
garlic cloves were dipped in each
particular biofungicide and/or Folicur
fungicide as previously mentioned in pot
experiment and garlic cloves without any
treatment were subjected as control.
Cloves were planted at the first week of
September in the two successive growing
seasons 2015/16 and 2016/17 on both
sides of each ridge at 10 cm apart in
solarized or unsolarized infested plots.
Fertilization and other culture practices
were carried out as recommended. White
rot incidence as a percentage of garlic
bulbs with symptoms was assessed at
harvest by pulling and observing all
garlic bulbs in each plot. Also, garlic
bulbs from each sub plot were harvested
and weighed (kg/sub plot) for yield
assessment.
Statistical analysis:
The obtained data
were statistically analyzed by analysis of
variance (ANOVA) using
MSTAT-C
program version 2.10 (1991). Means
were separation by Duncan test at P <
0.05 level.
Mahmoud Noher, 2018
30
Results
Integration between soil solarization
and dipping treatments of garlic cloves
on white rot incidence of garlic plants
under artificially infested soil:
Data
shown in Table (1) illustrate that, all
treatments significantly decreased white
rot disease incidence compared to
untreated treatment (without any
treatment). Solarization treatment led to
reduced percentage infection of white rot
(WR) of garlic plants with high
significant differences compared to
unsolarized infested soil. On the other
hand, dipping garlic cloves before
planting in four biofungicides
i.e.
Bio
Arc, Bio Zeid, Bio Nagi and Bio-4 and/or
Folicur fungicide caused significant
reduction of WR disease infection in
comparison with untreated cloves.
Treated garlic cloves with Folicur
fungicide was the best dipping treatment
that cause the highest reduction of WR %
followed by biofungicides
i.e.
Bio Nagi,
Bio Zeid, and Bio Arc, respectively.
Whereas treated garlic cloves with Bio-4
resulted the least one in this respect.
Integration between solarization of
infested soil and dipping treatments
increased the efficacy of WR reduction
with high significant differences
compared to un-solarized infested soil.
The superior treatments for controlling
white rot disease under the artificially
infested soil with
S. cepivorum
were soil
solarized plus Folicur fungicide followed
by soil solarized plus Bio Nagi and Bio
Zeid, respectively. Bio Nagi achieved
closer results to Folicur fungicide for
controlling WR incidence.
Table 1: Effect of soil solarization combined with or without dipping treatment with some biofungicides and/or
Folicur fungicide on disease incidence of white rot of garlic plants under pot experiment conditions.
Dipping treatment
Garlic white rot incidence (%)
WR Reduction (%)
Solarized
soil
*
Unsolarized
soil
Mean
Solarized
soil
*
Unsolarized
soil
Mean
Bio Arc
26.7
40.0
33.4
49.91
50.00
49.96
Bio Zeid
20.0
33.3
26.7
62.48
58.38
60.43
Bio Nagi
13.3
26.7
20.0
75.05
66.63
70.84
Bio-4
40.0
53.3
46.7
24.95
33.38
29.17
Folicur fungicide
6.7
13.3
`10.0
87.43
83.38
85.41
Control (untreated)
53.3
80.0
66.7
0.00
0.00
0.00
Mean
26.7
41.1
-
49.97
48.63
-
*
Un- Solarized soil i.e. exposed to direct sun-light only. LSD at 5% for: Soil solarization: (A) 0.59, -
Dipping treatments: (B) 1.01, interactions (A x B): 1.43.
Effect of combinations between soil
solarization and garlic cloves dipping
with some biofungicides and/or Folicur
fungicide on yield of garlic plants
under artificially infested soil in pot
experiment:
Data presented in Table (2)
show that all tested treatments caused
significant increase in garlic yield (g/pot)
compared to control. Garlic yield resulted
from solarization treatment was higher
than that resulted from un-solarized one.
Also, dipping treatment in different
biofungicides produce significant
increase in garlic yield compared to
untreated cloves. Bio Nagi, followed by
Bio Zeid and Bio Arc, respectively were
the best dipping treatments, meanwhile
Bio 4 and Folicur fungicide were the
least effective ones compared to control
(without dipping treatment). The most
Mahmoud Noher, 2018
31
superior treatment that increased yield of
garlic plants (g/pot) was soil solarization
combined with each of Bio Nagi, Bio
Zeid and Bio Arc, respectively, while
dipping treatment only of Bio 4 and
Folicur fungicide were the least effective
treatments in this respect compared to
control treatment.
Table 2: Effect of soil solarization combined with or without dipping treatment with
some biofungicides and/or Folicur fungicide on weight of garlic plants as g/pot under
pot experiment conditions.
Dipping treatment
Weight of garlic plants (g/pot)
Mean
Solarized soil
*
Un- Solarized soil
Bio Arc
210
165
187.5
Bio Zeid
250
190
220.0
Bio Nagi
290
220
255.0
Bio-4
180
140
160.0
Folicur fungicide
160
135
147.5
Control (untreated)
110
50
80.0
Mean
200.0
150.0
*
Un-Solarized soil i.e. exposed to direct sun-light only. LSD at 5% for: Soil solarization:
(A) 3.45, Dipping treatments: (B) 5.98, interactions (A x B): 8.46.
Effect of solarization treatment on
total count of fungi, bacteria and
actinomycetes (colony forming unit) in
garlic infested soil before and after
solarization under pot experiment
conditions:
According to the treatments
that mentioned previously, results in
Table (3) show the microbial populations
(fungi, bacteria and actinomycetes count)
in artificially infested soil with
S.
cepivorum
treated by VIF plastic as a
solarized treatment compared with un-
solarized infested soil (exposed to direct
sun light only) pre and post solarization
treatment and before planting. All the
microbial population counts in the
infested soil were significantly affected
by solarization treatment and the
sampling time (pre- & post solarization)
for determination total fungi, bacteria
and actinomycetes. Solarization
treatment caused significant reduction in
fungal counts in comparison with
untreated infested soil. On the other side,
the decreasing of fungal counts was
obviously detected at the end of
experiment. Concerning of bacteria and
actinomycetes counts, solarization
treatment caused a slightly significant
reduction in both bacteria and
actinomycetes counts in comparison
with untreated infested soil. Also, both
bacteria and actinomycetes counts were
differently affected slightly after
solarization compared to before one. No
significant differences was noticed
neither total of fungi, bacteria nor
actinomycetes counts taking pre
solarization (zero time)
whether in soil
covered with VIF or left to sunlight.
Mahmoud Noher, 2018
32
Table 3: Effect of solarization treatment on total count of fungi, bacteria and actinomycetes (cfu) in garlic
infested soil before and after solarization under pot experiment conditions
Treatment
Total fungi, Bacteria and Actinomycetes counts at Pre & post Solarization
Fungi (CFU/10
4
)
Bacteria CFU/10
6
)
Actinomycetes(CFU/10
4
)
*
Pre
**
Post
Mean
Pre
Post
Mean
Pre
Post
Mean
Solarized soil
39.09
4.52
21.81
5.93
5.14
5.54
1.76
1.62
1.69
Un- solarized soil
39.53
31.22
35.38
6.11
6.05
6.08
1.80
1.73
1.77
Mean
39.31
17.87
-
6.02
5.60
-
1.78
1.68
-
LSD. 5% for:
Soil solarization: (A)
1.684
0.111
0.050
Samples timing: (B)
1.710
0.034
0.042
A x B interactions
2.419
0.158
0.060
*
Pre solarization (Zero time) and
**
Post Solarization before planting
Effect of soil solarization combined
with some biofungicides and folicur
fungicide as dipping treatment on total
fungal count 30, 60 and 90 days after
planting in infested soil under pot
experiment conditions:
Data shown in
Table (4) illustrated the effect of dipping
treatment of garlic cloves in some
biofungicides and folicure fungicide
combined with or without soil
solarization treatment on fungal
population counts at 30, 60 and 90 days
after planting in artificially infested soil
with
S. cepivorum
. In general, all
treatments caused significant decreased
of fungal counts either 30, 60 or 90 days
from planting in comparison with un-
treated control. Solarization treatment
caused a highly significant reduction in
fungal counts in comparison with un-
solarized one during all sampling time.
The effect of solarization was decreased
gradually from the first sample time to
the last one. Regard for dipping
treatments, all tested biofungicides and
folicure fungicide significantly reduced
the total fungal counts after 30, 60 and
90 days from planting and this reduction
was gradually decreased from 30 days to
90 days. Folicure fungicide and Bio
Nagi followed by Bio Zeid were the best
ones in this respect during the
experiment. Meanwhile, Bio Arc and
Bio 4 were the least significant ones
compared with un-dipping treatment.
Concerning the interaction between soil
solarization treatment and dipping
treatments, the same results in Table (4)
stated that integration between
solarization treatment and the tested
biofungicides and folicure fungicide was
more effect in reducing fungal
population counts than the individual
treatment. Solarization treatment
combined with dipping treatment
i.e.
Folicure fungicide or Bio Nagi followed
by Bio Zeid were the best treatment in
reducing the total fungal counts after 30,
60 and 90 days from planting. On the
other hand, the total fungal population
count was significantly affected directly
after soil solarization and dipping
treatments to 30 days whereas increased
gradually from 60 to 90 days after
planting in comparison with untreated
control.
Mahmoud Noher, 2018
33
Table 4: Effect of soil solarization combined with or without dipping treatments with some biofungicides and/or Folicur
fungicide on total count of fungi (CFU/10
4
)in the garlic infested soil during different growth intervals after 30, 60 and 90
days of planting under pot experiment conditions.
Dipping
treatment
Total fungal counts (CFU/10
4
) after 30, 60 and 90 days of planting
in solarized and un-solarized infested soil
30 Days
60 Days
90 Days
Solar.
*
Un-Solar
Mean
Solar.
*
Un-Solar.
Mean
Solar.
*
Un-Solar.
Mean
Bio Arc
6.73
25.15
15.94
12.82
28.57
20.70
18.93
31.89
25.41
Bio Zeid
5.12
19.80
12.46
9.54
21.35
15.45
13.67
23.74
18.71
Bio Nagi
4.09
15.32
9.71
6.27
18.91
12.59
9.68
21.53
15.61
Bio-4
8.82
28.08
18.45
15.91
31.73
23.82
23.64
33.87
28.76
Folicur
3.64
13.92
8.78
5.83
15.17
10.50
8.29
18.83
13.56
Control
12.07
31.97
22.02
22.13
35.22
28.68
28.52
38.35
33.44
Mean
6.75
22.37
-
12.08
25.16
-
17.12
28.04
-
LSD. 5% for
Total fungal (CFU/10
4
) after 30, 60 and 90 days of planting
30 Days
60 Days
90 Days
Soil solarization: (A)
1.925
0.351
0.419
Dipping treatment:(B)
3.334
0.608
0.725
A x B interactions:
4.715
0.859
1.025
*
Un- Solarized soil i.e. exposed to direct sun-light only.
Effect of soil solarization combined
with some biofungicides and folicur
fungicide as dipping treatment on total
bacterial count 30, 60 and 90 days
after planting in infested soil under pot
experiment conditions:
Table (5)
showed the effect of integrated treatment
between dipping of garlic cloves in some
biofungicides and folicure fungicide
combined with or without soil
solarization treatment on bacterial
population counts 30, 60 and 90 days
after planting in artificially infested soil
with
S. cepivorum
. Generally, all tested
dipping treatments caused significant
increasing of bacterial counts 30, 60 or
90 days from planting in comparison
with un-treated control in both solarized
and un-solarized treatments. The total
bacterial count was significantly
decreased in solarized treatment in
comparison with un-solarized during the
three samples timing 30, 60 and 90 days
after planting. Solarization decreased
gradually bacterial populations from 30
days to 90 days from planting. Regard
for dipping treatments, Bio Arc followed
by Bio four were the best dipping
treatments gave the highest population of
bacterial counts during the three samples
timing 30, 60 and 90 days after planting
followed by Bio Nagi and Bio Zeid.
Meanwhile, Folicure fungicide caused
significant decreasing in total bacterial
count and was more effect in reducing
bacterial populations than un-dipping
treatment in both solarized and un-
solarized treatments. Integration between
soil solarization and Folicure fungicide
gave the highly reducing the total
bacterial counts after 30, 60 and 90 days
from planting. On the other side, the best
integrated treatment for improvement
increasing bacterial populations were un-
solarized treatment (exposed to direct
sun-light only) plus Bio Arc after 60 and
90 days followed by Bio four after 90
days from planting, respectively in
comparison with untreated control and
Folicure fungicide.
Mahmoud Noher, 2018
34
Table 5: Effect of soil solarization combined with or without dipping treatments with some biofungicides and/or Folicur
fungicide on total count of bacterial (CFU/10
6
) in the garlic infested rhizosphere soil during different growth intervals
after 30, 60 and 90 days of planting under pot experiment conditions.
Dipping
treatment
Total bacterial counts (CFU/10
6
) after 30, 60 and 90 days of planting
in solarized and un- solarized infested soil
30 Days
60 Days
90 Days
Solar.
*
Un-Solar
Mean
Solar.
*
Un-Solar.
Mean
Solar.
*
Un-Solar.
Mean
Bio Arc
15.39
21.23
18.31
17.88
34.17
26.03
23.15
37.68
30.42
Bio Zeid
12.65
16.48
14.57
14.07
19.26
16.67
16.52
23.17
19.85
Bio Nagi
13.49
17.30
15.40
15.86
20.91
18.39
16.12
22.06
19.09
Bio-4
14.83
20.73
17.78
16.52
25.85
21.19
19.78
28.43
24.11
Folicur
6.73
7.18
6.96
7.81
8.95
8.38
9.07
10.19
9.63
Control
8.94
10.55
9.75
9.67
14.36
12.02
11.33
17.09
14.21
Mean
12.01
15.58
-
13.64
20.58
-
30.42
30.42
-
LSD. 5% for
Total bacterial (CFU/10
6
) after 30, 60 and 90 days of planting
30 Days
60 Days
90 Days
Soil solarization: (A)
0.152
0.315
0.323
Dipping treatment:(B)
0.264
0.546
0.559
A x B interactions:
0.373
0.772
0.790
*
Un- Solarized soil i.e. exposed to direct sun-light only.
Effect of soil solarization combined
with some biofungicides and folicur
fungicide as dipping treatment on total
actinomycetes count 30, 60 and 90
days after planting in infested soil
under pot experiment conditions:
Table (6) clear the effect of soil
solarization treatment that combined
with dipping garlic cloves in some
biofungicides and folicure fungicide in
comparison with un-solarized soil and
undipped control on actinomycetes
population counts after 30, 60 and 90
days from planting in artificially infested
soil with
S. cepivorum
. Solarization
treatment caused significant reduction in
actinomycetes count compared to un-
solarized one during the three samples
timing 30, 60 and 90 days after planting.
All tested dipping treatments caused
significant increasing of actinomycetes
counts 30, 60 or 90 days from planting
except dipping treatment in Folicure
fungicide that caused significant
decreasing in total actinomycetes more
than un-dipping treatment in both
solarized and un-solarized treatments.
Bio Nagi and Bio Zeid were the best
biofungicides during the three different
growth intervals (30, 60 and 90 days of
planting) which increased actinomycetes
population. Meanwhile, Bio Arc and Bio
four were the least significant ones in
this respect compared with un-dipping
treatment. The effect of solarization on
actinomycetes populations was
decreased gradually from 30 days to 90
days from planting. Integration between
soil solarization and Folicure fungicide
gave the highly reducing the total
actinomycetes during the three sampling
intervals. On the other side, individual
dipping treatment of Bio Nagi followed
by Bio Zeid after 90 days after planting,
respectively gave the highest increasing
of actinomycetes count.
Mahmoud Noher, 2018
35
Table 6: Effect of soil solarization combined with or without dipping treatments with some biofungicides and/or Folicur
fungicide on total count of actinomycetes count (CFU/10
4
) in the garlic infested rhizosphere soil during different growth
intervals after 30, 60 and 90 days of planting under pot experiment conditions.
Dipping
treatment
Total actinomycetes count (CFU/10
4
) after 30, 60 and 90 days of planting
in solarized and unsolarized infested soil
30 Days
60 Days
90 Days
Solar.
*
Un-Solar.
Mean
Solar.
*
Un-Solar.
Mean
Solar.
*
Un-Solar.
Mean
Bio Arc
1.76
2.39
2.08
1.92
3.14
2.53
2.34
4.08
3.21
Bio Zeid
2.13
2.58
2.36
2.71
2.97
2.84
3.54
3.81
3.68
Bio Nagi
2.61
2.75
2.68
2.99
3.21
3.10
3.40
4.34
3.87
Bio-4
1.95
2.11
2.03
2.31
2.86
2.59
2.73
3.79
3.26
Folicur
1.18
1.27
1.23
1.62
1.85
1.74
1.93
2.26
2.10
Control
1.39
1.43
1.41
1.64
1.93
1.79
2.27
2.43
2.35
Mean
1.84
2.09
-
2.20
2.66
-
2.70
3.45
-
LSD. 5% for
Total actinomycetes (CFU/10
4
) after 30, 60 and 90 days of planting
30 Days
60 Days
90 Days
Soil solarization: (A)
0.127
0.084
0.065
Dipping treatment:(B)
0.220
0.146
0.113
A x B interactions:
0.311
0.206
0.160
*
Un-Solarized soil i.e. exposed to direct sun-light only.
Effect of integration between soil
solarization and garlic cloves dipping
treatments on white rot disease
incidence of garlic plants under field
conditions during the two successive
growing seasons 2015/16 and 2016/17:
Table (7) illustrate the combination
between soil solarization of naturally
infested soil with
S. cepivorum
and
dipping treatment in some biofungicides
and/or Folicur fungicide on percentage of
garlic white rot incidence
during the two
successive
growing seasons 2015/16 and
2016/17. All tested treatments
significantly decreased white rot
incidence compared to untreated
treatment (without any treatment) in two
successive growing seasons. Solarization
treatment was highly effect in reducing
white rot incidence of garlic plants with
high significant differences compared to
un-solarized naturally infested soil. On
the other hand, dipping of garlic cloves
before planting in the four tested
biofungicides and/or Folicur fungicide
caused highly significant reduction of
WR disease incidence in comparison
with untreated cloves. Dipping treatment
with Folicur fungicide gave the highest
significant reduction of WR % followed
by Bio Nagi and Bio Zeid, respectively
during the two growing seasons.
Whereas treated garlic cloves with Bio-4
followed by Bio Arc resulted the least
effective ones in this respect. Integration
between solarization of naturally
infested soil and dipping treatments
increased the efficacy of WR reduction
with high significant differences
compared to un-solarized soil. The
superior combination for controlling
white rot disease under the naturally
infested soil with
S. cepivorum
were soil
solarized plus Folicur fungicide followed
by soil solarized plus Bio Nagi and Bio
Zeid, respectively during the two
growing seasons 2015/16 and 2016/17.
Bio Nagi achieved closer results to
Folicur fungicide for controlling WR
incidence at the two successive seasons.
Mahmoud Noher, 2018
36
Table 7: Effect of soil solarization combined with or without dipping treatment with some
biofungicides and/or Folicur fungicide on disease incidence of white rot disease on garlic plants
under field conditions during the two successive growing seasons 2015/16 and 2016/17.
Season
Treatment
Garlic white rot disease incidence %
Mean
Solarized soil
*
Unsolarized soil
2015/16
Bio Arc
12.3
23.7
18.0
Bio Zeid
7.9
16.4
12.2
Bio Nagi
5.3
12.2
8.8
Bio-4
15.8
25.8
20.8
Folicur fungicide
3.2
10.6
6.9
Control (untreated)
27.6
35.4
31.5
Mean
12.0
20.7
-
2016/17
Bio Arc
13.6
25.1
19.4
Bio Zeid
9.2
18.3
13.8
Bio Nagi
6.7
14.5
10.6
Bio-4
16.9
27.6
22.3
Folicur fungicide
5.6
15.8
10.7
Control (untreated)
30.4
41.7
36.1
Mean
13.7
23.8
-
LSD. 5% for
2015/16
2016/17
Soil solarization: (A)
0.38
0.43
Dipping treatment: (B)
0.67
0.75
A x B interactions
0.94
1.06
*
Un- Solarized soil i.e. exposed to direct sun-light only.
Effect of integration between soil
solarization and garlic cloves dipping
treatments on garlic yield under field
conditions during the two successive
growing seasons 2015/16 and 2016/17:
Data presented in Table (8) illustrated
that all tested treatments caused
significant increase in garlic yield
(Kg/plot (10.5 m
2
)) compared to
untreated control (without any treatment)
during the two growing seasons 2015/16
and 2016/17. Solarization treatment was
more efficacy for improvement garlic
yield than un-solarized one (exposed to
direct sun-light only). On the other hand,
dipping treatment in different
biofungicides produce a significant
increase in garlic yield compared to
untreated cloves. Bio Nagi, followed by
Bio Zeid and Bio Arc, respectively were
the best dipping treatments for
increasing garlic yield, meanwhile Bio 4
and Folicur fungicide were the least
effective ones in this respect in both
growing seasons compared to control
(without dipping treatment). The most
superior integration treatment for
increasing garlic yield was solarization
treatment combined with each of Bio
Nagi, Bio Zeid and Bio Arc,
respectively, while dipping treatment
only of Bio 4 and Folicur fungicide were
the least effective treatments in this
respect compared to control treatment
during the two growing seasons 2015/16
and 2016/17.
Mahmoud Noher, 2018
37
Table 8: Effect of soil solarization combined with or without dipping treatment with
some biofungicides and/or Folicur fungicide on garlic yield (Kg/plot) under field
conditions during the two successive growing seasons 2015/16 and 2016/17.
Season
Treatment
Garlic yield (Kg/plot 10.5 m
2
)
Solarized soil
*
Unsolarized soil
Mean
2015/16
Bio Arc
19.4
15.7
17.6
Bio Zeid
23.8
18.3
21.1
Bio Nagi
25.6
20.6
23.1
Bio-4
17.7
15.4
16.6
Folicur fungicide
18.1
16.9
17.5
Control (untreated)
12.5
10.1
11.3
Mean
19.5
16.2
-
2016/17
Bio Arc
18.6
14.3
16.5
Bio Zeid
22.1
17.2
19.7
Bio Nagi
24.2
18.6
21.4
Bio-4
16.3
14.8
15.6
Folicur fungicide
17.9
15.7
16.8
Control (untreated)
11.4
9.5
10.5
Mean
18.4
15.0
-
LSD. 5% for
2015/16
2016/17
Soil solarization: (A)
0.35
0.34
Dipping treatments: (B)
0.60
0.58
A x B interactions
0.85
0.82
*
Un- Solarized soil i.e. exposed to direct sun-light only.
Discussion
During this investigation, the impact of
combination between solarization and
different biofungicides and/or Folicur
fungicide on the incidence of white rot
disease and the garlic yield was
investigated under artificially and
naturally infestation with
S. cepivorum
in
greenhouse and filed conditions,
respectively during the two successive
growing seasons 2015/16 and 2016/17.
Solarization treatment reduced
percentage of white rot (WR) disease of
garlic plants with significant differences
compared to un-solarized infested soil
under artificially and naturally infestation
with
S. cepivorum
. These results in
harmony with those obtained by
Satour et
al., (1989) who indicated that solarization
may control
Sclerotium cepivorum
the
causal pathogen of white rot disease in
onions. In
Egypt,
S
.
cepivorum
completely
controlled was done by solarization, even
in heavily infested soils
(Satour et al.,
1989). Several workers reported the
success of solarization treatment in
reducing plant diseases caused by soil-
borne pathogens (Keinath, 1995). Long-
term effects of soil solarization have
been observed for control of pink root
and white rot of onion (Abdel-Rahim et
al., 1988). Soil solarization was the most
effective treatment for eradicating
S.
cepivorum
from infested soil in the pots
and fields trials and years tested. Thus,
the results obtained in previous studies
on controlling garlic white rot in Spain
(Basallote-Ureba & Melero-Vara, 1993)
and elsewhere, on onion and garlic crops
(Pereira et al., 1996) were confirmed. In
previously field experiments in Egypt
results indicated a more satisfactory
Mahmoud Noher, 2018
38
long-term effect of soil solarization to
control onion WR despite furrow
irrigation (Satour et al., 1989), which is
determinant of inoculum spread from
non-solarized to solarized plots. It has
been reported that viability of
S
.
cepivorum
sclerotia is considerably
reduced by exposure to temperatures
above 30°C (Crowe & Hall, 1980) and
exposures to 40°C for 39 h killed at least
50% of them (Adams, 1987). The
increase in microbial processes induced
by solarization could affect
S
.
cepivorum
by increasing its vulnerability to soil
microorganisms (Katan, 1981). Dipping
garlic cloves before planting in four
biofungicides
i.e.
Bio Arc, Bio Zeid, Bio
Nagi and Bio-4 and/or Folicur fungicide
caused a high significant reduction of
WR disease incidence in comparison
with untreated cloves.
These findings are
in agreement with several researchers.
Among them
Ouf et al
.
(2008) studied
the effect of three biofungicides, Rhizo-
N, Plant Guard and Contans, against
S.
cepivorum
. The antagonistic units of the
biofungicides are
B. subtilis,
T.
harzianum
and
C. minitans
, respectively.
They found that all biofungicides
inhibited the growth of the pathogen.
Mohamed (2012)
found that using the
biofungicides Bio Zeid, Bio Arc and
Planta Guard under greenhouse condition
decreased the percentage of disease
incidence with rot and increased onion
bulb yield.
Khalifa et al. (2013) showed
that fungal bioagents
i.e.
Bio Nagi and
Bio Zeid were more effective than
bacterial bioagents
i.e.
Bio Arc and Bio-4
for controlling white rot disease of onion.
Mahdizadehnaraghi et al. (2015)
indicated that bioformulations of
antagonistic fungi including
Trichoderma
harzianum, T. asperellum,
and
Talaromyces flavus
can be used for
controlling garlic white rot which is one
of the most important fungal diseases
anywhere garlic is cultivated. The
application of fungal and bacterial
antagonists to the soil opens the
possibility of disease control without the
use of chemicals, and usually provides an
environmentally sound control measure.
Among the microorganisms reported to
provide biocontrol of
S. cepivorum
, one
of the most effective seemed to be
Trichoderma
spp. (Abd-El-Moity, 1992;
Chet, 1987; De Oliveira et al., 1984).
Bacillus subtilis
(Ehrenberg) Cohn was
also considered an effective biocontrol
agent, inhibiting mycelial growth of
S.
cepivorum
through antibiosis (Reddy et
al., 1992). Reino et al
.
(2008)
reported
that
Trichoderma
spp. produce different
secondary metabolites with antibiotic
activity and have been classified in
different groups based on their
biosynthetic origin or their chemical
structure, and they include non-volatile
(
i.e.
peptaibols) and volatile compounds
(e.g.
simple aromatic metabolites,
terpenes, the isocyano metabolites, some
polyketides, butenolides and pyrones.
Dipping treatment with Folicur fungicide
(tebuconazole) gave the highest
significant reduction of WR % under
greenhouse and field experiments during
the two successive growing seasons
followed by biofungicides
i.e.
Bio Nagi
and Bio Zeid, respectively. Whereas
treated garlic cloves with Bio-4 followed
by Bio Arc resulted the least effective
ones in this respect. These results were in
harmony with those obtained by Melero-
Vara et al. (2000). They found that,
treatment of garlic cloves with
tebuconazole (at 1ml of Folicur 25%)
achieved a significant reduction in the
Mahmoud Noher, 2018
39
rate of disease progress and the final
incidence of plant death by
Sclerotium
cepivorum.
In contrast, lower levels of
disease control were obtained when
selected isolates of
Trichoderma
harzianum
and
Bacillus subtilis
were
applied to the soil and cloves
respectively
.
Tebuconazole was very
effective for controlling garlic white rot
disease when applied to the soil or with
the garlic cloves (Felaifel et al., 2005;
Jackson et al., 1997) but it was highly
phytotoxic, causing seed and seedling
mortality when used as a seed treatment
for onion (Fullerton et al., 1995). The
combined treatment between bioagents
and fungicide or any other treatments
may be useful to increase the efficacy of
garlic or onion white rot disease control
(Bandyopadhyayl & Cardwel 2003). The
integration of the two most efficient
methods of control of WR of garlic,
i.e.
soil solarization and Folicur
(tebuconazole) treatment of garlic cloves,
is suggested as very satisfactory method
under high disease levels. This is of
particular interest when a long-term
effect of solarization is desired, since
clove treatment with tebuconazole would
be appropriate under low disease pressure
such as in the second year after soil
solarization. Integration between
solarization and dipping treatments
increased the efficacy of WR reduction
with high significant differences
compared to un-solarized infested soil
under greenhouse and filed conditions
during the two growing seasons 2015/16
and 2016/17. The most superior
combination treatments for controlling
white rot disease of garlic under
artificially and naturally infestation with
S. cepivorum
in greenhouse and filed
conditions, in the two growing seasons
were soil solarized plus Folicur fungicide
followed by soil solarized plus Bio Nagi
and Bio Zeid, respectively during the two
growing seasons 2015/16 and 2016/17.
Bio Nagi achieved closer results to
Folicur fungicide for controlling WR
incidence at the two successive seasons.
Melero-Vara et al. (2000) found that the
application of different methods using
soil solarization, bioagents (
T.
harzianum
,
B. subtilis
) and fungicide
(tebuconazole) were effective on
controlling garlic white rot (WR) and
crop yields and on the quality of garlic
bulbs (long-term effect) under field
conditions in southern Spain and soil
solarization provided the best control of
garlic white rot, bringing soil populations
of
S. cepivorum
to negligible levels and
garlic yields were improved. Therefore,
the use of these biological control agents
seems to be more appropriate as one
component of integrated control
practices that combines either with
chemical treatments or with soil
solarization (Chet 1987).
Pereira et al.
(1996) indicated that
T. harzianum
applied to solarized plots improved
control of
S. cepivorum
compared with
the results achieved with the addition of
B. subtilis
, applied after soil solarization.
Ulacio-Osorio et al. (2006) reported that
soil solarization significantly reduced
inoculum density (75%), viability (84%)
and disease incidence (88%), and
increased garlic yield by up to 152%,
compared with non-solarized treatments.
Abou-Zeid
et al
.
(2011) indicated that
using biofungicides (Bio Arc and Bio
Zeid) combined with solarization
treatment gave acceptable results for
controlling the major soil borne diseases
of tomato (fungal pathogens & root-knot
nematodes) and gave the best increasing
Mahmoud Noher, 2018
40
of tomato yield.
Abada et al. (2015)
showed that using of the two bioagents
B.subtilis
and
P.flurescens
, compost and
soil solarization resulted in significant
reduction to the severity of strawberry
Fusarium wilt with significant increase to
the fruit yield compared with control
treatment. In addition, the combination
between any of the tested bioagents and
soil solarization was more efficient in
reducing disease severity and increasing
fruit yield than when each of them was
used alone. Moreover, the combination
among the two bioagents + compost +
soil solarization was the most efficient in
this regard.
Concerning to garlic yield
under both greenhouse and filed
conditions, during the two growing
seasons 2015/16 and 2016/17, the
obtained results declared that garlic bulb
yield that resulted from solarization
treatment was higher than from un-
solarized one. Also, dipping treatment in
different biofungicides produce
significant increase in garlic yield
compared to untreated cloves. Bio Nagi,
followed by Bio Zeid and Bio Arc,
respectively were the best dipping
treatments, meanwhile Bio 4 and Folicur
fungicide were the least effective ones
compared to control (without dipping
treatment). The most superior integration
treatment for increasing garlic yield was
solarization treatment combined with
each of Bio Nagi, Bio Zeid and Bio Arc,
respectively, while dipping treatment
only of Bio 4 and Folicur fungicide were
the least effective treatments in this
respect compared to control treatment
during the two growing seasons. Satour
et al. (1989)
revealed that soil
solarization has a great potential for
increasing onion yield in the
Mediterranean region. Melero-Vara et al.
(2000) reported that soil solarization was
also highly effective and caused a
significant improvement in yield and
garlic quality. Our results in agreement
with a previous study on soil solarization
(Basallote-Ureba & Melero-Vara, 1993).
The obtained data illustrated that,
population densities of total fungi,
bacteria and actinomycetes were greatly
reduced directly after solarization in
solarized soil compared to before
solarization in both solarized and un-
solarized soil (exposed to direct sun
light).
Kamaluddeen and Simon (2013)
used soil solarization by covering
transparent polythene in summer season
comparing to control plots (without
solarized) which were left exposed to
direct sun light and counted total
microflora population at pre, post soil
solarization and after 30 days of soil
amendment. They showed that soil
microflora was greatly reduced in
solarized soil as compared to unsolarized
one. On the other hand, before
solarization, total count of soil
microflora (fungi, bacteria and
actinomycetes) showed no significant
difference between solarized and
unsolarized soil. The obtained data in
agreement with El-Shanawany et al.
(2004)
who found that, immediately
before starting soil solarization (at zero
time), total count number of genera,
number of species and density levels of
species of soil fungi did not show any
significant difference between mulched,
unmulched and shaded soils at 0-10 and
10-20 cm depths. This result indicating
homogeneity of the native
mycocommunity present in the tested
field. The decreasing of fungal counts
was obviously detected after finishing of
solarization treatment. Meanwhile, total
Mahmoud Noher, 2018
41
bacteria and actinomycetes counts, was
slightly significant reduced in
comparison with untreated infested soil.
Soil borne propagules of fungi that are
subjected to sublethal heat effects during
solarization appear to have an increased
sensitivity to antagonistic fungi and to
bacteria which are less affected by soil
solarization (Lifshitz et al. 1983).
Stapleton and DeVay (1982)
indicated
that
immediately after soil solarization,
the population densities of "total" fungi
were reduced by 85 to 90 percent in
different experimental plots. However,
population densities of thermotolerant
and thermophilic microorganisms
remained relatively high following
solarization, and increased to levels
higher than present in non-solarized soil.
Stapleton and Devay (1986) mentioned
that soil solarization has been effective as
a pre-plant and as a post plant treatment,
and has been compatible with chemical
soil treatments and also biological soil
amendments after solarization.
Concerning to fungal counts determined
either 30, 60 or 90 days from planting
under greenhouse conditions.
Solarization treatment caused a highly
significant reduction in fungal counts in
comparison with un-solarized one during
the three time of sampling 30, 60 and 90
days after planting. The suppressive
effect of solarization was more effective
during the first 30 days of planting, and
then it decreased gradually from 60 to 90
days after planting in comparison with
untreated control. These results in
harmony with those obtained by
El-
Shanawany et al. (2004), who reported
that the composition of soil fungal
community was altered in solarized soil.
Both total count and number of fungal
species detected were greatly reduced in
solarized soil as compared to unsolarized
soil. Plant pathogenic fungi are among
the most sensitive soil borne organisms
to soil solarization, especially species
that are unable to grow at temperatures
higher than 30° to 33°C (Stapleton &
DeVay, 1982). Sublethal temperatures
also may cause delays in germination of
propagules and reduced virulence in host
plants that vary with temperature and the
duration of exposure. Pullman et al
.
(1981) found that these effects of
sublethal temperatures were most
pronounced when the fungi were
exposed to temperatures of 37° to 39°C.
The longer a propagule was exposed to
sublethal heating, the longer was the time
required for germination. They suggested
that this relationship indicates that heat
damage accumulates gradually to a point
beyond which the propagule cannot
recover. During sublethal heating; all
living cells produce heat shock proteins
(Plesofsky-vig & Brambl, 1985). Heat
shock proteins are associated with the
acquistion of thermotolerance or
thermos/ability; however, fungi have a
transient heat shock response that is
shortlived, even if they are maintained at
high temperature (Plesofsky-vig &
Brambl, 1985). The overall effect of heat
shock proteins on the survival of fungi
during soil solarization is unknown.
Other effects of sublethal heating are
well documented, especially in the case
of fungi produced sclerotia such as
Sclerotium
cepivourum
and
S. rolfsii
where the rind of sclerotia becomes
cracked resulting in increased leakage of
various substances (Lifshitz et al., 1983).
Greenberger et al. (1984)
stated
that
many plant pathogenic fungi are
differentially sensitive to moist heat and
have been controlled by soil solarization.
Mahmoud Noher, 2018
42
They added that after soil solarization
the
propagules and weakened sclerotia of the
most fungal population are intensely
colonized by
Trichoderma
harzianum
and other micro-organisms.
Entwistle and Munasinge (1990) found
that
S. cepivorum
exposed to sublethal
temperatures, 35 or 40°C for 3 to 7 or 24
to 48 h, respectively, were colonized by
bacteria and fungi, mycelium production
in agar was delayed and the colonies
were smaller compared with unexposed
sclerotia; survival and germination in soil
were also reduced. Regard for
total
bacteria and actinomycetes population
count, obtained results raveled that
population densities of bacteria and
actinomycetes population count were
significantly reduced in solarized soil and
most reduction of total count occurred in
the first 30 days.
Stapleton et al
.
(1985)
reported that soil solarization is a special
mulching process which causes
hydrothermal disinfestation and other
physical and biological changes in soil
which are beneficial to plant health and
growth. Plastic film laid over moist soil
during periods of high air temperature,
usually for 1–2 months, can greatly
reduce or eradicate a number of
pathogens and pests including fungi,
bacteria, nematodes, arthropods and
weeds. However, the total count of
bacteria and actinomycetes was
significantly increased in solarized soil
after 60 days then it rapidly increased at
the 90 days interval. All tested dipping
treatments caused significant increasing
of bacterial and actinomycets count
during the three timing intervals in
comparison with un-treated control in
both solarized and un-solarized
treatments. Recolonization of solarized
soils includes saprophytic bacteria which
have less stringent nutritional
requirements than plant pathogens
(Misaghi & Grogan, 1969).
These
results
were
in harmony with several
investigators. Stapleton and DeVay
(1984)
declared that populations of
bacteria, including
Bacillus
species and
actinomycetes may be reduced during
solarization of soil compared with non-
solarized soil. Stapleton and DeVay
(1984) showed that solarization
increased the total numbers of bacteria
and actinomycetes in soil. Surprisingly,
after solarization,
Pseudomonas
species
quickly recolonize the soil and their
populations reach high levels (Gamliel et
al., 1987). Of great significance is the
change in populations of
Bacillus
species
during solarization; the percentage of
colonies in solarized soil increased
nearly 20-fold when compared with non-
solarized soil (Stapleton & DeVay,
1984). These bacteria are among those
which are rhizosphere competent and are
believed to contribute to the increased
growth response of plants grown in
solarized soil (Katan, 1987). There were
direct Effects of soil solarization on
microorganisms such as, the inability of
organisms to tolerate high temperatures
is related to an upper limit in the degree
of fluidity of membranes, beyond which
breakdown of membrane function may
be associated with membrane instability
(Sundarum, 1986). Additional causes for
the thermal decline of microorganisms at
high temperatures involve the sustained
inactivation of respiratory enzymes
(Sundarum, 1986). As well as, there were
indirect effects of soil solarization on
microorganisms for examples, cells of
plant pathogens weakened by heat stress
are more vulnerable by several orders of
magnitude to soil fumigants, to
Mahmoud Noher, 2018
43
antagonistic micro-organisms which are
more able to tolerate high soil
temperatures, and to changes in the gas
environment which may develop during
soil solarization. Also, changes occur in
the structure or filth of soil during
solarization, in soluble mineral
substances available for plant and
microbial growth, and in the populations
of soil borne micro-organisms (Stapleton
& DeVay. 1984). These changes affect
the inoculum density of plant pathogens,
and also their aggressiveness and
survival. Changes in the populations of
other soil borne micro-oganisms occur
during and after solarization which may
influence the disease suppressiveness of
soil and also the increased plant growth
response associated with solarized soils
(Stapleton et al., 1985).
Acknowledgements
The author is thankful to Prof. Dr. Nagi
Mohamed Abou Zeid Professor of Plant
Pathology, Supervisor of Micro-
organisms Identification, Biological
Control of Plant Diseases and Evaluation
of Biofungicides Unit, Plant Pathology
Research Institute, Agriculture Research
Center, Giza, Egypt, for helping about
technical and administrative assistance.
The author also express his gratitude to
Prof. Dr. Mamdouh Mohamed Abdel-
Fattah Khalifa, Head of Onion, Garlic
and Oil Crops Diseases Research
Department, Plant Pathology Research
Institute, Agriculture Research Centre,
Giza, Egypt, for providing the reference
isolate
Sclerotium cepivourum
used and
for helping about this study.
References
Abada KA, Abd-El-Latif Faten M, El-Dakar
Hala AM, 2015. Effect of combination
among bioagents, compost and soil
solarization on management of
strawberry Fusarium wilt. American
Journal of Life Sciences. 2(6-2): 39–46.
Abd-El-Moity TH, 1992. The use of
Trichoderma spp. to control soil-borne
pathogens in Egypt. In: Tjamos ES,
Papavizas GC and Cook RJ (eds)
Biological Control of Plant Diseases
Progress and Challenges for the Future.
NATO ASI Series A: Life Sciences,
Plenum Press, New York, USA, 230:
255–258
Abdel-Rahim MF, Satour MM, Mickail KY,
El-Eraki SA, Grinstein A, Chen Y and
Katan J, 1988. Effectiveness of soil
solarization in furrow-irrigated Egyptian
soils. Plants diseases 72: 143–146.
Abou El-Magd, MM., Zaki MF, Abo Sedera
SA and El-Shorbagy TT, 2014.
Evaluation of five garlic (Allium sativum
L.) cultivars under bio-chemical and
mineral fertilization. Middle East
Journal of Agriculture Research 3(4):
926–935.
Abou-Zeid NM, Mahmoud Nohair A, Khalil
AE, 2011. Efficiency of certain methyl
bromide alternatives and their
economical feasibility on tomato
infected with root-knot nematode and
fungi under field condition in Egypt. 4
th
International Conference on Alternative
Methods in Crop Protection. Evolution
of the European and French regulatory
frameworks. New means and innovative
strategies, New Century, Lille, France,
606-613 pp.
Mahmoud Noher, 2018
44
Adams PB, 1987. Effects of soil temperature,
moisture and depth on survival and
activity of Sclerotinia minor, Sclerotium
cepivorum and Sporidesmium
sclerotivorum. Plant Disease 71: 170–
174.
Bandyopadhyayl R, Cardwell KF, 2003.
Species of Trichoderma and Aspergillus
as biological control agents against plant
diseases in Africa. In Biological Control
in Integrated Pest Management Systems
in Africa (Neuenschwander, P.,
Borgemeister, C., Langewald, J., eds).
CABI Publishing, Wallingford, U.K.,
193–206 pp.
Basallote-Ureba MJ, Melero-Vara JM, 1993.
Control of garlic white rot by soil
solarization. Crop Protection 12: 219–
223.
Blaszczyk L, Siwulski M, Sobieralski K,
Lisiecka J, Jędryczka M, 2014.
Trichoderma spp. – application and
prospects for use in organic farming and
industry. Journal of Plant Protection
Research 54(4): 309–317.
Bo Ming Wu, Mike Davis, Tom Turini, 2010.
Developing new integrated strategies for
controlling white rot in garlic. Third
Annual Symposium Spotlights Research
Spring. California Garlic & Onion
Research Advisory Board.
Chet I, 1987. Trichoderma: application, mode
of action, and potential as a biocontrol
agent of soil borne plant pathogenic
fungi. In: Chet I (ed) Innovative
Approaches to Plant Disease Control.
Wiley-Interscience, New York, USA,
137–160 pp.
Cook RJ, Baker KF, 1988. The Nature and
Practice of Biological Control of Plant
Pathogens. American Phytopathological
Society, St. Paul Minnesota, USA, 539
pp.
Crowe FJ, Hall DH, 1980. Soil temperature
and moisture effects on Sclerotium
germination and infection of onion
seedlings by Sclerotium cepivorum.
Phytopathology 70: 74–78.
De Oliveira VL, De M Bellei M, Borges AC,
1984. Control of white rot of garlic by
antagonistic fungi under controlled
environmental conditions. Canadian
Journal of Microbiology 30: 884–889
Difco Manual, 1985. Dehydrated culture
media and reagents for microbiology.
Laboratories incorporated Detroit,
Michigan, 48232 USA, 350 pp.
Eleshmawiy KH, ElSharif LM, Hassan HB,
Saafan AM, 2010. Potentials of the
economic expansion in the production
and export of Egyptian garlic. Journal of
Natural Sciences 8: 279–287.
El-Shanawany AA, El-Ghamery AA, El-
Sheikh HH, Bashandy AA, 2004. Soil
solarization and the composition of soil
fungal community in Upper Egypt.
Assiut University Bulletin For
Environmental Researches 7(1): 137–
152.
Entwistle AR and Munasingue HL, 1990.
Evidence for damage in sclerotia of
Sclerotium cepivorum following subletal
heat treatment. In: Entwistle A.R.,
Mattusch P. (eds). Proceedings 4
th
International Workshop on Allium
White Rot, Braunschweig, Germany,
69–75 pp.
Felaifel MSA, Abdel-Momen SM, Khalifa
MMA, Al-Ashaal MS, 2005. Effect of
some triazol fungicides group on garlic
white rot diease control and its yield.
Mahmoud Noher, 2018
45
Mansoura University Journal of
Agricultural Sciences 30(9): 5169–5180.
Fullerton RA, Stewart A and Slade EA, 1995.
Use of demethylation inhibiting
fungicides (DMIs) for the control of
onion white rot (Sclerotium cepivorum
Berk.) in New Zealand. New Zealand
Journal of Crop and Horticultural
Science 23: 121–125.
Gamliel A, Hadar E, and Katan J, 1987.
Microbial phenomena related to
increased growth response in solarized
soils and to monoculture systems. In:
Proceedings of 7
th
Congress of the
Mediter. Phytopatholology Union, Spain,
72 pp.
Greenberger A, Yogev A, Katan J, 1984.
Biological control in solarized soils.
Proceedings of Sixth Congress of the
Mediter. Phytopatholology Union, Cairo,
Egypt, 112–114 pp.
Hovius MHY, Goldman IL, 2004. Evaluation
of long-day onions for resistance to
white rot infection using greenhouse and
laboratory techniques. Journal of the
American Society for Horticultural
Science 129(2): 258–265.
Jackson KJ, Duff AA, O’Donnell WE, 1997.
Tebuconazole (Folicur) shows potential
in the control of white rot (Sclerotium
cepivorum) in garlic in subtropical
Queensland, Australia. 2
nd
International
Symposium on edible Alliaceae,
Adelaide, Australia, 42 pp.
Johnson LF, Cur EA, Bono JH, Fribouring
HA, 1959. Methods for studying soil
microflora plant disease relationships.
Minneapolis publishing Co. USA, 178
pp.
Kakvan N, Heydari A, Zamanizadeh HR,
Rezaee S, Nraghi L, 2013. Development
of new bioformulations using
Trichoderma and Talaromyces fungal
antagonists for biological control of
sugar beet damping-off disease. Crop
Protection 53(1): 80–84.
Kamaluddeen, Sobita Simon, 2013. Effect of
soil solarization, bio-agents and organic
composts on blast of paddy.
International Journal of Botany and
Research 3(4): 21–28.
Katan J, 1981. Solar heating (solarization) of
soil for control of soil borne pests.
Annual Review of Phytopathology, 19:
211–236.
Katan J, 1987. Soil solarization.
In: Innovative Approaches to Plant
Disease Control. Ed. John Wiley &
Sons, New York, USA, 77-105 pp.
Keinath AP, 1995. Reduction in inoculum
density 0of Rhizoctonia solani and
control of belly rot on pickling
cucumber with solarization. Plant
Disease 79: 1213–1219.
Khalifa MMA, Fetyan Nashwa AH, Abdel
Magid MS, El-Sheery NI, 2017.
Effectiveness of potassium silicate in
suppression white rot disease and
enhancement physiological resistance of
onion plants, and its role on the soil
microbial community. Middle East
Journal of Agriculture Research 6 (2):
376–394.
Khalifa MMA, Mahmoud Noher A, Abou-
Zeid NM, 2013. Performance of some
biofungicides on the most onion
economic diseases compared to
recommended fungicide in Egypt. I-
White rot disease control and
economical feasibility. Egyptian Journal
of Applied Sciences 28(1): 40–65.
Mahmoud Noher, 2018
46
Lifshitz R, Tabachnik M, Katan J, Chet I,
1983. The effect of sublethal heating on
sclerotia of Sclerotium rolfsii. Canadian
Journal of Microbiology 29: 1607–1610.
Mahdizadehnaraghi Razak, Asghar Heydari,
Hamid Reza Zamanizadeh, Saeed
Rezaee, Jafar Nikan, 2015. Biological
control of garlic (Allium) white rot
disease using antagonistic fungi-based
bioformulations. Journal of Plant
Protection Research, 55(2): 136–141.
Melero-Vara JM, Prados-Ligero AM,
Basallote-Ureba MJ, 2000. Comparison
of physical, chemical and biological
methods of controlling garlic white rot.
European Journal of Plant Pathology
106: 581–588.
Misaghi I, Grogan RG, 1969. Nutritional and
biochemical comparisons of plant-
pathogenic and saprophytic fluorescent
pseudomonads. Phytopathology 59:
1436–1450.
Mohamed, Hala A, 2012. Integrated control
of onion white rot disease. M.Sc. Thesis
Faculty of Agriculture, Moshtohor
Benha University, Egypt, 134 pp.
MSTAT-C, 1991. A Software Program for
the Design, Management and Analysis of
Agronomic Research Experiments.
Michigan State University, USA, 400 pp.
Ouf S, Ali AMI, Ibrahem AE, 2008. In vitro
evaluation of the biocontrol activity of
some biofungieides on Sclerotium
cepivorum. International Journal of
Agriculture and Biology 10(3): 241–248.
Pereira JCR, Chaves GM, Zambolim L,
Matsouka K, Acuña RS, Vale FXR Do,
1996. Control of Sclerotium cepivorum
by the use of vermicompost, solarization,
Trichoderma harzianum and B. subtilis.
Summa Phytopathologica 22: 228–234.
Plesofsky-vig, N, Brambl R, 1985. The heat
shock response of fungi. Experimental
Mycology 9: 187–194.
Pullman GS, DeVay JE,, Garber RH, 1981.
Soil solarization and thermal death: a
logarithmic relationship between time
and temperature for four soil borne plant
pathogens. Phytopathology 71: 959–964.
Reddy MS, Rahe JE, Levesque CA, 1992.
Influence of onion seed bacterization on
germination and mycosphere microflora
of Sclerotium cepivorum sclerotia.
Canadian Journal of Microbiology 38:
1135–1143.
Reino JL, Guerrero RF, Hernandez-Galan R,
Collado IG, 2008. Secondary
metabolites from species of the
biocontrol agent Trichoderma.
Phytochemistry Reviews 7(1): 89–123.
Rolf AO, Bakken LR, 1987. Vibility of soil
bacteria: optimization of plate counting
technique and comparison between total
counts and plate counts within different
size groups. Microbial Ecology 13: 59–
74.
Satour MM, Abdel-Rahim MF, El-Yamani T,
Radwan A, Rabinowitch HD, Katan J,
Grinstein A, 1989. Soil solarization in
onion fields in Egypt and Israel: short-
and long-term effects. Acta
Horticulturae 225: 151–159.
Satyal Prabodh, Craft Jonathan D, Dosoky
Noura S, William N Setzer, 2017. The
chemical compositions of the volatile
oils of garlic (Allium sativum) and wild
garlic (Allium vineale). Foods 6(63): 1–
10.
Stapleton JJ, DeVay JE, 1982. Effect of soil
solarization on populations of selected
soil borne microorganisms and growth
Mahmoud Noher, 2018
47
of deciduous fruit tree seedlings.
Phytopathology 72: 323–326.
Stapleton JJ, DeVay JE, 1984. Thermal
components of soil solarization as related
to changes in soil and root microflora
and increased growth response.
Phytopathology 74: 255–259.
Stapleton JJ, DeVay JE, 1986. Soil
solarization: a non-chemical approach
for management of plant pathogens and
pests. Crop Protection 5: 190–198.
Stapleton JJ, Quick J, DeVay JE, 1985. Soil
solarization: effect on soil properties,
crop fertilizers and plant growth. Soil
Biology and Biochemistry 17: 369–373.
Sundarum TK, 1986. Physiology and growth
of thermophylic bacteria. p. 75.
In: Thermophiles: General. Molecular,
and Applied: Microbiology. T. D.
Brock, ed. John Wiley and Sons, New
York, USA, 316 pp.
Ulacio-Osorio D, Zavaleta-Mejía E,
Martínez-Garza A, Pedroza-Sandoval A,
2006. Strategies for management of
Sclerotium cepivorum Berk. in garlic.
Journal of Plant Pathology 88(3): 253–
261.
