Minia J. of Agric. Res. & Develop.
Vol.(26) No.4 pp 587 -607 , 2006
OCCURRENCE OF BACTERIAL LEAF BLIGHT OF GERANIUM
(PELARGONIUM ODORATISSIMUM AIT.)
IN EGYPT
H. M. Abdalla, *.; M. E. Ismail*;
Heidi I.G. Abo-Elnaga** and A. A. Galal*
*Department of Plant Pathology, Faculty of Agriculture, Minia University.
** Department of Plant Pathology, Fac. of Agric., Assiut University.
Received 26 Nov. 2006
Accepted 26 Dec. 2006
ABSTRACT
During 2004 growing season, in Beni-Suef and El-Minia
governorates, Egypt, geranium (Pelargonium odoratissmum),
growers suffered from leaf blight in most growing areas.
Isolation and identification trials showed that the causal
agent was bacteria. Six bacterial isolates were infected to P.
odoratissmum leaves causing leaf blight and their
pathogenicity varied, as isolate G1 was the most pathogenic
and G6 was the weakest. The isolates reacted similarly with
the majority of the used identification tests and they were
closely to Pseudomonas syringae pv. syringae bacteria.
Pseudomonas syringae pv. syringae isolates G1, G2 and
G3 have had the ability to infect leaves of basil, P. zonale,
marjoram, pat marigold, spear mint and sunflower but they
failed to infect alocasia, carrot, cucumber and soybean
leaves.
Survival study indicated that Pseudomonas syringae pv.
syringae isolate G1 could survive in infected leaf tissues of P.
odoratissmum for 5 months at 20°C and 30°C.
Soaking P. odoratissmum cuttings in resistance elicitors
solutions acquired P. odoratissmum plants resistance against
Pseudomonas syringae pv. syringae infection. However,
protection of P. odoratissmum against P syringae pv.
syringae infection was varied with both tested chemicals and
isolates. All chemicals used had no antibacterial effects
towards P. syringae pv. syringae isolates used.
H. M. Abdalla et. al.
INTRODUCTION
Geranium (Pelargonium odoratissimum Ait.) is one of the most
important aromatic crops in Egypt. The ornamental geranium, is a
traditional ornamental plant largely cultivated in Europe and Northern
America (Alonso et al,. 2004). This valuable crop is subjected to
various diseases attacks which frequently induce losses in its
plantations (Pardo, 1993 and Buck and Jeffers, 2004). Geranium
plants are attacked by several diseases, i.e. viruses ( Nameth, 1993);
fungi, Botrytis cinerea and Pythium aphanidermatum, P. irregulare,
and P. ultimum (Pardo, 1993; Buck, 2004 and Moorman and Kim,
2004). Abdel-Gawad, (1978) stated that the growing areas of
geranium in El-Minia governorate began to decrease mainly due to
cuttings rot disease caused by Rhizoctonia solani and Fusarium
moniliforme. He also reported a sereious loses from basal stem rot of
geranium cuttings (P. odoratissimum).
In Egypt, only few studies have been carried out on geranium
diseases specially that caused by bacteria. However, bacteria
Xanthomonas campestris pv. pelargonii (Dunbar and Stephens, 1992
and Abdel –Naeem and Ismail 2005) and Ralstonia solanacearum
(Almeida et al., 2003) had been recorded as geranium invaders.
In Beni-Suef and El-Minia governorates, geranium, P.
odoratissimum, growers are suffered from leaf spot of geranium
causing a serious problem in most growing areas. Our recent
observations in different localities showed that the leaf spot of P.
odoratissimum was highly destructive and widely spread in other
areas. During March 2004, a serious disease attacking leaves of
geranium plants was observed. The disease caused a necrotic leaf spot
and the dead leaf tissues often torn and fall out. A preliminary survey
study showed that leaf spot/blight incidence was 30 and 20% with
severity 12 and 8% in Beni-Suef and El-Minia governorates,
respectively. Thus, the present work was conducted to, 1) isolate and
identify the causal organism(s), 2) test the ability of isolated bacteria
to infect leaves of various plants, 3) determine the survival of the
pathogen in diseased leaf tissues, 4) study the effect of some resistance
elicitors on bacterial growth in vitro and 5) use resistance elicitors for
controlling geranium leaf spot.
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Bacterial leaf blight of geranium
MATERIAL AND METHODS
mso aaoolnosnac nha sa noitalosI:
Leaf samples from naturally infected plants, showing leaf
blight symptoms (Fig. 1) grown at Dallas (Beni-Suef) and Maghagha
(El-Minia) during 2004 growing season were used for isolation. The
diseased samples were washed with tap water, surface disinfested for
2 min in 1.0% sodium hypochlorite, washed 3 times by sterile water,
and blotted dried. Small portion of disinfested leaves was then
macerated in a few amounts of sterile water using sterilized mortar
and pestle. The resultant suspension was allowed to stand for about 20
min then loopfuls were streaked onto a plate containing a nutrient
glucose agar medium (NGA). The inoculated plates were kept under
daily observation for 7 days at 25°C. Single colonies from the
developing growth were transferred by loop exhaustion in three
successive tubes with slanted NGA to obtain pure cultures. The
isolated bacteria were tested for pathogenicity, identification and other
tests. The obtained isolates were designated as G1- G6.
Pathogenicity tests:
Pathogenicity trials of the bacterial isolates were determined by
inoculating healthy appearance plants grown in the Experimental Farm
of Dept. Plant Pathol., Fac. Agric., Minia Univ.(all geranium, P.
odoratissimum, cuttings used throughout this study were kindly
provided by Dr. Rajaa T. Ali, Dept. Hort., Fac. Agric., Minia
University) The inocula of bacteria were performed by preparing
bacterial suspension of each isolate after it was adjusted to obtain
about 109 colony forming units (CFU) using Milton Roy
Spectrophotometer at 600nm, OD 0.1 (Goth and Webb, 1981).
Methods of inoculation:
Bacterial suspension of the tested isolates was prepared as
described above. Three methods of inoculation were applied as
follows: Five leaves from each plants were atomized with the bacterial
suspension to run off; the other leaves were dusted with carborundum
and then rubbed with a cotton tips that had been soaked in the
bacterial suspension, and the last method was carried out by
puncturing the leaves with sterile teeth pick stalks that bearing small
portion of 24 h old bacterial growth of the tested isolates. Control
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H. M. Abdalla et. al.
plants were similarly treated as described for each inoculation
methods by using bacterial free – sterile water, and then the inoculated
leaves were covered with plastic bags to keep high moisture for 24h.
The inoculated plants were observed for the development of the
disease symptoms. Number of plants showed water-soaked areas were
assessed 14 days after inoculation (Galal, 1999).
Re- isolation was made from the previously inoculated leaves
and compared with the original inocula. A second inoculation was
performed with re- isolated bacteria to confirm Kokhs postulates.
Disease assessment:
Leaf spot/blight severity was assayed using an arbitrary 0 to 5.0
scale where 0 = no symptoms, 1 = 1-25%, 2 = 26-50%, and 3 = 5175% infected area of leaves and 5 = 76%- completely blighted
geranium, P. odoratissimum, leaves. Disease severity index (DSI) was
calculated according to the methods of Vakalounakis (1990) as
follows:
DSI = ∑ d / (d max x n) x 100
Whereas: d is the disease rating possible and n is the total
number of geranium leaves examined in each replicate.
Identification of the pathogens:
The most pathogenic bacterial isolates, e.g. G1, G2 and G3
were identified by studying their morphological, physiological and
biochemical characters listed in Table 2 recommended by Stapp
(1961), Breed et al. (1974), Lelliott and Stead (1987) and Klement et
al. (1990).
Ice nucleating ability of the isolated bacteria (In Vitro):
Ice nucleating ability (INA) of the bacterial isolates was
examined according to the method described by Paulin and Luisetti
(1978). Cultures grown on King,s medium B for 24 h at 22°C were
used for ice nucleation activity (INA) as described by Legard and
Schwartz (1987). Five milliliters from the initial suspension of each
isolate were immersed for 5 min in a cooled bath routinely at -5°C
(112 g NaCl /1000 ml distilled water). Positive results were recorded
if the bacterial suspension frozen within 5 min. Tubes with 5 ml NaCl
were used as control.
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Bacterial leaf blight of geranium
Hypersensitive reaction (HR) :
This was performed according to Klement et al., (1964). A
bacterial suspension was prepared from each isolate proved
pathogenic to geranium, P. odoratissimum, plants. The mesophyll
tissue of the leaf lamina of tobacco plants (Nicotiana tabacum was cv.
Burley) was injected with a bacterial suspension (about 1X109
CFU/ml) prepared by suspension 24 h old bacterial culture in
appropriate volume of sterile distilled water. Bacteria cell suspension
was then injected into interveinal parenchymatous tissue by sterile
hypodermic syringe. A separate leaf lamina was injected with sterile
distilled water as a negative control. The injected leaves were labeled
and the plants were maintained at room temperature and observed
daily.
Host range:
The most pathogenic isolates G1, G2 and G3 were singly
inoculated into the leaves of 10 plant species as listed in Table 3. Five
pots (5plant/pot) were used in each treatment. Inoculation was carried
out using wound inoculation method as described above. Blight
severity was assyed as described above.
Survival of P. syringae pv. syringae:
For assaying purpose, content of each bag 0.5 g (fresh weight)
diseased leaves was packed in poured nylon bags for assaying P.
syringae .pv. syringae according to the method described by Parashar
and Leben (1972). Three bags were set up in a randomized complete
block in two treatments (with CaCl2 and another without) in which the
nylon bags were put at 3 different degrees of temperature (10, 20 and
30°C). Detection for the presence of the pathogen was tested monthly
as previously described.
Effect of chemicals on bacterial growth In Vitro:
Erlenmeyer flasks (250 ml), each containing 100 ml of King,s
medium B solidify medium was autoclaved and cooled to about 45°C.
Stock solutions of the antioxidants concentrations were added to the
medium, to obtain the desire concentration, shaked vigorously and
poured into a sterile plates medium. Fresh bacterial suspension, 24 h
old, was washed from the solid KB medium and adjusted to 1X 108
CFU/ml by using Milton Roy spectrophotometer at 600 nm (OD
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H. M. Abdalla et. al.
0.1). From the bacterial suspension 100 µl was inoculated into the
plates and the bacteria was spread on the surface of the solid media in
Perti dishes by a glass rod then, incubated at 25°C.
Possible management of bacterial leaf spot using some resistance
elicitors:
Unless otherwise stated, trials were conducted in the
greenhouse using growing geranium, P. odoratissimum, in plastic bags
(5 cuttings per each) and five bags were used per treatment and each
experiment repeated twice. Five antioxidant compounds, i.e., ascorbic
acid (AA), citric acid (CA), propylgallate (PG), salicylic acid (SA).
Beside these compounds the analoge of SA pathway compound which
named benzothiodiazole (BTH) or acibenzolar-S-methyl (ABM) that
used as resistance elicitor under commercial name bion (in Europe) or
actiguard (in USA) were tested. Certain chemicals were dissolved in
distilled water individually to obtain solutions with 2 concentrations
100 and 200 ppm. Healthy appearance cuttings of geranium plants
were surface disinfected by immersing them in 1% sodium
hypochlorite for 2 min then washed thoroughly three times by sterile
distilled water and soaked in different certain test solutions with
various concentrations for 24 h. Control cuttings were soaked in
distilled water. After that, treated cuttings were sowed in plastic bags
contained sterilized soil as mentioned above. Two months old plants
were subjected for inoculation with Pseudomonas syringae pv.
syringae isolates G1, G2 and G3 similarly as described in
pathogenicity test. Fourteen days after inoculation disease severity
was assayed as described above.
Statistical analysis:
Standard deviation (SD) was calculated according to the
methods described by Gomez and Gomez (1984) to compare the
variances between treatments.
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Bacterial leaf blight of geranium
RESULTS AND DISCUSSION
Isolation and identification of the causal pathogen:
Six bacterial isolates (designated as G1- G 6) of motile, rod
shaped and Gram negative bacteria were isolated, on KB medium
from the leaves of six different geranium (P. odoratissimum) plants,
grown at Dallas (Beni-Suef) and Maghagha (El-Minia), showing a
typical leaf blight symptoms. Pathogenicity trial showed that three
isolates of the pathogen under investigation, were highly pathogenic
since they infected geranium (P. odoratissimum) plants causing 80 to
100% leaf spot severity, whereas, the other three isolates were weakly
pathogenic when tested on geranium leaves (Table 1). Isolate G1 was
the most pathogenic (Fig.1), inducing 100% infection, 5-7 days after
inoculation using wounding method than other methods (puncturing
and spray). Under the same condition, isolate G6 gave the least leaf
spot severity (30%). Pathogenicity of isolates was varied with
inoculation methods, wounding leaves by carborandum showed the
highest leaf spot severity followed by puncture inoculation method.
However, the least leaf spot severity was expressed by spraying
bacterial suspension without wounding. The weak pathogenic isolates
G4, G5 and G6 failed to cause leaf spot under spray without wounding
inoculation method.
Table 1: Disease severity on 60-day-old healthy geranium (Pelargonium
odoratissimum) leaves after inoculation with six bacterial
isolates.
Isolates and their
Severity of infection, according to the
sources
method inoculation,%n
Puncture
Spray
Wounding
G1 (Maghagha)
50 ± 2.4
30 ± 1.2
100
G2 (Maghagha)
50 ± 3.6
25 ± 1.4
85 ± 4.6
G3 (Dallas)
40 ± 2.2
15 ± 1.2
80 ± 4.3
G4 (Dallas)
20± 1.6
0.0
40 ± 2.4
G5 (Maghagha)
10± 1.2
0.0
40 ± 1.2
G6 (Dallas)
10 ± 1.4
0.0
30 ± 1.8
Control (uninoculated)
0.0
0.0
0.0
Data are means of 5 replicates  SD
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H. M. Abdalla et. al.
Fig.1 : Leaves of geranium Pelargonium odoratissimum exhibiting leaf
blight symptoms, resulting from natural infection (A) and
artificial inoculation with P. syringae pv. syringae isolate G1 to
leaves of geranium, P. odoratissimum (B) and to basil plants,
Ocimum basilicum (C).
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Bacterial leaf blight of geranium
Identification of pathogenic isolates:
The morphological and physiological properties of all isolates
are presented in Table 2. Data show that these isolates grew well on
nutrient glucose (1.5% agar) at 25°C. Colonies were whitish greyraised butyrous round 1.5-2 mm in diameter, while colonies were
whitish and smooth on potato dextrose agar (PDA) medium. All
isolates produced green fluorescent water–soluble pigment on King,s
medium that fluoresces blue green under ultra violet light. All tested
bacteria were positive for hypersensitive reaction (HR) when tested on
tobacco (Nicotiana tabacum cv. Burley) leaves. Furthermore, all
tested isolates of bacteria were motile, rods. Gram negative, strict
aerobic, catalase positive, oxidase negative, nonsporing, indicating
that all bacterial isolates were Pseudomonas syringae as reported by
other workers (Breed et al., 1974; Piening, 1976; Stancescu and
Severin, 1983, Bradbury, 1986 and Lelliott and Stead, 1987). Data
showed that the isolates reacted similarly with the majority of the used
tests. In addition, all bacterial isolates were positive for ice nucleation
activity test which considered a distinguishable test for Pseudomonas
syringae pv. syringae (Legard and Schwartz, 1987; Klement et al.,
1990; El-Sadek et al., 1992 and Galal, 1999 ). Accordingly the
characters of the isolates of bacteria are closely related to bacteria
Pseudomonas syringae pv. syringae Van Hall.
Host range:
Data indicated that Pseudomonas syringae pv. syringae isolates
G1, G2 and G3 had potential hosts beside geranium, P. odoratissmum
(Table 3). They were able to infect basil, sunflower, geranium
(Pelargonium. Zonale), pat marigold, spear mint and marjoram. No
symptoms appeared on leaves of soybean, cucumber, alocasia, and
carrot when inoculated by all tested bacterial isolates. However,
Pseudomonas syringae pv. syringae has a broad host range (Lelliott
and Stead, 1987; Tripepi and George, 1991 and El-Sadek et al., 1992
and Galal, 1999).
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H. M. Abdalla et. al.
Table 2: Morphological, biochemical and physiological characters
of geranium, Pelargonium odoratissimum, leaf blight isolated bacteria
Test
Shape of cell
Motility
Gram reaction
Pigment on CaCO3 agar
Sporulation
Rot potato slices
Aerobiosis
Gelatin liquefication
Starch hydrolysis
Aesculin hydrolysis
Levan production
Indole formation
Ammonia production
H2S production
Oxidase (Kovacs)
Nitrate reduction to nitrite
Tolerance to 4,5% NaCl
Catalase
Optimun pH
Maximum temperature
Optimum temperature
Utilize of sugars from
Arabinose
Galactose
Glucose
Fructose
Salicin
Lactose
Utilize of sugars from
Arabinose
Galactose
Glucose
Fructose
Salicin
Lactose
Maltose
Mannitol
Mannose
Glycerol
Trehalose
Sucrose
Xylose
HR
Ice nucleation
Results
G3
G4
Rod
Rod
+
+
D.G.F.P
D.G.F.P
aerobic
aerobic
±
±
+
+
+
+
+
+
5.0-8.0
37°C
27-30°C
+
+
G1
Rod
+
D.G.F.P
aerobic
+
+
+
+
G2
Rod
+
D.G.F.P
Aerobic
±
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
G5
Rod
+
D.G.F.P
aerobic
±
+
+
+
G6
Rod
+
D.G.F.P
Aerobic
±
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+ = Positive reaction, - = negative reaction, ± = Variable reaction, ? = not recorded
and DGFP= diffusible green fluorescent pigment. Each test was carried out 2 times
in triplicates.
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Bacterial leaf blight of geranium
Table 3: Reaction of different host plants to three isolates of geranium,
P. odoratissmum, leaf blight bacteria.
Host plant
Leaf blight severity caused by isolate,
G1
0.0
65±4
0.0
0,0
60±5
70±5
65±4
60±4
0.0
65±3
Alocasia (Alocasia sp.)
Basil (Ocimum basilicum)
Carrot (Dauncus carota cv. Balady)
Cucumber (Cucumis sativus)
Geranium (Pelargonium. zonale)
Marjoram (Marjoram hortensis)
Pat marigold (Calendula officinalis)
spear mint (Mentha spicata)
Soybean (Glycine max cv. Giza 21)
Sunflower (Helianthus annuus.)
Data are means of 5 replicates ± SD
G2
0.0
40±3
0.0
0,0
45±4
45±4
50±3
45±3
0.0
45±2
G3
0.0
40±3
0.0
0.0
40±4
45±4
45±3
40±3
0.0
40±4
Survival of Pseudomonas syringae pv. syringae:
The leaf surface environment is considered to be a stressful
habitat for bacterial populations due to the limitations of nutrients and
water availability, changes in temperature, and exposure to UV and
visible irradiation. Even if the environmental conditions on the leaf
surface are not extreme per se, epiphytic bacteria have to cope with
constantly changing conditions during the course of the day and
through leaf development. Despite this, a large diversity of
saprophytic and plant- pathogenic bacterial species are able to grow
and maintain large population sizes on leaf surface under these harsh
environmental conditions (Beattie and Lindow, 1995; 1999 and
Monier and Lindow, 2003).
Survival of Pseudomonas syringae pv. syringae varied with
different temperatures and also with CaCl2 (Table 4). Bacterium could
survive in infected leaf tissues of P. odoratissmum for 150 days at 20
and 30°C while only for 120 days at 10°C. These results coincided
with those reported by Abdel-Gawad et al (2002) who suggested that
diseased plant tissues left after fall season are a source of inoculum in
the soil for spring season for 9 months after burial. Wilson et al.
(1999) reported that phytopathogenic bacteria survive in the
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H. M. Abdalla et. al.
phyllospheres of both host and non host which are greater on
compatible than on incompatible or non host plants which may be
involved in colonization of healthy leaves under some environmental
conditions. Wilson and Lindow (1993) found that cells of
Pseudomonas syringae recovered from bean leaf surfaces and then
reapplied to leaves subsequently exposed to stressful field conditions
survived much better than cells grown in either solid or liquid culture
media.
Possible management of geranium leaf spots caused by P. syringae
pv. syringae:
Chemical soaking of geranium, (P. odoratissmum) cuttings was
significantly induced resistance in geranium plants against
Pseudomonas syringae pv. syringae infection (Table 5) when the
treated cuttings were sowed in noninfested soil from the test bacterial
isolates. Induced resistance varied with chemical compounds, their
concentration and bacterial isolates. Increasing concentration
enhanced geranium resistance by all chemicals used. Highest
protection against infection was pronounced by using BTH at 200 ppm
concentration 95, 94 and 93,3% protection against infection with P.
syringae pv. syringae isolates G1, G2 and G3, respectively, followed
by PG and AA.
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Bacterial leaf blight of geranium
Table 4: Survival of Pseudomonas syringae pv. syringae isolate G1
in geranium tissues at 10, 20 and 30°C.
Temp.
10°C
20°C
30°C
Storage
With CaCl2 +
Without CaCl2 +
period (day)
infected tissues
infected tissues
0.0
3.5X 10 7
3.5 X 10 7
30
4.5 X 106
3.2 X 106
60
2.9 X105
3.6 X105
90
2.1 X 103
2.8 X 103
120
8 X 102
7.4 X 102
150
-
-
180
-
-
0.0
4.6 X 107
3.9 X 107
30
1.1 X 107
3.1 X 107
60
7.2 X 106
6.4 X 106
90
2.4 X105
2.9 X105
120
3 X104
4.3 X104
150
1.3 X 102
2.2 X 102
180
-
-
0.0
3.9 X107
4.3 X107
30
2.8 X107
3.2 X107
60
5 X 106
5.7 X 106
90
4.6 X 105
5 X 105
120
2.1 X 104
2.9 X 104
150
1.1 X 102
2.1 X 102
180
-
-
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H. M. Abdalla et. al.
Table 5: Effect of chemicals cuttings soaking on leaf blight severity (%)
to geranium plants P. odoratissmum inoculated with
Pseudomonas syringae pv. syringae isolate G1
Conc.
Chemicals
Ascorbic acid
Citric acid
Salicilyic acid
Benzothiodiazole
Propylgallate
Control
Blight severity,
(ppm)
G1
%
protection
G2
%
protection
G3
%
protection
100
40±10
60.0
25±6.7
70.5
20±5
73.3
200
20±5
80.0
20±5
76.4
10±1.2
76.6
100
50±5
50.0
40±8.7
52.9
30±5
60.0
200
20±5
80.0
10±1.5
85.0
30±8.7
60.0
100
40±5.7
60.0
20±5
76.4
35±10
53.6
200
30±8.7
70.0
20±5
76.4
20±5
73.3
100
25±5.4
75.0
25±5.4
70.5
10±2.8
76.6
200
05±1
95.0
05±1
94.0
05±1.5
93.3
100
30±8.7
70.0
20±5
76.4
20±5
73.3
200
20±5
80.0
10±1.5
85.0
10±1.5
76.6
0.0
100
00.0
85
00.0
75
00.0
* Data are means of 3 replicates ± SD.
Effect of some resistance elicitors on the growth of bacteria:
Recent work showed no antibacterial effects for all resistance
elicitors against growth of all bacterial isolates tested (Table 6 ). On
the base of the obtained data we can assume that all resistance elicitors
have the ability to activate resistance mechanism(s) in plant per se
previously described. Inducing systemic resistance in the host plant
becomes a good target for minimizing disease incidence/severity with
least cost and without environmental pollution (Elad, 1992; Galal and
Abdou, 1996; Quintanilla and Brishammar, 1998 and Galal et al.
2003). However, acibenzolar-S methyl (ABM), a benzothiadiazole
(BTH), were released in Europe as BION (Syngenta Ltd., Basel,
Switzerland) and in the United States as Actigard (Syngenta Crop
Protection Inc., Greensboro, North Carolina). ABM was reported to
induce resistance in wheat against fungal pathogens (Görlach et al.,
1996), in bean against bacterial and fungal infections (Abo-Elyousr,
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Bacterial leaf blight of geranium
2006 and Siegrist et al., 1997.), and in tobacco and Arabidopsis spp.
against fungal, bacterial, and viral infections (Cole, 1999). ABM
complies with the definition of a systemic acquired resistance (SAR)
inducer: it gives protection to the same spectrum of pathogens, causes
the expression of the same molecular and biochemical markers (e.g.,
pathogenesis related proteins) as biological inducers, and does not
have direct antimicrobial activity (Kessmann et al., 1994). Resistance
inducers are not necessarily a replacement for traditional fungicides
and bactericides. Its use in conjunction with or alternated with these
pesticides may lead to a reduction of the number of applications and
perhaps dose rate (Lyon and Newton, 1999). It might also help to
extend the durability of resistance in cultivars with genes for
resistance to specific pathogen races (Romero et al., 2001).
Table 6:
Effect of some chemicals on bacterial growth of
Pseudomonas syringae pv. syringae isolate G1
Chemicals
Ascorbic acid
Citric acid
Salicilyic acid
Benzothiodiazole
Propylgallate
Control
No. of colonies /plate to isolate
Conc.
(ppm)
G1
G2
G3
100
200
100
200
100
200
100
200
100
200
0.0
240 ± 2.5
238 ± 1.0
237 ± 1.0
247 ± 2.0
231 ± 1.0
258 ± 1.5
189 ± 2.0
231 ± 1.0
221 ± 1.5
234 ± 1.0
246 ± 1.5
244 ± 1.0
235 ± 2.6
234 ± 2.3
242 ± 1.0
234 ± 2.1
258 ±1.0
220 ± 1.5
245 ± 0.57
230 ± 1.0
240 ± 1.0
254 ± 1.0
245 ± 0.58
242 ± 0.58
254 ± 1.0
244 ± 1.0
238 ±1.0
243 ± 1.5
220 ± 1.0
240 ±1.5
234 ± 1.0
238 ± 1.5
250 ± 1.5
Data are means of 3 replicates SD.
-601-
H. M. Abdalla et. al.
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‫‪Bacterial leaf blight of geranium‬‬
‫ظهور‪n‬مرض‪n‬اللفحه‪n‬البكتيريه‪n‬للعتر‪n‬في‪n‬مصر ‪n‬‬
‫‪n‬‬
‫حربي‪n‬مطاريد‪n‬عبد‪n‬هللا‪nn-nn*n‬ممدوح‪n‬عويس‪n‬اسماعيل*‪n n‬‬
‫هايدى‪n‬إبراهيم‪n‬جبر‪n‬أبو‪n‬النجا**‪n-n‬أنور‪n‬عبد‪n‬العزيز‪n‬جالل* ‪n‬‬
‫قسم أمراض النبات‪ -‬كلية الزراعة‪ -‬جامعة المنيا‪ -‬المنيا *‬
‫قسم أمراض النبات – كلية الزراعة – جامعة أسيوط **‬
‫لوحظ في محافظتي بني سويف والمنيا اثناء موسم ‪ 4002‬م أعراض تبقع‬
‫أوراق العتر في معظم المناطق المزروعة‪ .‬أوضحت محاوالت العزل والتعريف ان‬
‫المسبب هو بكتريا حيث تم عزل ‪ 6‬عزالت بكتيريه كانت كلها تصيب أوراق نباتات‬
‫العتر ولكنها اختلفت في قدرتها المرضية‪ .‬أوضحت النتائج ان عزله ‪ G1‬كانت‬
‫شديدة القدرة المرضية بينما كانت العزلة ‪ G6‬ضعيفة القدرة المرضية‪.‬‬
‫ أظهرت االختبارات الفسيولوجية والبيوكيميائية ان عزالت ‪ G3 ،G2 ،G1‬ذات‬‫القدرة المرضية العالية كانت متشابهه في التعريف الى بكتريا ‪Pseudomonas‬‬
‫‪ syringae pv. syringae.‬سيدوموناس سيرنجى طرز ممرض سيرنجى‬
‫ أظهرت دراسة المجال العوائلي ان العزالت ‪ G3 ،G2 ،G1‬لها القدرة على اصابة‬‫أوراق الريحان والبالرجونيم والبردقوش واألقحوان والنعناع وعباد الشمس بينما فشلت‬
‫العزالت في اصابة أوراق األلوكاسيا والجزر والخيار وفول الصويا‪.‬‬
‫ بينت الدراسة ان عزلة ‪ G1‬تستطيع البقاء في االنسجة المصابة لنباتات العتر لمدة‬‫‪ 5‬شهور على درجة ‪40،00‬م‪. o‬‬
‫ اكتسبت نباتات العتر مقاومة عند نقع العقل في محاليل محفزات المقاومة ضد مرض‬‫التبقع البكتيري واختلفت النتائج على حسب نوع الكيماويات والعزالت المختبرة‪.‬‬
‫ أظهرت الدراسة ايضاً ان مقاومة نباتات العتر للبكتريا اختلفت مع المواد المستخدمة‬‫وكذلك باختالف العزالت حيث كانت كل المواد الكيماوية محل الدراسة ليس لها أي‬
‫تأثير مضاد على نمو البكتريا نفسها‪.‬‬
‫‪-607-‬‬