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Effect of Fungal Infection and the Application of the Biological Agent EM 1™ on the Rate of Photosynthesis and Transpiration in Pea (Pisum Sativum L.) Leaves

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Abstract

Field experiments conducted during the years 2003-2005 showed that the rate of photosynthesis and transpiration decreased as a result of pea infection by Peronospora viciae. Foliar application of effective microorganisms (EM) combined with chemical control increased the rate of photosynthesis in pea, while other methods of EM application reduced net photosynthesis values (An). Chemical control and seed dressing with the tested biological agent caused a significant decrease in molar transpiration (E) values, compared to the control treatment. Soil application of EM contributed to inhibiting fungal pathogen infestation on pea plants.
POLISH JOURNAL OF NATURAL SCIENCES
Abbrev.: Pol. J. Natur. Sc., Vol 23(1): 35-47, Y. 2008
DOI 10.2478/v10020-008-0003-5
EFFECT OF FUNGAL INFECTION
AND THE APPLICATION OF THE BIOLOGICAL AGENT
EM 1
TM
ON THE RATE OF PHOTOSYNTHESIS
AND TRANSPIRATION IN PEA (PISUM SATIVUM L.)
LEAVES
Adam Okorski, Jacek Olszewski, Agnieszka Pszczółkowska,
Tomasz Kulik
University of Warmia and Mazury in Olsztyn
Chair of Diagnostics and Plant Pathophysiology
Abstract
Field experiments conducted during the years 2003-2005 showed that the rate of photosynthesis
and transpiration decreased as a result of pea infection by Peronospora viciae. Foliar application
of effective microorganisms (EM) combined with chemical control increased the rate of photosyn-
thesis in pea, while other methods of EM application reduced net photosynthesis values (An).
Chemical control and seed dressing with the tested biological agent caused a significant decrease
in molar transpiration (E) values, compared to the control treatment. Soil application of EM
contributed to inhibiting fungal pathogen infestation on pea plants.
K e y w o r d s: rate of photosynthesis, rate of transpiration, fungal pathogens, biological control.
WPŁYW INFEKCJI GRZYBOWEJ ORAZ APLIKACJI BIOLOGICZNEGO PREPARATU
EM 1
TM
NA INTENSYWNOŚĆ FOTOSYNTEZY I TRANSPIRACJI LIŚCI GROCHU
SIEWNEGO (PISUM SATIVUM L.)
Adam Okorski, Jacek Olszewski, Agnieszka Pszczółkowska, Tomasz Kulik
Uniwersytet Warmińsko-Mazurski w Olsztynie
Katedra Diagnostyki i Patofizjologii Roślin
S ł o w a k l u c z o w e: fotosynteza, transpiracja, patogeny grzybowe, biologiczna ochrona roślin.
Address: Adam Okorski, Uniwersity of Warmia and Mazury, Plac Łódzki 6, 10-727 Olsztyn, Poland,
phone: 089 523 34 92, e-mail: adam.okorski@uwm.edu.pl
Abstrakt
W badaniach polowych, przeprowadzonych w latach 2003-2005, stwierdzono zmniejszenie tempa
fotosyntezy i transpiracji na skutek infekcji grochu patogenem Peronospora viciae. Stosowanie
nalistne EM w połączeniu z ochroną chemiczną zwiększało intensywność fotosyntezy grochu,
natomiast inne sposoby aplikacji tego preparatu ograniczały jej wartość netto (An). Wartości
wskaźnika transpiracji molowej (E) po stosowaniu ochrony chemicznej oraz zaprawianiu nasion
preparatem biologicznym były istotnie niższe niż w obiekcie kontrolnym. Stosowanie doglebowe
preparatu biologicznego EM ograniczało występowanie patogenów grzybowych na roślinach.
Introduction
The photosynthetic capacity of plants is affected by abiotic and biotic stress
factors. Infections cause leaf blade damage which leads to a decrease in the rate
of photosynthesis, disappearance of chlorophyll and an increase in the rate
of respiration (S
CHOLES 1992). It is assumed that at an advanced stage
of a disease the rate of photosynthesis may be reduced by 75% (G
RZESIUK et al.
1999). A decrease in the rate of photosynthesis results from water unbalance
in the plant, changes in the structure of mesophyll cells, a reduction in
the number of chloroplasts and changes in their structure, an increase in the
concentration of carbohydrates, and a decrease in the concentration of CO
2
in leaf tissues around the lesion (PINKARD,MOHAMMED 2006). The process
of photosynthesis may also undergo certain modifications in consequence of
reduced activity of ribulose 1.5-biphosphate (RuBP) and ribulose 1.5-biphos-
phate carboxylase/oxygenase (RubisCO) (M
CELRONE,FORSETH 2004). The rate
of photosynthesis usually increases in the first phase of pathogenesis, but then
the rate of biochemical reactions involved in photosynthesis decreases rapidly.
The inhibition of photosynthesis is directly proportional to pathogen virulence
(P
INKARD,MOHAMMED 2006).
Apart from photosynthesis, infections may also modify other physiological
processes taking place in the plant. The metabolic activity of leaf cells increases
from the moment of infection, which is usually followed by an increase in
respiratory rate (B
ASSANEZI et al. 2001). The rate of transpiration changes as
well it may increase or decrease, depending on the mode of infection
(S
HTIENBERG 1992, BASSANEZI et al. 1997). An increase in the rate of transpira-
tion is caused by cuticle damage in infected leaves and damage to stomata due
to which they remain open, as well as by increased permeability of cell
membranes (B
ASSANEZI et al. 2002). A decrease in the rate of transpiration may
be a consequence of stomatal closure and a reduction in air volume contained
in plant tissues (resulting from the presence of hyphae), as well as of
hypertrophy of the mesophyll tissue, clogging of conducting tissues and
defoliation (B
ASSANEZI et al. 2002).
Adam Okorski et al.36
Under natural conditions, 12 to 54% of carbon taken in by plants during
photosynthesis is released by the root system, which stimulates the activity
of soil microbes (L
YNCH,WHIPPS 1990). The activity of rhizosphere microorgan-
isms is closely related to plant metabolism. They affect nutrient metabolism in
the soil and root formation. Increased availability and uptake of minerals have
a direct impact on photosynthesis. Rhizosphere microbes promote and stimulate
nutrient uptake and transport in the plant (E
L-SHATNAWI,MAKHADMEH 2001).
Increasing microbial diversity of soils improves the overall health and producti-
vity of plants. The lack of chemical control may result in excessive growth
of pathogenic fungi, which in turn substantially decreases the yield and deterio-
rates its quality (S
ADOWSKI et al. 2006). Therefore, biological disease control is
often applied as an alternative or in addition to chemical crop protection. The
effectiveness of biological and microbiological agents used as biofertilizers could
be increased by combining cultures of various specific antagonists (D
AVELOS et
al. 2004). Microbial inoculants (effective microorganisms) consist of around 70
species of microorganisms belonging to five groups, namely lactic acid bacteria,
photosynthetic bacteria, actinomycetes, yeast fungi and filamentous fungi (V
AL-
ARINI
et al. 2003). The application of EM has a beneficial effect on soil texture
and quality (K
HALIQ et al. 2006). In Poland the biopreparation EM
TM
is
registered as a soil enhancer recommended for use in ecological farming
(Certificate of Conformity no. Z/13/PR-20001/03/BP). It has been approved for
use by the National Institute of Hygiene, and proven safe in terms of human and
environmental health (Certificate no. PZH/HT-1448/2002).
The aim of the present study was to determine the effect of infections by
fungal pathogens and different methods of EM application on the rate
of photosynthesis and transpiration in pea under field conditions. The effec-
tiveness of EM in controlling pea diseases was also estimated.
Materials and Methods
Field investigations were conducted during the years 2003-2005 at the
Research and Experimental Station in Tomaszkowo near Olsztyn (NE Po-
land). An exact experiment was established on brown soil of quality class IVa
and good rye complex (2003) developed from silt, brown soil of quality class IVa
and good rye complex (2004) developed from medium silty loam, and brown soil
of quality class IIIb and very good rye complex (2005) developed from light
loam. Pea was grown with winter triticale (first and third year of the study)
and spring barley (second year) as a fore crop. The experiment was performed
in a randomized split-plot design, in four replications. Plot area was 16 m
2
.
The experimental factor was the method of EM application, i.e.:
Effect of Fungal Infection... 37
1. control treatment (no effective microorganisms or crop protection
chemicals);
2. chemical control (seed dressing T, fungicide Rovral Flo 250 SC, insecti-
cide Owadofos 540 EC, herbicide Basagran 480 SL);
3. soil application of EM combined with chemical control;
4. seed dressing with EM combined with chemical control;
5. foliar application of EM combined with chemical control;
6. soil application of EM, seed dressing with EM and foliar application
of EM.
Prior to soil application, effective microorganisms were proliferated as
recommended by the manufacturer (Greenland). A 0.1% solution of effective
microorganisms (1 dm
3
water: 1 cm
3
EM: 1 g saccharose) was stored in the dark
at a temperature of around 20
o
C for 14 days. Wet seed dressing with a 0.2% EM
solution was carried out for 30 min. The dose of EM solution used for soil and
foliar application was 200 dm
3
ha
-1
.
Gas exchange parameters
The rate of net photosynthesis An (µmol CO
2
m
-2
s
-1
) and the rate of molar
transpiration E (mmol H
2
Om
-2
s
-1
) were measured over the growing season,
from the beginning of flowering to pod setting, using a Li-Cor 6400 gas
analyzer (Portable Photosynthesis System, Licor, Lincoln, NB, USA). Read-
ings were taken at several-day intervals on leaves of the medium storey. Each
measurement was repeated 10 times.
Health of pea plants
The health status of the aboveground parts of pea plants was estimated at
the flowering stage, using the modified Hillstrand and Auld scale (1982): 0 – no
disease symptoms, 1 infection rate of 1-10%, 2 infection rate of 11-20%,
3 infection rate of 21-30%, 4 infection rate of 31-40%, 5 infection rate of
41-60%, 6 infection rate of 61-80%, 7 infection rate of 81-90%, 8-9
infection rate of 91-100%. The results provided a basis for calculating the
infection index (II), as described by McKinney
ACICOWA 1969).
Statistical analysis
The results were processed statistically by analysis of variance (ANOVA)
using STATISTICA software (Data Analysis Software System, ver. 6, StatSoft,
Adam Okorski et al.38
Inc. 2003 www.statsoft.com). The significance of differences between
mean values was estimated by Duncan’s test (p = 0.05 for infection index,
p = 0.01 for gas exchange parameters). The strength of linear relationships
between variables was determined by Pearson correlation analysis. The
coefficient of Pearson correlation (R) (p = 0.05) was calculated with the
use of STATISTICA 6.1.
Results
Pea Fusarium wilt was observed each year, but its severity was greater
in 2003 and 2005, when the infection index reached 8.0% and 8.3% respectively
(Table 1). In 2004 disease intensity was substantially lower (II = 4.8%). Pea
plants were also attacked by pathogens causing ascochytosis (Table 2, Table 3).
Its greater severity was observed in 2004, when infections rates reached 18.8%
for leaves and 7.3% for pods. Symptoms of downy mildew (Peronospora viciae)
were noted only in 2005 (Table 4). The incidence of all three diseases was
significantly affected by the method of EM application. The highest intensity
of Fusarium wilt was recorded in the control treatment (II = 11.1%) (Table 1),
while the lowest in plots where effective microorganisms were applied without
chemical control (II = 5.3%) and where spraying with EM was combined with
chemical control (II = 5.4%). The disease was also effectively controlled in
chemically-protected plots (II = 5.8%). In the case of downy mildew the highest
infection rates were recorded in the control treatment (II = 5.7%) (Table 4),
while the lowest in plots where soil application of EM was combined with
chemical protection (II =4.3%), which enabled to reduce disease severity by
24.6%, compared to the check. The intensity of ascochytosis was also
the highest in the control treatment, with regard to both pea leaves
Table 1
The occurrence of Fusarium root (Complex of Fusarium spp.) on pea (av. of II significant, %)
Year
2003 2004 2005
Experimental
combination
Average
K** 10.5 7.0 15.8 11.1
G 9.00 3.75* 6.75* 6.5*
Z 8.75 7.75 8.00* 8.2*
O 5.75* 4.50 6.00* 5.4*
GZO 7.00* 2.00* 6.75* 5.3*
FIH 7.00* 4.00* 6.50* 5.8*
Average 8.0 4.8* 6.5
* average of II significant at α = 0.05
K** control, G soil treated with Effective Microorganisms (EM), Z seeds treated with EM,
O foliage treated with EM, GZO – soil, foliage and seeds treatment with EM, FIH pesticide control
Effect of Fungal Infection... 39
Table 2
The occurrence of Ascochyta Complex (Ascochyta pisi, Mycosphaerella pinodes, Phoma medicaginis
var. pinodella) on leaf pea (av. of II significant, %)
Year
2003 2004 2005
Experimental
combination
Average
K** 0.0 26.5 16.8 14.4
G 0.0 12.75* 17.0 9.9*
Z 0.0 21.25* 13.8 11.7*
O 0.0 23* 13.0* 12.0*
GZO 0.0 11* 10.25* 7.1*
FIH 0.0 18.5* 15.8 11.4*
Average 0.0* 18.8 14.4*
* average of II significant at α = 0.05
** description under Table 1
Table 3
The occurrence of Ascochyta pod spot (Ascochyta pisi, Mycosphaerella pinodes, Phoma medicaginis
var. pinodella) (av. of II significant, %)
Year
2003 2004 2005
Experimental
combination
Average
K** 0.0 11.75 7.3 6.3
G 0.0 2.50* 4.25* 2.3*
Z 0.0 9.25* 2.25* 3.8*
O 0.0 11.0 3.50* 4.8*
GZO 0.0 3.00* 2.50* 1.8*
FIH 0.0 6.50* 3.00* 3.2*
Average 0.0* 7.3 3.8* 7
* average of II significant at α = 0.05
** description under Table 1
Table 4
The occurrence of downy mildew (Peronospora viciae) on pea leaf (av. of II significant, %)
Year
2003 2004 2005
Obiekt Average
K** 0.0 0.0 17.0 5.7
G 0.0 0.0 12.75* 4.3*
Z 0.0 0.0 14.50* 4.8
O 0.0 0.0 16.25 5.4
GZO 0.0 0.0 13.50* 4.5*
FIH 0.0 0.0 15.25* 5.1
Average 0.0* 0.0* 14.8
* average of II significant at α = 0.05
** description under Table 1
Adam Okorski et al.40
(II =14.4%) and pods (II = 6.3%) (Table 2, Table 3). The lowest infection rates
were noted when effective microorganisms were applied without chemical
control (7.1% and 1.8% for leaves and pods respectively).
Therateofphotosynthesis(An) was significantly different in particular
years of the study, reaching the highest level (16.7 µmol CO
2
m
-2
s
-1
)in2004and
the lowest (14.1 µmol CO
2
m
-2
s
-1
) in 2005 (Table 5). Net photosynthesis values
were significantly affected by the method of EM application. The highest rate
of photosynthesis (16.7 µmol CO
2
m
-2
s
-1
) was recorded in plots where foliar
application of EM was combined with chemical protection as well as in those
whereEMwereappliedwithoutchemicalcontrol(16.5µmol CO
2
m
-2
s
-1
)
(Table 5). The lowest rate of photosynthesis (13.7 µmol CO
2
m
-2
s
-1
) was
observed in plots where seed dressing with EM was combined with chemical
protection.
Table 5
Value of net photosynthetic rate An (µmol CO
2
m
-2
s
-1
) after aplication of EM
Year
2003 2004 2005
Obiekt Average
K*** 14.8 20.2 13.0 16.0
G 16.78** 14.85** 14.59** 15.40**
Z 13.8 15.13** 12.3 13.71**
O 16.3 18.97** 14.84** 16.68**
GZO 17.62** 16.98** 14.93** 16.5
FIH 15.1 13.99** 14.91** 14.67**
Average 15.7* 16.7 14.1**
* average of II significant at α = 0.05
** average of E significant at α = 0.01
*** description under Table 1
Table 6
Value of transpiration rate E (mm H
2
Om
-2
s
-1
) after aplication of EM
Year
2003 2004 2005
Obiekt Average
K*** 10.45 6.53 2.88 6.62
G 11.58** 5.91 2.99 6.83
Z 9.58 5.23** 2.46* 5.77**
O 11.03 4.85** 2.87 6.25
GZO 12.08** 5.94 2.82 6.95
FIH 10.01 4.70** 3.21* 5.97**
Average 10.27 6.13** 2.89**
* average of II significant at α = 0.05
** average of E significant at α = 0.01
*** description under Table 1
Effect of Fungal Infection... 41
Table 7
Simple correlations between the gas exchange (An and E) and Infection Index (II) of diseases
Disease Gas exchange RR
2
Fusarium root root An -0.20 0.04
E 0.09 0.01
Downy mildew An -0.52* 0.27*
E -0.74** 0.54*
Acochyta complex (leaf) An -0.03 0.001
E -0.76** 0.58**
Acochyta complex (pod spot) An 0.19 0.034
E -0.50* 0.25*
* R significant at α = 0.05
** R significant at α = 0.01
ab
net photosynthetic rate (µmol CO m s )
2-2-1
-6
-4
-2
0
2
4
6
8
10
12
14
16
18
2 4 6 8 10 12
14
transpiration rate (mmol H O
2
ms)
-2 -1
-5
0
5
10
15
20
25
30
-2
0
2
4
6
8
10
12
14
disease severity (%)
yx= 34.17 – 1.88
r = -0.52
11 12 13 14 15 16 17 18 19 20 21
-6
-4
-2
2
4
6
8
10
12
14
16
18
disease severity (%)
cd
yx= 14.9 – 1.6
= -0.74r
2 4 6 8 10 12
14
transpiration rate (mmol H O
2
ms)
-2 -1
2 4 6 8 10 12
14
transpiration rate (mmol H O
2
ms)
-2 -1
yx= 23.8 – 1.9
= -0.76r
disease severity (%)
disease severity (%)
yx= 7.3 – 0.57
r = -0.5
Fig. 1. Linear regression between: a – photosynthetic rate and disease severity of downy mildew (II);
and transpiration rate and disease severity, b downy mildew, c Ascochyta leaf spot,
d Ascochyta pod spot
The rate of molar transpiration (E) also differed significantly in particular
years, ranging from 10.79 (mmol H
2
Om
-2
s
-1
) in 2003 to 2.87 (mmol H
2
Om
-2
s
-1
)
in 2005 (Table 6). Seed dressing with EM combined with chemical control
substantially reduced transpiration values, to E=5.77 (mmol H
2
Om
-2
s
-1
) and
Adam Okorski et al.42
E=5.97 (mmol H
2
Om
-2
s
-1
), compared to the check. Over the experimental
period pea plants responded to biological and chemical disease control by
changes in the transpiration process.
The statistical analysis revealed that the rates of photosynthesis and
transpiration were affected not only by the method of crop protection, but also
by disease incidence. In 2005 the occurrence of downy mildew on pea leaves
significantly decreased the rate of photosynthesis. The coefficient of Pearson
correlation between photosynthesis rate and the severity of this disease was
R = -0.51 (Table 7, Figure 1a). The values of An were also lower in Fusarium
wilt-infected plants, but this trend was not confirmed by a statistical analysis
(R = -0.20). There was no significant correlation between the values of An and
ascochytosis severity (R = 0.03). A strong correlation was recorded between
the rate of molar transpiration E and infestation by fungal pathogens.
A decrease in the values of E (R = -0.74) was noted in the case of infection by
Peronospora viciae (Table 7, Figure 1b). The occurrence of ascochytosis on pea
leaves and pods also reduced the rate of transpiration, which was reflected in
the values of the coefficient of Pearson correlation: R = -0.74 and R = -0.50,
respectively (Table 7, Figure. 1c, Figure 1d).
Discussion
The effect of plant diseases on the rate of photosynthesis and other
parameters of gas exchange has been widely discussed by numerous authors.
In the majority of experiments conducted to date plants were inoculated under
controlled conditions. In such cases infection severity is dependent on the
amount of inoculum applied to plants and on the pathogenicity of isolates.
The present study was performed under conditions of natural infection, to
determine the interactions between the experimental factors and the impact
of the natural environment, considered important for agricultural practice.
In this experiment the rate of photosynthesis was significantly affected by the
degree of pea infestation by Peronospora viciae (coefficient of Pearson correla-
tion R = -0.51). The phenomenon of photosynthesis inhibition by pathogens
damaging leaf tissue has been already described in professional literature
(G
OICOECHEA et al. 2001, ROBERT et al. 2004).
It was found that other pathogenic factors had no significant influence
on photosynthesis values. The results reflect the interactions between a var-
iety of factors affecting the process of photosynthesis and environmental
impacts on infection levels. Pea infestation by fungal pathogens was relatively
low, due to weather conditions and the use of the tested biopreparation
(Figure 2a, Figure 2b). According to M
ARCINKOWSKA (1997), the incidence
Effect of Fungal Infection... 43
ab
5
10
15
20
25
mean of years 1961–1995 2003
2004 2005
(C)
o
0
25
50
75
100
125
April
May June
July
(mm)
July
JuneMay
April
0
Fig. 2. Pattern of weather conditions in growing periods (data according to the Meteorolgical Station
in Tomaszkowo)
of leaf-and-pod spot of peas is closely related to weather conditions during the
growing season, since the spread of this disease is observed at relative air
humidity of 95%.
The greatest severity of Fusarium wilt of peas is recorded during drought
and at high temperatures, which accelerate the development of this disease
(M
AJCHRZAK 1998, PAŃKA,SADOWSKI 1999). In the current study the highest
intensity of Fusarium wilt was noted in the first and third year. This period
was characterized by high temperatures and low precipitation (Figure 2a,
Figure 2b), which promoted the spread of the disease.
Downy mildew of peas is favored by cool, wet weather, and survives as
oospores on infected seeds until the next year (F
ALLOON et al. 2000). In this
experiment symptoms of downy mildew were observed in 2005, when precipi-
tation rates were high (Figure 2b). Transpiration values E were considerably
affected by fungal pathogens. The occurrence of all pathogens causing leaf
tissue infections reduced the rate of transpiration in pea plants. It seems that
infection resulted in the closure of stomata, to prevent water loss from the
plant. Necrotrophic pathogenic factors may cause stomatal closure over
the entire surface of leaf blades even if infection severity is low, which in turn
decreases the rate of photosynthesis (M
EYER et al. 2001) and affects transpira-
tion. In the case of this group of pathogens a reduction in the rate
of transpiration in infected plants is proportional to leaf lesion area (S
HTIEN-
BERG
1992). In the case of biotrophic pathogenic factors transpiration inhibi-
tion is related to the damaged leaf area to a lesser degree.
S
HTIENBERG (1992) demonstrated that transpiration values increased in
plants attacked by rust caused by a biotrophic pathogen. In the present study
Adam Okorski et al.44
another biotrophic pathogen Peronospora viciae was identified only in 2005,
when weather conditions favored disease development. Constant water deficits
doubtlessly affected the defense strategy of plants, part of which was stomatal
closure. This effect could be enhanced even by a low level of infection.
Literature data on the impact of biological disease control on gas exchange
parameters are scant. In this experiment the highest rate of photosynthesis
was recorded following foliar application of effective microorganisms. Similar
results were reported by X
U et al. (2000), who observed a higher rate of
photosynthesis in treatments where inoculants containing effective microor-
ganisms were applied, compared to the control treatment. Current results
confirmed the impact of effective microorganisms on the occurrence of diseases
associated with the soil environment, and leaf diseases. It was also found that
all methods of EM application reduced disease incidence in pea plants. Good
results were obtained in the case of biological disease control, applied alone or
combined with chemical methods. E
RRAMPALLI and BRUBACHER (2006) demon-
strated that a combination of biological and chemical pathogen control allowed
to increase the effectiveness of plant protection. However, it is important to
properly select biological and chemical agent to be applied together, so that to
make sure that the active substances contained in crop protection chemicals do
not inhibit the growth of microbial antagonists introduced into the soil
(F
RAVEL et al. 2005).
Conclusions
1. The tested biological agent (EM) reduced the incidence of pea diseases.
2. Foliar application of EM significantly increased the rate of photosyn-
thesis in pea.
3. Soil application of EM, seed dressing and chemical control decreased the
rate of photosynthesis in pea.
4. Seed dressing with the tested biological agent (EM) and chemical control
caused a significant decrease in molar transpiration values in pea.
5. The occurrence of downy mildew of peas significantly reduced the rate
of photosynthesis.
6. The occurrence of downy mildew and ascochytosis of peas decreased
the rate of molar transpiration.
Translated by ALEKSANDRA POPRAWSKA
Accepted for print 31.08.2007
Effect of Fungal Infection... 45
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Effect of Fungal Infection... 47
... The efficiency of plants under different stress environment conditions is evaluated by considering the leaf gas exchange medium as an indicator. Adverse effects of phytopathogens on plants' leaf gas exchange capacity were well described by Okorski et al. (2008) and Robert et al. (2004). In the present study, results revealed that a notable reduction in leaf gas exchange was observed. ...
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... Increased availability increases the uptake of nutrients, and therefore, positively influences photosynthesis. It has also been found that foliar application of EMs significantly increases plant photosynthetic activity [32]. Soil microorganisms promote nutrient uptake and transport in plants [33]. ...
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... Pathogen virulence dampens photosynthetic performance (Okorski et al. 2008). R. solani pathogenesis leads to downregulation of photosynthesis (Ghosh et al. 2017). ...
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... Aljarah (2016) rates the EM Bokashi technology as promising for managing seed rot and seeding damping-off caused by P. aphanidermatum and R. solani in cucumber. Soil application of EM contributed to inhibiting fungal pathogen infestation on pea plants (Okorski, Olszewski, Pszczółkowska, & Kulik, 2008). ...
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... Thus, these treatments of HS and/or EM can replace entirely or partially N mineral fertilizer, which reduce production costs and conserve the environment from chemical pollution hazards on human and animal health (Abbas et al., 2014). Okorski et al. (2008) found that foliar application of EM reduced the incidence of pea diseases and increased the rate of photosynthesis in pea. While, soil application of EM, seed dressing and chemical control decreased the rate of photosynthesis in pea and molar transpiration values in pea. ...
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... The root mass of the plants treated with EM-5 with the onion extract and the mixture of EM-A and EM-5 was signifi cantly higher in comparison to the root mass in the other combinations ( Figure 3). In addition to improving strawberry growth the Effective Microorganisms may increase the length of apple shoots and leaf surface (Sahain et al., 2007), cause the growth of the fresh root weight and increase their length (Okorski et al., 2008;Klama et al., 2010), signifi cantly raise the content of macro-nutrients in leaves (Kleiber et al., 2014). Different forms of the EM preparation had a differentiated infl uence in the strawberry fruit mass. ...
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... Thats why many researches focus on this subject and try to create more resistance against these factors. One of them is to increase the immune system of human and plants and provide better photosynthesis and all related physiologic activities ( Higa and Parr, 1994;Okorski et al., 2008;Ke et al., 2009;Datla et al., 2004) ...
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... Only small and often contradictory effects of the application of EM preparations on crop yields and plant development have been reported (Iwaishi, 2000;Xu, 2000;Bajwa, 2005;Priyadi et al., 2005;Javaid, 2006;Khaliq et al., 2006;van Vliet et al., 2006;Okorski et al., 2008). EM-applications have also been found to have no effects (Priyadi et al., 2005;Khaliq et al., 2006;van Vliet et al., 2006). ...
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Rhizoctonia solani , a soilborne necrotroph, causes sheath blight in rice which poses a major threat to global rice production. Besides rice sheath blight, it has a wide host range of other economically important crops like soybean, sugarcane, maize etc. Despite being the most hostile fungus, the mechanism involved in the R. solani pathobiology is poorly understood. Non-host resistance (NHR) is an emerging concept that allows breeders to transfer traits to food crops that would impart a broad-spectrum disease resistance. Several NHR genes are known to function against different pathogens of which Arabidopsis PEN1, PEN2 and PEN3 have been reported to limit the entry of non-adapted powdery mildews and provide cell wall based defenses against different fungi. Till now, there has been no study regarding the involvement of these PEN genes against R. solani. In this study, we have screened pen1, pen2-3 and pen3-1 against R. solani to explore their contribution in penetration resistance. Among the three pen mutants studied, pen2-3 allowed maximum penetration during the early hours of infection. R. solani colonization was also observed in pen1 and pen3-1 but the effect was less drastic than pen2-3 , suggesting the involvement of PEN2 in pre-invasive defense. To validate our hypothesis, we screened a complemented pen2 accession, PEN2-GFP , which showed restored penetration resistance comparable to Col-0. Altogether, our results demonstrate that PEN2 is involved in pre-penetration resistance, and contributes to NHR by enhanced disease resistance to R. solani.
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Infection of bean leaves by Colletotrichum lundemuthianum causes vein necrosis and subsequent localized wilting of the blade. The effect of infection on photosynthesis was investigated by imaging leaf chlorophyll fluorescence as a means of mapping stomatal and metabolic inhibition of photosynthesis. During infection, CO2 assimilation (An), stomatal conductance to water vapour, and photosynthetic electron transport rate (Jt) decreased, whereas dark respiration increased. An decreased more than was expected from the reduction in green leaf area, showing that photosynthesis was inhibited in apparently healthy areas. Under subsaturating irradiance, images of Jt in air showed that photosynthesis decreased gradually, with this effect shifting from green to necrotic areas. Sudden increase in CO2 concentration to 0·74% in the atmosphere around the leaf only partially reversed this inhibition, showing that both stomatal and metabolic inhibition occurred. Under limiting irradiance, decreases in Jt and in maximal Jt during high CO2 exposure as leaf damage severity increased suggested that metabolic inhibition was mediated through an inhibition of Ribulose 1·5-bisphosphate (RuBP) regeneration. Finally, the importance of our data in terms of assessing the loss of photosynthetic yield from visible symptoms – as is currently performed in epidemiology – is discussed.
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In Navarra, Northern Spain, Verticillium dahliae Kleb. is one of the pathogens that causes drastic reductions in pepper production. The aim of this study therefore was to describe how infection by V. dahliae affects gas exchange during the flowering of pepper in order to determine some possible factors contributing to the significant decrease of plant yield. Verticillium was inoculated when plants had started flowering. The first leaf wilting symptoms appeared on day 18 after inoculation, but leaf water potential rapidly decreased after infection. The inoculated plants produced more flowers than the controls between 15 and 33 days after inoculation, but flower production declined after day 33. Inoculated plants also suffered more defoliation and chlorophyll degradation. Leaf conductance and photosynthesis clearly decreased in both groups of plants as a consequence of senescence, but the values in those inoculated were significantly lower. Results suggest that the decrease in photosynthesis was in part due to defoliation and chlorophyll degradation, as well as premature flower fall. These factors contributed to the negative effects of Verticillium infection on pepper yield.
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Xylella fastidiosa is a xylem-limited bacterial plant pathogen that causes bacterial leaf scorch in its hosts. Our previous work showed that water stress enhances leaf scorch symptom severity and progression along the stem of a liana, Parthenocissus quinquefolia, infected by X. fastidiosa. This paper explores the photosynthetic gas exchange responses of P. quinquefolia, with the aim to elucidate mechanisms behind disease expression and its interaction with water stress. We used a 2 × 2-complete factorial design, repeated over two growing seasons, with high and low soil moisture levels and infected and non-infected plants. In both years, low soil moisture levels reduced leaf water potentials, net photosynthesis and stomatal conductance at all leaf positions, while X. fastidiosa-infection reduced these parameters at basally located leaves only. Intercellular CO2 concentrations were reduced in apical leaves, but increased at the most basal leaf location, implicating a non-stomatal reduction of photosynthesis in leaves showing the greatest disease development. This result was supported by measured reductions in photosynthetic rates of basal leaves at high CO2 concentrations, where stomatal limitation was eliminated. Repeated measurements over the summer of 2000 showed that the effects of water stress and infection were progressive over time, reaching their greatest extent in September. By reducing stomatal conductances at moderate levels of water stress, P. quinquefolia maintained relatively high leaf water potentials and delayed the onset of photosynthetic damage due to pathogen and drought-induced water stress. In addition, chlorophyll fluorescence measurements showed that P. quinquefolia has an efficient means of dissipating excess light energy that protects the photosynthetic machinery of leaves from irreversible photoinhibitory damage that may occur during stress-induced stomatal limitation of photosynthesis. However, severe stress induced by disease and drought eventually led to non-stomatal decreases in photosynthesis associated with leaf senescence.