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Fungicide impacts on photosynthesis in crop plants


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Fungicides are widely used to control pests in crop plants. However, it has been reported that these pesticides may have negative effects on crop physiology, especially on photosynthesis. An alteration in photosynthesis might lead to a reduction in photoassimilate production, resulting in a decrease in both growth and yield of crop plants. For example, a contact fungicide such as copper inhibits photosynthesis by destroying chloroplasts, affecting photosystem II activity and chlorophyll biosynthesis. Systemic fungicides such as benzimidazoles, anilides, and pyrimidine are also phytotoxic, whereas azoles stimulate photosynthesis. This article focuses on the available information about toxic effects of fungicides on photosynthesis in crop plants, highlighting the mechanisms of perturbation, interaction, and the target sites of different classes of fungicides.
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Fungicide impacts on photosynthesis in crop plants
lle Petit
Florence Fontaine
Parul Vatsa
Christophe Cle
Nathalie Vaillant-Gaveau
Received: 27 March 2011 / Accepted: 12 January 2012 / Published online: 1 February 2012
Ó Springer Science+Business Media B.V. 2012
Abstract Fungicides are widely used to control pests in
crop plants. However, it has been reported that these pes-
ticides may have negative effects on crop physiology,
especially on photosynthesis. An alteration in photosyn-
thesis might lead to a reduction in photoassimilate pro-
duction, resulting in a decrease in both growth and yield of
crop plants. For example, a contact fungicide such as
copper inhibits photosynthesis by destroying chloroplasts,
affecting photosystem II activity and chlorophyll biosyn-
thesis. Systemic fungicides such as benzimidazoles, ani-
lides, and pyrimidine are also phytotoxic, whereas azoles
stimulate photosynthesis. This article focuses on the
available information about toxic effects of fungicides on
photosynthesis in crop plants, highlighting the mechanisms
of perturbation, interaction, and the target sites of different
classes of fungicides.
Keywords Chlorophyll Crop plants Fungicides
Photosynthesis Photosystems Physiology
Phytotoxicity Stomatal closure Stress
Fungicides remain a vital solution to the effective control
of plant diseases, which are estimated to cause yield
reductions of almost 20 percent in major food and cash
crops worldwide. The great variety of known fungicides
can be classified into two main categories: contact and
systemic. Contact fungicides, such as copper or sulfur have
a preventive action by killing fungi as their spores germi-
nate, before mycelia can grow and develop within plant
tissues (Yuste and Gostincar 1999). Since their introduc-
tion in the 1960’s, systemic fungicides have gradually
replaced older non-systemic products, establishing higher
levels of disease control and developing new fungicide
markets. Systemic fungicides, known as curative or eradi-
cation fungicides, can also kill the fungus when mycelia
have penetrated into the parenchyma, stopping the dis-
persal or infection within the plant (Table 1, Yuste and
Gostincar 1999). Among systemic fungicides, benzimi-
dazoles are a group of organic fungicides that are exten-
sively used in agriculture along with the other classes of
All these types of compounds control a broad range of
fungi at relatively low application rates. However, the
effects of fungicides on crop growth depend on various
factors. Application of fungicides may affect crop physi-
ology by various disruptions such as growth reduction,
perturbation in the development of reproductive organs,
alteration of nitrogen, and/or carbon metabolism leading to
a lower nutrient availability for plant growth. The sensi-
tivity of some plant species may depend on the develop-
mental stage (i.e. more sensitive to the treatments at young
stages or during critical events such as reproduction) or the
type of pesticides used.
It has been previously reported that in response to a
stress, plants often mobilize nutrients and metabolite pro-
duction to develop defense mechanisms in detriment to
growth (Smith and Moser 1985). Under stress conditions,
plants firstly trigger their defence response for their sur-
vival because of the energetic cost of resistance and
A.-N. Petit F. Fontaine P. Vatsa C. Cle
N. Vaillant-Gaveau (&)
Laboratoire de Stress, De
fenses et Reproduction des Plantes,
URVVC EA 2069, Universite
de Reims Champagne-Ardenne,
UFR Sciences Exactes et Naturelles, Ba
timent 18, Moulin de la
Housse, BP 1039, 51687 Reims Cedex 2, France
Photosynth Res (2012) 111:315–326
DOI 10.1007/s11120-012-9719-8
Table 1 Basic chemical characteristics of fungicides (data from International Union of Pure Applied Chemistry)
Structures Primary mode of action in fungus
Copper and/or sulfate
Bordeaux mixture
Inhibit several enzymes involved in respiration and this multi-site action
(Leroux 2003)
Inhibit several enzymes involved in respiration and this multi-site action
(Leroux 2003)
Inhibit several enzymes involved in respiration and this multi-site action
(Leroux 2003)
Inhibits spore germination and mycelial growth (Leroux et al. 2002)
QoI inhibitors, which act to inhibit the respiratory chain at the level of
Complex III (Grossmann et al. 1999)
Inhibits spore germination and mycelial growth (Zhang et al. 2010)
Perturbe the osmo-regulatory signal transmission pathway (Pillonel and
Meyer 1997)
Inhibits spore germination and mycelial growth (Leroux et al. 2002)
Inhibits germ-tube elongation and mycelial growth (Ha
nbler and Pontzen
A sterol biosynthesis inhibitor: inhibits the 3-keto reductase involved in the
enzymatic complex of the sterol C-4 demethylation (Debieu et al. 2001)
Inhibits spore germination and mycelial growth
Multi-site action (Teisseire et al. 1999)
Inhibit mycelial growth
Indirect effect against germination of zoosporangia, zoospore motility,
cystospore germination, and oospore formation
Impairment of the ATP energy generation system
Inhibit several enzymes involved in respiration (Mitani et al. 2001)
Inhibition of sterol biosynthesis at the 14a-demethylation step (Haughan
et al. 1988)
Sterol C-14 demethylation inhibitor (Debieu et al. 1995)
316 Photosynth Res (2012) 111:315–326
growth. The intensity of the stress induced by pesticide
application and the intensity of plant response will thus
have a subsequent impact on the growth process if the
crops overcome the stress. According to the growth
reductions observed after agrochemical exposures, plants
may react by developing this kind of metabolite reorien-
tation. Therefore, the plant carbon and/or nitrogen primary
metabolism, which regulates the plant growth rate, appears
necessary to be investigated in order to understand more
precisely how pesticides can affect the crops (Saladin and
ment 2005).
Carbon metabolism is of particular importance for crop
culture and is reflected by both crop’s photosynthetic rate
and its management of carbohydrate reserves. Indeed,
photosynthesis alteration may lead to a decrease in pho-
toassimilate production and thus to plant yield and vigour.
A negative effect of sulfur-containing fungicides (particu-
larly lime sulfur) was revealed on apple production by a
loss of fruits and a delay in harvest (Palmer et al. 2003).
However, spray treatments did not influence shoot growth,
leaf area development or increment in trunk cross-sectional
area. Fungicide application programme containing Kocide
or slaked lime or use of both together, demonstrated that
Black spot incidence (caused by Venturia inaequalis), on
fruit at harvest was significantly higher on trees treated
with either Kocide or slaked lime compared to the controls.
When used together, however, control of Black spot was as
good as in the control. Dry eye rot incidence (caused by
Botrytis cinerea) was significantly higher on the trees
treated with lime sulfur (Palmer et al. 2003). Another study
about the effect of lime sulfur applied at different stages to
apple trees reported leaf phytotoxicity, revealed as necro-
sis, and a reduction of yield in terms of first class fruits
(Holb et al. 2003).
As stress increases, various photosynthetic processes
may be impaired, leading to a decrease in net photosyn-
thesis (Pn), equivalent to CO
assimilation (Fig. 1).
Stomatal closure, caused by a reduction in stomatal con-
ductance (gs), is often considered as an early physiological
response to stress, resulting in decreased Pn through lim-
ited CO
availability (Ci) in the mesophyll (Krause and
Weis 1991). Photosynthesis is one of the most studied and
best understood physiological process. Detailed biochem-
ical models of photosynthesis, including light reactions,
electron and proton transport, enzymatic reactions, and
regulatory functions have been recently developed (Laisk
et al. 2006). Life on earth is driven essentially by photo-
synthetic solar energy conversion. Photosynthetic organ-
isms use light energy for the synthesis of organic
molecules. In the case of plants, algae, and cyanobacteria,
oxygen is emitted into the atmosphere as a by-product of
photosynthesis. Fundamental to the photosynthetic process
Table 1 continued
Structures Primary mode of action in fungus
Sterol C-14 demethylation inhibitor (Debieu et al. 1995)
Sterol C-14 demethylation inhibitor (Gaita
n et al. 2005)
Sterol C-14 demethylation inhibitor (Debieu et al. 1995)
Inhibition of microtubule assembly which is due to their binding to tubulin, the main
protein of microtubules (Leroux and Descotes 1996)
Inhibition of microtubule assembly which is due to their binding to tubulin, the main
protein of microtubules (Leroux and Descotes 1996)
Inhibits germ tube elongation and initial mycelial
Inhibit biosynthesis of methionine affecting cystathionine-b-lyase
Prevention of fungal secretion of hydrolytic enzymes (Fritz et al. 1997)
Photosynth Res (2012) 111:315–326 317
is the ability of plants to absorb light energy that is then
converted into chemical energy. Light energy is captured
by pigments in the light-harvesting complex (LHC) pro-
teins and transferred to the reaction centers of the chloro-
plast thylakoid membrane. LHC proteins bind to
chlorophyll a, chlorophyll b, and carotenoids with weak
non-covalent bonds. LHC are assembled into two separate
yet biophysically linked photosystems: photosystem I (PSI)
and photosystem II (PSII) (Hillier and Babcock 2001). PSII
catalyzes light-induced electron transfer from water to
plastoquinone. The oxygen-evolving complex, located on
the luminal side of PSII is responsible for water oxidation
and produces protons, electrons, and molecular oxygen as a
by-product (Krause and Weis 1991). The protons are
involved in the formation of adenosine triphosphate (ATP),
the plant stock of energy, through the ATPase. The elec-
trons run along a complex transfer chain ending with the
formation of another energetic molecule, nicotinamide
adenine dinucleotide phosphate (NADP). Then ferredoxin
is reduced by a photochemical reaction at the level of PSI,
and the ferredoxin–NADP
reductase enzyme mediates
electron transfer from this reduced protein to NADP with
the formation of NADPH necessary for CO
fixation. An
alteration of any one of these processes can lead to Pn
Fig. 1 Schematic representation showing the interactions of the main
processes in C3 photosynthesis in higher plants (according to Baker
and Rosenqvist 2004) and impacts of fungicides (North east increase
and South east decrease). Photophosphorylation starts with the
absorption of light by the light-harvesting antenna complexes (LHCI
and LHCII) associated with photosystem II (PSII) and photosystem I
(PSI) in the chloroplast thylakoid membrane. This drives electron
transport from water via a series of electron carriers to NADP,
producing reducing power (NADPH) and a H
potential difference across the membrane. Dissipation of this proton
motive force by the passage of H
back across the membrane through
the ATPase drives the production of ATP. Ribulose 1,5-bisphosphate
carboxylase/oxygenase (Rubisco) catalyses the assimilation of CO
with ribulose 1,5-bisphosphate (RubP) in the carboxylation reaction
of the Calvin–Benson cycle in the stroma of the chloroplast. The
diffusion of atmospheric CO
into the leaf is regulated by the stomata
in the epidermis. Other reactions of the Calvin–Benson cycle utilize
NADPH and ATP to produce triose phosphates, which are required
for the synthesis of carbohydrates. NADPH and ATP are also used in
a range of other metabolic activities (e.g. nitrogen and sulfur
metabolism, lipid and pigment synthesis) in the chloroplast. Rubisco
can also catalyse the photorespiratory oxygenation of RubP, which
involves consumption of NADPH and ATP by the Calvin–Benson
cycle. O
can also be directly photoreduced by electron transfer from
PSI to produce superoxide, which is then rapidly dismutated to
hydrogen peroxide, which in turn is detoxified to water; this process is
often termed the Mehler-peroxidase reaction or the water–water
cycle. Cyt b/f cytochrome b6/f complex; PC plastocyanin; PQ
plastoquinone; PQH
318 Photosynth Res (2012) 111:315–326
inhibition. ATP and NADPH are then necessary for the
second step, i.e., the energy-consuming reductive conver-
sion of CO
into carbohydrates. These latter reactions
follow a cyclic sequence called the Calvin cycle. The key
enzyme of the cycle, Ribulose 1,5-bisphosphate carboxyl-
ase/oxygenase (Rubisco), is a prerequisite for CO
and catalyzes the carboxylation of ribulose 1,5-bisphos-
phate (RuBP). There is a strong evidence that Pn might
thus be limited by other biochemical processes occurring in
the mesophyll, such as Rubisco activity and RuBP regen-
eration (Krause and Weis 1991).
Apart from affecting wide variety of crop plants, fungi-
cyanobacteria (blue-green algae). The effect of pesticides on
cyanobacterial populations has been considered to be stim-
ulatory at low concentrations and inhibitory at high doses.
The rates of photosynthesis and respiration along with
chlorophyll content have been shown to decline in the
presence of Bavistin, a broad spectrum fungicide, containing
50% WP carbendazim (Rajendran et al. 2007). Previously, it
has been demonstrated that carbendazim 50% WP is effec-
tive against a wide range of pathogenic fungi and is highly
specific in its control of important plant pathogens on a
variety of crops, ornamental plants and plantation crops.
Dewez et al. (2005) demonstrated that when alga Scenedes-
mus obliquus was exposed to different copper concentrations
significant inhibition on the growth rate and chlorophyll
synthesis was noticed. Phytoremediation with microalgae has
been utilized for areas polluted with nutrients or heavy metals
(Perales-Vela et al. 2006); however, increasing environ-
mental pollution by pesticides might lead to consider mic-
roalgae as good candidates to remove these contaminants
from water at low cost (Dosnon-Olette et al. 2010).
The aim of this review is to make a thorough account of
the current available information about impacts of fungi-
cides on different crop varieties in relation to the photo-
synthetic process, relating different families of fungicides,
crop varieties, and photosynthetic parameters that are
affected. A large number of papers on the topic covered by
this review have been published since 1978. This review
summarizes the main findings in the field of agriculture,
photosynthesis, and fungicides. Furthermore, many articles
have reported negative effects of these products, but it does
not mean that all fungicides have negative effects.
Effect of contact fungicides on photosynthesis
Application of fungicides alters the crop physiology, in
terms of growth and development along with nitrogen, and/
or carbon metabolism (Saladin and Cle
ment 2005). This
former physiological trait is fundamental for crop culture
and is reflected by both photosynthetic rate and
mobilization of carbohydrate reserves. Indeed, as plants
rely on their ability to assimilate carbon through photo-
synthesis for their growth and overall vigor, photosynthesis
disruption may decrease both the yield and the vigor.
Several works on photosynthesis fluctuations after fungi-
cide application on various crops report modifications of
both photosynthetic activity and chlorophyll fluorescence
(Krugh and Miles 1996; van Iersel and Bugbee 1996;
Untiedt and Blanke 2004; Xia et al. 2006).
Several chemical compounds, based mainly on copper,
sulphur or fludioxonil, are used to prevent crop plant dis-
ease through non-systemic control programs. Copper is
commonly used both as a pesticide (e.g. Bordeaux mixture)
and as an algicide in agriculture. Copper is also an essential
plant micronutrient as a component of various proteins,
particularly those involved in both photosynthetic (plasto-
cyanin) and the respiratory (cytochrome oxidase) electron
transport chain (Baro
n et al. 1995). However, an excess is
strongly phytotoxic for crops. Toxicity symptoms were
observed in cucumber leaves by a pronounced inhibition of
Pn in mature leaves exposed to 20 lgg
in soil for 5 days
(Table 2). Although Pn decline which is associated with a
parallel decrease in gs, stomatal closure does not account
for Pn inhibition (Vinit-Dunant et al. 2002).
Inhibition of photosynthesis in the leaves of stressed
plants is most likely a consequence of an altered source-
sink relationship. Indeed, growth inhibition decreases car-
bohydrate export from leaves, causes both starch and
sucrose accumulations, and finally leads to a feedback
inhibition of photosynthesis (Vinit-Dunant et al. 2002).
However, Pn inhibition after copper exposure may be
due to a disturbance of other processes in photosynthesis.
Copper has a pronounced effect on chloroplast ultrastruc-
ture (Baszynski et al. 1988). In addition, chloroplast
destruction was observed in green algae exposed to copper
with enhanced peroxidative processes (Sandmann and
ger 1980). Copper alters the lipid chloroplast membrane
(Szalontai et al. 1999), affecting light reaction processes,
especially those associated with PSII (Baro
n et al. 1995).
Copper inhibits pigment accumulation and retards chloro-
phyll integration into the photosystems of barley (Caspi
et al. 1999). It inhibits both the synthesis of the chlorophyll
precursor, delta aminolevulinic acid and the activity of
protochlorophyllide reductase, an enzyme that catalyzes
the reductive formation of chlorophyllide from protochlo-
rophyllide during chlorophyll biosynthesis (Stiborova
et al.
1986). Most of the in vitro studies using isolated chloro-
plasts or excised leaves have reported an inhibition of the
photosynthetic electron transport both at the reducing side
of PSI and at the oxidizing side of PSII (Sandmann and
ger 1980). Another effect of copper-based fungicides
used in the treatment of plant disease is the suppression of
oxygen evolution, inducing a decrease in photosynthetic
Photosynth Res (2012) 111:315–326 319
capacity (Caspi et al. 1999). Sensitivity of PSII was con-
firmed with increased PSII inactivation under photoinhib-
itory conditions (Pa
et al. 1998). Action has also been
localized within the compounds of the thylakoid membrane
such as PSI (Samuelsson and Oquist 1980), the coupling
factor (Uribe and Stark 1982) and the ferredoxin-dependent
reactions (Shioi et al. 1978). Finally, a direct inhibition of
Rubisco by Mg
substitution or by interaction with SH-
groups of the ATPase may also account for the inhibition
of photosynthesis following exposure (van Assche and
Clijsters 1990).
A decrease in the disease severity and improvement in
the foliage colour and retention has been observed by
treatment with sulfur, which acts both as a plant nutrient
and a fungicide (Stone et al. 2004). Despite its efficiency,
treatments containing sulfur also cause phytotoxicity on
crops (Holb and Schnabel 2005). In his review, Ferree
(1979) summarized works in the 1930’s and 1940’s
reporting that sulfur and lime sulfur reduce leaf Pn. Ferree
et al. (1999) later found that a single spray of sulfur results
in a significant decrease in Pn of greenhouse grown apple
trees. Similarly, Palmer et al. (2003) reported that leaf
photosynthesis of Braeburn apple trees was significantly
reduced by almost 50% following sulfur treatments (lime
sulfur or Kumulus i.e. 800 g kg
). The reduction in Pn is
always accompanied by reduced stomatal conductance.
The phytotoxicity of cuproxat (copper sulfate at 0.54 g l
on photosynthesis was investigated in a cucumber crop
after using it as a pesticide treatment; the result was a
decreased Pn accompanied by a decreased stomatal con-
ductance and Ci, indicating that Pn inhibition is mostly
attributed to stomatal factors. However, cuproxat had no
significant effects on PSII activity (Xia et al. 2006).
The fungicide fludioxonil (fdx) [4-(2,2-difluoro-1,3-
benzodioxol-4-yl)-1H-pyrrole-3-carbonitrile], a phenyl-
pyrrole compound, is commonly used as a botryticide in
the vineyards (Rosslenbroich and Stuebler 2000). Fdx is a
non-systemic molecule and acts by inhibiting spore ger-
mination, germ-tube elongation, and the mycelium growth
of Botrytis cinerea (Table 1). It increases the glycerol
content in the fungus, leading to a perturbation of the
osmoregulation potential (Pillonel and Meyer 1997). Fdx
applied during flower and berry development, may thus
have significant consequences on yield. In grapevine, a
decrease in Pn was noticed 8 days after treatment although
fdx is not associated with a reduction in gs at 6 mM, the
recommended concentration (Saladin et al. 2003, Petit
et al. 2008a). In parallel studies, decrease in chlorophyll
contents and carotenoids after fungicide treatments
appeared to be dose-dependent (Saladin et al. 2003). It was
shown that fdx effects on Pn, were related neither to
inactivation of both Rubisco and other key enzymes of the
Calvin cycle, nor, to modification of CO
diffusion to
Rubisco. Pn recovered 10 days post-treatment, which
would mean that either fdx had only a slight deleterious
effect on plant photosynthesis or that grapevine has greater
capacity to overcome this temporary stress (Saladin et al.
2003; Petit et al. 2008a, b). Petit et al. (2009) suggest a
relationship between the application of the fungicide fdx
and the circadian rhythm of a plant’s photosynthesis.
Interpreting the effect of fdx spraying on grapevine pho-
tosynthesis, these authors showed a phenomenon of gating
Table 2 Effects of contact fungicides on crop physiology
Affected parameters Molecules References
Inhibition of Pn Copper Vinit-Dunant et al. (2002)
Sulfur (kumulus) Ferree (1979), Ferree et al. (1999), Palmer et al. (2003)
Copper sulfate (cuproxat) Xia et al. (2006)
Fludioxonil Saladin et al. (2003), Petit et al. (2008a, b)
Stomatal closure Copper Vinit-Dunant et al. (2002)
Sulfur (kumulus) Palmer et al. (2003)
Copper sulfate (cuproxat) Xia et al. (2006)
Inhibition of Ci Copper sulfate (cuproxat) Xia et al. (2006)
Inhibition of Rubisco Copper van Assche and Clijsters (1990)
Decreased of chlorophyll
(synthesis or content)
Copper Stiborova
et al. (1986)
Fludioxonil Saladin et al. (2003)
Modification on chloroplast
Copper Sandmann and Bo
ger (1980), Baszynski et al. (1988),
Caspi et al. (1999), Szalontai et al. (1999)
PSII inactivation Copper Baro
n et al. (1995), Caspi et al. (1999), Vinit-Dunant et al. (2002)
PSI inactivation Copper Samuelsson and Oquist 1980
Inhibition of other sites of
electron transport chain
Copper Shioi et al. (1978), Sandmann and Bo
ger (1980), Uribe and Stark
(1982), van Assche and Clijsters (1990), Baro
n et al. (1995)
320 Photosynth Res (2012) 111:315–326
for the first time, i.e. external stimuli of equal strength
applied at different times of the day can result in different
intensities of response. The time period for spraying also
was an important parameter in stress response. These data
suggest that a morning treatment results in a non-stomatal
limitation of Pn, while a midday treatment is more suitable
to treat grapevine because it is the time period that least
disrupts photosynthesis.
Folpet, used to control mildew and other fungal diseases
in grape (Table 1), is an uncoupling fungicide (uncouple
oxidative phosphorylation in mitochondria). The folpet
phytotoxicity was only investigated on duckweed (Lemna
minor L.), an aquatic macrophyte regularly used as a model
for non-target species in ecotoxicological studies (Teisseire
et al. 1999). Within the range of tested folpet concentra-
tions (0–30 mg l
), no significant effect of total chloro-
phyll content was observed. No data is available on the
cultivated plants.
Systemic fungicides: for better or for worse
A group of organic fungicides called benzimidazoles is
widely used in agriculture for pre- and post-harvest pro-
tection of crops against many fungal diseases, such as
anthracnose, fruit rot, or grey mould. Its key compound,
benomyl, is especially effective because it penetrates into
plants faster than carbendazim (methyl 2-benzimidazolec-
arbamate), its active metabolite (Upham and Delp 1973).
Benomyl is a broad spectrum fungicide currently employed
in agriculture, and many studies on the interaction between
fungi and vascular plants (for example mycorrhizae) use
benomyl as a systemic fungicide in order to get uninfected
plants (Carey et al. 1992; Merryweather and Fitter 1996). It
is possible that these fungicides may be phytotoxic to crops
(Table 3). Moreover, benomyl breaks down to n-butyl
isocyanate which may subsequently react to produce
n-butylamine or N-N
-dibutylurea (DBU). Products of
degradation of benomyl also contribute to the phytotoxicity
of the fungicide (van Iersel and Bugbee 1996). It was also
demonstrated that at a rate of 2.8 kg ha
, DBU reduces
cucumber biomass 3 weeks after treatment and inhibits Pn
of hydrilla 1 day after treatment (Shilling et al. 1994).
Benlate (50% benomyl) caused a seven-to-ten day decrease
in Pn of petunia and impatiens (van Iersel and Bugbee
1997) and DBU may be partly responsible for byside
benomyl deleterious effects on plant growth. Crops have
various sensitivities to DBU. Greenhouse studies revealed
that corn is unaffected by DBU, whereas DBU is phyto-
toxic when applied as a soil drench to cucumber (Shilling
et al. 1994). Indeed, physical symptoms in cucumber begin
with chlorosis at the leaf margins then extend to the whole
leaf and finally lead to necrosis (Shilling et al. 1994).
Similarly, Mihuta-Grimm et al. (1990) noted chlorosis and
stunting in tomato plants following applications of high
benomyl concentrations. Ultra structural examination of
cucumber chloroplasts 10 days after treatment with
5.6 kg ha
DBU showed dilation and a disorganization of
granal membranes (Shilling et al. 1994). Moreover, DBU
affects PSII; it causes elevated chlorophyll fluorescence in
cucumber leaf discs and inhibits photosynthetic oxygen
evolution in hydrilla. In isolated spinach chloroplasts, DBU
also reduces oxygen production and causes photo-induced,
ferricyanide reduction by PSII alone as well as NADP
reduction from a site in the electron transport chain prior to
oxidation of plastohydroquinone, explaining Pn reduction
(Querns et al. 1998).
Carbendazim applications result in changes to foliar
pigment concentrations (Garcia et al. 2002). The applica-
tion of doses lower than the recommended 2.6 mM
increases carotenoid concentrations, whereas a higher rate
([2.6 mM) of carbendazim causes a decrease in all foliar
pigments 2 weeks after treatment. These treatments with
carbendazim may trigger a photoprotection mechanism in
plants via carotenoids, which would interact with light to
alleviate damages caused by the fungicide application
(Garcia et al. 2002; Skillman and Osmond 1998).
Strobilurins, are another class of fungicides which are
considered as a very valuable tool for managing diseases.
Strobilurin fungicides are beta-methoxyacrylate com-
pounds that inhibit respiration in fungi by binding to the Qo
site of the cytochrome bc1 complex located in the inner
mitochondrial membrane (Bartlett et al. 2002; Wiggins and
Jager 1993). This blocks electron transport and so reduces
ATP synthesis. Strobilurin fungicides inhibit respiration in
cytochrome bc1 isolated from yeast, fly, rat, and corn
(Roehl and Sauter 1993) and wheat (Ko
hle et al. 1997).
They also inhibit respiration in intact wheat plants and in
spinach (Spinacia oleracea L.) leaf discs (Glaab and Kaiser
1999). When a fungicide preparation containing the stro-
bilurin kresoxim-methyl is applied to the wheat plants, a
reduction in the stomatal aperture is observed along with an
increase in Pn rate (Fig. 2; Grossmann et al. 1999;Ko
et al. 1997). This result was quite surprising, because a
direct relationship between Pn and gs is well established
where the stomatal aperture increases Pn by increasing
diffusive transport of carbon dioxide (Yu et al. 2001). In an
interesting work, Nason et al. (2007) demonstrated that
strobilurin fungicides reduced the rate of gs to water in the
leaves of wheat, barley and soya plants. Coincidently,
plants treated with strobilurin fungicides have a lower rate
of transpiration (T), a lower Ci and a lower Pn compared
with control plants or plants treated with a epoxiconazole
which is a triazole fungicide. Azoxystrobin is an uncou-
pling strobilurin fungicide. The only data concerning
impact of azoxystrobin on photosynthesis showed that
Photosynth Res (2012) 111:315–326 321
azoxystrobin does not affect the chlorophyll content in
winter wheat, however its application delayed the increase
of AOS, thus delaying the senescence of wheat and pro-
longing the duration of flag leaf photosynthesis (Zhang
et al. 2010).
Triazole compounds such as triadimefon (TDM), prop-
iconazole, hexaconazole, and paclobutrazol are the largest
and most important group of systemic compounds devel-
oped for control of crop fungal diseases caused by
Fusarium sp and Erysiphe necator. These fungicides may
present phytotoxicity for crops as well as stimulant effects
on plant physiology. Pn increased after triazole applica-
tions in rice seedlings and bhendi (Guirong et al. 1995;
Sujatha et al. 1999), after paclobutrazol applications in
apple (Hong et al. 1995) and after TDM (15–20 g m
applications in radish crops (Panneerselvam et al. 1997)
and elephant foot yam (Gopi et al. 2005). By contrast,
cyazofamid (0.22 g l
) inhibits Pn in cucumber crops, but
no effect was measured with flusilazole on the same plants
(Xia et al. 2006) (Table 3). Gas exchange analysis dem-
onstrated that the suppression of Pn induced by cyazofamid
is associated with an increase of Ci, suggesting that Pn
alteration is mostly attributed to non-stomatal factors (Xia
et al. 2006). TDM also increases Pn along with Ci and gs in
maize (Kasele et al. 1995). To contrast, TDM treatments
induce stomatal closure in bean (Fletcher and Hofstra
1988), wheat (Sairam et al. 1989), elephant foot yam (Gopi
et al. 2005), radish (Panneerselvam et al. 1997), and mul-
berry plants (Sreedhar 1991). TDM treatments increased
the level of abscisic acid content in various plants, inducing
stomatal closure (Fletcher and Hofstra 1988; Panneersel-
vam et al. 1997; Gopi et al. 2005).
In the mesophyll, the number of cells per unit area in
both palisade and spongy layers and chloroplast number
per cell in the leaves of Chinese potato increased with
hexaconazole and paclobutrazol treatments (Kishorekumar
et al. 2006). The use of triazoles enhanced chlorophyll and
carotenoid contents in rice seedlings (Guirong et al. 1995)
Table 3 Effects of systemic fungicides on crop physiology
Family Affected parameter Active ingredient References
Anilides Inhibition of Pn Fenhexamid Petit et al. (2008b)
Repression of Rubisco genes Fenhexamid Petit et al. (2008b)
Azoles Inhibition of Pn Cyazofamid Xia et al. (2006)
Stimulation of Pn Paclobutrazol Hong et al. (1995)
Triadimefon Kasele et al. (1995), Panneerselvam et al. (1997),
Gopi et al. (2005)
Stomatal operture Triadimefon Kasele et al. (1995)
Stomatal closure Triadimefon Fletcher and Hofstra (1988), Sairam et al. (1989),
Sreedhar (1991), Panneerselvam et al. (1997),
Gopi et al. (2005)
Increased Ci Cyazofamid Xia et al. (2006)
Triadimefon Kasele et al. (1995)
Increased chlorophyll and
chloroplast contents
Paclobutrazol Kishorekumar et al. (2006)
Triadimefon Buchenauer and Rohner (1981), Gao et al. (1988),
Muthukumarasamy and Panneerselvam (1997),
Gopi et al. (1999)
Hexaconazole Kishorekumar et al. (2006)
Reduced oxygen evolution
and electron transport
Epoxiconazole Benton and Cobb (1997)
Benzimidazoles Inhibition of Pn Dibutylurea Shilling et al. (1994), Querns et al. (1998)
Chlorophyll declined Carbendazim Mihuta-Grimm et al. (1990), Garcia et al. (2002)
Carotenoids increased Carbendazim Garcia et al. (2002)
Disorganization of chloroplasts Dibutylurea Shilling et al. (1994)
PSII inactivation Dibutylurea Shilling et al. (1994)
Inhibition of electron transport Dibutylurea Querns et al. (1998)
Pyrimidines Inhibition of Pn Pyrimethanil Saladin et al. (2003)
Modifications of pigment concentrations Pyrimethanil Saladin et al. (2003)
Strobilurine Stomatal closure Kresoxim-methyl Grossmann et al. (1999)
Increased chlorophyll Kresoxim-methyl Grossmann et al. (1999)
322 Photosynth Res (2012) 111:315–326
and bhendi (Sujatha et al. 1999). TDM treatments
increased chlorophyll content in the leaves of the tomato
(Buchenauer and Rohner 1981), radish (Muthukumarasamy
and Panneerselvam 1997), cowpea (Gopi et al. 1999), and
wheat (Gao et al. 1988). Triazole compounds increase the
level of cytokinin, which might stimulate chlorophyll
biosynthesis (Jaleel et al. 2008). Triazoles accelerate
chloroplast differentiation, and chlorophyll production,
enlarged chloroplasts while also protecting the integrity of
chlorophyll (Fletcher et al. 2000; Jaleel et al. 2008). By
contrast, foliar application of epoxiconazole retards the
growth of cleavers (Benton and Cobb 1997). In addition,
7 days after treatment, epoxiconazole clearly reduces
oxygen evolution, determined as electron flow from water
to ferricyanide, and thus the associated electron transport
capability of isolated thylakoids (Benton and Cobb 1997).
Use of fungicides in the vineyards leads to an effective
protection against a wide variety of pathogens but at the
same time, generates long term residues in food and the
environment. Photosynthesis alteration was revealed by
reduction in Pn accompanied by changes in gs and Ci
including modifications of dark respiration after fungicide
treatment (van Iersel and Bugbee 1996; Untiedt and Blanke
2004; Xia et al. 2006). Considering fluorescence, the rel-
ative quantum yield of PSII (UPSII) and the maximal
quantum efficiency of PSII (Fv/Fm) were reduced by some
fungicides and were attributed to decrease in photochemi-
cal quenching (qP) (Krugh and Miles 1996). Fungicides of
the anilide family (pyrimethanil) and pyrimidine family
(fenhexamid) are newly synthesized pesticides used for
chemical control of Botrytis cinerea in viticulture.
Regarding pyrimethanil, the effects differ according to the
studied model. Using in vitro grown plantlets of grapevine,
6 mM pyrimethanil causes a decline in Pn and in photo-
synthetic pigment concentrations 7 days after application
(Saladin et al. 2003). In cuttings, pyrimethanil also inhibits
Pn but without reduction in chlorophyll concentrations.
In the vineyard, differences have been observed according
to cultivars. Pyrimethanil increases Pn and pigment con-
centrations in Chardonnay, whereas a decrease of these
parameters is observed in Pinot noir and Pinot Meunier
(Saladin et al. 2003). Petit et al. (2008b) demonstrated a
decrease in Pn following fenhexamid (1.5 kg ha
) 7 days
after treatment in the vineyard. Pn modification is mostly
attributed to non-stomatal limitation since the reduction of
photosynthesis is associated with few changes in Ci despite
gs decline. However, PSII activity is not affected. Addi-
tionally, decreased Pn is coupled with repression of genes
encoding Rubisco small and large subunits.
Conclusions and prospects
Fungicides constitute one of the most effective and inte-
grative method to control diseases against phytopathogenic
fungus in agriculture. However, the toxicity and the
Fig. 2 Site of action of
different class of fungicides
observed in fungi. ER
Endoplasmic reticulum
Photosynth Res (2012) 111:315–326 323
pollution generated by fungicides cannot be neglected. The
toxic effect of a given pesticide on seeds depends on its
distribution, persistence, metabolism, its active form, and
its concentration. Some pesticides interfere with the met-
abolic pathways of plants and some interfere specifically
with the photosynthetic process.
This review examines the toxic effects of a number of
different classes of fungicides on photosynthesis. They are
of importance in modern agriculture and in crop protection
but the modes of action are still not known indeed. How-
ever, this review does refer to the relevant literature and
illustrates the need for further research in this area to
mitigate against the deleterious effects. This is particularly
important for some of the older treatments such as copper.
Many findings indicate that some fungicides may affect the
photosynthetic process. Some pesticides lead to Pn alter-
ation through stomatal closure, while others affect the
structure and the functioning of chloroplasts. Certain
molecular compounds have no effect, whereas a few of
them, such as the azoles, stimulate Pn. Triadimefon and
hexaconazole could be used as a potential tool to manip-
ulate carbohydrate metabolism (Gomathinayagam et al.
2007). Photosynthesis is a complex physiological process.
More research highlighting and decoding each component
of the photosynthetic electron transport chain for example
PSI, PSII, Cyt b/f, and ATP synthase would be necessary.
In addition to damages caused by pesticides to crops, all
pesticides are potentially harmful to human health and
environment. Therefore taking into consideration the nega-
tive effects due to the use of chemicals for disease control, it
is of great importance to develop new active ingredients,
which could be used at such a dose where it shows high
specific toxicity to the target fungi and low toxicity to rest of
the species and have a curative effect. Among other desired
properties, having a low runoff potential and a rapid bio-
degradation potential might be good from an environmental
perspective. In addition to this, designing and testing active
ingredients that are less exposed to the risk of pathogen
resistance development and that do not present a risk during
experimental process would be very useful for the human
health and environment as well. New axes of research in this
area require attention. It would be indispensible to look for
new targets for example functional genomics. The diversi-
fication of chemical structures, along with combinatorial
chemistry and screening systems are some approaches that
will confer their benefits in the coming times.
Moreover, pesticide applicability can be compromised
by the emergence of resistant pathogen strains. Thus, the
need exists to curtail pesticide use, which will reduce the
environmental impact of this cultural practice. To this
purpose, there is an increasing demand to develop alter-
native methods for plant disease control. Another alterna-
tive strategy commonly used to control fungi is the
activation of plant defence mechanisms using a variety of
biotic and abiotic inducers.
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... In order to evaluate the possible effect of the application of the biostimulant RAZORMIN ® on pepper plants, subjected to the application of the fungicide azoxystrobin, on the photosynthetic process, different parameters that directly define the photochemical activity, such as chlorophyll a fluorescence, the concentration of photosynthetic pigments and photosynthetic efficiency were studied. The study of these parameters is very interesting because, in addition to indicating the vitality of plants, they provide an estimation of the phytotoxic effect caused by azoxystrobin and possible generation of ROS derived from the existence of failures in the photochemical activity of chloroplasts [20,37,69]. ...
... This is probably because strobilurins bind to the Qi site of the chloroplast cytochrome bf complex, resulting in a blockage of electron transport between photosystem II (PSII) and photosystem I (PSI) [70]. phytotoxic effect caused by azoxystrobin and possible generation of ROS derived from the existence of failures in the photochemical activity of chloroplasts [20,37,69]. , and production of fresh biomass of the aerial part (C). ...
... It was observed that the application of the fungicide azoxystrobin significantly reduced the concentration of chlorophyll a (Table 8). These results confirm those of other studies, since it has been observed that application of this type of fungicide inhibits both the synthesis of the precursor of chlorophylls and delta amino-laevulinic acid, and the activity of protochlorophyllide reductase, leading to a significant reduction in the concentration of photosynthetic pigments [20,70]. The protective effect of RAZORMIN ® application reducing the phytotoxic effect of azoxystrobin application was confirmed by the increase in leaf chlorophyll a concentration, with values similar to those of control plants. ...
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Use of biostimulants for stimulating plant growth and mitigating the negative impacts of biotic and abiotic stresses is a promising strategy to achieve higher crop yields. Fungicides such as azoxystrobin are used to control several pests and fungal diseases in plants but at the cost of altering various physiological processes; thereby, leading to reduced crop yields. The efficiency of the compound RAZORMIN® as a biostimulant product while taking into account its role in plant growth stimulation and fungicide azoxystrobin stress mitigation was evaluated in this study. The efficacy of RAZORMIN® was assessed considering its impact on the stimulation of growth-related physiological processes and stress mitigation mechanism, e.g., reactive oxygen species (ROS) detoxification. Application of RAZORMIN® significantly increased plant growth by improving fresh weight, photosynthetic efficiency, net photosynthesis rate, gas exchange, nitrogen (N) metabolism (with increases in soluble amino acids, foliar N concentration, and N use efficiency), growth hormone concentrations (mainly gibberellins and cytokinins), nutritional status of plants (producing a greater accumulation of phosphorus, potassium, calcium, magnesium, sulfur, zinc, molybdenum, iron, and boron), and sugars concentration. Furthermore, the application of RAZORMIN® on plants under fungicide azoxystrobin stress demonstrated its anti-stress and protective role by stimulating the antioxidant defense system and improving photosynthetic efficiency.
... Moreover, much of the existing literature indicate that fungicides are harmful to the ecosystem, and conventional use will also bring the threat of environmental impact [86]. Additionally, the application of fungicides may affect crop physiology through various disturbances, such as reduced growth, disturbance of the development of reproductive organs, changes in nitrogen and/or carbon metabolism, resulting in reduced nutrient utilization for plant growth [87]. In addition, organic coffee production does not use pesticides. ...
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Coffee is grown in more than 80 countries as a cash crop and consumed worldwide as a beverage and food additive. It is susceptible to fungal infection during growth, processing and storage. Fungal infections, in particular, can seriously affect the quality of coffee and threaten human health. The data for this comprehensive review were collected from the United States Department of Agriculture, Agricultural Research Service (USDA ARS) website and published papers. This review lists the fungal species reported on coffee based on taxonomy, life mode, host, affected plant part and region. Five major fungal diseases and mycotoxin-producing species (post-harvest diseases of coffee) are also discussed. Furthermore, we address why coffee yield and quality are affected by fungi and propose methods to control fungal infections to increase coffee yield and improve quality. Endophytic fungi and their potential as biological control agents of coffee disease are also discussed.
... Pesticides impact the crop physiology through various disruptions, such as perturbation in the development of the reproductive organs, growth reduction, and alteration of the carbon and/or nitrogen metabolism, leading to a lower nutrient availability for plant growth [114]. These disruptions will partly depend on the type of pesticide used [115]. Some important effects may only become apparent after repeated treatments and not necessarily translate into visible necrosis [116]. ...
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Background: The World Health Organization (WHO) states that “If it is not safe, it is not food”, as it does not serve its purpose to provide proper and safe nutrition. The Food and Agriculture Organization (FAO) reiterates that Sustainable Agriculture that seeks to increase yields while limiting the need for application of pesticides or synthetic fertilizers; only can relate Food Security with Food Safety. As the second largest agrarian country of the world, India has also become one of the largest users of pesticides. Surveys have shown that Indian food is laced with one of the highest amount of toxic pesticide residues in the world. Hence, analysis of pesticide residues in food has become the governing criteria for ensuring food safety. The Food Safety and Standards Authority of India (FSSAI) have laid down science based standards towards food safety based on the Codex standards, which are the reference for the international trade in food. However, it has been found that pesticide monitoring in food is most difficult in countries where that monitoring is arguably most needed. This is because the present chromatographic techniques though can precisely determine the presence of every chemical at the minute level but the process is hugely expensive, complex, time-consuming and require specific resources and infrastructure which offer major hindrance towards regular analysis for monitoring of food safety. Especially for a country like India, with absolute dominance of marginal farmers in vegetable cultivation, lack of awareness, resource scarcity, inability to take economic risk and flaws in maintaining the standard practices w.r.t. chemical usage enhances the availability of pesticides in food product. Moreover the short time gap between the field harvest of vegetables and consumption, limits the scope for safety analysis even if the infrastructure and economics is not considered. In this background an effective, simple, and affordable method is needed to enable pesticide residue analysis in situations of limited resources more so for Safe & Sustainable Agriculture Scope & Approach: In this scenario, the Colorimetric Pesticide Assay Test can be a Real Game Changer in the Food Safety Arena and a Crucial ‘Sustainability Tool’ for Safe & Sustainable Agriculture. This test method although utilized round the globe to identify the pesticides residues both in a quantitative and qualitative manner, lack a standard protocol towards safety evaluation of vegetables in terms of detecting the presence/absence of the major pesticide groups. Another crucial point is how to measure in the most affordable and transparent manner. Then it has to be made available for small, marginal and resource poor farmers, who are more than 95% of the total farming community. Inhana Organic Research Foundation (IORF), Kolkata in collaboration with Krishi Vigyan Kendra, Nadia (ICAR) initiated a research work in June, 2020 to develop a Protocol for Colorimetric Pesticide Assay Test of vegetables with the objectives of (i) Most Authentic and Speedy Measurement of the major groups of pesticides viz. organochlorine, organophosphate, synthetic pyrethroids, carbamates and neonicotinoids, that are used during vegetable production, (ii) Identifying the collective presence/ absence of the pesticide residues up to the lowest- group specific permissible limits (same type of pesticides in terms of chemical structure) and (iii) Standardization of the Method towards its effective utilization for large scale Pesticide Residue Study in the most economical manner. The Support from IBM, India for Clean Food Production – A Safe and Sustainable Agricultural Initiative; helped in the efforts to standardize the Colorimetric Assay Test Protocol towards safety evaluation of the vegetables. The standardization process involved the analysis of more than 1200 samples of 30 major vegetables produced in India. Vegetable samples were sourced from open markets, certified organic counters and from the farmers’ field where the concept of Clean Food Program was 1st initiated by IORF in collaboration with KVK, Nadia (ICAR). Also the vegetable samples were sourced during different seasons i.e., winter (Period : November – February), monsoon (Period : July – October) and summer (Period : March – June). Key Findings & Conclusion: The newly standardized Colorimetric Pesticide Assay Test Protocol can enable detection of the collective presence/ absence of pesticides up to group specific- lowest permissible limit; for more than 90 percent of the pesticides- permitted for use in India, for most of the banned chemicals, as well as chances of residual presence in case of chemicals like DDT and its isomer. In addition; this Assay Test protocol can also be utilized for detecting the presence/ absence of toxic heavy metals such as Hg2+, Cd2+, Cu2+, Pb2+ and a wide range of other toxic substance of known/unknown origin related to human health and safety. Moreover the Colorimetric Pesticide Assay Test Protocol opens up the scope for large scale and frequent food safety analysis due to the affordable cost (1/10th to 1/15th of the Conventional Cost of Residue Analysis) and significant reduction in the analysis time (1/10th of the time required for Residue Analysis using High Performance Liquid Chromatography, HPLC).
Soybean grain productivity is largely due to a complex of factors, in particular, the efficiency of symbiotic systems formed with nodule bacteria, the activity of growth processes and the formation of vegetative and generative organs by plants, as well as their adaptive plasticity under various environmental factors. The article presents the results of studying the peculiarities of the formation of soybean plant productivity upon seed pre-treatment with fungicides of different classes and inoculation with nodule bacteria on the day of sowing. Objective. To study the dynamics of seed germination, formation of vegetative and generative organs and soybean harvest, functioning of soybean-rhizobial symbiosis, as well as the state of photosynthetic pigment system — content of chlorophyll a and b and carotenoids in the leaves upon seed pre-treatment with fungicides Fever and Standak Top and bacterization with Bradyrhizobium japonicum 634b on the day of sowing. Methods. Microbiological, physiological, biochemical, statistical. Results. Fungicides did not exert toxicity in terms of seed germination, and soybean seed germination under the action of Fever exceeded parameters in the control plants by 20 % (at Day 5 after sowing) and by 7 % (at Day 8). It has been shown that fungicides increased plant height, aboveground mass and accelerated the formation of generative organs (flowers) by plants but did not significantly affect root mass. It was found that fungicides had a pronounced toxic (inhibitory) effect on soybean-rhizobial symbiosis upon seed pre-treatment: the process of nodule formation was suppressed in the initial stages of symbiosis, nitrogen fixation activity was lower than in the control plants by 80–48 % depending on soybean development phase. Thus, the effect of fungicides Fever and Standak Top upon seed pretreatment and inoculation with nodule bacteria on the day of sowing was characterized by significant suppression of functional activity of the symbiotic apparatus in the first half of soybean vegetation and its gradual recovery during formation of generative organs. Although fungicides inhibit the formation and functioning of legume-rhizobial symbiosis but their positive effect on the plant itself (seed germination, plant height, aboveground mass accumulation, dynamics of generative organ formation), as well as the ability of plants to adapt to stress at the biochemical level (stabilization of the content of photosynthetic pigments in the leaves) allowed to form a crop of soybean seeds at or slightly above the level of control. Conclusion. Physiological and biochemical features of the reaction of soybean-rhizobial symbiosis to the action of different fungicides that we had established must be taken into account in developing new strategies to protect plants from pathogens of various aetiologies with the involvement of physiologically active substances having fungicidal activity in combination with inoculation.
In the agricultural domain, chemical pesticides are repetitively and harshly used to kill harmful pests, but they often pose a serious threat to microbial diversity, soil fertility and agricultural output.
Species of the genus Trichoderma are known as the producers of many biologically active substances, in particular, enzymes that have found their practical application in many industries. In addition, the active Trichoderma strains are used as biological control agents of plant pathogenic micromycetes. Trichoderma strains are able to exhibit antagonistic properties against plant pathogens very effectively due to their peculiarities: high growth rate; synthesis of chitinolytic enzymes and secondary metabolites with antifungal activity. Thus, highly active Trichoderma strains has been successfully used to control plant pathogenic isolates of Fusarium, Alternaria, Botrytis, Sclerotinia, Verticillium, Pythium and other genera. The aim of the study was to evaluate the antagonistic activity of 100 Trichoderma strains against eight test-cultures of plant pathogenic micromycetes of different species and to select the most active strains for further studies of their physiological properties. Methods. Cultures of the studied fungi were grown on potato-dextrose agar. The antagonistic activity of fungi of the genus Trichoderma against fungal plant pathogens was carried out using the conventional method of dual culture. The percentages of growth inhibition of plant pathogens were calculated, and on the basis of these values the antagonistic activity of strains were concluded. Microsoft Excel and Origin 8.0 (OriginLab) packages were used for statistical data processing. Results. According to the results of a study of the antagonistic activity of Trichoderma strains against plant pathogenic micromycetes in general, it was shown that the strains have a high level of antifungal activity. Thus, the most numerous group (38%) of the total studied Trichoderma strains were “highly active” ones that inhibited the growth of plant pathogens from 70 to 80%. The second largest group (27%) was “moderately active” strains with 60–70% inhibition of plant pathogenic test cultures. The smallest (6%) but the most active group consisted of the “most active” strains with an average value of the inhibition more than 80%. Thus, almost three quarters (71%) of the studied Trichoderma strains showed a high level of antagonistic activity against plant pathogens with the inhibition more than 60%. In addition, only 17% of Trichoderma strains were “inactive” and 12% of them showed insufficient activity with growth inhibition of plant pathogens less than 50%. Notably, 35% of Trichoderma strains were active against all eight test cultures of plant pathogenic micromycetes. Conclusions. The studied Trichoderma strains have significant antagonistic potential both for individual strains of plant pathogenic micromycetes and for all studied plant pathogens. The involvement of a wide range of test cultures of plant pathogens, as well as significant amount (100) of Trichoderma strains allowed a more objective and systematic assessment of the antagonistic potential of fungi of this genus. Thus, our study of action of the wide range of Trichoderma strains against test cultures of different species showed that the fungi of the genus Trichoderma were effective antagonists of plant pathogenic fungi. The 38% of Trichoderma strains showed a high level of antifungal action and inhibited the growth of plant pathogens by 70% and more. Only 12% of strains showed less than 50% activity. In addition, 35% of Trichoderma strains were active against all eight tested plant pathogen test cultures. The significant amount of studied Trichoderma strains was highly active, and they can be used as a basis for further research to obtain effective biological control agents of plant pathogenic micromycetes.
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Soil fertility management has two requirements: establishing and maintaining the soil pH and essential plant nutrient elemental content within their desired ranges for that soil type and crop or cropping sequence, with its associated cultural management practices. It is obvious that none of the soil fertility management systems will meet all these requirements. However, there are basic principles that do apply, requiring moderate modification to suit the specifications of soil type, crop species, and climatic/weather characteristics. Management requirements for achieving a moderate yield and average product quality, require fewer inputs and skill requirements than those required for achieving maximum yield and highest product quality, the latter not allowing for errors in procedural practices. For most cropping situations, the maximum biological yield potential based on the combination of soil and plant parameters is unknown. It is also not possible to advance quickly from a moderate soil fertility/plant nutrition status to one that results in high yield or quality product achievement. Those management practices applied to one set of soil, plant, or climatic conditions are not applicable to all ranges of conditions. Hence, this chapter tends to discuss the problems of soil fertility and productivity, nutrients and mining and imbalance, and inadequate plant nutrients supply in Nigeria’s agriculture, as well as the problems affecting the use of chemical fertilizers, the types, and role of organic sources of plant nutrients. Finally, a case will be made for integrated nutrient supply that combines chemical fertilizers with biological and organic sources.
Fungicides applied singly are frequently used to ensure disease control in the cultivation of leafy vegetables. The behavior of fungicide mixtures and their impact on plant biochemical and antioxidant status was poorly investigated. The main goal of this study was to compare the impact of fluazinam, a separately applied fungicide, and its mixtures (dithianon+fluazinam, dodine+fluazinam) during dissipation on biochemical compounds and the antioxidant profile in lettuce. Additionally, the behavior of dithianon and dodine applied singly was examined. We noted a longer dissipation time of fluazinam in mixtures (DT50= 6.31 and DT50=4.80) compared to separate application (DT50= 3.36) as well as a shortened dithianon and dodine degradation in mixtures. Moreover, dithianon, dodine and fluazinam applied separately affected the reduction of chlorophylls (43%) and carbohydrates (56%) as well as the induction of carotenoids (37%), protein (40%) and phenolic compounds (50%) in a different dissipation time. Furthermore, fluazinam mixtures intensified accumulation of carotenoids (up to 106.1 µg g⁻¹), protein (21.9 mg g⁻¹) and phenolic compounds (1410 µg g⁻¹), while reduction of carbohydrates (3.4 µg g⁻¹), compared to separate application. For the first time, we revealed that non-enzymatic antioxidants are the first line of defense in ROS scavenging caused by fungicides (up to the 12th h), while antioxidant enzymes (CAT, POD, SOD) play a secondary role in supporting stress mitigation. Results of the study can be applied to the horticultural practice in lettuce cultivation and shed a new light on plant biochemistry under fungicide stress conditions.
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Pesticides are large groups of chemical compounds including herbicides, insecticides, fungicides, nematicides, rodenticides, and plant growth regulators etc., commonly used for crop protection against pests. Indiscriminate utilization of pesticides could adversely impose the risk to food safety, the environment and the living population. Farmers are ignoring the risk associated with pesticides used, safety guidelines, and protective directives in crop management. The improper utilization of pesticides caused the degradation of the quality and fertility of the soil as well as disturbing the nutrient cycling, which leads to heavy metal deposition and toxicity. Excessive exposure of the pesticide to the insect population will be created the development of insect pest resistance, resurgence and decline of the population of the natural enemies. Disposal of unwanted pesticides waste is responsible for the pollution of the water reservoir, groundwater, and pond water sources. The bio-magnification of contaminant cause health associated risk in human beings and animal at different levels of the food chain. In this chapter, we are discussing in detail the risk associated with pesticide application and crop management.
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Dibutylurea (DBU), a breakdown product of benomyl, may be partially responsible for the previously reported phytotoxicity of the fungicide Benlate DF. We quantified the effect of DBU on the growth of two popular bedding plant species, petunia ( Petunia × hybrida ) and impatiens ( Impatiens wallerana Hook. f.). DBU reduced photosynthesis of both species, and its effect strongly depended on the amount of DBU applied. The effects of DBU were most apparent 2 to 4 days after treatment, at which time 1.20 g·m ⁻² (corresponding to 10% DBU in Benlate DF at maximum labeled drench rate) inhibited photosynthesis completely. DBU also decreased flower number and caused marginal necrosis. DBU effects were more pronounced in low relative humidity. Benlate DF containing 3.1% DBU and an equivalent amount of reagent grade DBU had similar effects on photosynthesis and petunia necrosis. Our results showed that DBU is responsible for at least part of the phytotoxic symptoms that can be caused by Benlate DF. However, other ingredients or breakdown products may also contribute to the phytotoxic symptoms of Benlate DF.
Juwel®, a new fungicide developed by BASF Aktiengesellschaft combines two active ingredients: the strobilurin compound Kresoxim-methyl and the triazol compound Expoxiconazole. In addition to its excellent and long lasting fungicidal activity against all important cereal crop pathogens, Juwel® has influence on the C- and N-assimilation of the plant as shown in test systems free of pathogens. The contents of ethylene and other plant hormones are also modified, which may be the reason for enhanced stress resistance and greening effects of plants after treatment with Juwel®. Since these special metabolic and regulatory changes are independant of fungal attack, the physiological effects of Juwel® are discussed to be the most likely cause for the superieur increase in yield compared to other fungicides.
The effect of copper on photoinhibition of photosystem II in vivo was studied in bean (Phaseolus vulgaris L. cv Dufrix). The plants were grown hydroponically in the presence of various concentrations of Cu²⁺ ranging from the optimum 0.3 μm(control) to 15 μm. The copper concentration of leaves varied according to the nutrient medium from a control value of 13 mg kg⁻¹ dry weight to 76 mg kg⁻¹ dry weight. Leaf samples were illuminated in the presence and absence of lincomycin at different light intensities (500–1500 μmol photons m⁻² s⁻¹). Lincomycin prevents the concurrent repair of photoinhibitory damage by blocking chloroplast protein synthesis. The photoinhibitory decrease in the light-saturated rate of O2 evolution measured from thylakoids isolated from treated leaves correlated well with the decrease in the ratio of variable to maximum fluorescence measured from the leaf discs; therefore, the fluorescence ratio was used as a routine measurement of photoinhibition in vivo. Excess copper was found to affect the equilibrium between photoinhibition and repair, resulting in a decrease in the steady-state concentration of active photosystem II centers of illuminated leaves. This shift in equilibrium apparently resulted from an increase in the quantum yield of photoinhibition (ΦPI) induced by excess copper. The kinetic pattern of photoinhibition and the independence of ΦPI on photon flux density were not affected by excess copper. An increase in ΦPI may contribute substantially to Cu²⁺ toxicity in certain plant species.
Individual spinach plants (Spinacia oleracea L., c.v. Matador) sensitive to excess copper were grown on a nutrient medium containing toxic amounts of the metal, and the characteristics of its photosynthetic apparatus were examined. In chloroplasts isolated from Cu-treated plants the accumulation of plastid pigments and lipoquinones was lower than in controls and it decreased with the increase of copper toxicity. The loss of photochemical activity of photosystem I and photosystem II was observed at the late stage of leaf degradation (the leaves turned yellow). The loss of photosystem II activity was faster than that of photosystem I. Consequently, changes in chlorophyll distribution of light harvesting chlorophyll-protein complexes were observed. The CPa level, being the presumable reaction center of photosystem II, decreased significantly. The fine structure of chloroplasts revealed degradation of grana stacks and stroma lamellae depending on the stage of their degeneration, an increase in the number and size of plastoglobuli and intrathylakoidal inclusions. The results obtained have been discussed with regard to direct or indirect effects of copper in chloroplasts of plants sensitive to excess copper.