American Journal Of Agriculture And Horticulture Innovations
33
https://theusajournals.com/index.php/ajahi
VOLUME
Vol.05 Issue05 2025
PAGE NO.
33-36
10.37547/ajahi/Volume05Issue05-09
Phosphate-Mobilizing Rhizobacteria As Biocontrol
Agents Against Wheat Diseases Caused by Bipolaris
Sorokiniana
Zakiryaeva S.I.
PhD, senior scientists of Institute of microbiology, Academy of Sciences, Republic of Uzbekistan
Received:
31 March 2025;
Accepted:
29 April 2025;
Published:
31 May 2025
Abstract:
Bipolaris sorokiniana are a destructive hemibiotrophic pathogen causing root and crown rot, leaf spot
and black mold of cereal crops, which significantly reduces grain yield and quality worldwide. This study
investigated the antagonistic activity of 20 strains of phosphate-mobilizing wheat rhizobacteria from the genera
Rahnella, Enterobacter, Bacillus, Paenibasillus and Pseudomonas against wheat diseases caused by B. sorokiniana.
It was found that out of 20 strains of rhizobacteria 5 strains (Enterobacter clocae 7, Bacillus cereus 23,
Pseudomonas kilonensis 24, P. kilonensis 26, P. kilonensis 30) 100% inhibited the growth of phytopathogen B.
sorokiniana.
Keywords:
Bipolaris sorokiniana, phosphate-mobilizing rhizobacteria, wheat, antagonistic activity, biological
control.
Introduction:
Wheat (Triticum aestivum) is one of the
most widely grown crops in the world. In 2018, its
production exceeded 734 million tons on an area of 214
million ha [1]. Wheat production is constrained by
biotic stresses, chief among which are yield-limiting
diseases worldwide. Out of more than 200 wheat
diseases, about 50 cause significant economic losses [2-
7]. Diseases cause approximately 20% yield loss
annually. Rust, spot blight, root rot, parsha, septoriosis,
powdery mildew, fusarium and other viral, nematode
and bacterial diseases are considered the most
damaging [8-11].
Wheat has been a key food crop in the world for
thousands of years. However, its yield is often reduced
by various biotic stresses [12]. Among the most
dangerous pathogens that affect the leaves, stems and
grain of wheat is Bipolaris sorokiniana. This fungus has
been repeatedly associated with the occurrence of
spotting on wheat, leading to yield losses ranging from
16 to 43%, especially in regions with a warm and humid
climate [13].
One of the important soil diseases of wheat is common
root rot, caused by Bipolaris sorokiniana (Sacc. in
Sorok.) Shoem. The micromycete Bipolaris sorokiniana
is a globally distributed pathogen of common root rot,
leaf spot, seedling blight, bunt blight and black spot on
wheat and barley. This fungus is one of the most serious
leaf spot diseases in both crops in warm growing
regions and causes significant yield losses. High
temperature and high relative humidity favor the
spread of the disease, especially in intensive irrigated
wheat and rice production systems in South Asia. B.
sorokiniana can develop endophytically, epiphytically,
persist for long periods of time in soil and on plant
debris. The chemical mechanisms of such good
adaptability of this fungus to different environments
are still poorly understood [14-19].
Among the various diseases caused by B. sorokiniana,
leaf spots of wheat and barley are the most important,
especially under the high temperature and humidity
conditions typical for some agricultural regions [20].
This phytopathogen poses a serious threat to more
than a thousand plant species, including the major
cereal crops wheat, barley, rye, maize, rice, and millet
[21]. Moreover, in 2021, B. sorokiniana was reported
for the first time on lentil cultivar Syria 229, expanding
the potential host range of this pathogen [22].
In recent years, attention to the search for biocontrol
American Journal Of Agriculture And Horticulture Innovations
34
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American Journal Of Agriculture And Horticulture Innovations (ISSN: 2771-2559)
agents has increased, and it is important to identify
antagonistic strains that can complement cultural and
chemical defense methods under field conditions.
Therefore, the aim of this study was to investigate the
antagonistic
activity
of
phosphate-mobilizing
rhizosphere
bacteria
of
wheat
against
the
phytopathogen B. sorokiniana.
METHODS
The objects of research were 20 local strains of
phosphate-mobilizing
rhizobacteria
of
wheat.
Rhizobacterial strains were cultured at t=28±2ºС for 5
days under aerobic conditions on peptone liquid
nutrient medium with glucose. The fungus was
cultivated in liquid Czapeka nutrient medium (20 g
glucose, 2 g NaNO3, 1 g KH2PO4, 0.5 g MgSO4
・
7H2O,
0.5 g KCl, water up to 1 l, pH 6) [23]. Phytopathogenic
fungi of B. sorokiniana were obtained from the
collection of microorganisms of the Institute of
Genetics.
The antagonistic activity of rhizobacterial cultures was
tested using the well method [24]. The magnitude of
antagonistic activity was measured by the diameter of
fungal growth inhibition zones around the wells after
incubation at 28°C for 3-5 days. Repetition of the
experiment was three times. Statistical analysis of the
results was carried out using Excel software package.
RESULTS AND DISCUSSION
In a previous study, we isolated rhizobacteria from the
rhizosphere of wheat and screened them for their
phosphate-mobilizing capabilities, identifying the most
efficient strains based on their ability to solubilize
inorganic phosphates [25]. In the present study, we
further evaluated the biocontrol potential of these
phosphate-mobilizing rhizobacteria by assessing their
antagonistic activity against Bipolaris sorokiniana, a
major fungal pathogen responsible for spot blotch
disease in wheat.
A total of 20 phosphate-mobilizing rhizobacterial
strains, taxonomically affiliated with the genera
Rahnella, Enterobacter, Bacillus, Paenibacillus, and
Pseudomonas, were selected for antagonism assays
against B. sorokiniana. The antagonistic activity of
phosphate-mobilizing
rhizobacteria
against
the
phytopathogenic fungus Bipolaris sorokiniana was
evaluated in vitro using well method on Czapeka
(Figure 1 and 2).
Out of the 20 tested strains, 11 exhibited varying
degrees of antagonistic activity against the
phytopathogen. Notably, five strains - Enterobacter
cloacae 7, Bacillus cereus 23, Pseudomonas kilonensis
24, P. kilonensis 26, and P. kilonensis 30 showed
complete inhibition (100%) of fungal mycelial growth,
indicating strong antagonistic potential. These strains
formed clear inhibition zones and demonstrated rapid
colonization around the fungal growth area, likely due
to the secretion of antifungal metabolites, lytic
enzymes, or siderophores.
Figure 1. Effect of rhizobacterial strains belonging to the genera Rahnella, Enterobacter, Bacillus, Paenibacillus
and Pseudomonas on the growth of the wheat phytopathogen Bipolaris sorokiniana (%)
American Journal Of Agriculture And Horticulture Innovations
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American Journal Of Agriculture And Horticulture Innovations (ISSN: 2771-2559)
Moderate inhibition was observed for Rahnella
aquatilis strains 10 and 17, which suppressed fungal
growth by 60%. E. cloacae 18, B. subtilis 31, and
Paenibacillus dendritiformis 25 inhibited the pathogen
by 50%, whereas R. aquatilis 14 demonstrated a
comparatively lower inhibition rate of 40%. The
remaining nine strains did not exhibit any noticeable
antagonistic effect against B. sorokiniana, suggesting
either the absence of antifungal activity or insufficient
production of inhibitory compounds under the
experimental conditions.
Figure 2. Antagonistic activity of phosphate-mobilizing rhizobacteria against Bipolaris sorokiniana: E. cloacae
7, E. cloacae 8, B. cereus 23, P. kilonensis 24, P. kilonensis 26, P. kilonensis 30
These findings highlight the diversity in biocontrol
capacity among phosphate-mobilizing rhizobacteria.
The strong antifungal activity exhibited by strains such
as P. kilonensis and E. cloacae suggests their potential
utility in the development of bioinoculants for
integrated disease management in wheat cultivation.
The dual functionality of these strains - phosphate
solubilization and pathogen suppression - positions
them as promising candidates for sustainable
agricultural practices aimed at enhancing crop
productivity and reducing dependence on chemical
fertilizers and fungicides.
Further studies are warranted to elucidate the specific
mechanisms of antagonism, including the identification
of secondary metabolites and their modes of action, as
well as the performance of these strains under
greenhouse and field conditions. Thus, of the 20 local
phosphate-mobilizing rhizobacterial strains studied, 11
showed antagonistic activity against B. sorokiniana. The
strains E. cloacae 7, B. cereus 23, P. kilonensis 24, P.
kilonensis 26 and P. kilonensis 30 demonstrated the
highest activity, inhibiting the growth of B. sorokiniana
by 100%, respectively.
CONCLUSION
B. sorokiniana is a dangerous pathogen that affects the
roots, crown, stems, leaves, and grains of wheat,
leading
to
significant
yield
losses.
Effective
management strategies should focus not only on
limiting the fungus in the above-ground parts of the
plant but also on reducing its presence in the soil.
Based on the obtained results, it can be concluded that
local rhizobacterial strains exhibit antagonistic and
antifungal activity against B. sorokiniana. As a result,
rhizobacterial cultures showing high activity can be
recommended as starter cultures for developing
biofungicides to protect wheat from B. sorokiniana, and
effective bioproducts can be created on this basis. An
alternative method for combating pathogenic fungi
that cause diseases in agricultural plants is the
introduction of bacteria with high biofungicidal
properties into the soil and the rhizosphere of plants.
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