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 VOLUME Vol.05 Issue05 2025 

PAGE NO. 33-36 

DOI 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 

 

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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 35 https://theusajournals.com/index.php/ajahi 

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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