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Common bean rust disease caused by Uromyces appendiculatus. (A,B) Naturally infected plants showing the symptoms of the rust disease; (C-E) Pathogenicity test exhibiting the ability of uredospores to re-infect the plants under greenhouse conditions. Developing of uredial lesions on the upper (C,D) and lower epidermis (E) of bean leaves.
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This study aimed to evaluate the efficacy of endophytic bacterium to control common bean rust disease under greenhouse conditions. Endophytic bacterium Pseudomonas putida ASU15 was isolated from fresh asymptomatic common bean, identified using biochemical and molecular characteristics. In vitro, the inhibitory effect of different concentrations of...
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Context 1
... uredospores of U. appendiculatus were obtained from heavily infected bean plants in El-Menia Governorate, Egypt. Interestingly, rust-infected common bean plants in the field showed typical symptoms of the disease (Figure 1). Numerous reddish brown circular pustules of 1-2 mm in diameter, representing uredial lesions, develop on the upper and lower sides of bean leaves. ...
Context 2
... collected the uredospores from uredial lesions of the naturally infected bean leaves and used them to re-infect bean plants cultivated in the greenhouse of Assiut University. The pathogenicity test exhibited the ability of U. appendiculatus spores to aggressively infect the plants, producing intensive symptoms of the disease (Figure 1). ...
Citations
... Admassie et al. [79] reported lipases as one of the most important antagonistic compounds liberated by Pseudomonas fluorescens and Enterobacter cloacae in the control of P. capsici. The P. putida strain AUS15, isolated from fresh beans, represented direct biocontrol efficacy against Uromyces appendiculatus through lipolytic, chitinolytic, and proteolytic activities [102]. Streptomyces puniceus with strong lipase activity exhibited significant inhibition to the growth of Verticillium dahliae, and Valsa mali [118]. ...
... The lipase's mode of action is hydrolyzing different lipid substrates by breaking ester bonds down and producing glycerol, fatty acids, and other alcohols. These enzymes can also induce the plant immune system by liberating lipids [102]. The last discussed extracellular hydrolytic enzyme, amylase, breaks down starch into maltose and glucose sugars. ...
Background: Phytopathogens, encompassing fungi, bacteria, viruses, and nematodes, pose a significant threat to the agricultural industry by causing substantial economic losses through severe plant diseases. The excessive use of synthetic fungicides to combat phy-topathogens has raised environmental and human health concerns. Results: Consequently, there is an increasing demand for safe and environmentally friendly biopesticides to align with consumer preferences for uncontaminated food. One particularly promising alternative to synthetic fungicides involves harnessing biocontrol bacteria that produce extracellular hydrolytic enzymes. These enzymes serve to effectively manage phytopathogens while concurrently fostering sustainable plant protection. Among the pivotal hydrolytic enzymes generated by biocontrol bacteria are chitinase, cellulase, protease, lipase, glucanase, and amylase. These enzymes exert their influence by breaking down the cell wall, proteins, and DNA of phytopathogens, thereby establishing a dependable method of biocontrol. Conclusions: Recognizing the critical role of these hydrolytic enzymes in sustainable biocontrol, this review seeks to delve into their primary functions, contribution to sustainable plant protection, and mechanisms of action. Through an exploration of the potential presented by biocontrol bacteria and their enzymatic mechanisms, we can discern effective and environmentally conscious strategies for managing phytopathogens in agriculture.
... Representatives of the species have been implicated in bioremediation, plant growth promotion, the biocontrol of phytopathogens, and other biotechnological purposes [63]. P. putida strains have been shown to inhibit phytopathogenic bacteria [64], fungi [65,66], and nematodes [67] both in vitro and in planta. In addition to their wide metabolic capabilities, studies have shown that strains of P. putida also harbor T6SS clusters [49,68]. ...
Bacteria from the genus Pseudomonas have been extensively studied for their capacity to act as biological control agents of disease and pests and for their ability to enhance and promote crop production in agricultural systems. While initial research primarily focused on the human pathogenic bacteria Pseudomonas aeruginosa, recent studies indicate the significance of type VI secretion (T6SS) in other Pseudomonas strains for biocontrol purposes. This system possibly plays a pivotal role in restricting the biological activity of target microorganisms and may also contribute to the bolstering of the survival capabilities of the bacteria within their applied environment. The type VI secretion system is a phage-like structure used to translocate effectors into both prokaryotic and eukaryotic target cells. T6SSs are involved in a myriad of interactions, some of which have direct implications in the success of Pseudomonas as biocontrol agents. The prevalence of T6SSs in the genomes of Pseudomonas species is notably greater than the estimated 25% occurrence rate found in Gram-negative bacteria. This observation implies that T6SS likely plays a pivotal role in the survival and fitness of Pseudomonas. This review provides a brief overview of T6SS, its role in Pseudomonas with biocontrol applications, and future avenues of research within this subject matter.
... The shoot length and fresh biomass were also significantly increased by plants inoculated with bacterial isolates, and our results agree with previous reports that IAA production by endophytic bacterial species is beneficial for promoting plant growth (Karnwal, 2009). Conversely, several studies have noted that microbial metabolites can contain natural compounds that hinder seed germination (Abo-Elyousr et al., 2021;He et al., 2022). For instance, Zonno and Vurro (2002) found that certain toxins produced by bacteria and fungi hindered the germination of Orobanche ramosa seeds, suggesting potential use in controlling parasitic plants. ...
... For instance, Zonno and Vurro (2002) found that certain toxins produced by bacteria and fungi hindered the germination of Orobanche ramosa seeds, suggesting potential use in controlling parasitic plants. Similarly, Abo-Elyousr et al. (2021) demonstrated that P. putida ASU15 inhibited U. appendiculatus urediniospore germination by increasing bacterial concentration. In our research, we observed inhibitory effects on wheat seed germination and seedling vigor from diverse endophytic and rhizospheric isolates from different sources. ...
... The shoot length and fresh biomass were also significantly increased by plants inoculated with bacterial isolates, and our results agree with previous reports that IAA production by endophytic bacterial species is beneficial for promoting plant growth (Karnwal, 2009). Conversely, several studies have noted that microbial metabolites can contain natural compounds that hinder seed germination (Abo-Elyousr et al., 2021;He et al., 2022). For instance, Zonno and Vurro (2002) found that certain toxins produced by bacteria and fungi hindered the germination of Orobanche ramosa seeds, suggesting potential use in controlling parasitic plants. ...
... For instance, Zonno and Vurro (2002) found that certain toxins produced by bacteria and fungi hindered the germination of Orobanche ramosa seeds, suggesting potential use in controlling parasitic plants. Similarly, Abo-Elyousr et al. (2021) demonstrated that P. putida ASU15 inhibited U. appendiculatus urediniospore germination by increasing bacterial concentration. In our research, we observed inhibitory effects on wheat seed germination and seedling vigor from diverse endophytic and rhizospheric isolates from different sources. ...
... The shoot length and fresh biomass were also significantly increased by plants inoculated with bacterial isolates, and our results agree with previous reports that IAA production by endophytic bacterial species is beneficial for promoting plant growth (Karnwal, 2009). Conversely, several studies have noted that microbial metabolites can contain natural compounds that hinder seed germination (Abo-Elyousr et al., 2021;He et al., 2022). For instance, Zonno and Vurro (2002) found that certain toxins produced by bacteria and fungi hindered the germination of Orobanche ramosa seeds, suggesting potential use in controlling parasitic plants. ...
... For instance, Zonno and Vurro (2002) found that certain toxins produced by bacteria and fungi hindered the germination of Orobanche ramosa seeds, suggesting potential use in controlling parasitic plants. Similarly, Abo-Elyousr et al. (2021) demonstrated that P. putida ASU15 inhibited U. appendiculatus urediniospore germination by increasing bacterial concentration. In our research, we observed inhibitory effects on wheat seed germination and seedling vigor from diverse endophytic and rhizospheric isolates from different sources. ...
... The shoot length and fresh biomass were also significantly increased by plants inoculated with bacterial isolates, and our results agree with previous reports that IAA production by endophytic bacterial species is beneficial for promoting plant growth (Karnwal, 2009). Conversely, several studies have noted that microbial metabolites can contain natural compounds that hinder seed germination (Abo-Elyousr et al., 2021;He et al., 2022). For instance, Zonno and Vurro (2002) found that certain toxins produced by bacteria and fungi hindered the germination of Orobanche ramosa seeds, suggesting potential use in controlling parasitic plants. ...
... For instance, Zonno and Vurro (2002) found that certain toxins produced by bacteria and fungi hindered the germination of Orobanche ramosa seeds, suggesting potential use in controlling parasitic plants. Similarly, Abo-Elyousr et al. (2021) demonstrated that P. putida ASU15 inhibited U. appendiculatus urediniospore germination by increasing bacterial concentration. In our research, we observed inhibitory effects on wheat seed germination and seedling vigor from diverse endophytic and rhizospheric isolates from different sources. ...
Salinity stress, a significant global abiotic stress, is caused by various factors such as irrigation with saline water, fertilizer overuse, and drought conditions, resulting in reduced agricultural production and sustainability. In this study, we investigated the use of halotolerant bacteria from coastal regions characterized by high salinity as a solution to address the major environmental challenge of salinity stress. To identify effective microbial strains, we isolated and characterized 81 halophilic bacteria from various sources, such as plants, rhizosphere, algae, lichen, sea sediments, and sea water. We screened these bacterial strains for their plant growth-promoting activities, such as indole acetic acid (IAA), phosphate solubilization, and siderophore production. Similarly, the evaluation of bacterial isolates through bioassay revealed that approximately 22% of the endophytic isolates and 14% of rhizospheric isolates exhibited a favorable influence on seed germination and seedling growth. Among the tested isolates, GREB3, GRRB3, and SPSB2 displayed a significant improvement in all growth parameters compared to the control. As a result, these three isolates were utilized to evaluate their efficacy in alleviating the negative impacts of salt stress (150 mM, 300 mM, and seawater (SW)) on the growth of wheat plants. The result showed that shoot length significantly increased in plants inoculated with bacterial isolates up to 15% (GREB3), 16% (GRRB3), and 24% (SPSB2), respectively, compared to the control. The SPSB2 strain was particularly effective in promoting plant growth and alleviating salt stress. All the isolates exhibited a more promotory effect on root length than shoot length. Under salt stress conditions, the GRRB3 strain significantly impacted root length, leading to a boost of up to 6%, 5%, and 3.8% at 150 mM, 300 mM, and seawater stress levels, respectively. The bacterial isolates also positively impacted the plant’s secondary metabolites and antioxidant enzymes. The study also identified the WDREB2 gene as highly upregulated under salt stress, whereas DREB6 was downregulated. These findings demonstrate the potential of beneficial microbes as a sustainable approach to mitigate salinity stress in agriculture.
... Mizubuti et al. (1995) and Zyton and Hassan (2017) tested the ability of the tested bio-agents, B. subtilis and B. thuringiensis and significantly caused reduction in the germination of U. appendiculatus uredospores. The obtained data also are in harmony with those reported by Ismail and Afifi (2019) and Abo-Elyousr et al. (2021) who indicated that uredospore germination of U. appendiculatus in vitro were affected by the biotic and abiotic factors, also these results agree with those obtained by Abeysinghe (2009) who mentioned that the use of rhizobacteria reduce U. appendiculatus uredospore germination. ...
... Thus, results obtained are compatible with the findings concerning the acquire here in inducing systemic resistance (SAR) due to the treatment with the tested biotic or abiotic factors (Walters et al., 2013;Prasannath, 2017 andSarhan et al., 2018), Therefor, biotic and abiotic inducers have potential in agriculture regarding the managing of plant pathogens (Reddy et al., 2014). Bioagents treatments i.e., B. subtilis, P. polymyxa, T. harzianum, and T. viride, significantly reduced rust severity and (AUDPC) also the disease increase rate (r-value), the obtained data agree with several investigations that confirm the role of biological control application to suppression of plant disease and successfully inhibit the growth of the target pathogen with several disease suppression mechanisms (competition for nutrients; occlusion of pathogen; toxin inactivation; stimulation of host growth; induction of host defence;) under both greenhouse and field conditions (Elliott et al., 2009;O'Brien 2017 andAbo-Elyousr et al., 2021). ...
... In Egypt, Zyton and Hassan (2017) reported that B. subtilis and B. thuringiensis had greatest inhibitory effect under field conditions against pea rust (U. pisi) uredospores reached to 74.7 and 59.4 %. More recently, Ismail and Afifi (2018) and Abo-Elyousr et al. (2021) indicated that biotic factors, Bacillus pumilus, B. subtilis, Pseudomonas putida, Trichoderma harzianum, T. asperellum and T. viride, controlling bean rust disease (Uromyces appendiculatus) resulted in significant decrease of disease severity and AUDPC as indicated spores germination direct suppression. The treatment of chemicals inducers Ascorbic acid, Bion, Potassium citrate, Salicylic acid, were significantly reduced bean rust severity, AUDPC and r-value during the two successive growing seasons (2019 and 2020) compared to the control treatment, meanwhile were significantly effective in increasing of polyphenol oxidase (PPO), peroxidase (PO) and Catalase (CA) enzyme activities. ...
... On the other hand, another study reported that P. putida strain JD204, isolated from wheat roots, was reported to activate resistance by the over-expression of the resistancerelated genes [24]. Also, P. putida ASU15 was applied during pathogen inoculation; it resulted in a higher reduction in disease severity of common bean rust (69.9%) compared to its application before pathogen inoculation (54.9%) [30]. P. putida can produce various antibiotics, siderophores, and a small amount of hydrogen cyanide (HCN). ...
Wheat stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is a destructive disease that causes significant yield losses in wheat production worldwide, including in Egypt. The use of biocontrol agents is among the best eco-friendly management strategies to control this disease, as they are more sustainable and environmentally friendly than traditional chemical control methods. In a comparative analysis, antioxidant enzyme activity and various management approaches were compared with two bacterial biocontrol agents, Bacillus subtilis and Pseudomonas putida. This study showed the remarkable efficacy of endophytic bacteria, B. subtilis and P. putida, in mitigating wheat stripe rust infection across three wheat varieties, namely Misr1, Gimmeiza11, and Sids12. B. subtilis exhibited superior performance compared to P. putida, resulting in infection types of 1 and 2.66, respectively, following inoculation. The highest reduction rate was observed with Tilit fungicide (500 ppm), followed by B. subtilis and Salicylic acid (1000 ppm), respectively. Variations in wheat varieties’ response to Pst infection were observed, with Misr1 exhibiting the lowest infection and Sids12 showing high susceptibility. Among the tested inducers, Salicylic acid demonstrated the greatest reduction in disease infection, followed by Indole acetic acid, while Oxalic acid exhibited the lowest decrease. Additionally, the study evaluated the activities of five antioxidant enzymes, including Catalase, Ascorbate peroxidase (APX), glutathione reductase (GR), Superoxide dismutase (SOD), and peroxidase (POX), in the wheat-stripe rust interaction under different integrated management approaches. The wheat variety Misr1 treated with Tilit (500 ppm), B. subtilis, Salicylic acid, Montoro (500 ppm), and P. putida exhibited the highest increase in all enzymatic activities. These findings provide valuable insights into the effectiveness of B. subtilis and P. putida as biocontrol agents for wheat stripe rust control in Egypt, emphasizing their potential role in sustainable, integrated, and environmentally friendly management practices.
... Bacillus species have been reported as endophytes of Allium crops [72,73]. According to Wang et al., B. siamensis isolated from A. sativum bulbs significantly inhibited the white rot disease caused by Sclerotium cepivorum while promoting plant growth [16]. In the present study, isolates exhibiting the highest biocontrol potential against foliar pathogens also belonged to the genus Bacillus. ...
Foliar diseases caused by Stemphylium and Colletotrichum species are among the major biotic factors limiting Welsh onion production in Taiwan. Owing to concerns about the environment and the development of pathogen resistance to existing fungicides, biological control using endophytes is emerging as an eco-friendly alternative to chemical control. The aim of the present study was to isolate endophytes from healthy Welsh onion leaves and investigate their antagonistic potential against the major phytopathogenic fungi associated with Welsh onion plants in Taiwan. A total of 109 bacterial and 31 fungal strains were isolated from healthy Welsh onion leaves and assigned to 16 bacterial and nine fungal genera using morphological and molecular characterization based on DNA sequence data obtained from nuclear internal transcribed spacer (nrITS) (fungi) and 16S rRNA (bacteria). Evaluation of these endophytic isolates for biocontrol activity against leaf blight pathogens Colletotrichum spaethianum strain SX15-2 and Stemphylium vesicarium strain SX20-2 by dual culture assay and greenhouse experiments resulted in the identification of two bacterial isolates (GFB08 and LFB28) and two fungal isolates (GFF06 and GFF08) as promising antagonists to leaf blight pathogens. Among the four selected isolates, Bacillus strain GFB08 exhibited the highest disease control in the greenhouse study. Therefore, Bacillus strain GFB08 was further evaluated to understand the mechanism underlying its biocontrol efficacy. A phylogenetic analysis based on six genes identified Bacillus strain GFB08 as B. velezensis. The presence of antimicrobial peptide genes (baer, bamC, bmyB, dfnA, fenD, ituC, mlna, and srfAA) and the secretion of several cell wall degrading enzymes (CWDEs), including cellulase and protease, confirmed the antifungal nature of B. velezensis strain GFB08. Leaf blight disease suppression by preventive and curative assays indicated that B. velezensis strain GFB08 has preventive efficacy on C. spaethianum strain SX15-2 and both preventive and curative efficacy on S. vesicarium strain SX20-2. Overall, the current study revealed that healthy Welsh onion leaves harbour diverse bacterial and fungal endophytes, among which the endophytic bacterial strain, B. velezensis strain GFB08, could potentially be used as a biocontrol agent to manage the leaf blight diseases of Welsh onion in Taiwan
... 80% of the fungal cell wall is made up of polysaccharides, which provide stiffness to the cell wall through a network of glycosidic bonds (Złotko et al., 2019). When lytic enzymes interfere with the bonds of the fungal cell wall, they decompose the cell wall, leading to cell death (Abo-Elyousr et al., 2021). The most abundantly secreted lytic enzymes that are associated with perforation, modification, and degradation of the structure of the cell wall are cellulases, proteases, 1,3-glucanases, and chitinases. ...
Plant pathogens are considered a major constraint in decreasing the quality and quantity of plants and plant products by attacking the seed from its germination to the harvesting stage. To date, various multifunctional chemical pesticides have been applied to control these infectious entities, but these chemical pesticides are not as effective in controlling them. That is why "bacterial endophytes," an alternative to these chemical pesticides, have been determined in the history of mankind through multidisciplinary ways. At the same time, these endophytes work to save the living environment, improve plant growth, and control infectious plant pathogens. The current study summarizes and analyzes the pioneering and recent works on plant bacterial endophytes and their mechanisms as biocontrol agents/plant growth promotion, interaction with the host plant, root
colonization, systemic colonization of aerial plant tissues, phytohormone production and modulation, host specificity, genes expressed in the endosphere, multi-omics approaches to improve endophyte use, and biopesticide formulation by these bacterial endophytes. The manuscript highlights the most necessary information about bacterial endophytes, and the study will play a vital role in the further use and handling of these bacterial endophytes for sustainable agricultural production.
