scholarly journals Secretion-Based Modes of Action of Biocontrol Agents with a Focus on Pseudozyma aphidis

Plants ◽  
2021 ◽  
Vol 10 (2) ◽  
pp. 210
Author(s):  
Dhruv Aditya Srivastava ◽  
Raviv Harris ◽  
Gilli Breuer ◽  
Maggie Levy
Keyword(s):  
Crop Production ◽  
Fossil Fuels ◽  
Plant Pathogens ◽  
Biocontrol Agent ◽  
Growth Promotion ◽  
Biocontrol Agents ◽  
Environmental Concerns ◽  
Modes Of Action ◽  
Complex Modes ◽  
Pseudozyma Aphidis

Plant pathogens challenge our efforts to maximize crop production due to their ability to rapidly develop resistance to pesticides. Fungal biocontrol agents have become an important alternative to chemical fungicides, due to environmental concerns related to the latter. Here we review the complex modes of action of biocontrol agents in general and epiphytic yeasts belonging to the genus Pseudozyma specifically and P. aphidis in particular. Biocontrol agents act through multiple direct and indirect mechanisms, which are mainly based on their secretions. We discuss the direct modes of action, such as antibiosis, reactive oxygen species-producing, and cell wall-degrading enzyme secretions which can also play a role in mycoparasitism. In addition, we discuss indirect modes of action, such as hyperbiotrophy, induced resistance and growth promotion based on the secretion of effectors and elicitors from the biocontrol agent. Due to their unique characteristics, epiphytic yeasts hold great potential for use as biocontrol agents, which may be more environmentally friendly than conventional pesticides and provide a way to reduce our dependency on fungicides based on increasingly expensive fossil fuels. No less important, the complex mode of action of Pseudozyma-based biocontrol agents can also reduce the frequency of resistance developed by pathogens to these agents.

scholarly journals Pseudozyma aphidis Induces Salicylic-Acid-Independent Resistance to Clavibacter michiganensis in Tomato Plants

Plant Disease ◽  
2015 ◽  
Vol 99 (5) ◽  
pp. 621-626 ◽  
Author(s):  
Omer Barda ◽  
Or Shalev ◽  
Shanee Alster ◽  
Kobi Buxdorf ◽  
Aviva Gafni ◽  
...  
Keyword(s):  
Salicylic Acid ◽  
Pseudomonas Syringae ◽  
Crop Production ◽  
Xanthomonas Campestris ◽  
Plant Pathogens ◽  
Biologically Active ◽  
Biocontrol Agents ◽  
Clavibacter Michiganensis ◽  
Tomato Plants ◽  
Pseudozyma Aphidis

The ability of plant pathogens to rapidly develop resistance to commonly used pesticides challenges efforts to maximize crop production. Fungal biocontrol agents have become an important alternative to chemical fungicides as a result of environmental concerns regarding conventional pesticides, including resistance issues. The complex mode of action of biocontrol agents reduces the likelihood that pathogens will develop resistance to them. We recently isolated a unique, biologically active isolate of the epiphytic fungus Pseudozyma aphidis. We show that the extracellular metabolites secreted by our P. aphidis isolate can inhibit Xanthomonas campestris pv. vesicatoria, X. campestris pv. campestris, Pseudomonas syringae pv. tomato, Erwinia amylovora, Clavibacter michiganensis, and Agrobacterium tumefaciens in vitro. Moreover, application of Pseudozyma aphidis spores on tomato plants in the greenhouse significantly reduced (by 60%) the incidence of bacterial wilt and canker disease caused by C. michiganensis subsp. michiganensis on those plants as well as disease severity by 35%. Furthermore, infected plants treated with P. aphidis were 25% taller than control infected plants. We found that P. aphidis activates PR1a—and other pathogenesis-related genes in tomato plants—and can trigger an induced-resistance response against C. michiganensis that proceeds in a salicylic-acid-independent manner, as shown using NahG-transgenic tomato plants.

scholarly journals The Significance of Bacillus spp. in Disease Suppression and Growth Promotion of Field and Vegetable Crops

2020 ◽  
Vol 8 (7) ◽  
pp. 1037 ◽  
Author(s):  
Dragana Miljaković ◽  
Jelena Marinković ◽  
Svetlana Balešević-Tubić
Keyword(s):  
Plant Growth ◽  
Plant Pathogens ◽  
Growth Promotion ◽  
Disease Suppression ◽  
Biocontrol Agents ◽  
Systemic Resistance ◽  
Steady Increase ◽  
Vegetable Crops ◽  
Wide Range ◽  
Bacillus Spp

Bacillus spp. produce a variety of compounds involved in the biocontrol of plant pathogens and promotion of plant growth, which makes them potential candidates for most agricultural and biotechnological applications. Bacilli exhibit antagonistic activity by excreting extracellular metabolites such as antibiotics, cell wall hydrolases, and siderophores. Additionally, Bacillus spp. improve plant response to pathogen attack by triggering induced systemic resistance (ISR). Besides being the most promising biocontrol agents, Bacillus spp. promote plant growth via nitrogen fixation, phosphate solubilization, and phytohormone production. Antagonistic and plant growth-promoting strains of Bacillus spp. might be useful in formulating new preparations. Numerous studies of a wide range of plant species revealed a steady increase in the number of Bacillus spp. identified as potential biocontrol agents and plant growth promoters. Among different mechanisms of action, it remains unclear which individual or combined traits could be used as predictors in the selection of the best strains for crop productivity improvement. Due to numerous factors that influence the successful application of Bacillus spp., it is necessary to understand how different strains function in biological control and plant growth promotion, and distinctly define the factors that contribute to their more efficient use in the field.

scholarly journals Biocontrol of Rhizoctonia Stem and Root Rot of Poinsettia with Burkholderia cepacia and Binucleate Rhizoctonia

Plant Disease ◽  
2002 ◽  
Vol 86 (1) ◽  
pp. 47-53 ◽  
Author(s):  
J. Hwang ◽  
D. M. Benson
Keyword(s):  
Disease Control ◽  
Root Rot ◽  
Burkholderia Cepacia ◽  
Crop Production ◽  
Root Colonization ◽  
Biocontrol Agent ◽  
Biocontrol Agents ◽  
Production Cycle ◽  
Binucleate Rhizoctonia ◽  
Control Application

Strategies for applying Burkholderia cepacia (strain 5.5B) and Pesta formulations of binucleate Rhizoctonia (BNR) isolates (BNR621 and P9023) were evaluated for biocontrol of Rhizoctonia stem and root rot of poinsettia caused by R. solani. During propagation, one application of B. cepacia suppressed stem rot, while application of either isolate of BNR did not. In contrast, after transplanting rooted poinsettias, one application of either BNR isolate was more effective for suppression of stem and root rot than application of B. cepacia. Sequential application of B. cepacia at propagation followed by a BNR isolate at transplanting was more effective over the crop production cycle than multiple applications of one biocontrol agent or combination application of both biocontrol agents. Root colonization by both biocontrol agents after transplanting rooted poinsettias was affected by application strategy. The least root colonization by both biocontrol agents occurred in the combination application. The highest root colonization by the BNR isolates was observed in the sequential application that provided the most effective disease control. Application of different biocontrol agents during the different production phases of poinsettia was effective for disease control, but understanding the interaction between biocontrol agents and root colonization was important to develop the best application strategy.

scholarly journals Genome Mining of Antimicrobial Gene Clusters from Phyllospheric Bacteria Isolated from Solanum Lycopersicum and Lactuca Sativa to Identify Biocontrol Properties

2021 ◽  
Author(s):  
Claudia Y. Muñoz ◽  
Lu Zhou ◽  
Yunhai Yi ◽  
Oscar P. Kuipers
Keyword(s):  
Antimicrobial Activity ◽  
Plant Growth ◽  
Plant Pathogens ◽  
Growth Promotion ◽  
Genome Mining ◽  
Gene Clusters ◽  
Biocontrol Agents ◽  
Biosynthetic Gene ◽  
Biosynthetic Gene Clusters ◽  
Microbe Interactions

Abstract BackgroundBiocontrol agents are sustainable eco-friendly alternatives for chemical pesticides that cause adverse effects in the environment and toxicity in animals including humans. An improved understanding of the phyllosphere microbiology is of vital importance for biocontrol development. Most studies have been directed towards beneficial plant-microbe interactions and ignore the pathogens that might affect humans when consuming vegetables. In this study we extended this perspective and investigated potential biocontrol strains isolated from the tomato and lettuce phyllosphere that can promote plant growth and antagonize mammalian pathogens as well as plant pathogens. Subsequently, we mined into their genomes for discovery of antimicrobial biosynthetic gene clusters (BGCs), several of which are good candidates to produce protectants against microbial plant and mammalian pathogens.Results The antimicrobial activity of 69 newly isolated strains from a healthy tomato and lettuce phyllosphere against several plant and mammalian pathogens was determined with plates assays. Three strains with the highest antimicrobial activity against the relevant pathogens were selected and characterized (Bacillus subtilis STRP31, Bacillus velezensis SPL51, and Paenibacillus sp. PL91). All three strains showed a plant growth promotion effect by the production of volatile compounds (VOCs) on tomato and lettuce. In addition, genome mining of these isolates showed the presence of a large variety of biosynthetic gene clusters. A total of 39 BGCs were identified, of which several are already known, such as bacilysin, bacillibactin, surfactin, subtilomycin, etc., but also several novel ones. Further analysis revealed that among the novel BGCs, one NRPS and two bacteriocins are encoded which were analyzed in more depth.Conclusions Several antimicrobial BGCs were found in the selected strains, including the rediscovery of known ones, but also the discovery of novel ones. Our study serves as support for subsequent examination and characterization of novel antimicrobial metabolites, and the possibility of developing biocontrol agents.

scholarly journals Biological Control of Root Pathogens in Rockwool and Other Hydroponic Systems

HortScience ◽  
1995 ◽  
Vol 30 (4) ◽  
pp. 750B-750
Author(s):  
M.L. Matheny
Keyword(s):  
Biological Control ◽  
Environmental Conditions ◽  
Crop Production ◽  
Biocontrol Agent ◽  
Initial Period ◽  
Biocontrol Agents ◽  
Additional Advantage ◽  
Root Diseases ◽  
Edaphic Conditions ◽  
Hydroponic Systems

One of the main difficulties in controlling root diseases biologically has been the inability of biocontrol agents to establish and persist in the rhizosphere. The inability of biocontrol agents to establish and persist is often attributed to competition from indigenous microorganisms for space and nutrients and to fluctuations in environmental conditions. The use of biocontrol agents over the entire geographic range of a crop also has been limited by differences in environmental and edaphic conditions from field to field and region to region. An advantage of hydroponic crop production in greenhouses is that environmental conditions such as temperature, moisture, pH, and growth medium can be consistently controlled in a house and from site to site. An additional advantage of many hydroponic systems is that they are virtually sterile upon planting. This initial period of virtual sterility greatly reduces competition for an introduced biocontrol agent. In addition, these systems are usually pathogen-free upon planting allowing the establishment of a biocontrol agent prior to pathogen introduction. Last, the temperatures, high moisture levels, and pH ranges of hydroponic systems can be ideal for the proliferation of many biocontrol agents. With all of these advantages for the use of biocontrol agents in hydroponic systems, our company, and many labs around the world, have focused their attention on developing biological control agents for these systems. I will provide a review of research focused on controlling root diseases of vegetables grown in rockwool and other hydroponic systems.

scholarly journals A window into fungal endophytism in Salicornia europaea: deciphering fungal characteristics as plant growth promoting agents

2019 ◽  
Vol 445 (1-2) ◽  
pp. 577-594 ◽  
Author(s):  
Bliss Ursula Furtado ◽  
Sonia Szymańska ◽  
Katarzyna Hrynkiewicz
Keyword(s):  
Plant Growth ◽  
Endophytic Fungi ◽  
Crop Production ◽  
Plant Pathogens ◽  
Growth Promotion ◽  
Salicornia Europaea ◽  
Dematiaceous Fungi ◽  
Pectolytic Activity ◽  
Plant Growth Promoting ◽  
Growth Promoting

Abstract Aim Plant-endophytic associations exist only when equilibrium is maintained between both partners. This study analyses the properties of endophytic fungi inhabiting a halophyte growing in high soil salinity and tests whether these fungi are beneficial or detrimental when non-host plants are inoculated. Method Fungi were isolated from Salicornia europaea collected from two sites differing in salinization history (anthropogenic and naturally saline) and analyzed for plant growth promoting abilities and non-host plant interactions. Results Most isolated fungi belonged to Ascomycota (96%) including dematiaceous fungi and commonly known plant pathogens and saprobes. The strains were metabolically active for siderophores, polyamines and indole-3-acetic acid (mainly Aureobasidium sp.) with very low activity for phosphatases. Many showed proteolytic, lipolytic, chitinolytic, cellulolytic and amylolytic activities but low pectolytic activity. Different activities between similar fungal species found in both sites were particularly seen for Epiccocum sp., Arthrinium sp. and Trichoderma sp. Inoculating the non-host Lolium perenne with selected fungi increased plant growth, mainly in the symbiont (Epichloë)-free variety. Arthrinium gamsii CR1-9 and Stereum gausapatum ISK3-11 were most effective for plant growth promotion. Conclusions This research suggests that host lifestyle and soil characteristics have a strong effect on endophytic fungi, and environmental stress could disturb the plant-fungi relations. In favourable conditions, these fungi may be effective in facilitating crop production in non-cultivable saline lands.

scholarly journals Molecular Aspects of Plant Growth Promotion and Protection by Bacillus subtilis

2020 ◽  
pp. MPMI-08-20-0225
Author(s):  
Christopher Blake ◽  
Mathilde Nordgaard Christensen ◽  
Ákos T. Kovács
Keyword(s):  
Bacillus Subtilis ◽  
Plant Growth ◽  
Crop Production ◽  
Plant Pathogens ◽  
Current Knowledge ◽  
Growth Promotion ◽  
Bacterial Colonization ◽  
Control Plant ◽  
Microbial Interactions ◽  
Systemic Resistance

Bacillus subtilis is one of the most widely studied plant growth–promoting rhizobacteria. It is able to promote plant growth as well as control plant pathogens through diverse mechanisms, including the improvement of nutrient availability and alteration of phytohormone homeostasis as well as the production of antimicrobials and triggering induced systemic resistance, respectively. Even though its benefits for crop production have been recognized and studied extensively under laboratory conditions, the success of its application in fields varies immensely. It is widely accepted that agricultural application of B. subtilis often fails because the bacteria are not able to persist in the rhizosphere. Bacterial colonization of plant roots is a crucial step in the interaction between microbe and plant and seems, therefore, to be of great importance for its growth promotion and biocontrol effects. A successful root colonization depends thereby on both bacterial traits, motility and biofilm formation, as well as on a signal interplay with the plant. This review addresses current knowledge about plant-microbial interactions of the B. subtilis species, including the various mechanisms for supporting plant growth as well as the necessity for the establishment of the relationship.

scholarly journals Soil Bacteria as Potential Biological Control Agents of Fusarium Species Associated with Asparagus Decline Syndrome

2021 ◽  
Vol 11 (18) ◽  
pp. 8356
Author(s):  
Eduardo De la Lastra ◽  
María Camacho ◽  
Nieves Capote
Keyword(s):  
Plant Growth ◽  
Protective Effect ◽  
Plant Pathogens ◽  
Growth Promotion ◽  
Fusarium Species ◽  
Control Plant ◽  
Hydrolytic Enzymes ◽  
Biocontrol Agents ◽  
Alternative Methods ◽  
Mycelium Growth

To avoid the use of agrochemicals in agriculture, alternative methods are emerging to control plant pathogens. Some plant growth-promoting rhizobacteria (PGPR) can be used as biocontrol agents since they can induce protection against pathogens. The aim of this study was to evaluate the protective effect of several PGPR strains against the main Fusarium species involved in asparagus decline syndrome (ADS): F. proliferatum, F. oxysporum f. sp. asparagi and F. redolens. In vitro antagonism assays showed that all the bacteria inhibited the mycelium growth of the three Fusarium species. The most effective strains (Streptomyces fradiae Hvs6, Bacillus paralicheniformis Hvs2 and Bacillus velezensis FC37) were tested to evaluate their protective effect on asparagus plants inoculated with pathogenic Fusarium isolates. Strains FC37 and Hvs2 were the most effective in controlling pathogenic F. proliferatum and F. oxysporum f. sp. asparagi, but neither could protect against F. redolens isolates. The production of hydrolytic enzymes such as β-glucosidase, amylase and protease by these bacterial strains could be involved in the structural degradation of the fungal cell wall. In addition, the production of toxic volatile compounds, such as hydrogen cyanide, may inhibit the fungal growth, and the production of phosphate solubilizers could be related to the plant growth promotion. These results suggest that strains FC37 and Hvs2 could be used as potential biocontrol agents as a sustainable and environmentally friendly control strategy for ADS-affected fields.

scholarly journals Deciphering Trichoderma–Plant–Pathogen Interactions for Better Development of Biocontrol Applications

2021 ◽  
Vol 7 (1) ◽  
pp. 61
Author(s):  
Alsayed Alfiky ◽  
Laure Weisskopf
Keyword(s):  
Crop Production ◽  
Biocontrol Agent ◽  
Growth Promotion ◽  
Growth Conditions ◽  
Plant Diseases ◽  
Full Potential ◽  
Ecological Interactions ◽  
Plant Pathogen Interactions ◽  
Negative Growth ◽  
Diverse Plant

Members of the fungal genus Trichoderma (Ascomycota, Hypocreales, Hypocreaceae) are ubiquitous and commonly encountered as soil inhabitants, plant symbionts, saprotrophs, and mycoparasites. Certain species have been used to control diverse plant diseases and mitigate negative growth conditions. The versatility of Trichoderma’s interactions mainly relies on their ability to engage in inter- and cross-kingdom interactions. Although Trichoderma is by far the most extensively studied fungal biocontrol agent (BCA), with a few species already having been commercialized as bio-pesticides or bio-fertilizers, their wide application has been hampered by an unpredictable efficacy under field conditions. Deciphering the dialogues within and across Trichoderma ecological interactions by identification of involved effectors and their underlying effect is of great value in order to be able to eventually harness Trichoderma’s full potential for plant growth promotion and protection. In this review, we focus on the nature of Trichoderma interactions with plants and pathogens. Better understanding how Trichoderma interacts with plants, other microorganisms, and the environment is essential for developing and deploying Trichoderma-based strategies that increase crop production and protection.

Effect of the endophytic plant growth promoting Enterobacter ludwigii EB4B on tomato growth

2020 ◽  
Vol 13 (2) ◽  
pp. 54-65 ◽  
Author(s):  
M.E.A. Bendaha ◽  
H.A. Belaouni
Keyword(s):  
Root Length ◽  
Biocontrol Agent ◽  
Growth Promotion ◽  
Dry Weight ◽  
Antagonistic Activity ◽  
Rrna Gene ◽  
Plant Growth Promoting ◽  
Enterobacter Ludwigii ◽  
Tomato Growth

SummaryThis study aims to develop a biocontrol agent against Fusarium oxysporum f.sp. radicis-lycopersici (FORL) in tomato. For this, a set of 23 bacterial endophytic isolates has been screened for their ability to inhibit in vitro the growth of FORL using the dual plate assay. Three isolates with the most sound antagonistic activity to FORL have been qualitatively screened for siderophore production, phosphates solubilization and indolic acetic acid (IAA) synthesis as growth promotion traits. Antagonistic values of the three candidates against FORL were respectively: 51.51 % (EB4B), 51.18 % (EB22K) and 41.40 % (EB2A). Based on 16S rRNA gene sequence analysis, the isolates EB4B and EB22K were closely related to Enterobacter ludwigii EN-119, while the strain EB2A has been assigned to Leclercia adecarboxylata NBRC 102595. The promotion of tomato growth has been assessed in vitro using the strains EB2A, EB4B and EB22K in presence of the phytopathogen FORL. The treatments with the selected isolates increased significantly the root length and dry weight. Best results were observed in isolate EB4B in terms of growth promotion in the absence of FORL, improving 326.60 % of the root length and 142.70 % of plant dry weight if compared with untreated controls. In the presence of FORL, the strain EB4B improved both root length (180.81 %) and plant dry weight (202.15 %). These results encourage further characterization of the observed beneficial effect of Enterobacter sp. EB4B for a possible use as biofertilizer and biocontrol agent against FORL.

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