Screening of the High-Rhizosphere Competent Limoniastrum monopetalum’ Culturable Endophyte Microbiota Allows the Recovery of Multifaceted and Versatile Biocontrol Agents

Halophyte Limoniastrum monopetalum, an evergreen shrub inhabiting the Mediterranean region, has well-documented phytoremediation potential for metal removal from polluted sites. It is also considered to be a medicinal halophyte with potent activity against plant pathogens. Therefore, L. monopetalum may be a suitable candidate for isolating endophytic microbiota members that provide plant growth promotion (PGP) and resistance to abiotic stresses. Selected for biocontrol abilities, these endophytes may represent multifaceted and versatile biocontrol agents, combining pathogen biocontrol in addition to PGP and plant protection against abiotic stresses. In this study 117 root culturable bacterial endophytes, including Gram-positive (Bacillus and Brevibacillus), Gram-negative (Proteus, Providencia, Serratia, Pantoea, Klebsiella, Enterobacter and Pectobacterium) and actinomycete Nocardiopsis genera have been recovered from L. monopetalum. The collection exhibited high levels of biocontrol abilities against bacterial (Agrobacterium tumefaciens MAT2 and Pectobacterium carotovorum MAT3) and fungal (Alternaria alternata XSZJY-1, Rhizoctonia bataticola MAT1 and Fusarium oxysporum f. sp. radicis lycopersici FORL) pathogens. Several bacteria also showed PGP capacity and resistance to antibiotics and metals. A highly promising candidate Bacillus licheniformis LMRE 36 with high PGP, biocontrol, metal and antibiotic, resistance was subsequently tested in planta (potato and olive trees) for biocontrol of a collection of 14 highly damaging Fusarium species. LMRE 36 proved very effective against the collection in both species and against an emerging Fusarium sp. threatening olive trees culture in nurseries. These findings provide a demonstration of our pyramiding strategy. Our strategy was effective in combining desirable traits in biocontrol agents towards broad-spectrum resistance against pathogens and protection of crops from abiotic stresses. Stacking multiple desirable traits into a single biocontrol agent is achieved by first, careful selection of a host for endophytic microbiota recovery; second, stringent in vitro selection of candidates from the collection; and third, application of the selected biocontrol agents in planta experiments. That pyramiding strategy could be successfully used to mitigate effects of diverse biotic and abiotic stresses on plant growth and productivity. It is anticipated that the strategy will provide a new generation of biocontrol agents by targeting the microbiota of plants in hostile environments.

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

Microorganisms ◽

10.3390/microorganisms8071037 ◽

2020 ◽

Vol 8 (7) ◽

pp. 1037 ◽

Cited By ~ 1

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.

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Olea europaea L. Root Endophyte Bacillus velezensis OEE1 Counteracts Oomycete and Fungal Harmful Pathogens and Harbours a Large Repertoire of Secreted and Volatile Metabolites and Beneficial Functional Genes

Microorganisms ◽

10.3390/microorganisms7090314 ◽

2019 ◽

Vol 7 (9) ◽

pp. 314 ◽

Cited By ~ 8

Author(s):

Manel Cheffi ◽

Ali Chenari Bouket ◽

Faizah N. Alenezi ◽

Lenka Luptakova ◽

Marta Belka ◽

...

Keyword(s):

Secondary Metabolites ◽

Plant Growth ◽

Fungal Pathogens ◽

Biocontrol Agents ◽

Economic Losses ◽

Bacillus Velezensis ◽

Strong Activity ◽

Rarefaction Analysis ◽

Olive Trees ◽

Large Repertoire

Oomycete and fungal pathogens, mainly Phytophthora and Fusarium species, are notorious causal agents of huge economic losses and environmental damages. For instance, Phytophthora ramorum, Phytophthora cryptogea, Phytophthora plurivora and Fusarium solani cause significant losses in nurseries and in forest ecosystems. Chemical treatments, while harmful to the environment and human health, have been proved to have little or no impact on these species. Recently, biocontrol bacterial species were used to cope with these pathogens and have shown promising prospects towards sustainable and eco-friendly agricultural practices. Olive trees prone to Phytophthora and Fusarium disease outbreaks are suitable for habitat-adapted symbiotic strategies, to recover oomycetes and fungal pathogen biocontrol agents. Using this strategy, we showed that olive trees-associated microbiome represents a valuable source for microorganisms, promoting plant growth and healthy benefits in addition to being biocontrol agents against oomycete and fungal diseases. Isolation, characterization and screening of root microbiome of olive trees against numerous Phytophthora and other fungal pathogens have led to the identification of the Bacillus velezensis OEE1, with plant growth promotion (PGP) abilities and strong activity against major oomycete and fungal pathogens. Phylogenomic analysis of the strain OEE1 showed that B. velezensis suffers taxonomic imprecision that blurs species delimitation, impacting their biofertilizers’ practical use. Genome mining of several B. velezensis strains available in the GenBank have highlighted a wide array of plant growth promoting rhizobacteria (PGPR) features, metals and antibiotics resistance and the degradation ability of phytotoxic aromatic compounds. Strain OEE1 harbours a large repertoire of secreted and volatile secondary metabolites. Rarefaction analysis of secondary metabolites richness in the B. velezenis genomes, unambiguously documented new secondary metabolites from ongoing genome sequencing efforts that warrants more efforts in order to assess the huge diversity in the species. Comparative genomics indicated that B. velezensis harbours a core genome endowed with PGP features and accessory genome encoding diverse secondary metabolites. Gas Chromatography-Mass Spectrometry (GC-MS) analysis of OEE1 Volatile Organic Compounds (VOCs) and Liquid Chromatography High Resolution Mas Spectrometry (LC-HRMS) analysis of secondary metabolites identified numerous molecules with PGP abilities that are known to interfere with pathogen development. Moreover, B. velezensis OEE1 proved effective in protecting olive trees against F. solani in greenhouse experiments and are able to inhabit olive tree roots. Our strategy provides an effective means for isolation of biocontrol agents against recalcitrant pathogens. Their genomic analysis provides necessary clues towards their efficient implementation as biofertilizers.

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In planta selection of plant growth promoting endophytic bacteria for rice (Oryza sativa L.)

Journal of soil science and plant nutrition ◽

10.4067/s0718-95162014005000039 ◽

2014 ◽

pp. 0-0 ◽

Cited By ~ 7

Author(s):

H Etesami ◽

H Mirsyed Hosseini ◽

H.A Alikhani

Keyword(s):

Oryza Sativa ◽

Plant Growth ◽

Endophytic Bacteria ◽

Oryza Sativa L ◽

In Planta ◽

Plant Growth Promoting ◽

Growth Promoting ◽

Selection Of

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The Potential of New Streptomyces Isolates as Biocontrol Agents Against Fusarium Spp

“Agriculture for Life Life for Agriculture” Conference Proceedings ◽

10.2478/alife-2018-0093 ◽

2018 ◽

Vol 1 (1) ◽

pp. 594-600

Author(s):

Mihaela Ursan ◽

Oana Alina Boiu-Sicuia ◽

Cătălina Voaides ◽

Vasilica Stan ◽

Corina Bubueanu ◽

...

Keyword(s):

Plant Pathogens ◽

Plant Protection ◽

Screening Method ◽

Biocontrol Agents ◽

Fungal Resistance ◽

Bacterial Strains ◽

Fusarium Spp ◽

Streptomyces Species ◽

Streptomyces Spp ◽

Wide Range

Abstract The excessive use of synthetic pesticides for plant pathogens control could cause possible harmful side-effects to humans and animals, environmental pollution, residual toxicity, affects soil characteristics or induce the development of fungal resistance. Alternative ways for fungal contamination control involve natural products, based on microorganisms, many of them being already available for use. The selection and characterization of new biological agents useful for plant pathogens control are permanent goals for plant protection researches. In the last decade, several studies revealed that Streptomyces species are promising biocontrol agents against a wide range of phytopathogenic fungi, including Fusarium spp., one of the most important wheat pathogens. In our study, 60 strains of Streptomyces spp. were isolated from soil or compost and evaluated for in vitro antifungal abilities by dual confrontation method. At least 30% of the isolates presented inhibitory activity against F. culmorum and F. graminearum. The bacterial strains were also tested for their ability to produce various bioactive compounds, possible involved in fungal inhibition. The capacity of some of the bacterial isolates to produce cellulases, amylases, lipases and volatile metabolites was proved. In addition, a new screening method for chitinases production was developed, based on the use of a combination of Congo red and Lugol solutions, which allowed the detection of chitinases in several Streptomyces spp. strains. Moreover, the reduction of the level of some Fusarium mycotoxins was detected by HPTLC analysis. As a conclusion, antagonistic interactions between Streptomyces isolates and fusaria could involve antibiosis, competition and parasitism and suggested that at least some of the selected isolates could be used in obtaining biological control products.

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Impact of Abiotic Stresses on Plant Virus Transmission by Aphids

Viruses ◽

10.3390/v12020216 ◽

2020 ◽

Vol 12 (2) ◽

pp. 216 ◽

Cited By ~ 2

Author(s):

Manuella van Munster

Keyword(s):

Climate Change ◽

Abiotic Stresses ◽

Plant Pathogens ◽

Plant Defence ◽

Virus Transmission ◽

Plant Viruses ◽

Research Field ◽

Viral Transmission ◽

In Planta ◽

Elevated Atmospheric Co2

Plants regularly encounter abiotic constraints, and plant response to stress has been a focus of research for decades. Given increasing global temperatures and elevated atmospheric CO2 levels and the occurrence of water stress episodes driven by climate change, plant biochemistry, in particular, plant defence responses, may be altered significantly. Environmental factors also have a wider impact, shaping viral transmission processes that rely on a complex set of interactions between, at least, the pathogen, the vector, and the host plant. This review considers how abiotic stresses influence the transmission and spread of plant viruses by aphid vectors, mainly through changes in host physiology status, and summarizes the latest findings in this research field. The direct effects of climate change and severe weather events that impact the feeding behaviour of insect vectors as well as the major traits (e.g., within-host accumulation, disease severity and transmission) of viral plant pathogens are discussed. Finally, the intrinsic capacity of viruses to react to environmental cues in planta and how this may influence viral transmission efficiency is summarized. The clear interaction between biotic (virus) and abiotic stresses is a risk that must be accounted for when modelling virus epidemiology under scenarios of climate change.

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The Application of Trichoderma Strains or Metabolites Alters the Olive Leaf Metabolome and the Expression of Defense-Related Genes

Journal of Fungi ◽

10.3390/jof6040369 ◽

2020 ◽

Vol 6 (4) ◽

pp. 369

Author(s):

Roberta Marra ◽

Mariangela Coppola ◽

Angela Pironti ◽

Filomena Grasso ◽

Nadia Lombardi ◽

...

Keyword(s):

Gene Expression ◽

Phenolic Compounds ◽

Plant Growth ◽

Plant Pathogens ◽

Expression Profiles ◽

Gene Expression Profiles ◽

Leaf Spot Disease ◽

Olive Leaf ◽

Olive Leaves ◽

Olive Trees

Biocontrol fungal strains of the genus Trichoderma can antagonize numerous plant pathogens and promote plant growth using different mechanisms of action, including the production of secondary metabolites (SMs). In this work we analyzed the effects of repeated applications of selected Trichoderma strains or SMs on young olive trees on the stimulation of plant growth and on the development of olive leaf spot disease caused by Fusicladium oleagineum. In addition, metabolomic analyses and gene expression profiles of olive leaves were carried out by LC–MS Q-TOF and real-time RT-PCR, respectively. A total of 104 phenolic compounds were detected from olive leave extracts and 20 were putatively identified. Targeted and untargeted approaches revealed significant differences in both the number and type of phenolic compounds accumulated in olive leaves after Trichoderma applications, as compared to water-treated plants. Different secoiridoids were less abundant in treated plants than in controls, while the accumulation of flavonoids (including luteolin and apigenin derivatives) increased following the application of specific Trichoderma strain. The induction of defense-related genes, and of genes involved in the synthesis of the secoiridoid oleuropein, was also analyzed and revealed a significant variation of gene expression according to the strain or metabolite applied.

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

10.21203/rs.3.rs-633887/v1 ◽

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.

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Durability of efficacy of microbial bioprotectants against plant diseases

10.19103/as.2021.0093.05 ◽

2021 ◽

pp. 103-122

Author(s):

Marc Bardin ◽

◽

Thomas Pressecq ◽

Philippe C. Nicot ◽

Yousra Bouaoud ◽

...

Keyword(s):

Plant Pathogens ◽

Current Knowledge ◽

Plant Protection ◽

Plant Protection Products ◽

Plant Diseases ◽

Field Efficacy ◽

Selection Of

Plant pathogens can develop resistance to conventional plant protection products but their ability to overcome the effect of microbial bioprotectants is still poorly known. However, various studies show that susceptibility of plant pathogens to microbial bioprotectants can be highly variable. This may contribute to the inconsistent efficacy of microbial bioprotectants sometimes observed in the field. An important question is whether the widespread use of microbial bioprotectants in the field could conduct to the selection of even more resistant phenotypes of plant pathogens. This chapter highlights current knowledge concerning erosion of microbial bioprotectants against plant pathogens and its possible consequences for field efficacy.

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Advances in screening approaches for the development of microbial bioprotectants to control plant diseases

10.19103/as.2021.0093.02 ◽

2021 ◽

pp. 33-86

Author(s):

Wagner Bettiol ◽

◽

Flávio Henrique Vasconcelos de Medeiros ◽

Josiane Barros Chiaramonte ◽

Rodrigo Mendes ◽

...

Keyword(s):

Plant Pathogens ◽

Plant Protection ◽

Control Plant ◽

Control Programme ◽

Plant Diseases ◽

Advantages And Disadvantages ◽

Fungal Plant Pathogens ◽

Soil Rhizosphere ◽

Selection Of ◽

Screening Approaches

The success of a biological control programme depends on the isolation and selection of antagonists. There is an enormous diversity of culturable microbial species in the soil, rhizosphere, phylloplane, spermosphere and carposphere, which can be used in the isolation and selection of antagonists. The structures of fungal plant pathogens concerned with survival and infection may also be sources of antagonists. Although non-culturable microorganisms and microbiome-based strategies have great potential for development as commercial products in disease control, more knowledge is needed to understand the mechanisms involved in interactions between plants and complex microbial communities. Methods of isolation and selection of the most commercially exploited groups of antagonists and their advantages and disadvantages are discussed in this chapter as well as those of non-traditional antagonists. Finally, possible strategies for engineering the soil and host microbiome to actively promote plant protection against pathogens are discussed.

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