Synergism between fungal enzymes and bacterial antibiotics may enhance biocontrol

The interactions between biocontrol fungi and bacteria may play a key role in the natural process of biocontrol, although the molecular mechanisms involved are still largely unknown. Synergism can occur when different agents are applied together, and cell wall degrading enzymes (CWDEs) produced by fungi can increase the efficacy of bacteria. Pseudomonas spp. produce membrane-disrupting lipodepsipeptides (LDPs) syringotoxins (SP) and syringomycins (SR). SR are considered responsible for the antimicrobial activity, and SP for the phytotoxicity. CWDEs of Trichoderma spp. synergistically increased the toxicity Of SP25-A or SRE purified from P. syringae against fungal pathogens. For instance, the fungal enzymes made Botrytis cinerea and other phytopathogenic fungi, normally resistant to SP25-A alone, more susceptible to this antibiotic. Pseudomonas produced CWDEs in culture conditions that allow the synthesis of the LDPs. Purified bacterial enzymes and metabolites were also synergistic against fungal pathogens, although this mixture was less powerful than the combination with the Trichoderma CWDEs. The positive interaction between LDPs and CWDEs may be part of the biocontrol mechanism in some Pseudomonas strains, and co-induction of different antifungal compounds in both biocontrol bacteria and fungi may occur

Organic Amendments, Beneficial Microbes, and Soil Microbiota: Toward a Unified Framework for Disease Suppression

Organic amendments (OAs) and soilborne biocontrol agents or beneficial microbes (BMs) have been extensively studied and applied worldwide in most agriculturally important plant species. However, poor integration of research and technical approaches has limited the development of effective disease management practices based on the combination of these two bio-based strategies. Insights into the importance of the plant-associated microbiome for crop productivity, which can be modified or modulated by introducing OAs and/or BMs, are providing novel opportunities to achieve the goal of long-term disease control. This review discusses novel ways of functionally characterizing OAs and how they may be used to promote the effect of added biocontrol agents and/or beneficial soil microbiota to support natural suppressiveness of plant pathogens

Trichoderma: a multipurpose, plant-beneficial microorganism for eco-sustainable agriculture

Trichoderma is a cosmopolitan and opportunistic ascomycete fungal genus including species that are of interest to agriculture as direct biological control agents of phytopathogens. Trichoderma utilizes direct antagonism and competition, particularly in the rhizosphere, where it modulates the composition of and interactions with other microorganisms. In its colonization of plants, on the roots or as an endophyte, Trichoderma has evolved the capacity to communicate with the plant and produce numerous multifaceted benefits to its host. The intricacy of this plant-microorganism association has stimulated a marked interest in research on Trichoderma, ranging from its capacity as a plant growth promoter to its ability to prime local and systemic defence responses against biotic and abiotic stresses and to activate transcriptional memory affecting plant responses to future stresses. This Review discusses the ecophysiology and diversity of Trichoderma and the complexity of its relationships in the agroecosystem, highlighting its potential as a direct and indirect biological control agent, biostimulant and biofertilizer, which are useful multipurpose properties for agricultural applications. We also highlight how the present legislative framework might accommodate the demonstrated evidence of Trichoderma proficiency as a plant-beneficial microorganism contributing towards eco-sustainable agriculture

Modulation of Tomato Response to Rhizoctonia solani by Trichoderma harzianum and Its Secondary Metabolite Harzianic Acid

The present study investigated the transcriptomic and metabolomic changes elicited in tomato plants (Solanum lycopersicum cv. Micro-Tom) following treatments with the biocontrol agent Trichoderma harzianum strain M10 or its purified secondary metabolite harzianic acid (HA), in the presence or the absence of the soil-borne pathogen Rhizoctonia solani. Transcriptomic analysis allowed the identification of differentially expressed genes (DEGs) that play a pivotal role in resistance to biotic stress. Overall, the results support the ability of T. harzianum M10 to activate defense responses in infected tomato plants. An induction of hormone-mediated signaling was observed, as shown by the up-regulation of genes involved in the ethylene and jasmonate (ET/JA) and salicylic acid (SA)-mediated signaling pathways. Further, the protective action of T. harzianum on the host was revealed by the over-expression of genes able to detoxify cells from reactive oxygen species (ROS). On the other hand, HA treatment also stimulated tomato response to the pathogen by inducing the expression of several genes involved in defense response (including protease inhibitors, resistance proteins like CC-NBS-LRR) and hormone interplay. The accumulation of steroidal glycoalkaloids in the plant after treatments with either T. harzianum or HA, as determined by metabolomic analysis, confirmed the complexity of the plant response to beneficial microbes, demonstrating that these microorganisms are also capable of activating the chemical defenses

Calcium-mediated perception and defense responses activated in plant cells by metabolite mixtures secreted by the biocontrol fungus Trichoderma atroviride

<p>Abstract</p> <p>Background</p> <p>Calcium is commonly involved as intracellular messenger in the transduction by plants of a wide range of biotic stimuli, including signals from pathogenic and symbiotic fungi. <it>Trichoderma </it>spp. are largely used in the biological control of plant diseases caused by fungal phytopathogens and are able to colonize plant roots. Early molecular events underlying their association with plants are relatively unknown.</p> <p>Results</p> <p>Here, we investigated the effects on plant cells of metabolite complexes secreted by <it>Trichoderma atroviride </it>wild type P1 and a deletion mutant of this strain on the level of cytosolic free Ca²⁺and activation of defense responses. <it>Trichoderma </it>culture filtrates were obtained by growing the fungus alone or in direct antagonism with its fungal host, the necrotrophic pathogen <it>Botrytis cinerea</it>, and then separated in two fractions (>3 and <3 kDa). When applied to aequorin-expressing soybean (<it>Glycine max </it>L.) cell suspension cultures, <it>Trichoderma </it>and <it>Botrytis </it>metabolite mixtures were distinctively perceived and activated transient intracellular Ca²⁺elevations with different kinetics, specific patterns of intracellular accumulation of reactive oxygen species and induction of cell death. Both Ca²⁺signature and cellular effects were modified by the culture medium from the knock-out mutant of <it>Trichoderma</it>, defective for the production of the secreted 42 kDa endochitinase.</p> <p>Conclusion</p> <p>New insights are provided into the mechanism of interaction between <it>Trichoderma </it>and plants, indicating that secreted fungal molecules are sensed by plant cells through intracellular Ca²⁺changes. Plant cells are able to discriminate signals originating in the single or two-fungal partner interaction and modulate defense responses.</p

Factors affecting the production of Trichoderma harzianum secondary metabolites during the interaction with different plant pathogens

Strains of Trichoderma spp. produce numerous bioactive secondary metabolites. The in vitro production and antibiotic activities of the major compounds synthesized by Trichoderma harzianum strains T22 and T39 against Leptosphaeria maculans, Phytophthora cinnamomi and Botrytis cinerea were evaluated. Moreover, the eliciting effect of viable or nonviable biomasses of Rhizoctonia solani, Pythium ultimum or B. cinerea on the in vitro production of these metabolites was also investigated. T22azaphilone, 1-hydroxy-3-methyl-anthraquinone, 1,8-dihydroxy-3-methyl-anthraquinone, T39butenolide, harzianolide, harzianopyridone were purified, characterized and used as standards. In antifungal assays, T22azaphilone and harzianopyridone inhibited the growth of the pathogens tested even at low doses (1-10 mu g per plug), while high concentrations of T39butenolide and harzianolide were needed (> 100 mu g per plug) for inhibition. The in vitro accumulation of these metabolites was quantified by LC/MS. T22azaphilone production was not enhanced by the presence of the tested pathogens, despite its antibiotic activity. On the other hand, the anthraquinones, which showed no pathogen inhibition, were stimulated by the presence of P. ultimum. The production of T39butenolide was significantly enhanced by co-cultivation with R. solani or B. cinerea. Similarly, viable and nonviable biomasses of R. solani or B. cinerea increased the accumulation of harzianopyridone. Finally, harzianolide was not detected in any of the interactions examined. The secondary metabolites analysed in this study showed different levels of antibiotic activity. Their production in vitro varied in relation to: (i) the specific compound; (ii) the phytopathogen used for the elicitation; (iii) the viability of the elicitor; and (iv) the balance between elicited biosynthesis and biotransformation rates. The use of cultures of phytopathogens to enhance yields of Trichoderma metabolites could improve the production and application of novel biopesticides and biofertilizers based on the active compounds instead of the living microbe. This could have a significant beneficial impact on the management of diseases in crop plants

Study of proteome pattern of Pseudomonas fluorescens strain UTPF68 in interaction with Trichoderma atroviride strain P1 and tomato

Saprophitic Pseudomonas species are root-colonizing bacteria that can improve plant health. Efficient exploitation of these bacteria in agriculture requires knowledge of traits that enhance ecological performance in the rhizosphere. Some Pseudomonas fluorescens strains present biocontrol properties, protecting the roots of some plant species against plant pathogens. These bacteria induce systemic resistance in the host plant, so it can better resist attack by a true pathogen. The bacteria outcompete other (pathogenic) soil microbes, e.g., by siderophores, giving a competitive advantage at scavenging for iron. The bacteria produce compounds antagonistic to other soil microbes, such as phenazine - type antibiotics or hydrogen cyanide. In this study  the changes in the protein profile of P. fluorescens strain UTPF68, involved in the multiple interactions between plant (tomato) and an antagonistic agent (Trichoderma atroviride strain P1) investigated. Two-dimensional electrophoresis was used to analyze separately collected proteins from each one, two or three partner interactions. The results about differential produced spots in Pseudomonas proteome in each collation, showed that 18 differential spots became visible as new, 16 spots were absent, 17 spots were up-regulated and 1 spot was down-regulated, when Tomato-Pseudomonas (TP) condition was compared with control Pseudomonas alone (P). Also more than 84 differential spots were accumulated in proteome of Pseuodomonas due to the presence of Trichoderma, as new, absent, increased and decreased spots. By comparison of conditions revealed 2 protein spots that detected by MS, have newly expressed in present of Plant and Trichoderma. These proteins corresponded to arginine deiminase of P. putida GB-1 and Chaperonin GroEL protein of P. putida S16 that their expressions associated to stress condition.The results indicated that the presence of Plant and Trichoderma induces major changes in the protein profile of Pseudomonas