Governing bodies throughout the world, particularly in Europe, are now implementing legislative mandates with the objective of decreasing dependence on pesticides in agriculture to increase consumer and environmental safety. In order to reduce the risks associated with pesticide applications and reduce dependency on their use, Directives will promote low pesticide-input by implementing integrated pest management (IPM), and provide the means to establish the necessary conditions and measures to employ these practices, as well as to ensure security of commercial products. One approach includes the use of biological control agents and their products as alternatives to synthetic agro-chemicals. Trichoderma spp. are widely studied fungi and are among the most commonly used microbial biological control agents (MBCAs) in agriculture. They are presently marketed as bio-pesticides, biofertilizers, growth enhancers and stimulants of natural resistance. The efficacy of this fungus can be attributed to their ability to protect plants, enhance vegetative growth and contain pathogen populations under numerous agricultural conditions, as well as to act as soil amendments/inoculants for improvement of nutrient ability, decomposition and biodegradation. The living fungal spores (active substance) are incorporated in various formulations, both traditional and innovative, for applications as foliar sprays, pre-planting applications to seed or propagation material, post-pruning treatments, incorporation in the soil during seeding or transplant, watering by irrigation or applied as a root drench or dip. Trichoderma-based preparations are marketed worldwide and used for crop protection of various plant pathogens or increase the plant growth and productivity in diverse cultivated environments such as fields, greenhouses, nurseries; in the production of a variety of horticultural, fruits, trees and ornamental crops. A survey was conducted of Trichoderma-containing products found on the international market to obtain an overall perspective of the: 1) geographical distribution, 2) product composition and identity of Trichoderma species selected, 3) contents combined with Trichoderma in the products -other microbial species or substances in the mix, 4) number of products available globally and geographically, 5) number of products registered or having use specifications, 6) product formulations and applications, 7) manufacturer claims -target use, target pests, product type and effects of applications. The largest distribution of Trichoderma bioproducts is found in Asia, succeeded by Europe, SouthCentral America and North America. The majority of the labels indicated fungicidal properties, but only 38% of the marketed merchandise are registered. Ten Trichoderma species are specifically indicated, but many labels indicate a generic Trichoderma sp. or spp. mix in the list of ingredients. The most common formulation is a wettable powder, followed by granules. Generally, Trichoderma are applied to the seed or propagation material at...

Plants host a mesmerizing diversity of microbes inside and around their roots, known as the microbiome. The microbiome is composed mostly of fungi, bacteria, oomycetes, and archaea that can be either pathogenic or beneficial for plant health and fitness. To grow healthy, plants need to surveil soil niches around the roots for the detection of pathogenic microbes, and in parallel maximize the services of beneficial microbes in nutrients uptake and growth promotion. Plants employ a palette of mechanisms to modulate their microbiome including structural modifications, the exudation of secondary metabolites and the coordinated action of different defence responses. Here, we review the current understanding on the composition and activity of the root microbiome and how different plant molecules can shape the structure of the root-associated microbial communities. Examples are given on interactions that occur in the rhizosphere between plants and soilborne fungi. We also present some well-established examples of microbiome harnessing to highlight how plants can maximize their fitness by selecting their microbiome. Understanding how plants manipulate their microbiome can aid in the design of next-generation microbial inoculants for targeted disease suppression and enhanced plant growth.

Beneficial microbes typically produce bioactive molecules that can affect the interactions of plants with their pathogens. Many secondary metabolites may also have antibiotic properties, which enable the producing microbe to inhibit and/or kill other microorganisms i.e. competing for a nutritional niche. Indeed, some of these compounds have been found to play an important role in the biocontrol of plant diseases by various beneficial microbes used worldwide for crop protection and bio-fertilization. In addition to direct toxic activity against plant pathogens, biocontrol-related metabolites may also increase disease resistance by triggering systemic plant defence activity, and/or enhance root and shoot growth. Fungi belonging to the Trichoderma genus are well known producers of secondary metabolites with a direct activity against phytopathogens and compounds that substantially affect the metabolism of the plant. The widescale application of selected metabolites to induce host resistance and/or to promote crop yield may become a reality in the near future and represents a powerful tool for the implementation of IPM strategies.

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Plant roots release complex mixtures of bioactive molecules, including compounds that affect the activity and modify the composition of the rhizosphere microbiome. In this work, we investigated the initial phase of the interaction between tomato and an effective biocontrol strain of Trichoderma harzianum (T22). We found that root exudates (RE), obtained from plants grown in a split-root system and exposed to various biotic and abiotic stress factors (wounding, salt, pathogen attack), were able to stimulate the growth and act as chemoattractants of the biocontrol fungus. On the other hand, some of the treatments did not result in an enhanced chemotropism on Fusarium oxysporum f. sp. lycopersici, indicating a mechanism that may be selective for nonpathogenic microbes. The involvement of peroxidases and oxylipins, both known to be released by roots in response to stress, was demonstrated by using RE fractions containing these molecules or their commercial purified analogs, testing the effect of an inhibitor, and characterizing the complex pattern of these metabolites released by tomato roots both locally and systemically.