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Journal ArticleDOI

Trichoderma species--opportunistic, avirulent plant symbionts.

TL;DR: Root colonization by Trichoderma spp.
Abstract: Trichoderma spp. are free-living fungi that are common in soil and root ecosystems. Recent discoveries show that they are opportunistic, avirulent plant symbionts, as well as being parasites of other fungi. At least some strains establish robust and long-lasting colonizations of root surfaces and penetrate into the epidermis and a few cells below this level. They produce or release a variety of compounds that induce localized or systemic resistance responses, and this explains their lack of pathogenicity to plants. These root-microorganism associations cause substantial changes to the plant proteome and metabolism. Plants are protected from numerous classes of plant pathogen by responses that are similar to systemic acquired resistance and rhizobacteria-induced systemic resistance. Root colonization by Trichoderma spp. also frequently enhances root growth and development, crop productivity, resistance to abiotic stresses and the uptake and use of nutrients.

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Citations
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Journal ArticleDOI
TL;DR: This review restricts itself to bacteria that are derived from and exert this effect on the root and generally designated as PGPR (plant-growth-promoting rhizobacteria), which can be direct or indirect in their effects on plant growth.
Abstract: Several microbes promote plant growth, and many microbial products that stimulate plant growth have been marketed. In this review we restrict ourselves to bacteria that are derived from and exert this effect on the root. Such bacteria are generally designated as PGPR (plant-growth-promoting rhizobacteria). The beneficial effects of these rhizobacteria on plant growth can be direct or indirect. This review begins with describing the conditions under which bacteria live in the rhizosphere. To exert their beneficial effects, bacteria usually must colonize the root surface efficiently. Therefore, bacterial traits required for root colonization are subsequently described. Finally, several mechanisms by which microbes can act beneficially on plant growth are described. Examples of direct plant growth promotion that are discussed include (a) biofertilization, (b) stimulation of root growth, (c) rhizoremediation, and (d) plant stress control. Mechanisms of biological control by which rhizobacteria can promote plant growth indirectly, i.e., by reducing the level of disease, include antibiosis, induction of systemic resistance, and competition for nutrients and niches.

3,761 citations


Cites background from "Trichoderma species--opportunistic,..."

  • ...Predation and parasitism, the major biocontrol mechanism used by some (fungal) Trichoderma species, is based on enzymatic destruction of the fungal cell wall (36)....

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Journal ArticleDOI
TL;DR: Biocontrol strains of fluorescent pseudomonads produce antifungal antibiotics, elicit induced systemic resistance in the host plant or interfere specifically with fungal pathogenicity factors during root colonization.
Abstract: Particular bacterial strains in certain natural environments prevent infectious diseases of plant roots. How these bacteria achieve this protection from pathogenic fungi has been analysed in detail in biocontrol strains of fluorescent pseudomonads. During root colonization, these bacteria produce antifungal antibiotics, elicit induced systemic resistance in the host plant or interfere specifically with fungal pathogenicity factors. Before engaging in these activities, biocontrol bacteria go through several regulatory processes at the transcriptional and post-transcriptional levels.

2,263 citations

Journal ArticleDOI
TL;DR: The main functions of rhizosphere microorganisms and how they impact on health and disease are reviewed and several strategies to redirect or reshape the rhizospheric microbiome in favor of microorganisms that are beneficial to plant growth and health are highlighted.
Abstract: Microbial communities play a pivotal role in the functioning of plants by influencing their physiology and development. While many members of the rhizosphere microbiome are beneficial to plant growth, also plant pathogenic microorganisms colonize the rhizosphere striving to break through the protective microbial shield and to overcome the innate plant defense mechanisms in order to cause disease. A third group of microorganisms that can be found in the rhizosphere are the true and opportunistic human pathogenic bacteria, which can be carried on or in plant tissue and may cause disease when introduced into debilitated humans. Although the importance of the rhizosphere microbiome for plant growth has been widely recognized, for the vast majority of rhizosphere microorganisms no knowledge exists. To enhance plant growth and health, it is essential to know which microorganism is present in the rhizosphere microbiome and what they are doing. Here, we review the main functions of rhizosphere microorganisms and how they impact on health and disease. We discuss the mechanisms involved in the multitrophic interactions and chemical dialogues that occur in the rhizosphere. Finally, we highlight several strategies to redirect or reshape the rhizosphere microbiome in favor of microorganisms that are beneficial to plant growth and health.

1,752 citations


Cites background from "Trichoderma species--opportunistic,..."

  • ...Especially Trichoderma species have received considerable attention for the production of antimicrobial compounds (Vyas & Mathur, 2002; Harman et al., 2004; Mathivan et al., 2005; Elad, 2008; Druzhinina et al., 2011)....

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Journal ArticleDOI
TL;DR: Features of the rhizosphere that are important for nutrient acquisition from soil are reviewed, with specific emphasis on the characteristics of roots that influence the availability and uptake of phosphorus and nitrogen.
Abstract: The rhizosphere is a complex environment where roots interact with physical, chemical and biological properties of soil. Structural and functional characteristics of roots contribute to rhizosphere processes and both have significant influence on the capacity of roots to acquire nutrients. Roots also interact extensively with soil microorganisms which further impact on plant nutrition either directly, by influencing nutrient availability and uptake, or indirectly through plant (root) growth promotion. In this paper, features of the rhizosphere that are important for nutrient acquisition from soil are reviewed, with specific emphasis on the characteristics of roots that influence the availability and uptake of phosphorus and nitrogen. The interaction of roots with soil microorganisms, in particular with mycorrhizal fungi and non-symbiotic plant growth promoting rhizobacteria, is also considered in relation to nutrient availability and through the mechanisms that are associated with plant growth promotion.

1,476 citations


Cites background from "Trichoderma species--opportunistic,..."

  • ...…diversity of bacteria and fungi that typically colonize the rhizosphere and are able to stimulate plant growth through either a ‘biofertilizing’ (direct) effect or through mechanisms of ‘biocontrol’ (indirect effect; Bashan and Holguin 1997; and see Raaijmakers et al. 2009; Harman et al. 2004; Fig....

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Journal ArticleDOI
TL;DR: The use of microorganisms and the exploitation of beneficial plant–microbe interactions offer promising and environmentally friendly strategies for conventional and organic agriculture worldwide.
Abstract: Plant-associated microorganisms fulfill important functions for plant growth and health. Direct plant growth promotion by microbes is based on improved nutrient acquisition and hormonal stimulation. Diverse mechanisms are involved in the suppression of plant pathogens, which is often indirectly connected with plant growth. Whereas members of the bacterial genera Azospirillum and Rhizobium are well-studied examples for plant growth promotion, Bacillus, Pseudomonas, Serratia, Stenotrophomonas, and Streptomyces and the fungal genera Ampelomyces, Coniothyrium, and Trichoderma are model organisms to demonstrate influence on plant health. Based on these beneficial plant–microbe interactions, it is possible to develop microbial inoculants for use in agricultural biotechnology. Dependent on their mode of action and effects, these products can be used as biofertilizers, plant strengtheners, phytostimulators, and biopesticides. There is a strong growing market for microbial inoculants worldwide with an annual growth rate of approximately 10%. The use of genomic technologies leads to products with more predictable and consistent effects. The future success of the biological control industry will benefit from interdisciplinary research, e.g., on mass production, formulation, interactions, and signaling with the environment, as well as on innovative business management, product marketing, and education. Altogether, the use of microorganisms and the exploitation of beneficial plant–microbe interactions offer promising and environmentally friendly strategies for conventional and organic agriculture worldwide.

1,350 citations


Cites background from "Trichoderma species--opportunistic,..."

  • ...…al. 2004), Pseudomonas (Haas and Défago 2005; Loper et al. 2007), Rhizobium (Long 2001), Serratia (De Vleeschauwer and Höfte 2007), Stenotrophomonas (Ryan et al. 2009), and Streptomyces (Schrey and Tarkka 2008) and the fungal genera Ampelomyces, Coniothyrium, and Trichoderma (Harman et al. 2004)....

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  • ...2009), and Streptomyces (Schrey and Tarkka 2008) and the fungal genera Ampelomyces, Coniothyrium, and Trichoderma (Harman et al. 2004)....

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  • ...The recent progresses achieved with genomic technologies will certainly help to optimize these Table 1 Representatives of microbial inoculants Microorganisms Name of the product Plants, pathogens, or pathosystems Company Ampelomyces quisqualis M-10 AQ10 Biofungicide Powdery mildew on apples, cucurbits, grapes, ornamentals, strawberries, and tomatoes Ecogen Azospirillum spp. Biopromoter Paddy, millets, oilseeds, fruits, vegetables, sugarcane, banana Manidharma Biotech Bacillus subtilis FZB24 FZB24 li, TB, WG RhizoPlus Potatoes, vegetables, ornamentals, strawberries, bulbs, turf, and woods AbiTep Bacillus subtilis strain GB03 Kodiak Growth promotion; Rhizoctonia and Fusarium spp. (Gustafson); Bayer CropScience Bacillus pumilus GB34 YiedShield Soil-borne fungal pathogens (Gustafson); Bayer CropScience Bacillus subtilis QST716 Serenade Tobacco, tomato, lettuce, spinach AgraQuest Bacillus subtilis GB03, other B. subtilis, B. lichenformis, and B. megaterium Companion Rhizoctonia, Pythium, Fusarium, and Phytophthora Growth Products Bradyrhizobium japonicum Soil implant+ Soy bean Nitragin Coniothyrium minitans Contans WG, Intercept WG Sclerotinia sclerotiorum, S. minor Prophyta Biologischer Pflanzenschutz Delftia acidovorans BioBoost Canola Brett-Young Seeds Limited Paecilomyces lilacinus Bioact WG Nematodes Prophyta Biologischer Pflanzenschutz Phlebiopsis gigantea Rotex Heterobasidium annosum E~nema Biologischer Pflanzenschutz Pseudomonas chlororaphis Cedomon Leaf stripe, net blotch, Fusarium sp., sot blotch, leaf spot, etc. on barley and oats BioAgri AB Pseudomonas fluorescens A506 BlightBan A506 Frost damage, Erwinia amylovora, and russetinducing bacteria on almond, apple, peach, pear, etc. NuFarm Pseudomonas trivialis 3Re-27 Salavida Lettuce Sourcon Padena Pseudomonas spp. Proradix Rhizoctonia solani Sourcon Padena Serratia plymuthcia HRO-C48 RhizoStar Strawberries, oilseed rape Prophyta Biologischer Pflanzenschutz Streptomyces griseoviridis K61 Mycostop Phomopsis spp., Botrytis spp., Pythium spp., Phythophora spp. Kemira Agro Oy Trichoderma harzianum T22 RootShield, PlantShield T22, Planter box Pythium spp., Rhizoctonia solani, Fusarium spp. Bioworks processes....

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  • ...These comprise members of the bacterial genera Azospirillum (Okon 1994; Cassán and García Salamone 2008), Bacillus (Jacobsen et al. 2004), Pseudomonas (Haas and Défago 2005; Loper et al. 2007), Rhizobium (Long 2001), Serratia (De Vleeschauwer and Höfte 2007), Stenotrophomonas (Ryan et al. 2009), and Streptomyces (Schrey and Tarkka 2008) and the fungal genera Ampelomyces, Coniothyrium, and Trichoderma (Harman et al. 2004)....

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  • ...While IAA is involved in many bacteria–plant signaling (Spaepen et al. 2007), an important role of auxin signaling for plant growth promotion was also shown for Trichoderma spp. (Contreras-Cornejo et al. 2009)....

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References
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Journal ArticleDOI
TL;DR: Rhizobacteria-mediated induced systemic resistance (ISR) is effective under field conditions and offers a natural mechanism for biological control of plant disease.
Abstract: Nonpathogenic rhizobacteria can induce a systemic resistance in plants that is phenotypically similar to pathogen-induced systemic acquired resistance (SAR). Rhizobacteria-mediated induced systemic resistance (ISR) has been demonstrated against fungi, bacteria, and viruses in Arabidopsis, bean, carnation, cucumber, radish, tobacco, and tomato under conditions in which the inducing bacteria and the challenging pathogen remained spatially separated. Bacterial strains differ in their ability to induce resistance in different plant species, and plants show variation in the expression of ISR upon induction by specific bacterial strains. Bacterial determinants of ISR include lipopolysaccharides, siderophores, and salicylic acid (SA). Whereas some of the rhizobacteria induce resistance through the SA-dependent SAR pathway, others do not and require jasmonic acid and ethylene perception by the plant for ISR to develop. No consistent host plant alterations are associated with the induced state, but upon challenge inoculation, resistance responses are accelerated and enhanced. ISR is effective under field conditions and offers a natural mechanism for biological control of plant disease.

2,146 citations

Journal ArticleDOI
TL;DR: Multiple microbial interactions involving bacteria and fungi in the rhizosphere are shown to provide enhanced biocontrol in many cases in comparison with biocOntrol agents used singly.
Abstract: The loss of organic material from the roots provides the energy for the development of active microbial populations in the rhizosphere around the root. Generally, saproptrophs or biotrophs such as mycorrhizal fungi grow in the rhizosphere in response to this carbon loss, but plant pathogens may also develop and infect a susceptible host, resulting in disease. This review examines the microbial interactions that can take place in the rhizosphere and that are involved in biological disease control. The interactions of bacteria used as biocontrol agents of bacterial and fungal plant pathogens, and fungi used as biocontrol agents of protozoan, bacterial and fungal plant pathogens are considered. Whenever possible, modes of action involved in each type of interaction are assessed with particular emphasis on antibiosis, competition, parasitism, and induced resistance. The significance of plant growth promotion and rhizosphere competence in biocontrol is also considered. Multiple microbial interactions involving bacteria and fungi in the rhizosphere are shown to provide enhanced biocontrol in many cases in comparison with biocontrol agents used singly. The extreme complexity of interactions that can occur in the rhizosphere is highlighted and some potential areas for future research in this area are discussed briefly.

1,818 citations

Journal ArticleDOI
TL;DR: Past research indicates that the mechanisms are many and varied, even within the genus Trichoderma, and in order to make the most effective use of biocontrol agents for the control of plant diseases, it must understand how the agents work and what their limitations are.
Abstract: Fungal species belonging to the genus Trichoderma are worldwide in occurrence and easily isolated from soil, decaying wood, and other forms of plant organic matter. They are, for the most part, classified as imperfect fungi, in that they have no known sexual stage. Rapid growth rate in culture and the production of numerous spores (conidia) that are varying shades of green characterize fungi in this genus. The reverse side of colonies is often uncolored, buff, yellow, amber, or yellow-green, and many species produce prodigious quantities of thick-walled spores (chlamydospores) in submerged mycelium (8). The potential of Trichoderma species as biocontrol agents of plant diseases was first recognized in the early 1930s (31), and in subsequent years, control of many diseases has been added to the list (1,3,5,7,9,11,19, 23,29,34,37,40). This has culminated in the commercial production of several Trichoderma species for the protection and growth enhancement of a number of crops in the United States (24), and in the production of Trichoderma species and mixtures of species in India, Israel, New Zealand, and Sweden (D. R. Fravel, personal communication). One of the most interesting aspects of the science of biological control is the study of the mechanisms employed by biocontrol agents to effect disease control. Past research indicates that the mechanisms are many and varied, even within the genus Trichoderma. In order to make the most effective use of biocontrol agents for the control of plant diseases, we must understand how the agents work and what their limitations are. We can then develop effective means of culturing, storing, applying, and utilizing biocontrol agents so that we harness their best effort for disease control. The selected research papers cited in this article were chosen because they illustrate what has been learned about mechanisms involved in biocontrol with Trichoderma species.

1,467 citations

Journal ArticleDOI
TL;DR: The demonstration that PGPR strains release different volatile blends and that plant growth is stimulated by differences in these volatile blends establishes an additional function for volatile organic compounds as signaling molecules mediating plant–microbe interactions.
Abstract: Several chemical changes in soil are associated with plant growth-promoting rhizobacteria (PGPR). Some bacterial strains directly regulate plant physiology by mimicking synthesis of plant hormones, whereas others increase mineral and nitrogen availability in the soil as a way to augment growth. Identification of bacterial chemical messengers that trigger growth promotion has been limited in part by the understanding of how plants respond to external stimuli. With an increasing appreciation of how volatile organic compounds signal plants and serve in plant defense, investigations into the role of volatile components in plant–bacterial systems now can follow. Here, we present chemical and plant-growth data showing that some PGPR release a blend of volatile components that promote growth of Arabidopsis thaliana. In particular, the volatile components 2,3-butanediol and acetoin were released exclusively from two bacterial strains that trigger the greatest level of growth promotion. Furthermore, pharmacological applications of 2,3-butanediol enhanced plant growth whereas bacterial mutants blocked in 2,3-butanediol and acetoin synthesis were devoid in this growth-promotion capacity. The demonstration that PGPR strains release different volatile blends and that plant growth is stimulated by differences in these volatile blends establishes an additional function for volatile organic compounds as signaling molecules mediating plant–microbe interactions.

1,434 citations


"Trichoderma species--opportunistic,..." refers background in this paper

  • ...Recently, phenotypically similar growth promotion by bacteria was shown to be induced by the release of the volatile compounds acetoin and 2,3-butanedio...

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