In vitro antagonism of Trichoderma species against six fungal plant pathogens [Biological disease control]

Research on the mechanisms employed by the biocontrol agent Trichoderma virens to suppress cotton (Gossypium hirsutum) seedling disease incited by Rhizoctonia solani has shown that mycoparasitism and antibiotic production are not major contributors to successful biological control. In this study, we examined the possibility that seed treatment with T. virens stimulates defense responses, as indicated by the synthesis of terpenoids in cotton roots. We also examined the role of these terpenoid compounds in disease control. Analysis of extracts of cotton roots and hypocotyls grown from T. virens-treated seed showed that terpenoid synthesis and peroxidase activity were increased in the roots of treated plants, but not in the hypocotyls of these plants or in the untreated controls. Bioassay of the terpenoids for toxicity to R. solani showed that the pathway intermediates desoxyhemigossypol (dHG) and hemigossypol (HG) were strongly inhibitory to the pathogen, while the final product gossypol (G) was toxic only at a much higher concentration. Strains of T. virens and T. koningii were much more resistant to HG than was R. solani, and they thoroughly colonized the cotton roots. A comparison of biocontrol efficacy and induction of terpenoid synthesis in cotton roots by strains of T. virens, T. koningii, T. harzianum, and protoplast fusants indicated that there was a strong correlation (+0.89) between these two phenomena. It, therefore, appears that induction of defense response, particularly terpenoid synthesis, in cotton roots by T. virens may be an important mechanism in the biological control by this fungus of R. solani-incited cotton seedling disease.

Induction of terpenoid synthesis in cotton roots and control of Rhizoctonia solani by seed treatment with Trichoderma virens. [Erratum: 2003 Dec., v. 93, no. 12, p. 1606.]

The plant-Trichoderma-pathogen triangle is a complicated web of numerous processes Trichoderma spp are avirulent opportunistic plant symbionts In addition to being successful plant symbiotic organisms, Trichoderma spp also behave as a low cost, effective and ecofriendly biocontrol agent They can set themselves up in various patho-systems, have minimal impact on the soil equilibrium and do not impair useful organisms that contribute to the control of pathogens This symbiotic association in plants leads to the acquisition of plant resistance to pathogens, improves developmental processes and yields and promotes absorption of nutrient and fertilizer use efficiency Among other biocontrol mechanisms, antibiosis, competition and mycoparasitism are among the main features through which microorganisms, including Thrichoderma, react to the presence of other competitive pathogenic organisms, thereby preventing or obstructing their development Stimulation of every process involves the biosynthesis of targeted metabolites like plant growth regulators, enzymes, siderophores, antibiotics, etc This review summarizes the biological control activity exerted by Trichoderma spp and sheds light on the recent progress in pinpointing the ecological significance of Trichoderma at the biochemical and molecular level in the rhizosphere as well as the benefits of symbiosis to the plant host in terms of physiological and biochemical mechanisms From an applicative point of view, the evidence provided herein strongly supports the possibility to use Trichoderma as a safe, ecofriendly and effective biocontrol agent for different crop species

https://www.mdpi.com/2223-7747/9/6/762/pdf

Trichoderma: The “Secrets” of a Multitalented Biocontrol Agent

Biological functions of Trichoderma spp. for agriculture applications

Rhizosphere filamentous fungi of the genus Trichoderma, a dominant component of various soil ecosystem mycobiomes, are characterized by the ability to colonize plant roots. Detailed knowledge of the properties of Trichoderma, including metabolic activity and the type of interaction with plants and other microorganisms, can ensure its effective use in agriculture. The growing interest in the application of Trichoderma results from their direct and indirect biocontrol potential against a wide range of soil phytopathogens. They act through various complex mechanisms, such as mycoparasitism, the degradation of pathogen cell walls, competition for nutrients and space, and induction of plant resistance. With the constant exposure of plants to a variety of pathogens, especially filamentous fungi, and the increased resistance of pathogens to chemical pesticides, the main challenge is to develop biological protection alternatives. Among non-pathogenic microorganisms, Trichoderma seems to be the best candidate for use in green technologies due to its wide biofertilization and biostimulatory potential. Most of the species from the genus Trichoderma belong to the plant growth-promoting fungi that produce phytohormones and the 1-aminocyclopropane-1-carboxylate (ACC) deaminase enzyme. In the present review, the current status of Trichoderma is gathered, which is especially relevant in plant growth stimulation and the biocontrol of fungal phytopathogens.

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Trichoderma: The Current Status of Its Application in Agriculture for the Biocontrol of Fungal Phytopathogens and Stimulation of Plant Growth

Trichoderma spp. are proposed as major plant growth-promoting fungi that widely exist in the natural environment. These strains have the abilities of rapid growth and reproduction and efficient transformation of soil nutrients. Moreover, they can change the plant rhizosphere soil environment and promote plant growth. Pinus sylvestris var. mongolica has the characteristics of strong drought resistance and fast growth and plays an important role in ecological construction and environmental restoration. The effects on the growth of annual seedlings, root structure, rhizosphere soil nutrients, enzyme activity, and fungal community structure of P. sylvestris var. mongolica were studied after inoculation with Trichoderma harzianum E15 and Trichoderma virens ZT05, separately. The results showed that after inoculation with T. harzianum E15 and T. virens ZT05, seedling biomass, root structure index, soil nutrients, and soil enzyme activity were significantly increased compared with the control (p < 0.05). There were significant differences in the effects of T. harzianum E15 and T. virens ZT05 inoculation on the growth and rhizosphere soil nutrient of P. sylvestris var. mongolica (p < 0.05). For the E15 treatment, the seedling height, ground diameter, and total biomass of seedlings were higher than that those of the ZT05 treatment, and the rhizosphere soil nutrient content and enzyme activity of the ZT05 treatment were higher than that of the E15 treatment. The results of alpha and beta diversity analyses showed that the fungi community structure of rhizosphere soil was significantly different (p < 0.05) among the three treatments (inoculated with T. harzianum E15, T. virens ZT05, and not inoculated with Trichoderma). Overall, Trichoderma inoculation was correlated with the change of rhizosphere soil nutrient content.

https://www.mdpi.com/1999-4907/10/9/758/pdf

Effects of Two Trichoderma Strains on Plant Growth, Rhizosphere Soil Nutrients, and Fungal Community of Pinus sylvestris var. mongolica Annual Seedlings

Trichoderma is a filamentous fungus that is widely distributed in nature. As a biological control agent of agricultural pests, Trichoderma species have been widely studied in recent years. This study aimed to understand the inhibitory mechanism of Trichoderma virens ZT05 on Rhizoctonia solani through the side-by-side culture of T. virens ZT05 and R. solani. To this end, we investigated the effect of volatile and nonvolatile metabolites of T. virens ZT05 on the mycelium growth and enzyme activity of R. solani and analyzed transcriptome data collected from side-by-side culture. T. virens ZT05 has a significant antagonistic effect against R. solani. The mycelium of T. virens ZT05 spirally wraps around and penetrates the mycelium of R. solani and inhibits the growth of R. solani. The volatile and nonvolatile metabolites of T. virens ZT05 have significant inhibitory effects on the growth of R. solani. The nonvolatile metabolites of T. virens ZT05 significantly affect the mycelium proteins of R. solani, including catalase (CAT), superoxide dismutase (SOD), peroxidase (POD), selenium-dependent glutathione peroxidase (GSH-Px), soluble proteins, and malondialdehyde (MDA). Twenty genes associated with hyperparasitism, including extracellular proteases, oligopeptide transporters, G-protein coupled receptors (GPCRs), chitinases, glucanases, and proteases were found to be upregulated during the antagonistic process between T. virens ZT05 and R. solani. Thirty genes related to antibiosis function, including tetracycline resistance proteins, reductases, the heat shock response, the oxidative stress response, ATP-binding cassette (ABC) efflux transporters, and multidrug resistance transporters, were found to be upregulated during the side-by-side culture of T. virens ZT05 and R. solani. T. virens ZT05 has a significant inhibitory effect on R. solani, and its mechanism of action is associated with hyperparasitism and antibiosis.

https://www.mdpi.com/2223-7747/9/7/912/pdf

Inhibitory Mechanism of Trichoderma virens ZT05 on Rhizoctonia solani.

Dark septate endophytes (DSEs) exert a vital role in promoting plant growth, improving mineral absorption, biological disease control, and enhancing plant stress resistance. The effects of dark septate endophyte strain, Phialocephala bamuru A024 on damping-off biocontrol, plant development, nutrients within the rhizosphere soil, as well as bacterial communities in the annual seedlings of P. sylvestris var. Mongolica were studied. According to our findings, following P. bamuru A024 inoculation, the damping-off disease morbidity decreased significantly compared with control, some physiological indices such as β-1,3-glucanase, chitinase enzyme activity as well as a soluble protein and proline content in P. sylvestris var. mongolica were elevated under R. solani stress. After inoculation with P. bamuru A024, the biomass in seedlings, nutrients in soil, root structure index, together with activities of soil enzymes were remarkably up-regulated relative to control (p < 0.05). As suggested by the results of high-throughput sequencing, the microbial structure in the rhizosphere soil of the P. sylvestris var. mongolica showed significant differences (p < 0.05) after P. bamuru A024 inoculation compared to control treatment and the rhizosphere soil bacterial community structure after DSE A024 inoculation was positively correlated to the main soil nutrition indices.

https://www.mdpi.com/2223-7747/9/7/913/pdf

Effects of Dark Septate Endophytes Strain A024 on Damping-off Biocontrol, Plant Growth and the Rhizosphere Soil Enviroment of Pinus sylvestris var. mongolica Annual Seedlings.

This research investigates the mechanism of increased salinity tolerance of ectomycorrhizal fungi-inoculated P. sylvestris var. mongolica to provide a theoretical basis for the application of the fungus in saline soils. Growth effects due to inoculation of seedlings with Suillus luteus (a symbiotic ectomycorrhizal fungus), were determined in four kinds of saline–alkali soils. Growth and physiological indicators, including photosynthetic characteristics, plant height, biomass, photosynthetic pigments, catalase (CAT) and superoxide dismutase (SOD) enzyme levels, and malondialdehyde (MDA), an organic marker for oxidative stress, and soluble protein levels were determined. Mycorrhizal colonization rate decreased with increasing saline–alkalinity and growth of inoculated seedlings was significantly enhanced. Biomass and chlorophyll contents also increased significantly. SOD and CAT activities were higher than in non-inoculated seedlings. However, MDA content decreased in inoculated seedlings. Soluble protein content did not increase significantly. Inoculation with a symbiotic ectomycorrhizal fungus could enhance the saline–alkali tolerance of P. sylvestris var. mongolica. Growth and physiological performance of inoculated seedlings were significantly better than that of uninoculated seedlings. The results indicate that inoculated P. sylvestris var. mongolica seedlings may be useful in the improvement of saline–alkali lands.

Effects of an ectomycorrhizal fungus on the growth and physiology of Pinus sylvestris var. mongolica seedlings subjected to saline–alkali stress

Pinus sylvestris var. mongolica is an important tree species for ecological construction and environmental restoration owing to its rapid growth rate and excellent stress resistance. Pinus sylvestris var. mongolica sphaeropsis blight is a widespread disease caused by Sphaeropsis sapinea. This study was focused on non-infected (CK) and infected (SS) Pinus sylvestris var. mongolica plants in Zhanggutai area, Liaoning Province, China. Illumina high-throughput sequencing based on the templates of sequencing-by-synthesis working with reversible terminators is a widely used approach. In the present study, systematic differences in relationships among rhizosphere soil physicochemical properties, bacterial community structure, diverse bacterial genera, and alpha diversity indices between the two categories were evaluated. The current findings are as follows: (1) Shannon’s index of SS soil was significantly higher than CK, and it was significantly lower in May than July and September (p < 0.05). (2) Non-metric multidimensional scaling (NMDS) showed a difference in bacterial community structure during May (spring), July (summer), and September. (3) At the phylum level, no significant difference was found in the bacterial genera between CK and SS soil for three seasons; however, at the genus level, there were about 19 different bacterial genera. The correlation studies between 19 different bacterial genera and environmental factors and α-diversity indicated that bacterial genera of non-infected and infected Pinus sylvestris var. mongolica were distributed differently. The bacterial genera with CK were positively correlated with soil physicochemical properties, while a negative correlation was found for SS. In conclusion, the differences in nutrient and microbial community structure in the rhizosphere soil of Pinus sylvestris var. mongolica are the main causes of shoot blight disease.

Effects of Sphaeropsis Blight on Rhizosphere Soil Bacterial Community Structure and Soil Physicochemical Properties of Pinus sylvestris var. mongolica in Zhanggutai, China

Saiyaremu Halifu

Papers

Effects of Two Trichoderma Strains on Plant Growth, Rhizosphere Soil Nutrients, and Fungal Community of Pinus sylvestris var. mongolica Annual Seedlings

Inhibitory Mechanism of Trichoderma virens ZT05 on Rhizoctonia solani.

Effects of Dark Septate Endophytes Strain A024 on Damping-off Biocontrol, Plant Growth and the Rhizosphere Soil Enviroment of Pinus sylvestris var. mongolica Annual Seedlings.

Effects of an ectomycorrhizal fungus on the growth and physiology of Pinus sylvestris var. mongolica seedlings subjected to saline–alkali stress

Effects of Sphaeropsis Blight on Rhizosphere Soil Bacterial Community Structure and Soil Physicochemical Properties of Pinus sylvestris var. mongolica in Zhanggutai, China