Effects of Soil Moisture and Temperature on the Saprophytic Ability of Trichoderma Harzianum
TL;DR: Esti?
Abstract: Measurements of competitive saprophytic colonization were used to evaluate the activity of Tricho? derma harzianum in non-sterile soil under conditions of varying soil moisture and temperature. Esti? mates of activity based on levels of colonization, determined after homogenization of substrate pieces, were more discriminating than those based on the number of colonized pieces. T. harzianum was found to be most active at soil matric potentials from -0.5 to -1.0 bar, with activity declining at matric potentials of 0.0, -7.5, and -15.0 bars. The saprophytic activity of T. harzianum was greatest at temperatures from 15 to 21 C. The optimum temperature for competitive colonization was several
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TL;DR: Information on the ecology and biological control of plant pathogenic Pythium species is reviewed with the premise that a clear understanding of the ecology of the pathogen will assist in the development of efficacious biocontrol agents.
Abstract: Soilborne root diseases caused by plant pathogenic Pythium species cause serious losses in a number of agricultural production systems, which has led to a considerable effort devoted to the development of biological agents for disease control. In this article we review information on the ecology and biological control of these pathogens with the premise that a clear understanding of the ecology of the pathogen will assist in the development of efficacious biocontrol agents. The lifecycles of the pathogens and etiology of host infection also are reviewed, as are epidemiological concepts of inoculum-disease relationships and the influence of environmental factors on pathogen aggressiveness and host susceptibility. A number of fungal and bacterial biocontrol agents are discussed and parallels between their ecology and that of the target pathogens highlighted. The mechanisms by which these microbial agents suppress diseases caused by Pythium spp., such as interference with pathogen survival, disruption of the...
357 citations
Cites background from "Effects of Soil Moisture and Temper..."
...…comparison of environmental influences on saprophytic activity revealed that T. harzianum was most active between –0.05 and –0.1 MPa and 15 to 21°C (Eastburn and Butler, 1991), conditions that also favor many phytopathogenic Pythium spp. Trichoderma harzianum suppresses Pythium damping-off at…...
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...1 MPa and 15 to 21°C (Eastburn and Butler, 1991), conditions that also favor many phytopathogenic Pythium spp....
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TL;DR: Results suggest that the CWDEs NAGase and β-1,3-glucanase and sclerotia parasitism are key components of Trichoderma spp.
101 citations
Cites background from "Effects of Soil Moisture and Temper..."
...Furthermore, environmental factors such as solar radiation, humidity, and temperature and soil microbial community have their own influence on antagonists, making it difficult to reduce to only a few factors the causes of variation seen between the two field essays (Bae and Knudsen, 2005; Eastburn and Butler, 1991; Naar and Kecskés, 1998)....
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...…solar radiation, humidity, and temperature and soil microbial community have their own influence on antagonists, making it difficult to reduce to only a few factors the causes of variation seen between the two field essays (Bae and Knudsen, 2005; Eastburn and Butler, 1991; Naar and Kecskés, 1998)....
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01 Jan 2004
TL;DR: Trichoderma mutants significantly reduced wilt disease incidence and improved yield and mineral contents of tomato plants under both saline and non-saline soil conditions, as well as, under infested and natural conditions.
Abstract: This work aims to apply γ- irradiation in a breeding program of Trichoderma harzianum to enhance its biocontrol ability against F. oxysporum through increasing their production of antifungal metabolites (i.e., hydrolytic enzymes,antibiotics and total phenols) under salt stress conditions. Exposing a wild-type culture of the mycoparasitic fungus T. harzianum to gamma irradiation induced two stable salt-tolerant mutants (Th50M6 & Th50M11).Under saline conditions, both mutants greatly surpassed their wild type strain in growth rate, sporulation and biological proficiency against Fusarium oxysporum, the causal agent of tomato wilt disease. Tolerant T. harzianum mutants detained a capability to grow and convinced sporulation in growth media containing up to 69 mM NaCl. In comparison with their parent strain, characterization of both mutants confirmed that they have reinforced contents of proline and hydroxyproline, relatively higher sodium content compared to potassium, calcium or magnesium contents, higher level of total phenols. Data also showed that mutants produce certain active metabolites including; extracellular-enzymes of chitinases, cellulases, β-galactosidases, as well as, some antibiotics i.e., trichodermin, gliotoxin and gliovirin. Trichoderma mutants significantly reduced wilt disease incidence and improved yield and mineral contents of tomato plants under both saline and nonsaline soil conditions, as well as, under infested and natural conditions. T. harzianum mutants were also more efficient in dropping the F. oxysporum growth in rhizosphere compared to the wild type strain. Population density of both mutants in rhizosphere far exceeded those of T. harzianum wild type strain.
80 citations
Cites background from "Effects of Soil Moisture and Temper..."
...They also display a decisive outcome on saprophytic ability (14), on the interaction with other fungi (19), as well as on enzyme production (21)....
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TL;DR: Among non-pathogenic microorganisms, Trichoderma seems to be the best candidate for use in green technologies due to its wide biofertilization and biostimulatory potential.
Abstract: 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.
77 citations
TL;DR: Water activity and pH are probably the most important environmental parameters affecting the activities of mycoparasitic Trichoderma strains and it is important to collect information on the effects of these factors on mycelial growth and on the in vitro activities of extracellular enzymes involved in nutrient competition.
Abstract: Aims: Water activity (aw) and pH are probably the most important environmental parameters affecting the activities of mycoparasitic Trichoderma strains. Therefore it is important to collect information on the effects of these factors on mycelial growth and on the in vitro activities of extracellular enzymes involved in nutrient competition (e.g. β-glucosidase, cellobiohydrolase and β-xylosidase) and mycoparasitism (e.g. N-acetyl-β-glucosaminidase, trypsin-like protease and chymotrypsin-like protease) of Trichoderma strains with biocontrol potential.
Methods and Results: Water activity and pH dependence of the linear mycelial growth of five examined Trichoderma strains belonging to three different species groups was examined on yeast extract and soil extract media. Maximal growth rates were observed at aw 0·997 and pH 4·0 in the case of all strains. The activities of the examined extracellular enzymes at different aw and pH values were determined spectrophotometrically after incubation with chromogenic p-nitrophenyl and p-nitroaniline substrates. Maximal enzyme activities were measured at aw 0·950 for β-glucosidase, trypsin-like protease and chymotrypsin-like protease, at 0·910 for cellobiohydrolase and at 0·993 for β-xylosidase and N-acetyl-β-glucosaminidase enzymes. Optimal pH values are suggested to be at 5·0 for β-glucosidase, cellobiohydrolase and N-acetyl-β-glucosaminidase, at 3·0 for β-xylosidase, at 6·0 for trypsin-like protease and between 6·0 and 7·0 for chymotrypsin-like protease activities, respectively.
Conclusions: Extracellular enzymes of the examined mycoparasitic Trichoderma strains are able to display activities under a wider range of aw and pH values than those allowing mycelial growth.
Significance and Impact of the Study: Data about the effects of aw and pH on mycelial growth and extracellular enzyme activities of Trichoderma reveal useful information about the applicability of biocontrol strains in agricultural soils with specific water and pH relations.
74 citations
Cites background from "Effects of Soil Moisture and Temper..."
...harzianum (Badham 1991; Eastburn and Butler 1991), and about the in vitro effects of water relations on growth, enzyme secretion and extracellular enzyme activities of a T....
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...Besides the effects of low temperature (Magan 1988; Eastburn and Butler 1991; Antal et al. 2000), heavy metals (Babich et al....
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...Besides the effects of low temperature (Magan 1988; Eastburn and Butler 1991; Antal et al. 2000), heavy metals (Babich et al. 1982; Somashekar et al. 1983; Frank et al. 1993; Kredics et al. 2001a,b), pesticides (Stratton 1983; Beatty and Sohn 1986) and antagonistic bacteria (Naár and Kecskés…...
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...…germination and germ tube growth of Trichoderma species (Magan 1988), on growth, competitive and saprophytic abilities of T. harzianum (Badham 1991; Eastburn and Butler 1991), and about the in vitro effects of water relations on growth, enzyme secretion and extracellular enzyme activities of a T.…...
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References
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TL;DR: In this paper, a number of experimental results are presented which show the variation of the pH values of several soils when samples of each are shaken with CaCl/sub 2/ solutions of different concentrations.
Abstract: A number of experimental results are presented which show the variation of the pH values of several soils when samples of each are shaken with CaCl/sub 2/ solutions of different concentrations. These results are then interpreted on the basis of the ratio law-derived from the Gouy theory of the electrical double layer - and it is shown that the pH values and electrolyte concentrations show the expected relationship, provided the latter is not too large. The importance of the connection between pH and electrolyte concentration in the routine measurement of soil pH is emphasized, and it is pointed out that such measurements must be carried out using an electrolyte solution of known composition in order to obtain comparable results from different soils. It has been found that 0.01 M CaCl/sub 2/ is the most satisfactory for use in normal non-saline soils where the surface density of electrical charge on the colloidal material is high and independent of the solution composition: This electrolyte concentration is such that measurements made with the usual glass electrode/saturated calomel cell give accurate and reproducible values which are largely independent of the soil/solution ratio, and is yet sufficiently dilute to allow a satisfactory calculation of themore » lime potential characteristic of the soil sample.« less
510 citations
130 citations
TL;DR: Propagules of Trichoderma generally formed less than 3 per cent of the total fungal propagules in a variety of forest soils in the southeastern U.S. and Washington State, but under conditions of excessive moisture, strains of T. hamatum and T. pseudokoningii Rifai were the dominant forms.
Abstract: Propagules of Trichoderma generally formed less than 3 per cent of the total fungal propagules in a variety of forest soils in the southeastern U.S. and Washington State. The largest populations were found in the F and H organic horizons of the forest floor or under conditions of excessive moisture. T. viride Pers. ex S.F. Gray and T. polysporum (Link ex Pers.) Rifai were largely restricted to cool temperate regions; whereas, T. harzianum Rifai was characteristic of warm climates. T. koningii Oud. and T. hamatum (Bon.) Bain, were the most widely distributed species aggregates and were found in all the climatic regions investigated. Under conditions of excessive moisture, strains of T. hamatum and T. pseudokoningii Rifai were the dominant forms.
103 citations
TL;DR: The weaker saprophyte, H. sativum, proved, however, to be more sensitive than C. ramosa to antibiotics produced by other soil micro-organisms, and in spore germination tests with purified fungal antibiotics in vitro, Hsativum proved more sensitive to eight of the ten substances tested than did C.Ramosa.
Abstract: Factors influencing the saprophytic colonizing ability of two cereal root-rot fungi, Curvularia ramosa, a vigorous competitive saprophyte, and Helminthosporium sativum, a weak competitive saprophyte, have been investigated. The observed difference in their competitive saprophytic ability could not be ascribed either to a difference in rate of growth or to the ability of the stronger saprophyte, C. ramosa, to produce an antibiotic. The weaker saprophyte, H. sativum, proved, however, to be more sensitive than C. ramosa to antibiotics produced by other soil micro-organisms. Thus, in spore germination tests with purified fungal antibiotics in vitro, H. sativum proved more sensitive to eight of the ten substances tested than did C. ramosa and was only slightly less sensitive than C. ramosa to the remaining two antibiotics. H. sativum was found also to be generally more sensitive than C. ramosa to the antagonistic effects of certain common soil bacteria. Of the seven bacterial species tested, five caused an appreciable reduction in germ tube development and two reduced germination in H. sativum whereas none of the bacterial species inhibited either spore germination or germ tube development of C. ramosa, and three actually stimulated germ tube development by this fungus.
94 citations