Showing papers on "Trichoderma harzianum published in 1998"

Genes from mycoparasitic fungi as a source for improving plant resistance to fungal pathogens.

Abstract: Disease resistance in transgenic plants has been improved, for the first time, by the insertion of a gene from a biocontrol fungus. The gene encoding a strongly antifungal endochitinase from the mycoparasitic fungus Trichoderma harzianum was transferred to tobacco and potato. High expression levels of the fungal gene were obtained in different plant tissues, which had no visible effect on plant growth and development. Substantial differences in endochitinase activity were detected among transformants. Selected transgenic lines were highly tolerant or completely resistant to the foliar pathogens Alternaria alternata, A. solani, Botrytis cinerea, and the soilborne pathogen Rhizoctonia solani. The high level and the broad spectrum of resistance obtained with a single chitinase gene from Trichoderma overcome the limited efficacy of transgenic expression in plants of chitinase genes from plants and bacteria. These results demonstrate a rich source of genes from biocontrol fungi that can be used to control diseases in plants.

Induced systemic resistance in Trichoderma harzianum T39 biocontrol of Botrytis cinerea

Abstract: Biocontrol of Botrytis cinerea with Trichoderma spp is generally believed to result from direct interaction of the biocontrol agent with the pathogen or from a Trichoderma-induced change in environmental conditions that affects B cinerea development In this work we provide arguments for the participation of induced plant defence in T harzianum T39 control of B cinerea In tomato, lettuce, pepper, bean and tobacco, T harzianum T39 application at sites spatially separated from the B cinerea inoculation resulted in a 25–100%percnt; reduction of grey mould symptoms, caused by a delay or suppression of spreading lesion formation Given the spatial separation of both micro-organisms, this effect was attributed to the induction of systemic resistance by T harzianum T39 The observation that in bean the effect of T harzianum T39 was similar to that of the rhizobacterium Pseudomonas aeruginosa KMPCH, a reference strain for the induction of systemic resistance, confirmed this hypothesis Since B cinerea control on tobacco leaves sprayed with T harzianum T39 was similar to the control on leaves from T harzianum T39 soil-treated plants, induction of plant defence might also participate in biocontrol on treated leaves

Analysis of the β-1,3-Glucanolytic System of the Biocontrol Agent Trichoderma harzianum

Abstract: The biocontrol agent Trichoderma harzianum IMI206040 secretes beta-1,3-glucanases in the presence of different glucose polymers and fungal cell walls. The level of beta-1,3-glucanase activity secreted was found to be proportional to the amount of glucan present in the inducer. The fungus produces at least seven extracellular beta-1,3-glucanases upon induction with laminarin, a soluble beta-1,3-glucan. The molecular weights of five of these enzymes fall in the range from 60,000 to 80,000, and their pIs are 5.0 to 6.8. In addition, a 35-kDa protein with a pI of 5.5 and a 39-kDa protein are also secreted. Glucose appears to inhibit the formation of all of the inducible beta-1,3-glucanases detected. A 77-kDa glucanase was partially purified from the laminarin culture filtrate. This enzyme is glycosylated and belongs to the exo-beta-1,3-glucanase group. The properties of this complex group of enzymes suggest that the enzymes might play different roles in host cell wall lysis during mycoparasitism.

The expression of genes involved in parasitism by Trichoderma harzianum is triggered by a diffusible factor

Abstract: The mycoparasite Trichoderma harzianum has been extensively used in the biocontrol of a wide range of phytopathogenic fungi. Hydrolytic enzymes secreted by the parasite have been directly implicated in the lysis of the host. Dual cultures of Trichoderma and a host, with and without contact, were used as means to study the mycoparasitic response in Trichoderma. Northern analysis showed high-level expression of genes encoding a proteinase (prb1) and an endochitinase (ech42) in dual cultures even if contact with the host was prevented by using cellophane membranes. Neither gene was induced during the interaction of Trichoderma with lectin-coated nylon fibres, which are known to induce hyphal coiling and appressorium formation. Thus, the signal involved in triggering the production of these hydrolytic enzymes by T. harzianum during the parasitic response is independent of the recognition mediated by this lectin-carbohydrate interaction. The results showed that induction of prb1 and ech42 is contact-independent, and a diffusible molecule produced by the host is the signal that triggers expression of both genes in vivo. Furthermore, a molecule that is resistant to heat and protease treatment, obtained from Rhizoctonia solani cell walls induces expression of both genes. Thus, this molecule is involved in the regulation of the expression of hydrolytic enzymes during mycoparasitism by T. harzianum.

Management of powdery mildew and gray mold of cucumber by Trichoderma harzianum T39 and Ampelomyces quisqualis AQ10

Abstract: Two biocontrol preparations were tested for their ability to control Sphaerotheca fusca and Botrytis cinerea on greenhouse cucumber. Trichoderma harzianum T39 (TRICHODEX) spray reduced powdery mildew severity by up to 97% but its efficacy declined to 18–55% control as the epidemic progressed. Unlike on young leaves, on older leaves the control of powdery mildew by T. harzianum T39 was poor. Ampelomyces quisqualis (AQ10) was very effective against powdery mildew, achieving up to 98% of control. Its effectiveness declined with the progress of the epidemic but unlike the other biocontrol agent it retained significant control capability on older leaves. Two aliphatic petroleum distillate oil products improved the efficacy of both biocontrol agents. The co-application of T. harzianum T39 and A. quisqualis AQ10 was tested on cucumber plants infected with powdery mildew followed by fruit gray mold infection. It resulted in no improvement of the control of powdery mildew, and in an improvement of gray mold control, the latter probably because of the use of additive oil (ADDQ) along with the second biocontrol preparation. There was no significant interference between the biocontrol agents in the co-application treatment as compared with the application of each agent alone; the level of population of T. harzianum T39 remained similar and the parasitism of S. fusca by A. quisqualis was not nullified. The application of T. harzianum T39 to soil instead of spraying it resulted in 75–90% lower powdery mildew coverage on the leaves. It was concluded that the mode of action of T. harzianum T39 in powdery mildew control is induced resistance, not mycoparasitism or antibiotic action.

Morphological and Molecular Identification of Trichoderma Isolates on North American Mushroom Farms

Abstract: Green mold disease (causal agent, Trichoderma) has resulted in severe crop losses on mushroom farms worldwide in recent years. We analyzed 160 isolates of Trichoderma from mushroom farms for morphological, cultural, and molecular characteristics and classified these isolates into phenotypic groups. The most common group comprised approximately 40% of the isolates and was identified as a strain of Trichoderma harzianum. This group was consistently recovered from farms with severe green mold disease but not from farms with little or no problem. In addition, the strain identified as the major cause of green mold disease in Ireland and the United Kingdom grouped with these North American isolates in having very similar randomly amplified polymorphic DNA patterns.

Ecological Studies of Transformed Trichoderma harzianum Strain 1295-22 in the Rhizosphere and on the Phylloplane of Creeping Bentgrass.

Abstract: A β-glucuronidase (GUS) reporter gene and a hygromycin B (hygB) phosphotransferase gene were integrated separately into the Trichoderma harzianum strain 1295-22 genome, using biolistic transformation. The mycelial growth and biocontrol ability of the transformed strains did not differ from that of the original strain. The transformed Gus+-kanamycin-resistant (Gus+KanR) strains were used to monitor growth and interactions with Rhizoctonia solani on creeping bentgrass plants. The hygB-resistant (hygBR) strains were used to selectively recover strain 1295-22 from the rhizosphere soil and phylloplane of creeping bentgrass after spray applications. The population levels of two hygBR strains and the original strain were very similar for all treatments. All three strains persisted for the duration of the experiment (28 days) in both the rhizosphere soil and on leaves, although population levels declined somewhat over the course of the experiment in unautoclaved soils. In this study, the results demonstr...

Cytotoxic Substances Produced by a Fungal Strain from a Sponge: Physico-chemical Properties and Structures

Abstract: Five novel metabolites, trichodenones A-C (1-3), harzialactone A (4) and B (5), have been isolated together with known R-mevalonolactone (6) from the culture broth of a strain of Trichoderma harzianum OUPS-N115 originally separated from the sponge Halichondria okadai. Their structures have been elucidated by spectral evidence. Among them, 1-3 exhibited significant cytotoxicity against cultured P388 cells.

Purification and Characterization of Exo-β-d-Glucosaminidase from a Cellulolytic Fungus,Trichoderma reesei PC-3-7

Abstract: Cellulose, chitin, and chitosan consist of β-1,4-linked glucopyranoses, and their differences are in functional groups at the C-2 positions of their constituent sugars, i.e., the hydroxyl, acetamido, and amino groups, respectively. Chitin is one of the most abundant forms of biomass next to cellulose (9). On the other hand, chitosan, a partially or fully deacetylated form of chitin, has been found only in the cell walls of limited groups of fungi in nature (2). Chitosan has had various applications, e.g., as a carrier of immobilized enzymes and a metal-removal and cohesive reagent for purification of waste streams (27). In commercial use, chitosan is obtained by chemical deacetylation of chitin. It also has biological activities. One such activity is to elicit plant defense reactions. This defense system includes formation of fungal cell wall-degrading enzymes such as endo-β-1,3-glucanase and chitinase (19) and production of phytoalexin (10). The other biological activity of chitosan is growth inhibition of bacteria and fungi (15). Chitosanases have been found in a variety of microorganisms, including bacteria and fungi (1, 6, 12, 24, 26, 30, 31). Furthermore, plant chitosanases, which also provide defensive reactions to attacks by fungal pathogens, were recently reported (5). Most purified chitosanases have been characterized as endo-type enzymes which cleave chitosans at random, and their reaction velocities are highly dependent on the degree of acetylation (D.A.) of the chitosan. On the other hand, the purification and characterization of an exo-type chitosanase called exo-β-d-glucosaminidase, which releases glucosamine (GlcN) continuously from the nonreducing end of the substrate, have so far been reported only for an actinomycete, Nocardia orientalis (21). Biological degradation of naturally occurring chitin in a partially deacetylated form is thought to be carried out by a two-step process (26). First, endo-type enzymes such as chitinase and chitosanase hydrolyze the chitinous material to oligosaccharides consisting of N-acetylglucosamine (GlcNAc) and GlcN. Second, the resulting oligomers are degraded completely to GlcNAc and GlcN by two exo-type enzymes, exo-β-d-N-acetylglucosaminidase and exo-β-d-glucosaminidase. However, the latter enzyme has not been studied at all except for that in N. orientalis. On the other hand, the former enzyme is distributed widely from animals to microorganisms, and its enzymological properties are well-characterized. The genus Trichoderma, which belongs among deuteromycetes, is known as a high-cellulase producer. Trichoderma reesei secretes at least two cellobiohydrolases (exo type; EC 3.1.2.91), four endoglucanases (EC 3.1.2.4), and two β-glucosidases (EC 3.1.2.20). These enzymes have already been purified or their genes have been cloned (22). Trichoderma harzianum is known as a mycoparasite and secretes multiple chitin-degrading enzymes, including endochitinase (EC 3.1.2.13), exochitinase, and exo-β-d-N-acetylhexosaminidase, and some of their genes have been cloned (4, 8, 11, 25). We found that T. reesei secretes multiple chitosanolytic enzymes into a culture medium under cellulase-noninducible conditions. In this paper, we describe the identification, purification, and characterization of the exo-β-d-glucosaminidase from the hyper-cellulolytic fungus T. reesei PC-3-7. We also discuss the catalytic mechanism of exo-β-d-glucosaminidase on the basis of 1H nuclear magnetic resonance (NMR) spectroscopy of the hydrolysate. To our knowledge, this is the first report on the exo-β-d-glucosaminidase from eukaryotes.

What exactly is Trichoderma harzianum

Abstract: Trichoderma harzianum is neotypified by an isolate from the type locality, and this neotype is fully described. It is compared with original herbarium specimens and recent isolates of T. at...

Phylogenic relationships of Trichoderma harzianum causing mushroom green mold in Europe and North America to other species of Trichoderma from world-wide sources

Abstract: Nucleotide sequences of internal transcribed spacers (ITS-1 and ITS-2) and the 5.8 S gene of the ribosomal DNA repeat were examined in 15 lines of Trichoderma spp. Six lines representing four bioty...

Evaluation of plant based formulations of trichoderma harzianum for the management of meloidogyne incognita on egg plant

Abstract: Aqueous extracts of neem (Azadirachta indica), castor (Ricinus communis) and pongamia (Pongamia pinnata) cakes were evaluated as substrates for mass production of the biological control agent, Trichoderma harzianum which was used in the management of Meloidogyne incognita in egg plant under fields conditions Castor cake extract at 10% gave maximum growth of mycelial mat and spore production of T harzianum compared with moderate growth in 10% pongamia cake and 5% castor cake extracts Application of plant based formulations of T harzianum to nursery beds of egg plant was effective in producing vigorous seedlings (increase in plant height and seedling weight) with the least root galling The above treatments also increased root colonization and parasitization of M incognita females by T harzianum

Biological control of Sclerotinia sclerotiorum attacking soybean plants. Degradation of the cell walls of this pathogen by Trichoderma harzianum (BAFC 742). Biological control of Sclerotinia sclerotiorum by Trichoderma harzianum.

Abstract: Two experiments of biological control of Sclerotinia sclerotiorum, one in the greenhouse and the other in the field, were carried out with soybean and Trichoderma harzianum as host and antagonist, respectively. Significant control of disease was achieved in both experiments, but there were no significant differences in plant growths. In the greenhouse, the application of T. harzianum as alginate capsules, increased the survival of soybean plants more than 100% with respect to the disease treatment. In the field, T. harzianum treated plants survived 40% more than those from the disease treatment, showing a similar survival level to control plants. Besides, a significant reduction (62.5%) in the number of germinated sclerotia was observed in the Trichoderma treated plot. Chitinase and 1,3-β- glucanase activities were detected when T. harzianum was grown in a medium containing Sclerotinia sclerotiorum cell walls as sole carbon source. In addition, electrophoretic profiles of proteins induced in T. harzianum showed quantitative differences between major bands obtained in the media induced by S. sclerotiorum cell walls and that containing glucose as a sole carbon source.

Effect of Metabolites Produced by Trichoderma harzianum Biotypes and Agaricus bisporus on Their Respective Growth Radii in Culture

Abstract: Trichoderma harzianum biotypes Th1, Th2, and Th3 produced volatile metabolites in vitro which had similar fungistatic effects on the growth of Agaricus bisporus . Metabolites present in agar colonized by these strains also inhibited mycelial growth of A. bisporus , although the reduction in growth was less in the presence of metabolites produced by biotype Th2 than that in the presence of metabolites produced by Th1 or Th3. A. bisporus produced metabolites in liquid culture that inhibited the growth of Th1 and Th3 but stimulated the growth of Th2. A compound(s) responsible for the inhibition and stimulation was extracted from A. bisporus culture filtrate and from compost-grown fruit bodies with n -butanol, but the identity of the compound(s) was not determined. We suggest that the stimulation of Th2 by metabolites produced by A. bisporus and the relatively low level of inhibition of A. bisporus by Th2 facilitate colonization of compost by both fungi. However, as compost colonization reaches a maximum, a change in the competitive balance in favor of Th2 results in the inhibition of fruit body production by A. bisporus and the devastating green mold epidemics affecting mushroom production.

Efficacy of Trichoderma harzianum as a biological control of Fusarium oxysporum in container-grown Douglas-fir seedlings

Abstract: Inoculating a soilless medium with encapsulated Trichoderma harzianum did not affect any aspect of Douglas-fir (Pseudotsuga menziesii var. glauca [Beissn.] Franco) seed germination or subsequent growth. Results of inoculating medium with a known pathogenic isolate of Fusarium oxysporum alone, or concurrently with T. harzianum, were the same: high levels of damping-off, low amounts of hypocotyl and root disease in midsummer, and significant reductions in height growth. When seedling roots grew through T. harzianum-inoculated medium before growing into a mixture of T. harzianum-F. oxysporum-inoculated medium, mortality was reduced about 50%. Although contamination by resident Fusarium occurred, subsequent root colonization was significantly reduced in T. harzianum-amended growing medium.

Availability of phosphorus and sulfur of insecticide origin by fungi

Abstract: Thirteen fungal species isolated from soil treated with pesticides were tested for their ability to mineralize and degrade three organophosphate insecticides currently used in Egypt (Cyolan®, Malathion® and Dursban®) in liquid media free from phosporus (P) and sulfur (S). All fungal species grew successfully on the culture media treated with the three used doses of insecticides (10, 50 and 100 ppm active ingredient) but the growth rate varied with the species, the insecticide and the doses. At 10 ppm level, insecticide degradation expressed in term of organic P mineralization (calculated as % of applied P) was the highest with all fungi tested. Organic P mineralization from pesticides was decreased by increasing the dose used to 50 and 100 ppm. The highest amount of P mineralized was observed with Cyolan® followed by Malathion® whilst P mineralization from Dursban® proceeded very slowly. Aspergillus terreus showed the greatest potential to mineralize organic P followed by A. tamarii, A. niger, Trichoderma harzianum and Penicillium brevicompactum whilst the remaining fungi only moderately mineralized the organic P component of the insecticides tested. Organic sulfur mineralization by the used fungal species paralleled, to some extent, organic P mineralization. The extracellular protein content of culture filtrates in the presence of various doses of insecticides was also decreased by increasing insecticide concentrations. The extracellular protein was significantly correlated with P and S mineralization (r = 0.89** and 0.64**, respectively) whilst correlation with cell dry mass was not significant (r = 0.03 and 0.003) suggesting a direct relationship between pesticide degradation and microbial protein production. The addition of P or S to the growth media enhanced extracellular protein excretion, and increased organic P and S mineralization by the most potent species tested (A. niger, A. tamarii, A. terreus and T. harzianum). This increment was significant in most cases, especially at the higher application rates. The relationship between extracellular protein excretion and organic P and S mineralization from insecticides was highly significant with the addition of inorganic phosphorus (r = 0.96** and 0.83**, respectively) or sulfur (r = 0.85** and 0.89**, respectively) to the growth media.

Filamentous fungi preservation in distilled water.

Abstract: Some methods for keeping the fungal Culture Collection have been used. However, the choice of either one on the basis that must ensure the cultural genetic stability and its phenotipic characteristics. In this work the preservation method in distilled water recognized in the literature as a single, economic and certain method that guarantie the survival of fungus cultures for long periods was used. 26 strains of generus and species: Aspergillus niger, Aspergillus candidus, Fusarium sp., Fusarium moniliforme, Mucor griseocyanum, Syncephalastrum sp., Trichoderma sp., Trichoderma harzianum and Trichoderma koningii were preserved. Enough inoculum from well developed cultures (mainly spores and hyphae) poured in flasks with sterile distilled water warranted a 100% of survival of those microorganisms for two years. At the same time no apparent changes were observed in respect to morphology and macroscopic features.