Showing papers on "Trichoderma harzianum published in 1996"
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TL;DR: Before biocontrol can become an important component of plant-disease management, it must be effective, reliable, consistent and economical and to meet these criteria, superior strains exhibiting improved biocOntrol activity as well as an expanded host range must become available.
Abstract: Molecular mechanisms of lytic enzymes involved in the biocontrol activity of Overview The many achievements of modern agriculture notwithstanding , certain cultural practices have actually enhanced the destructive potential of crop diseases caused by fungi. These practices include the use of genetically uniform crop plants in continuous monoculture, the use of plant cultivars susceptible to pathogens, .and the use of nitrogenous fertilizers at concentrations that increase disease susceptibility. Plant-disease control has thus become heavily dependent on fungicides to combat the wide variety of fungal diseases that threaten agricultural crops (Vliaard e t al., 1993). Studies aimed at replacing pesticides with environmentally safer methods are currently being conducted at many research centres. Biological control is a potent means of reducing the damage caused by plant pathogens and is environmentally nonhazardous. Although commercialized systems for the biological control of plant diseases are few, intensive activity is currently being geared towards the development of an increasing number of biocontrol agents. Potential agents for biocontrol activity are rhizosphere-compatible fungi and bacteria which exhibit antagonistic activity towards plant pathogens. Before biocontrol can become an important component of plant-disease management , it must be effective, reliable, consistent and economical. To meet these criteria, superior strains exhibiting improved biocontrol activity as well as an expanded host range must become available (Goldman e t al., 1994; Harman et a/., 1989). This goal requires extensive study of the molecular and cellular biology of the antagonistic interactions between the biocontrol agent and the phytopathogenic fungi. The acquired knowledge can be used for genetic manipulations to improve existing biocontrol agents. Tricho&rrncr spp. are common fungi, found in almost any soil. Members of this genus are antagonistic to other fungi, including plant-pathogenic species. Possible mechanisms involved in Trichoderma antagonism are : (a) antibiosis, whereby the fungi produce volatile or nun-Trzchoderma attacks another fungus by excreting lytic enzymes (such as proteases, glucanases and chitinases) that enable it to degrade the latter's cell walls and utilize and have been shown to have a direct antifungai effect (Lorito e l al., 1993). Via these mechanisms, Tri~hoderma antagonizes other fungi, thereby serving as a potential biological control agent of plant harzianum involved in mycoparasitism Chitinases Chitin, an unbranched homopolymer of 1,4-Blinked AT-acetyl-D-glucosamine (GlcNAc), is the second most abundant polymer in nature, after cellulose. It does not occur in plants, vertebrates or prokaryotes, but is abundant as a structural polymer in most fungi and insects, including those …
245 citations
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TL;DR: Cell wall turnover is identified as a major target of mycoparasitic antagonism because of an inhibition of the membrane-bound beta-1,3-glucan synthase of the host by the peptaibols, which inhibit the resynthesis of cell wall beta- glucans, sustain the disruptive action of beta-Glucanases, and all together enhance the fungicidal activity.
Abstract: We have investigated the molecular basis for the reported synergism between peptaibols and cell wall hydrolytic enzymes in the antagonism of phytopathogenic fungi by Trichoderma harzianum. beta-Glucan synthase activity on isolated plasma membranes of Botrytis cinerea was inhibited in vitro by the peptaibols trichorzianin TA and TB, and this inhibition was reversed by the addition of phosphatidylcholine. beta-Glucan synthesis in vivo, assayed by the incorporation of [2-(3)H]glucose into cell wall material, was inhibited by the presence of peptaibols, and this inhibition was synergistic with exogenously added T. harzianum beta-1,3-glucanase. This synergism is therefore explained by an inhibition of the membrane-bound beta-1,3-glucan synthase of the host by the peptaibols, which inhibit the resynthesis of cell wall beta-glucans, sustain the disruptive action of beta-glucanases, and all together enhance the fungicidal activity. Therefore, we have identified cell wall turnover as a major target of mycoparasitic antagonism.
181 citations
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TL;DR: The expression of the various N-acetylglucosaminidases and endochitinases during mycoparasitism was found to be regulated in a very specific and finely tuned manner that was affected by the host.
Abstract: The chitinolytic system of the biocontrol agent Trichoderma harzianum is made up of two beta-1,4-N-acetylglucosaminidases and four endochitinases. The expression of the various N-acetylglucosaminidases and endochitinases during mycoparasitism was found to be regulated in a very specific and finely tuned manner that was affected by the host. When T. harzianum was antagonizing Sclerotium rolfsii, an N-acetylglucosaminidase of 102 kDa (CHIT 102) was the first to be induced. As early as 12 h after contact, its activity diminished, and another N-acetyl-glucosaminidase of 73 kDa (CHIT 73) was expressed at high levels. However, when T. harzianum was antagonizing Rhizoctonia solani, the chitinase expression patterns differed considerably. Twelve hours after contact, CHIT 102 activity was elevated, and the activities of three additional endochitinases at 52 kDa (CHIT 52), 42 kDa (CHIT 42), and 33 kDa (CHIT 33) were detected. As the antagonistic interaction proceeded, CHIT 102 activity decreased, whereas the activity of the endochitinases gradually increased. The differential expression of T. harzianum chitinases may influence the overall antagonistic ability of the fungus against a specific host
173 citations
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TL;DR: Germination and germ-tube elongation of conidia of the pathogen Botrytis cinerea on bean leaves were reduced in the presence of the biocontrol agent Trichoderma harzianum T39, but this did not result in complete prevention of disease development on the leaves.
Abstract: Germination and germ-tube elongation of conidia of the pathogen Botrytis cinerea on bean leaves were reduced in the presence of the biocontrol agent Trichoderma harzianum T39. A reduction of 20 to 50% in germ-tube biomass was observed 20 h after inoculation. This reduction in germination did not result in complete prevention of disease development on the leaves. One day after inoculation, disease severity on leaves infected by the pathogen with and without the biocontrol agent was similar (-10% necrotic area). Subsequently, the disease developed rapidly in the control leaves and caused almost complete necrosis, whereas in the presence of T harzianum T39 the necrotic area reached only -50% of the leaf surface. The production of pectin-degrading enzymes by B. cinerea was measured up to 4 days after inoculation. Up to 1.3 enzyme units of polygalacturonase (PG), 9 microequivalents of NaOH, which express the activity of pectin methyl esterase (PME), and up to 1.5 units of pectate lyase (PL) were detected on bean leaves. Under the same conditions, the biocontrol agent, T harzianum T39, did not produce any of these enzymes. On leaves infected with B. cinerea in the presence of the biocontrol agent, the activity of the pathogen's PG was reduced by 40 to 83%. This was reflected on an activity gel by the faintness of these PG isoenzymes and the delay in their appearance. An up to 100% reduction in PME activity and a -30% reduction in PL activity also were recorded. We suggest that T. harzianum T39 acts by reducing the enzyme activities of the pathogen. An indirect effect of enhancing the defense mechanism of the host plant is discussed.
160 citations
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TL;DR: Hphal mycoparasitism, rather than sclerotinia parasitism, is suggested to be the mechanism by which T. harzianum controls S. sclerotiorum under these conditions.
Abstract: Hyphal interactions between the mycoparasite Trichoderma harzianum (BAFC Cult. No. 72) and the soilborne plant pathogenic fungus Sclerotinia sclerotiorum were investigated in dual culture and in sterilized soil, by light and scanning electron microscopy. In dual culture, T. harzianum hyphae grew towards and coiled around the S. sclerotiorum hyphae. Dense coils of hyphae of T. harzianum and partial degradation of the Sclerotinia cell wall were observed in later stages of the parasitism. In sterile soil, conidia of T. harzianum germinated and the developing mycelium made contact with that of S. sclerotiorum, forming short branches and appressorium-like bodies which aided in holding and penetrating the host cell wall. An in vitro system was developed to test the ability of T. harzianum to control Sclerotinia wilt in cucumber and lettuce: coating seeds with T. harzianum conidia reduced the pre- and post-emergence effect of S. sclerotiorum in cucumber by 69 and 80%, respectively, and in lettuce by 46 and 72%, respectively. In the greenhouse, the disease caused by S. sclerotiorum in lettuce was reduced by treating seedlings with a peat-bran preparation of T. harzianum. Despite the non-significance of the reduction in disease, Trichoderma-treated lettuce seedlings were much more developed than controls. In sunflower, significant reductions (in the range of 68 to 84%) in disease incidence were obtained by incorporating the peat-bran T. harzianum preparation into the seedling rooting mixture. Hyphal mycoparasitism, rather than sclerotial parasitism, is suggested to be the mechanism by which T. harzianum controls S. sclerotiorum under these conditions.
142 citations
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TL;DR: Root colonization by selected biocontrol agents was evaluated for pepper, tomato and citrus, and found to be generally between 76 to 100% in both greenhouse ebb and flow, and bench-produced plants.
122 citations
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TL;DR: The interaction between Trichoderma harzianum and sclerotia of the soilborne plant pathogen Sclerotium rolfsii was studied by scanning and transmission electron microscopy to assess the potential role of enzymatic hydrolysis in the antagonistic process.
Abstract: The interaction between Trichoderma harzianum and sclerotia of the soilborne plant pathogen Sclerotium rolfsii was studied by scanning and transmission electron microscopy (SEM and TEM, respectively) to assess the potential role of enzymatic hydrolysis in the antagonistic process. SEM investigations revealed that hyphae of T. harzianum grew abundantly on the sclerotial surface and formed a dense branched mycelium that appeared to establish contact with the outer host cells through a thin mucilage. Observation of cross-sections of parasitized sclerotia by light microscopy showed that hyphae of the antagonist multiplied on the sclerotial surface and displayed the ability to penetrate the rind. Growth of the antagonist in the rind layer was mainly intracellular, and host-wall penetration was achieved by means of constricted hyphae. Ultrastructural observations showed that Trichoderma growth and development coincided with extensive host cell alterations, such as retraction and aggregation of the cytoplasm and vacuole breakdown. In the invaded outer rind cells, host cell walls apparently were not altered, as judged by their preserved structure. In contrast, cell breakdown due to host cell-wall disruption was observed more frequently in inner rind cells adjacent to medullary cells. Ingress of T harzianum hyphae in the medulla was characterized mainly by a change in the mode of growth from intra- to intercellular. Trichoderma hyphae did not penetrate the medullary cells, although the latter showed pronounced alterations, such as cytoplasm disorganization and aggregation. The use of wheat germ agglutinin/ovomucoid-gold complex for localization of chitin monomers resulted in regular labeling of both host and antagonist cell walls, even when sclerotia were massively colonized. Chitinolytic degradation at a distance from the site of Trichoderma penetration was never observed. There was no indication of cell-wall disorganization in either the host or the antagonist, as shown by the regular distribution of labeling, even in zones of penetration by constricted Trichoderma hyphae. In the medulla, gold labeling was regularly distributed over the thick host cell walls, even when the medullary cells showed obvious signs of disorganization. When ultrathin sections of parasitized sclerotia were incubated with the gold-complexed β-1,3-glucanase for localization of β-1,3-glucans, a regular distribution of gold particles was observed over the walls of both outer and inner rind cells, even when these exhibited a disorganized cytoplasm that was reduced to a few remnants of aggregated material. Incubation with gold-complexed lipoprotein lipase yielded a pattern of labeling similar to that obtained with gold-complexed β-1,3-glucanase. Gold particles were evenly distributed over the host cell walls in the rind layer.
119 citations
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TL;DR: The appearance of the corresponding N-acetyl-β-D-glucosaminidase protein paralleled the pattern of nag 1 expression, thereby suggesting that its formation is regulated at the level of transcription.
Abstract: A 72-kDa N-acetyl-β-D-glucosaminidase was purified from the mycoparasitic fungus Trichoderma harzianum P1; antibodies were raised against it, and aa-sequences were obtained. The antibody reacted with a single 72-kDa protein band in culture filtrates of T. harzianum grown on chitin, and was subsequently used to clone the corresponding nag1 gene from a λgt11 cDNA expression library. It was interrupted by two short introns and encoded a protein of 580 amino acids. The deduced protein sequence contained aa-sequence areas of high similarity to N-acetyl-glucosaminidases from other eukaryotes such as Candida albicans, and invertebrate and vertebrate animal tissues. The highest similarity was observed with the corresponding gene from the silkworm. The aa-sequence of a tryptic fragment of purified N-acetyl-β-D-glucosaminidase from T. harzianum corresponded to a deduced aa sequence from a portion of the cloned gene, thus verifying that the protein is encoded by nag 1. Southern analysis showed that nag 1 is present as a single-copy gene in T. harzianum. Expression of nag1-mRNA was strongly induced upon growth on chitin, N-acetyl-glucosamine and the cell walls of Botrytis cinerea used as a carbon source. The appearance of the corresponding N-acetyl-β-D-glucosaminidase protein, as determined by Western analysis, paralleled the pattern of nag 1 expression, thereby suggesting that its formation is regulated at the level of transcription.
106 citations
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TL;DR: Findings suggest that ech-42 expression in T. harzianum is regulated by binding of Cre1 to two single sites in the e ch-42 promoter, binding of a "mycoparasitic" protein-protein complex to the ech -42 promoter in vicinity of the Cre1 binding sites, and functional inactivation of Cre 1 upon mycopar asitic interaction to enable the formation of the mycopARasitic protein-DNA complex.
Abstract: ↵ Present address: Otto Warburg Center for Agricultural Biotechnology, The Hebrew University of Jerusalem, Faculty of Agriculture, Rehovot, Israel.
104 citations
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TL;DR: The interaction between the saprophytic fungus Trichoderma harzianum and the arbuscular mycorrhizal (AM) fungus Glomus intraradices was studied by transmission electron microscopy to delineate precisely the relationship established between both partners.
Abstract: In the present study, the interaction between the saprophytic fungus Trichoderma harzianum and the arbuscular mycorrhizal (AM) fungus Glomus intraradices was studied by transmission electron microscopy (TEM) to delineate precisely the relationship established between both partners. An axenic system, divided into four compartments, proved useful for studying the interaction between T. harzianum and the extramatrical phase of G. intraradices. This experimental model, based on root-organ culture to obtain typical mycorrhizal infections, was selected as a reliable means of obtaining mycorrhizal spores and mycelium in root-free compartments. TEM observations of samples from the interaction region showed that hyphae of T. harzianum proliferated abundantly at the spore surface and penetrated the thick host wall through local hydrolysis of the wall polymers. Hyphae of the antagonist also were seen in the subtending hyphae of the AM fungus, and they grew actively in the main host hyphae. This massive colonization was associated with marked cell damage, involving partial to complete disorganization of the cytoplasm, which led in most cases to loss of the protoplasm and apparent bursting of the main hyphae of G. intraradices, resulting in the release of the actively proliferating Trichoderma hyphae. At an advanced stage of the colonization process, the main hyphae of G. intraradices were perforated in many places. The use of wheat germ agglutinin/ovomucoid-gold complex for the localization of chitin monomers resulted in regular labeling of the host cell walls even when spores, subtending hyphae, and main hyphae of G. intraradices were colonized massively. Chitinolytic degradation was seen only in areas adjacent to the sites of Trichoderma penetration. According to our observations, the interaction between T. harzianum and G. intraradices involves the following events : (i) recognition and local penetration of the antagonist into mycorrhizal spores ; (ii) active proliferation of antagonist cells in mycorrhizal hyphae; and (iii) release of the antagonist through moribund hyphal cells.
101 citations
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TL;DR: Biological control of bunch rot of grape with Trichoderma harzianum can be an effective method of management of this disease.
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TL;DR: RutC-30 appeared to be tolerant of the endochitinase and can be used as a production host for this enzyme, which has antifungal activity toward plant pathogens.
Abstract: The chromosomal endochitinase gene (ThEn-42) of the mycoparasite fungus Trichoderma harzianum P1 was isolated and overexpressed in the filamentous fungus Trichoderma reesei under the promoter of the major cellulase gene cbhl1. The host strain RutC-30 did not produce any endogenous endochitinase activity. The prepro region of the T harzianum endochitinase was correctly processed in T. reesei. No differences in expression were observed when the prepro region was replaced with the CBHI signal sequence. Shake flask cultivation yielded 130 mg of active enzyme per liter, which in terms of activity represents about a 20-fold increase over the endochitinase activity produced by T. harzianum. The presence of multiple copies of the expression cassette in the transformant resulted in limitation in transcription and/or regulation factors needed for full activity of the cbh1 promoter, although this was not the major limiting factor for higher expression of endochitinase. The endochitinase was very sensitive to an acidic protease at the late stages of T. reesei cultivation. T. reesei RutC-30 appeared to be tolerant of the endochitinase and can be used as a production host for this enzyme, which has antifungal activity toward plant pathogens.
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TL;DR: Two formulations were tested for their ability to control brown patch caused by Rhizoctonia solani, dollar spot caused by Sclerotinia homoeocarpa, and Pythium root rot and blight caused by Pythium graminicola and all three diseases were significantly reduced by this treatment.
Abstract: Trichoderma harzianum strain 1295-22 is a commercially available biocontrol agent that is strongly rhizosphere competent and able to control several plant pathogenic fungi. Two formulations were tested for their ability to control brown patch caused by Rhizoctonia solani, dollar spot caused by Sclerotinia homoeocarpa, and Pythium root rot and blight caused by Pythium graminicola. In growth chamber trials, soils planted with creeping bentgrass were amended with the granular formulation to give 10 6 cfu/g. All three diseases were significantly reduced by this treatment. Populations of Pythium spp. were suppressed under laboratory conditions by strain 1295-22. In field trials conducted over 4 years, strain 1295-22 reduced dollar spot severity relative to untreated plots. Monthly applications of granular or peat-based formulations of T harzianum 1295-22 reduced initial disease severity by as much as 71% and delayed disease development by up to 30 days. The persistence of strain 1295-22 in soil core samples from treated creeping bentgrass greens was also measured. After application of strain 1295-22, soil populations of Trichoderma spp. increased 100-fold relative to populations in untreated plots. Population levels remained at least an order of magnitude greater in treated than in untreated plots. Even after overwintering, population levels remained at or above 105 cfu/g of dry weight of the sample.
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TL;DR: Cultural methods are described which aid rapid differentiation of four distinct taxa of T. harzianum and five other species from the mushroom environment and some difficulties are discussed concerning differentiation of Trichoderma spp.
Abstract: A major epidemic of green mould in mushroom compost in Northern Ireland lasting for 6 months was caused by a single taxon of Trichoderma harzianum (Th2). This has continued to be the principal taxon causing losses in Ireland over a 9-year period. A separate taxon, Th4, is responsible for a more recent epidemic in North America. Cultural methods are described which aid rapid differentiation of four distinct taxa of T. harzianum and five other species from the mushroom environment. After developing a standard cultural method, isolates were grouped visually by features such as growth rate at 27°C, amount of aerial mycelium, and the effect of light on sporulation form and timing. Most of these groups of isolates had significantly different growth rate ratios from each other at 27°C/17°C. Furthermore isolates within groups which had been separated by culture features alone were closely homologous as regards their microscopic morphological features such as phialides and phialospores. Two factors underlining the importance of using a standard cultural method in aiding identification were that culture morphology was shown to vary widely on different media and spore size was found to vary significantly with incubation temperature. Some difficulties are discussed concerning differentiation of Trichoderma spp. using classical microscopic features alone.
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TL;DR: The efficacy of a formulation of Trichoderma harzianum T39 for control of grey mould (Botrytis cinerea) on grapevine was examined in 133 experiments conducted under diverse commercial conditions.
Abstract: The efficacy of a formulation of Trichoderma harzianum T39 for control of grey mould (Botrytis cinerea) on grapevine was examined in 133 experiments conducted under diverse commercial conditions. The experiments were carried out between 1988 and 1994 in 19 countries and on 34 varieties. The average disease incidence in the untreated plots of all experiments was 42 2.3% (mean standard error). In general, the reduction of disease achieved by T. harzianum application was lower than that obtained by chemical fungicides: 36.3 2.7% disease reduction in biocontrol treatments and 52.3 2.6% in the exclusively chemical treatments. Control efficacy declined when the interval between application and assessment dates increased to 5 weeks. The experiments also included treatments in which T. harzianum was integrated with chemical fungicides, the two being applied alternately, and a reduced chemical treatment in which only chemicals were applied, and only at the times when chemicals were applied in the integrated treatm...
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TL;DR: Simultaneous use of biocontrol agents against pathogens gave better control than their individual application in management of wilt disease complex of pigeonpea caused by the nematode Heterodera cajani and the fungus Fusarium udum.
Abstract: Glomus mosseae, Trichoderma harzianum, and Verticillium chlamydosporium were used alone and in combination for the management of wilt disease complex of pigeonpea caused by the nematode Heterodera cajani and the fungus Fusarium udum. Treatment of plants inoculated with pathogens increased plant length, shoot dry weight, number of nodules, and reduced nematode multiplication and wilting index. Simultaneous use of biocontrol agents against pathogens gave better control than their individual application. T. harzianum had an adverse effect on root colonizaiton by G. mosseae. Parasitism of nematodes by V. chlamydosporium was also reduced in the presence of T. harzianum. The highest reduction in nematode multiplication was observed when all three biocontrol agents were used together.
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TL;DR: In this article, an endo-β-1,3-glucanase from the culture filtrate of T. harzianum was purified by gel filtration on Sephacryl S-200, followed by hydrophobic interaction chromatography on phenyl-Sepharose.
Abstract: β-1,3-Glucanases are produced by Trichoderma harzianum when it is grown in the presence of chitin or isolated cell wall from fungi. An endo-β-1,3-glucanase from the culture filtrate of T. harzianum was purified by gel filtration on Sephacryl S-200, followed by hydrophobic interaction chromatography on phenyl-Sepharose. A typical procedure provided 134-fold purification with a 3.6% yield. The molecular mass of the purified endo-β-1,3-glucanase was found to be approximately 36 kDa, as estimated by sodium dodecyl sulfate – polyacrylamide gel electrophoresis on a 10% w/v slab gel. The enzyme was active toward glucans containing β-1,3-linkages and hydrolysed laminarin to form oligosaccharides. The Km and Vmax values for β-1,3-ghicanases, using laminarin as substrate, was 1.18 mg∙mL−1 and 1.26 U∙mL−1, respectively. The pH optimum for the enzyme was pH 4.4 and maximum activity was obtained at 45–50 °C. Enzyme activity was strongly inhibited in the presence of HgCl2 and stimulated by cations such as Zn2+ and Ca2+...
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TL;DR: Temperature had a greater effect than vapour pressure deficit (VPD) on the efficacy of biocontrol in suppression of tomato stem rot caused by Botrytis cinerea and suppression of B. cine Andrea was specifically reduced on rotting stem pieces.
Abstract: The effectiveness ofTrichoderma harzianum in suppression of tomato stem rot caused byBotrytis cinerea was examined on tomato stem pieces and on whole plants. Ten days after simultanous inoculation withB. cinerea andT. harzianum, the incidence of infected stem pieces was reduced by 62–84%, the severity of infection by 68–71% and the intensity of sporulation by 87%. Seventeen days after inoculation of wounds on whole plants, the incidence of stem rot was reduced by 50 and 33% at 15 and 26 °C, respectively, and the incidence of rot at leaf scar sites on the main stem was reduced by 60 and 50%, respectively. Simultanous inoculation and pre-inoculation withT. harzianum gave good control ofB. cinerea (50 and 90% disease reduction, 10 days after inoculation). The rate of rotting was not reduced by the biocontrol agent once infection was established. However, sporulation byB. cinerea was specifically reduced on these rotting stem pieces. Temperature had a greater effect than vapour pressure deficit (VPD) on the efficacy of biocontrol. Suppression ofB. cinerea incidence byT. harzianum on stem pieces was significant at 10 °C and higher temperatures up to 26 °C. Control of infection was significantly lower at a VPD of 1.3 kPa (60% reduction), than at VPD<1.06 kPa (90–100% control). Reductions in the severity of stem rotting and the sporulation intensity of grey mould were generally not affected by VPD in the range 0.59–1.06 kPa. Survival ofT. harzianum on stems was affected by both temperature and VPD and was greatest at 10 °C at a low VPD and at 26 ° C at a high VPD.
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TL;DR: The action of Trichoderma harzianum on the interactions between target decay basidiomycetes was investigated and the action of the mould's diffusible metabolites, as distinct from the other modes of antagonism, was studied.
15 Dec 1996
TL;DR: Trichoderma harzianum in combination with neem, karanj and castor oil cakes was effective in increasing the growth of acid lime seedlings and reducing the population of Tylenchulus semipenetrans both in soil roots.
Abstract: Trichoderma harzianum in combination with neem, karanj and castor oil cakes was effective in increasing the growth of acid lime seedlings and reducing the population of Tylenchulus semipenetrans both in soil roots. The parasitization of citrus nematode females with T. harzianum increased in the presence of the oil cakes.
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TL;DR: In 9 years of advisory experience in the British Isles and in virulence tests in the laboratory and field, only one of three distinct taxa of T. harzianum, namely Th2, consistently colonized mushroom compost either in vitro or in mushroom houses.
Abstract: In 9 years of advisory experience in the British Isles and in virulence tests in the laboratory and field, only one of three distinct taxa of T. harzianum, namely Th2, consistently colonized mushroom compost either in vitro or in mushroom houses. A single particle of contaminated spawn initiated colonies up to 30 cm in diameter. Four other Trichoderma species common in the mushroom environment rarely caused problems. Circumstantial evidence suggested airborne dust to be a main source of contamination of compost or its packing machinery, along with transmission on workers' clothing, pallets, load covers, trailers and by vectors such as mites, mushroom flies and mice. The Th2 isolate of T. harzianum was recovered from all of these sources but, in two tests, it did not survive peak heating. The control measures described here, based on strict hygiene, proved effective. Timing of colonization was important, also temperature of spawn run. Type of compost, as judged by analysis, appeared not to be important. In the field, spawning with peat based 'spawn' instead of grain spawn failed to prevent colonization, whereas in vitro, it reduced it. In the absence of any spawn, Th2 only grew strongly in microwaved or autoclaved compost. Reasons for this are discussed.
10 Feb 1996
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TL;DR: Four species of bacteria and fungi isolated from the phylloplane of lemon cv.
Abstract: Four species of bacteria (Bacillus subtilis, B. polymyxa, Pseudomonas fluorescens and Serratia marcescens) and 3 species of fungi (Aspergillus terreus, Trichoderma viride and Trichoderma harzianum) isolated from the phylloplane of lemon cv. Assam lemon, inhibited in vitro growth of Xanthomonas campestris pv. citri, the incitant of citrus canker. When the antagonists were tested for their efficacy in the control of citrus canker by applying them over crop foliage of Assam lemon, they also reduced citrus canker incidence under field conditions. B. subtilis was the most effective antagonist exhibiting max. (14.7 mm) inhibition of the pathogen and reducing the disease incidence by 61.9%.
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TL;DR: The population of both the interacting organisms and soil available phosphorus were highest in combined inoculation treatments indicating a synergistic interaction between the inoculated organisms.
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TL;DR: Harziphilone and fleephilone showed inhibitory activity against the binding of REV-protein to RRE RNA with IC50 values of 2.0 microM and 7.6 microM, respectively, however both compounds did not protect CEM-SS cells from acute HIV infection at concentration levels up to 200 micrograms/ml using an XTT dye reduction assay.
Abstract: During the screening of the natural products for their ability to inhibit the binding of REV (regulation of virion expression) protein to [33P] labeled RRE (REV responsive element) RNA, two novel fungal metabolites, harziphilone and fleephilone, were isolated from the butanol - methanol (1:1) extract of the fermentation broth of Trichoderma harzianum by bioassay guided fractionation. The structures of these two new compounds were established by spectroscopic methods. Harziphilone and fleephilone showed inhibitory activity against the binding of REV-protein to RRE RNA with IC50 values of 2.0μM and 7.6μM, respectively. However both compounds did not protect CEM-SS cells from acute HIV infection at concentration levels up to 200μg/ml using an XTT dye reduction assay. In addition, harziphilone demonstrated cytotoxicity at 38μM against the murine tumor cell line M-109.
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TL;DR: A bioassay using stem sections was developed to study wound infection and to screen potential fungal antagonists for activity against Botrytis and the successful application of antagonists to whole plants using both aqueous suspensions and gel secateurs is described.
Abstract: Botrytis cinerea infects stem wounds of greenhouse tomatoes and can cause serious economic losses. A bioassay using stem sections was developed to study wound infection and to screen potential fungal antagonists for activity against Botrytis. Cladosporium cladosporioides reduced infection from 80-100% to 0-10%. A much smaller proportion of Trichoderma harzianum gave this reduction. Similar results were obtained on whole plants. Penicillium isolates varied widely in activity. The concentration of Cladosporium and Trichoderma which gave the highest level of protection was c. 10 8 cfu/mL. When only half the wound was treated, simulating poor spray coverage, Cladosporium isolates still prevented infection. By contrast, Trichoderma isolates and four fungicides failed to give the same level of protection. The ability of certain fungal isolates to colonize the wound surface was thought to be partly responsible for this activity. The successful application of antagonists to whole plants using both aqueous suspensions and gel secateurs is described.
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TL;DR: In vitro inhibition of Heterobasidion annosum by fungi isolated from the surface and inside of Norway spruce stumps, ten Verticillium bulbillosum strains from Fagus sylvatica L. mycorrhizoplane, and three lignivorous basidiomycetes from culture collections was evaluated in a search for potential biocontrol candidates.
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TL;DR: A suitable medium was developed from modified Richard's medium plus V8 juice (RM8) to produce high levels of desiccation-tolerant conidia of Trichoderma harzianum strain 1295-22 and the use of a 48-h-old culture inoculum rather than conidial inoculum to start fermentation reduced the time required to complete the shift from vegetative growth to phialide formation.
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TL;DR: In this article, a novel endochitinase agar-plate assay was developed and used to identify 11 full-length cDNAs encoding ENC I (ENC I) from aTrichoderma harzianum cDNA library by expression in yeast.
Abstract: A novel endochitinase agar-plate assay has been developed and used to identify 11 full-length cDNAs encoding endochitinase I (ENC I) from aTrichoderma harzianum cDNA library by expression in yeast. The 1473-bpchil cDNA encodes a 424-residue precursor protein including both a signal sequence and a propeptide. The deduced ENC I amino-acid sequence is homologous to other fungal and bacterial chitinases, and the enzyme cross-reacts with a polyclonal antiserum raised against chitinase A1 fromBacillus circulans. TheT. harzianum endochitinase I was secreted into the culture medium by the yeastSaccharomyces cerevisiae in a functionally active form. The purified recombinant enzyme had a molecular mass of 44 kDa, an isoelectric point of 6.3, a pH optimum of 7.0 and a temperature optimum of 20 °C.
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TL;DR: In this article, nine Trichoderma harzianum strains were screened for beta-xylosidase activity when grown in solid-state cultures on media containing wheat bran as the carbon source.
Abstract: Nine Trichoderma harzianum strains were screened for beta-xylosidase activity when grown in solid-state cultures on media containing wheat bran as the carbon source. All strains produced beta-xylosidase activity, the most active being in extracts of cultures of T. harzianum strain 4. A beta-xylosidase was purified by ammonium sulfate precipitation, ultrafiltration, gel filtration, and ion exchange chromatography from solid-state cultures of T. harzianum strain C. Enzyme preparations yielded a single band when stained for protein following eletrophoresis. The molecular weight value, calculated following SDS-PAGE, was determined to be 60 kDa. beta-Xylosidase was most active at pH 4.0-4.5 and 70 degrees C. This enzyme had a Km value of 0.053 mM. The phenol-sulfuric acid method detected the presence of a small amount of carbohydrate in the purified enzyme preparation. beta-Xylosidase was active against some p-nitrophenylglycosides. The enzyme was inactive against xylan and PNPG. beta-xylosidase activity was inhibited by xylose and SDS. Iodoacetamide, dithiothreitol, gluconolactone, glucose, and mercuric chloride failed to inactivate this enzyme's activity. A synergistic effect was observed when beta-xylosidase from T. harzianum strain C and beta-xylanase from Aspergillus fumigatus were incubated with pretreated arabinoxylan.