Trichoderma harzianum

About: Trichoderma harzianum is a research topic. Over the lifetime, 4731 publications have been published within this topic receiving 96796 citations.

Downy mildew resistance induced by Trichoderma harzianum T39 in susceptible grapevines partially mimics transcriptional changes of resistant genotypes

Abstract: Downy mildew, caused by Plasmopara viticola, is one of the most severe diseases of grapevine and is commonly controlled by fungicide treatments. The beneficial microorganism Trichoderma harzianum T39 (T39) can induce resistance to downy mildew, although the molecular events associated with this process have not yet been elucidated in grapevine. A next generation RNA sequencing (RNA-Seq) approach was used to study global transcriptional changes associated with resistance induced by T39 in Vitis vinifera Pinot Noir leaves. The long-term aim was to develop strategies to optimize the use of this agent for downy mildew control. More than 14.8 million paired-end reads were obtained for each biological replicate of T39-treated and control leaf samples collected before and 24 h after P. viticola inoculation. RNA-Seq analysis resulted in the identification of 7,024 differentially expressed genes, highlighting the complex transcriptional reprogramming of grapevine leaves during resistance induction and in response to pathogen inoculation. Our data show that T39 has a dual effect: it directly modulates genes related to the microbial recognition machinery, and it enhances the expression of defence-related processes after pathogen inoculation. Whereas several genes were commonly affected by P. viticola in control and T39-treated plants, opposing modulation of genes related to responses to stress and protein metabolism was found. T39-induced resistance partially inhibited some disease-related processes and specifically activated defence responses after P. viticola inoculation, causing a significant reduction of downy mildew symptoms. The global transcriptional analysis revealed that defence processes known to be implicated in the reaction of resistant genotypes to downy mildew were partially activated by T39-induced resistance in susceptible grapevines. Genes identified in this work are an important source of markers for selecting novel resistance inducers and for the analysis of environmental conditions that might affect induced resistance mechanisms.

Isolation and characterization of PRA1, a trypsin-like protease from the biocontrol agent Trichoderma harzianum CECT 2413 displaying nematicidal activity

Abstract: Mycoparasitic Trichoderma strains secrete a complex set of hydrolytic enzymes under conditions related to antagonism. Several proteins with proteolytic activity were detected in culture filtrates from T. harzianum CECT 2413 grown in fungal cell walls or chitin and the protein responsible for the main activity (PRA1) was purified to homogeneity. The enzyme was monomeric, its estimated molecular mass was 28 kDa (SDS-PAGE), and its isoelectric point 4.7–4.9. The substrate specificity and inhibition profile of the enzyme correspond to a serine-protease with trypsin activity. Synthetic oligonucleotide primers based on N-terminal and internal sequences of the protein were designed to clone a full cDNA corresponding to PRA1. The protein sequence showed <43% identity to mammal trypsins and 47–57% to other fungal trypsin-like proteins described thus far. Northern analysis indicated that PRA1 is induced by conditions simulating antagonism, is subject to nitrogen and carbon derepression, and is affected by pH in the culture media. The number of hatched eggs of the root-knot nematode Meloidogyne incognita was significantly reduced after incubation with pure PRA1 preparations. This nematicidal effect was improved using fungal culture filtrates, suggesting that PRA1 has additive or synergistic effects with other proteins produced during the antagonistic activity of T. harzianum CECT 2413. A role for PRA1 in the protection of plants against pests and pathogens provided by T. harzianum CECT 2413 is proposed.

Competitive saprophytic ability and cellulolytic activity of rhizosphere-competent mutants of Trichoderma harzianum

Abstract: Ahmad, J. S., and Baker, R. 1987. Competitive saprophytic ability and cellulolytic activity of rhizosphere-competent mutants of Trichoderma harzianum. Phytopathology 77:358-362. Competitive saprophytic ability (CSA) of strains of Trichoderma spp. cellobiose, carboxymethyl cellulose, or cotton linters as sole sources of was determined by the modified Cambridge method (sensu Garrett). Two carbon, mutants produced more cellulase than the wild types. The amount rhizosphere-competent mutants of T. harzianum (T-95 and T12B) had of cellulase produced by these strains was directly correlated with CSA and higher CSA indices than four rhizosphere-incompetent Trichoderma spp. RC. RC of the mutants, therefore, can be at least partially explained by and strains. CSA was directly correlated with rhizosphere competence their capacity to utilize cellulose substrates associated with the root. (RC). When the strains were grown for 6 days on Czapek-Dox broth with Benomyl-tolerant mutants of Trichoderma harzianum Rifai MATERIALS AND METHODS applied to seeds c'olonized roots; however, the wild-type strains and species of the same fungus applied to seed did not colonize the Soil. Nunn sandy loam was used in these investigations. Water rhizosphere (1,2). The reason(s) why such mutants were content of43.2-kg portions was adjusted to-0.03 bar, andthesoil rhizosphere-competent, however, was not explored. Here we test was stored for 48 hr before use. Soil characteristics were reported one hypothesis to explain why the mutants were rhizosphere(2). competent-that is, mutation resulted in (besides benomyl Trichoderma spp. and strains. Four strains of T. harzianum tolerance) more efficient utilization of substrates found in the (T-95 [ATCC 60850], T-12B, WT, and T-12) and one strain each of rhizoplane or root surface. T. koningii (T-8) and T. viride (T-S-I) used in these investigations According to Garrett (8), \"the share of a substrate obtained by were described previously (2). Only benomyl-tolerant mutants Tany particular fungal species will be determined partly by its 95 and T-12B were rhizosphere-competent (1). intrinsic competitive saprophytic ability and partly by the balance CSA assay. To test CSA of Trichoderma spp., the Cambridge between its inoculum potential and that of competing species.\" In method (8) was modified. Strains of Trichoderma spp. were grown tests for rhizosphere competence (RC), both the mutants and the on potato-dextrose agar (PDA). Mutants tolerant to benomyl wild types had the same population density when applied to seed were grown on PDA containing 10 jig a.i. benomyl per milliliter. (1,2). The ability to colonize the root, therefore, could be linked to Plates were incubated for 8 days at 25 C, flooded with sterile the competitive saprophytic ability (CSA) of the mutants. distilled water, and conidia were gently freed from the culture with Garrett (8) lists production of and tolerance to antibiotics a brush. The suspension was sieved through four layers of among attributes of successful root-surface and rhizosphere fungi. cheesecloth, centrifuged at 2,500 g for 15 min, and resuspended in None of our strains have obvious antibiotic activity in vitro except sterile distilled water three times. Conidia were counted with a for a routing factor seen in the hyphal cytoplasm at microscopic hemacytometer and then adjusted to the desired concentrations. levels affecting Pythium spp. (9). Tolerance to antibiotics among Freshly harvested conidia were added to 7.2 kg of previously benomyl-tolerant mutants currently is being explored, moistened and incubated field soil at the rate of 101, 10', 10', and Garrett (8) does not list \"enzymes for cellulase degradation\" as a 104 conidia per gram of soil. No conidia were added in controls. necessary attribute of rhizosphere fungi, presumably, because The soil was mixed thoroughly by hand and distributed in nine amino acids and reducing sugars commonly are thought to be the 11-cm-diameter plastic pots. predominant root exudates. Recently, however, Foster et al (7) Clean, mature, polished winter wheat straw was cut in 1-cm demonstrated that the mucilage overlying the root surface in the segments; each segment included a node. Twenty pieces were region of elongation constitutes the remains of the outer primary buried randomly in each pot. The pots were arranged in a wall of root epidermal cells. Microorganisms were seen embedded completely randomized design, covered with plastic to conserve in this mucilage, and cellulose is a major component of primary cell moisture at -0.03 bar, and incubated in the dark. No water was walls. Conversely, mutants of Trichoderma spp. have been easily added to the pots. All 20 pieces, from each treatment including a obtained with higher cellulase activity than their wild-type parents noninfested control, were removed from the pots after 2, 4, or 6 (11,12). The purpose of this study was to test the hypothesis that days, washed in tap water to remove all adhering soil and debris, rhizosphere-competent mutants utilize cellulose substrates on or and surface-disinfested in a mixture of 1. 1% sodium hypochlorite near roots more efficiently than wild types. solution and 5% ethanol for 5 min. Segments were plated on a medium selective for Trichoderma (5) and incubated at 25 C for 5 days. Percent colonization of wheat pieces by Trichoderma for each treatment at a given time was determined. There were three The publication costs of this article were defrayed in part by page charge payment. This replicates per treatment, and all experiments were repeated twice. article must therefore be hereby marked \"advertisement\" in accordance with 18 U.S.C. § In experiments where cellophane disks were substituted for 1734 solely to indicate this fact. straw pieces, the disks were obtained by punching holes (6 mm diameter) in an untreated cellophane sheet. Disks were removed © 1987 The American Phytopathological Society from the pots after incubation for 2, 4, or 6 days, washed in sterile