Genetic relatedness of Trichoderma sect. Pachybasium species based on molecular approaches

Effect of Trichoderma spp. on Fusarium wilt disease of tomato

Seven isolates of Trichoderma spp. (T1 to T7) from Egypt were evaluated in vitro by bioassay for their potential to antagonize Fusarium oxysporum f.sp. lycopersici (FOL, the causal pathogen of tomato wilt disease). The highest percentage of inhibition against the tested pathogenic isolate were obtained with Trichoderma isolate (T7) followed by Trichoderma isolate (T3). In greenhouse experiments, the application of the highly antagonistic isolates of Trichoderma spp. (T3 and T7) led to a significant decrease of disease severity compared to the untreated control treatment. The lowest severity was achieved with the T3 isolate (24.8%) followed by isolate T7 (34.6%) compared with the other tested isolates. To understand the ability of Trichoderma isolates to protect against wilt disease, its induced systemic resistance in tomato plants has been studied. The expression of a defense-related gene (β-1,3-glucanase gene) was assessed by real-time RT-PCR in tomato plants to test the accumulation kinetics of transcripts encoding PR proteins in the roots of tomato in control (only with the pathogen), T3&FOL, and T7&FOL treatments. The highest degree of gene expression was found in tomato plants which were treated with T3&FOL compared with control (pathogen only). Two species of antagonistic Trichoderma (T3& T7) were characterized based on molecular tools using internal transcribed spacers (ITS1 and ITS4). The results of genetic characterization identified two different species of Trichoderma (T. atroviride and T. longibrachiatum).

Trichoderma cyanodichotomus sp. nov., a new soil-inhabiting species with a potential for biological control

During a biodiversity survey of Trichoderma (Ascomycota, Hypocreales, Hypocreaceae) in coastal and lake wetlands of China, a new species, Trichoderma cyanodichotomus, was isolated from Dongting Lake wetland of Hunan province. The strain TW21990-1 was characterized as having two types of conidia and producing a distinct blue–green pigment on potato dextrose agar and cornmeal dextrose agar. The taxonomic position was analyzed using three molecular markers, internal transcribed spacer rDNA, translation elongation factor 1-alpha, and RNA polymerase II subunit B, revealing less than 95.0% homology with all known Trichoderma species. The combined phylogenetic tree further identified T. cyanodichotomus as an independent subgroup belonging to Section Pachybasium, with no close relatives. In vitro antagonistic activity by dual-culture assay exhibited broad inhibition against various plant pathogens, including Botryosphaeria dothidea, Pythium aphanidermatum, Rhizoctonia solani, and Verticillium dahliae. In addition, TW21990-1 demonstrated moderate hydrolase activity of cellulase, chitinase, β-1,3-glucanase, and protease, which might be involved in mycoparasitism. Greenhouse experiments showed strong biocontrol effects against tomato damping-off incited by P. aphanidermatum, together with increased seedling height and weight gain. The identification of T. cyanodichotomus will provide useful information for sufficient utilization of fungal resources.

DNA barcoding survey of Trichoderma diversity in soil and litter of the Colombian lowland Amazonian rainforest reveals Trichoderma strigosellum sp. nov. and other species

The diversity of Trichoderma (Hypocreales, Ascomycota) colonizing leaf litter as well as the rhizosphere of Garcinia macrophylla (Clusiaceae) was investigated in primary and secondary rain forests in Colombian Amazonia. DNA barcoding of 107 strains based on the internal transcribed spacers 1 and 2 (ITS1 and 2) of the ribosomal RNA gene cluster and the partial sequence of the translation elongation factor 1 alpha (tef1) gene revealed that the diversity of Trichoderma was dominated (71 %) by three common cosmopolitan species, namely Trichoderma harzianum sensu lato (41 %), Trichoderma spirale (17 %) and Trichoderma koningiopsis (13 %). Four ITS 1 and 2 phylotypes (13 strains) could not be identified with certainty. Multigene phylogenetic analysis and phenotype profiling of four strains with an ITS1 and 2 phylotype similar to Trichoderma strigosum revealed a new sister species of the latter that is described here as Trichoderma strigosellum sp. nov. Sequence similarity searches revealed that this species also occurs in soils of Malaysia and Cameroon, suggesting a pantropical distribution.

A new cultivation independent approach to detect and monitor common Trichoderma species in soils

A set of primers was developed for the detection, identification and quantification of common Trichoderma species in soil samples. Based on a broad range master alignment primers were derived to amplify an approximate 540 bp fragment comprising the internal transcribed spacer region 1 (ITS 1), 5.8S rDNA and internal transcribed spacer region 2 (ITS 2) from all taxonomic Clades of the genus Trichoderma. The primer set was applied to test strains as well as community DNA isolated from arable and forest soil. For all tested isolates the corresponding internal transcribed spacer regions of Trichoderma spp. strains were amplified, but none of non-Trichoderma origin. PCR with community DNA from soil yielded products of the expected size. Analysis of a clone library established for an arable site showed that all amplified sequences originated exclusively from Trichoderma species mainly being representatives of the Clades Hamatum, Harzianum and Pachybasioides and comprising most of the species known for biocontrol ability. In a realtime PCR approach the primer set uTf/uTr also proved to be a suitable system to quantify DNA of Trichoderma spp. in soils.

SCAR-based real time PCR to identify a biocontrol strain (T1) of Trichoderma atroviride and study its population dynamics in soils

Strains of Trichoderma spp. are known for their antagonistic properties against plant pathogens, some are already on the market, others are under development. In order to launch a strain on the market its perfect identification at the species and strain levels is needed. The aim of this study is to (i) design a SCAR marker for specific identification of strain T1 of Trichoderma atroviride and (ii) monitor population dynamics of this strain in soil by real time PCR. A primer pair targeting a 141-bp fragment enabled specific detection of this strain without cross detection of autochthonous populations of Trichoderma in several field soils. In two soils, population dynamics assessed by real time PCR and the soil plate technique gave similar results. The molecular tools developed in this study satisfy the requirement for specific identification of the biocontrol strain and for detection and quantification of T. atroviride T1 population in complex environments.

Cell wall-degrading isoenzyme profiles of Trichoderma biocontrol strains show correlation with rDNA taxonomic species

Trichoderma is known for being the most frequently used biocontrol agent in agriculture. A fundamental part of the Trichoderma antifungal system relies on a series of genes coding for a variety of extracellular lytic enzymes. Characterization of the polymorphism between five putative isoenzymatic activities [beta-1,3-glucanase (EC 3.2.1.39, EC 3.2.1.58), beta-1,6-glucanase (EC 3.2.1.75), cellulase (EC 3.2.1.4; EC 3.2.1.21, EC 3.2.1.91), chitinase (EC 3.2.1.30, EC 3.2.1.52), protease (EC 3.4.11; EC 3.4.13-19; EC 3.4.21-24, EC 3.4.99)] was carried out using 18 strains from three sections of Trichoderma. Of these, seven strains were from T. sect. Pachybasium, nine from T. sect. Trichoderma and two from T. sect. Longibrachiatum. Thirty-seven different alleles in total were identified: 13 for beta-1,3-glucanase, four for beta-1,6-glucanase, three for cellulase, eight for chitinase and nine for protease activity. A dendrogram (constructed by the unweighted pair group method with arithmetic averages) based on isoenzymatic data separated the 18 strains into three main enzymatic groups: T. harzianum, T. atroviride/T. viride/T. koningii and T. asperellum/T. hamatum/T. longibrachiatum. Isoenzymatic groupings obtained from biocontrol strains are discussed in relation to their phylogenetic location, based on their sequence of internal transcribed spacer 1 in ribosomal DNA and their antifungal activities.