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The objective of this study was to determine the potential of strains of Trichoderma asperellum, Lieckfeldt & Nirenberg to control M. incognita, (Kofoid and White) Chitwood. Under laboratory conditions (in vitro), six native strains of T. asperellum (Ta.25, Ta.1, Ta.90, Ta.78, Ta.79, and T.13) were selected for their high antagonistic capability, production of various metabolites, and adaptation to different environmental conditions and substrates. For the in vitro trial, 1/10, 1/25, 1/50 dilutions and the pure filtrate of each strain were tested, including a control treatment with sterile water. For the study under semi-controlled conditions, tomato (Solanum lycopersicum L.) plants were inoculated with 2.5 second instar juveniles (J) per gram of soil and, after 72 hours, 107CFU of the strain Ta.90 were added per pot The treatments were: healthy plants (absolute control), plants + Ta.90, plants +Ta.90 + nematodes, plants + nematodes, and nematodes + Ta.90 (without plants). The parameters evaluated after 35 days were galling index (IA), number of eggs per root system, plant height, stem diameter, root length, number of leaves, and weight of fresh root. High mortality levels were shown by all the T. asperellum strain filtrates; the strain Ta.90 stood out with 90% mortality at 24 hours. In the pot trial, this latter strain significantly reduced the number of eggs per female compared with the unapplied control, and attenuated the effect of the nematode on parameters such as plant height, stem diameter, number of leaves, and root fresh weight. [ABSTRACT FROM AUTHOR]

Disease caused by Rhizoctonia solani Kühn infestations has become a growing problem for commercially important crops. Although this fungus is usually controlled through the application of chemicals, the heavy ecological and financial toll of the latter has prompted for research on biopesticides as a viable alternative. Trichoderma spp. is a well-known fungus often used for the biological control of crop pests, whose anti-fungal mechanisms include competition for the substrate, antibiosis and/or mycoparasitism. In the present work, we have used molecular techniques (sequencing of amplicons from the internal transcribed spacer of ribosomal DNA and the EF1A translation elongation factor) for the taxonomic identification of 13 Trichoderma spp. isolates in our collection, also evaluating their antibiotic effect on strains from three anastomosis groups of R. solani (AG-2.1, AG-5, AG-8) by the cellophane method. The sequences obtained from all isolates exhibited 100 % identity with deposited T. asperellum Samuels sequences in TrichoBLAST/GenBank, enabling their taxonomic assignment to this species. When analyzed by in vitro tests, over 70 % of the isolates exhibited a fungistatic effect towards R. solani, with the remaining strains exhibiting fungicidal activity; these results were later corroborated by technical efficacy tests under field conditions. Isolates 3, 13, 17, 75, 78, 85 and 90 were selected as potential biocontrol agents due to their high antibiotic activity and technical efficacy under field conditions. [ABSTRACT FROM AUTHOR]

The incidence of diseases caused by Rhizoctonia solani Kühn increases every year. Control of this disease is mainly done with the application of chemicals, more highly toxic. For this reason it is necessary to apply new control alternatives Trichoderma spp. is one of the biological control of this pathogen, for the friendly behavior and the different mechanisms of action, such as competition for the substrate, antibiosis and/or mycoparasitism. The present work had as objectives the molecular identification and the pathogenic evaluation, against R. solani isolates, of 13 isolates of the genus Trichoderma. For this, the antibiotic effect of Trichoderma asperellum on three R. solani anastomosis groups (AG-2.1, AG-5, AG-8) was evaluated by the method of cellophane. The characterization was carried out by sequencing the Internal Transcribed Spacer (ITS) of the rDNA region, as well as the EF1A translation elongation factor. Over 70 % of the strains tested showed fungistatic effect, whereas the rest showed fungicide effect. This was corroborated by the technical effectiveness under field conditions. After sequencing and comparison of data obtained with other sequences deposited in TrichoBLAST/GenBank, we found that all isolates showed 100 % identity with the T. asperellum Samuels species. Isolates 3, 13, 17, 75, 78, 85 and 90 were selected as promissory for their high antibiotic potential and technical efficacy in field conditions. [ABSTRACT FROM AUTHOR]

Trichoderma species fungi secret hydrolytic enzymes which allow them to penetrate the cell walls of phytopathogenic fungi. The glucanases are enzymes that hydrolyze the (3-glucans of the cell wall of phytopathogens such as Sclerotium rolfsii, Rhizoctonia solani and Pythium sp. The aim of this work was to carry out the dynamics of glucanase induction of ten Trichoderma spp. isolates evaluating the enzymatic activities at the first, third, fifth and seventh days of the cultures in three liquid media: basal medium, basal medium supplemented with chitin 0,5% and basal medium supplemented with gelatine 0,2%. The isolates 1, 13 y 17 reached the highest levels of glucanase specific activity during the induction with the basal medium supplemented with gelatine. The basal medium also resulted to be a good inductor of those enzymes. [ABSTRACT FROM AUTHOR]

The endophytic and stimulating effect of four strains of Trichoderma asperellum Samuels, Lieckfeldt & Nirenberg (Ta. 13, Ta. 78, Ta. 85, and Ta. 90) on Phaseolus vulgaris (Cv. BAT-304) was evaluated under semi-controlled conditions. The number of leaves and roots, plant height, root length, fresh foliar and root mass, dry foliar and root mass, endophytic capacity in roots, foliar content of N, P, K and the induction of peroxidase enzymes (POD), polyphenoloxidases (PPO), and phenylalanine ammonium lyases (PAL) were determined. The evaluations were carried out in 15-day old plants sown at two times:1) plant sowing and soil inoculation with Trichoderma at the same time, 2) planting seven days after soil inoculation with the fungus). The strain Ta. 85 produced the greatest stimulation in terms of number of leaves, plant height and root length with the first time of sowing. All the strains were endophytic for the bean cultivar studied. Ta. 90 and Ta.85 increased the leaf content of N with the first sowing time, whereas Ta. 78, Ta. 85, and Ta. 90 did it with the second sowing time. Only Ta. 78 increased the leaf K with respect to the control with the second sowing time. The plants treated with Ta. 78 showed higher POD, PPO and PAL enzymatic activities with respect to the control plants. Ta. 13 increased POD and PPO activities, whereas Ta. 85 and Ta. 90 only the PPO activity. The results suggest that strain Ta. 85 inoculated at bean planting is efficient in stimulating growth, whereas Ta. 78 stood out in nutrition and induction of possible resistance in this crop. [ABSTRACT FROM AUTHOR]

Use of fungi of the Trichoderma genus for the biological control of pests and diseases is based, to a large extent, on their secretion of hydrolytic enzymes. The latter include chitinases and glucanases, which degrade the cell wall of phytopathogenic fungi as well as the cuticle of insects and nematodes. The aim of this study was to assess the induction dynamics of chitinases and glucanases in ten strains of Trichoderma spp. grown in liquid media with different inducers: basal medium, basal medium supplemented with 0.5% chitin and basal medium supplemented with 0.2% gelatin. Chitinase and glucanase activity were evaluated at the first, third, fifth and seventh day of culture. The highest values of chitinase activity were obtained in basal and basal media supplemented with chitin; β-1.3-glucanase, on the other hand, exhibited higher levels of activity in basal and basal media supplemented with gelatin. [ABSTRACT FROM AUTHOR]

Use of fungi of the Trichoderma genus for the biological control of pests and diseases is based, to a large extent, on their secretion of hydrolytic enzymes. The latter include chitinases and glucanases, which degrade the cell wall of phytopathogenic fungi as well as the cuticle of insects and nematodes. The aim of this study was to assess the induction dynamics of chitinases and glucanases in ten strains of Trichoderma spp. grown in liquid media with different inducers: basal medium, basal medium supplemented with 0.5% chitin and basal medium supplemented with 0.2% gelatin. Chitinase and glucanase activity were evaluated at the first, third, fifth and seventh day of culture. The highest values of chitinase activity were obtained in basal and basal media supplemented with chitin; β-1.3-glucanase, on the other hand, exhibited higher levels of activity in basal and basal media supplemented with gelatin. [ABSTRACT FROM AUTHOR]