Anais do Congresso Paranaense de Microbiologia
Anais do III Congresso Paranaense de Microbiologia

Biological control of plant pathogens has become an alternative to the use of agrochemicals being less aggressive to the environment. The use of antagonistic microorganisms offers attractive protection against diseases without the adverse effects of chemicals such as health risks, biodiversity decrease and pathogen resistance. The mechanisms involved in biocontrol include competition for nutrients, secretion of chitinases, production of inhibitors and mycoparasitism. Chitinases (EC 3.2.1.14) are responsible for the hydrolysing the glycosidic bonds of chitin into dimeric and monomeric compounds. Many research involving the fungus Trichoderma spp has been made due to its efficiency in the biocontrol of a wide range of plant pathogens. The present work aimed to evaluate different carbon sources in the production of chitinase by different Trichoderma isolates. Six Trichoderma isolates, designated ISO T25, ISO T33, ISO T37, ISO T38, ISO T39 and TCA5, were inoculated in 2% of Vogel liquid medium containing 0.2% of yeast extract, 1% of inductive substrates of chitinase production: chitin powder, silkworm chrysalis flour, Sclerotinia sclerotiorum mycelium, shrimp shell, flaked chitin, colloidal chitin or cicada exoskeleton. Distilled water was added sufficient to complete 25ml. All assays were performed in an orbital rotary incubator at 28 °C, with agitation rate of 180 rpm for 7 days. Chitinase activity was determined by quantifying the number of μmoles of N-acetylglucosamine released per minute per ml of enzyme extract from the hydrolysis of colloidal chitin as a substrate. The produced N-acetylglucosamine was measured by the Morgan-Elson method for hexosamines. The results indicated that all strains of Trichoderma spp. were able to produce the chitinase in liquid medium in the presence of chitin powder, silkworm chrysalis flour, mycelium of Sclerotinia sclerotiorum, shrimp shell, colloidal chitin, flaky chitin and cicada exoskeleton. Comparison of the mean of chitinolytic activity of the strains revealed that Trichoderma harzianum (TCA5) present the higher enzymatic activity when chitin powder was used as the only source of carbon (347.5 U/ml-1), followed by T37 isolate with 309.0 U/ml-1. Using silkworm chrysalis flour, T. harzianum also exhibited 285.4 U/ml-1 of enzymatic activity. These results suggest that the production and application of chitinases by these Trichoderma strains constitutes a promising field in the biocontrol of phytopathogens.