Brown spot caused by Bipolaris oryzae is an important rice disease in Southern coast of Caspian Sea, the
major rice growing region in Iran. A total of 45 Trichoderma isolates were obtained from rice paddy fields in
Golestan and Mazandaran provinces which belonged to Trichoderma harzianum, T. virens and T. atroviride
species. Initially, they were screened against B. oryzae by antagonism tests including dual culture, volatile
and nonvolatile metabolites and hyperparasitism. Results showed that Trichoderma isolates can significantly
inhibit mycelium growth of pathogen in vitro by producing volatile and nonvolatile metabolites Light
microscopic observations showed no evidence of mycoparasitic behaviour of the tested isolates of
Trichoderma spp. such as coiling around the B. oryzae. According to in vitro experiments, Trichoderma
isolates were selected in order to evaluate their efficacy in controlling brown spot in glasshouse using seed
treatment and foliar spray methods. Concerning the glasshouse tests, two strains of T. harzianum
significantly controlled the disease and one strain of T. atroviride increased the seedling growth. It is the
first time that the biological control of rice brown spot and increase of seedling growth with Trichoderma
species have been studied in Iran.