Algae and cyanobacterias produce several different compounds with biological activity against microorganisms as well as inducers of the mechanisms of plant defense. Thus, the expression of Tobacco mosaic virus (TMV) symptoms on tobacco leaves treated with cyanobacterias or algae was investigated. When tobacco plants were treated two days before the inoculation, it was verified that the cells suspensions from strains 004/02, 008/02, Anabaena sp., and Nostoc sp. 61 of cyanobacteria and strain 061/02 of alga as well as the preparations of the intracellular content from 004/02 strain (4 C) and the medium filtrated from 061/02 strain (61 M) reduced the number of local lesions caused by TMV on tobacco leaves, cultivar TNN. Furthermore, it was also verified that Anabaena sp., Nostoc sp. 21 (cyanobacteria), Nostoc sp. 61 and 090/02 (alga) strains showed direct effects on the semipurified virus. Therefore, it is suggested that the cyanobacterias and the algae studied produce compounds that can show direct effects on TMV and/or activate the defense mechanisms of the plants.
biological control; induced resistance
