Bull. Spec. CORESTA Symposium, Kallithea, 1990, p. 168, P11, ISSN.0525-6240

Involvement of free radicals and superoxide dismutase in the blue mold resistance of tobacco

Bulgarian Academy of Science, Institute of Genetics, Sofia, Bulgaria.
The concentratio of free unpaired electrons (corresponding to the free radicals level) was investigated in tobacco seedlings during blue mold pathogenesis. The method of electron paramagnetic (spin) resonance was applied. The activity of the superoxide dismutase (SOD), an enzyme destroying free radicals and thus implicated in their control, was also determined. Blue mold resistant and susceptible tobacco genotypes were used in the experiments. A sharp and important increase of free radicals level was established in the resistant genotype at the initial stage of blue mold disease, accompanied (or caused) by a drop in the SOD activity; at the later stages, the level of free radicals was lowered, and the SOD activity was increased. Opposite responses were observed in the susceptible genotype. It is supposed that the burst of free radicals triggers a chain of defense reactions, related to the expression of blue mold resistance in tobacco. The role of SOD in this phenome non is suggested.