Selective response of Ricinus communis seedlings to soil borne rhizoctonia infection

Seedlings of Ricinus communis tolerated soil-borne Rhizoctonia infection in strain dependent manner. There was no connection revealed between pathogenicity of strains and their origin or taxonomic position, however, the castor plant proved to be susceptible to most strains highly pathogenic to other host plants as well. Rhizoctonia zeae (teleomorph: Waitea circinata), a species new for European flora, was less aggressive to R. communis as the most potent R. solani strains. The effect of Rhizoctonia infection on mass accumulation of hypocotyls was more prominent than that on cotyledons. The protein content and glutathione S-transferase (GST) activity increased in parallel with evolution of disease syndrome. Metalaxyl, an acetanilide type systemic anti-oomycete fungicide induced locally the GST activity in R. communis cotyledons with 24 hours lag phase, and this induction was altered in the seedlings grown in Rhizoctonia infested soil by strain dependent manner. It might be concluded, that the stress response related detoxication mechanisms of plants in tolerant host/parasite pairs take effect at higher level than in highly susceptible relationships.