Abstract
The effect of ascorbigen and 1′-methylascorbigen on the disease resistance of bean (Phaseolus vulgaris L.,. cv. Debreceni Tarka) to the fungal pathogen Uromyces phaseoli Pers. is reported. Contrary to ascorbigen, pretreatment of bean plants with 1′-methylascorbigen, as in the case of other endogenous N-, O- and S-methyl compounds, induced the double immune response leading to the biochemical immunization of plants. The effectiveness of protection depended on the dosage of the applied 1′-methylascorbigen and on the time interval between the chemical pretreatment and inoculation. Results of our greenhouse experiments revealed, in accordance with previous results, that the presence of the N-methyl group in the 1′-methylascorbigen molecule is the precondition of the effect, and formaldehyde formed from this N-methyl group and its reaction products (e.g. singlet oxygen, ozone) can have a determining role in the manifestation of the effect.