Polyamines: Induction and Effect on Rust Disease Control of Bean

Abstract

Two experiments were conducted to evaluate the potential effect of polyamine induction (putrescence, spermidine and spermine) in bean plants on control of rust disease caused by Uromyces appendiculatus under both greenhouse and field conditions. Three concentrations, 0.5, 1.0 and 1.5 mM of putrescine, ornithine and arginine were used as precursors of diamine putrescence, the triamine spermidine and tetraamine spermine. In the greenhouse, the disease severity and the number of pustules and uredospores were substantially reduced by all tested concentrations of polyamines precursors. At the same time, spraying of precursors of polyamines led to significant increases in levels of free putrescence, spermine and spermidine during the 21 days of experimental period. Meanwhile, treated leaves also exhibited significant increase in the amount of soluble conjugated putrescence, spermidine and spermine. These changes were accompanied by significant increase in the activity of soluble ornithine decarboxylase (ODC) and polyamine oxidase (PAO) during the 21 days of experimental period. Polyamines concentrations, ODC activity and PAO activity were greatly decreased in inoculated control treatment. Levels of free, soluble conjugated polyamines, ODC activity and PAO activity were greatly increased following treatment with putrescine at 1 mM. Moreover, significant increases in activities of plant defence related enzymes, peroxidase, polyphenoloxidase, free and conjugated phenol contents and pathogen related proteins were recorded in treated plants compared with untreated infected plants. In field trials, twice application of precursor of polyamines led to a significant reduction in rust disease infection and the number of pustules and uredospores during growth periods. Significant increases in growth characters and final yield were obtained in comparison with the untreated control. The most effective treatment was putrescine at 0.5 and 1.0 mM. However, high effect was also obtained by ornithine and arginine at 1.0 and 1.5 mM. It is concluded that the potential activity of these compounds may be related to the accumulation of diamine putrescence and polyamines spermidine and spermine and specifically to their toxicity and role in resistance. It was suggested that induction of polyamines may become a promising new approach for controlling rust disease of bean plants.