Vegetos

Abstract

The natural resistance of plants to disease is based not only on preformed mechanisms, but also on induced mechanisms. The defense mechanisms present in resistant plants may also be found in susceptible ones. In this study, the activities of polyphenol, phenylalanine ammonia lyase (PAL), polyphenoloxidase (PPO), and peroxidase (POD) were assayed in cluster bean seedlings (Cyamopsis tetragonoloba L.) at 0, 24, 48, 72, 96, 120, 144 and 168 h after they were infested by Macrophomina phaseolina using spectrophotometric analysis. The results indicated that pathogen infestation increased the activities of polyphenols, PAL, PPO, and POD. The polyphenols and enzymes showed different activity levels at different times after the infestation. The polyphenol content reached the highest peak at 120 h by 39% in comparison to control. The PAL activity reached the first high peak by 32% at 48 h and the highest peak by 37% at 96 h compared to the control. The PPO activity reached the first high peak by 42% at 48 h and the highest peak by 80% at 120 h, and the POD activity reached the highest peak by 39% at 48 h and another higher peak value by 67% at 120 h. The results suggest that the enhanced activities of the polyphenols and enzymes may contribute to bioprotection of cluster bean plants against M. phaseolina infestation.