Abstract: “Mannitol is important in pathogenesis to counteract antioxidant defences induced in both plant and animal hosts. Proline accumulation in plants under stressed conditions causes the activation of proline biosynthesis. Both mannitol and proline are scavengers of ROS and play an important role in host-pathogen interaction by allowing the fungus to suppress ROS mediated plant responses. The aim of this study was to characterize the effect on mannitol production and proline accumulation during infection of Alternaria alternata and its toxins with tomato plant leading to cell damage or death. Alternaria alternata was isolated from a naturally infected tomato plant and characterized by molecular techniques using PCR amplification. The production of mannitol in plant tissues infected with the pathogen and its toxins were observed and confirmed by using TLC and HPLC analysis that mannitol being produced in plant infected tissues but not in the healthy plant tissues. Proline content also increas”

Keywords: Alternaria alternata; Reactive Oxygen Species (ROS); Tenuazonic Acid (TeA); Alternariol (AOH); Mannitol; Proline