Title : Comparative evaluation of biochemical changes in tomato (Lycopersicon esculentum Mill.) infected by Alternaria alternata and its toxins (TeA, AOH and AME)
Abstract:
The present study investigates the phytotoxic effect of metabolites produced by phytopathogenic fungi Alternaria alternata. We have evaluated the physiological response associated with defence signalling network and the biochemical and molecular changes relevant to three potent phytotoxins including tenuazonic acid, alternariol, and alternariol monomethyl ether. The necrotic lesions produced by pathogen were found to be as similar as those infiltrated with these toxins in tomato plants. The biochemical changes due to toxins induced cell death are characterized by increased H2O2 production, increased activity of defence related antioxidative enzymes such as SOD, APx, CAT and GR in order to maintain the level of H2O2 produced due to these toxins. APx, CAT and GR were increased for first 48 hours and then decreased furthermore whereas the SOD activity was found to be higher for the first 24 hours and then decreased successively. The isoenzymatic profile of SOD and CAT were found to be higher in pathogen treated plants compared to control. The cellular damages due to phytotoxic effect include lipid peroxidation as evidenced by increased MDA content and reduced chlorophyll content. The assessments of cell death were measured by Evans blue dye and the DAB staining predicts the possible sites of H2O2 accumulation as remarkable from reddish brown coloration of tissues ultimately leading to cell death and DNA damages. Thus, a fine tuning occurs for the defense related antioxidative enzymes against detoxification of key ROS molecules and are effectively regulated in tomato plant against pathogen treated and metabolites challenged oxidative stress.
Key words: Alternaria alternata, pathogen, phytotoxic metabolites, toxins, Polymerase chain reaction (PCR)
During the presentation we will discuss about the Pathogenic fungus Alternaria alternata and its toxins. We will discuss about the isolation, identification and purification of Alternaria alternata pathogen. We will discuss about the Alternaria toxins their isolation, purification and characterization by different liquid chromatography techniques. We will also discuss the effects of these toxins on the tomato plants and comparative evaluation of physiological and biochemical changes induced by the phytopathogenic Alternaria alternata during pathogenesis in tomato plants.
