Journal of Plant Pathology Archive

Abstract:

Leaf spot caused by Alternaria alternata is a prevalent disease of Withania somnifera, a high value medicinal plant. The severity of infection is closely related with the progression of the disease. In the present work, various biochemical parameters such as free proline, total chlorophyll, total protein, lipid peroxidation, ion leakage and the activity of some antioxidant enzymes were analyzed to assess the post infectional changes associated with infection. As disease progressed, a decrease of chlorophyll and total protein content was observed. The lowest level of total chlorophyll (16 fold decrease) was observed when the severity of infection was at its peak. A significant increase in free proline content, lipid peroxidation and ion leakage was also observed. Antioxidant enzymes behaved in a differential way. Catalase, ascorbate peroxidase, guaiacol peroxidase and superoxide dismutase specific activities showed a significant increase concomitantly with disease progression. By contrast, glutathione reductase and monodehydroascorbate reductase decreased significantly (2.5 and 6.5 folds, respectively) as disease progressed. Besides superoxide dismutase, the other antioxidant enzymes analysed did not have a significant correlation with the number of spots/cm2 leaf area. Although the present study suggests a complex pattern of post infectional changes, the information obtained is useful for a better understanding of host pathogen interaction.