Atul KumarRai, Shreya2019-07-162019-07-162019-06http://krishikosh.egranth.ac.in/handle/1/5810114896Brassica juncea commonly known as Indian Mustard is one of the most important winter oilseed crops of the world. This crop is the third leading source of oil in the world after soybean and palm. It is primarily grown to produce edible oil and meal for animal feed. Alternaria blight is one of the most severe diseases of this crop causing a major yield loss both in terms of productivity and oil content. An experiment was conducted on Brassica juncea (var.) Varuna plants that were infected with Alternaria blight in order to observe the effect of selenium on the disease. Selenium was foliar applied as sodium selenite in two concentrations i.e. 50 and 75ppm, 24 hrs prior to disease inoculation. Treatments included infection with Alternaria, Alternaria + Se (50 ppm), Alternaria + Se (75 ppm), Se (50 ppm), Se (75 ppm) and control. Different physiological and biochemical studies were done at different time intervals. It was found that the disease infected plants that were pretreated with selenium showed increased stem height and leaf number as compared to the plants that were not treated with selenium. Also, various biochemical parameters including proline content, phenol, catalase and ascorbate peroxidase activity showed greater values and lower malondialdehyde content for selenium treated diseased plants as compared to those that were not treated with selenium. Moreover, lower disease index values, number and size of spots were observed for the diseased plants that were pretreated with selenium. Through molecular studies, it was also observed that Alternaria + Se (75 ppm) showed more relative gene expression of MAPK3 gene as compared to Alternaria infected plants that were not pretreated with selenium, which may explain the role of this gene in tolerance of 75 ppm selenium treated Brassica juncea plants against Alternaria blight. The increased levels of antioxidants and better growth as a result of selenium treatment might be a reason for reducing the severity of Alternaria blight in Brassica juncea with better results for 75 ppm selenium as compared to 50 ppm Se.ennullThesis