Effect of Alternaria blight infection on biochemical parameters, quantity and quality of oil of mustard genotypes

Plant defense ability against Alternaria blight infection and subsequent impact on yield and oil quality of mustard was investigated in leading Indian mustard varieties, viz., RSPR-69, Pusa Mahak, RH-30 and PC-5 as check variety. Contents of ascorbic acid, total phenol, activity of superoxide dismutase (SOD) and peroxidase (POX) activity, and cell protecting enzymes, viz., phenylalanine ammonia lyase (PAL), polyphenol oxidase (PPO) increased in infected leaves. Alternariabrassicae infection caused increase in proline, total protein, total amino acid levels along with simultaneous reduction in total sugar, chlorophyll and relative water content (RWC) levels. Variety PC-5, which was found to be most resistant against Alternaria blight infection recorded maximum rise in all the protecting enzymes and antioxidants, viz., PAL (28.25 %), PPO (43.49 %), POX (21.12 %), SOD (28.87 %), ascorbic acid (16.30 %), total phenol (34.40 %) content, proline (77.91 %), total soluble protein (34.62 %) and total amino acid contents (3.70 %), and lowest reduction in total sugar (−21.30 %), chlorophyll (−13.9 %) and RWC (−3.0 %), followed by Pusa Mahak. Test weight, oil content and iodine number value decreased with a concurrent rise in peroxide and sapofication values due to Alternaria blight infection. On the basis of lowest decline in quantity and quality parameters, viz., yield (−11.50 %), oil quantity (−12.70 %), iodine value (−8.85 %) along with least rise in peroxide and saponification values (7.81 and 7.30 %), variety Pusa Mahak was found to be comparable to the check variety PC-5. © 2015, Indian Society for Plant Physiology.