~ 653 ~ International Journal of Chemical Studies 2019; 7(6): 653-657 P-ISSN: 2349–8528 E-ISSN: 2321–4902 IJCS 2019; 7(6): 653-657 © 2019 IJCS Received: 10-09-2019 Accepted: 12-10-2019 Archana Negi Department of Plant Pathology, College of Agriculture, GBPUA&T, Pantnagar, U.S. Nagar, Uttarakhand, India Jitendra Singh Department of Soil Science, College of Agriculture, SVBPUA&T, Modipuram, Meerut, Uttar Pradesh, India Nandani Shukla Department of Plant Pathology, College of Agriculture, GBPUA&T, Pantnagar, U.S. Nagar, Uttarakhand, India Pradeep Kumar Department of Plant Pathology, College of Agriculture, GBPUA&T, Pantnagar, U.S. Nagar, Uttarakhand, India Corresponding Author: Archana Negi Department of Plant Pathology, College of Agriculture, GBPUA&T, Pantnagar, U.S. Nagar, Uttarakhand, India Induction of defence related biochemical responses by different treatments (elicitors, bioagents, antibiotics and chemicals) in citrus against Xanthomonas axonopodis pv. citri Archana Negi, Jitendra Singh, Nandani Shukla and Pradeep Kumar Abstract The glasshouse and laboratory experiments were conducted to evaluate the enzymatic activity of the antioxident enzymes viz; Phenylalanine ammonia lyase (PAL), Catalase (CAT) and Peroxidase (PO) against X. axonopodis pv. citri for different treatments at, Department of Plant Pathology, College of Agriculture, G.B.P.U.A. &T., Pantnagar. Experiment was laid out in Completely Randomized Design (CRD) in glass house comprising ten treatment combinations replicated thrice, where the pretreatment of citrus plants with Pant bioagent 2, Pant bioagent 3, L-methionine, GABA and Salicylic acid induced the levels of plant defense and thus induced disease resistance against X. axonopodispv.citri. These compounds can be used as effective alternative compounds to copper bactericides for the management of citrus canker. Keywords: Xanthomonas axonopodis pv. citri, Citrus, phenylalanine ammonia lyase (PAL), catalase (CAT), peroxidase (PO) 1. Introduction Citrus canker is one of the most devastating diseases caused by Xanthomonas axonopodis pv. citri and is of great economic importance all over the citrus growing area of the world including India, affecting fruit production, productivity and economic value of citrus crop. There are three types of citrus canker disease caused by different pathovars and variants of the bacteria viz; Canker A caused by group of X. axonopodis pv. citri strains originally found in Asia, Canker B caused by group of strains of X. axonopodis pv. aurantifolli strains originally found in South America and third is Canker C caused by the same form as Canker B i.e. X. axonopodis pv. aurantifolli originally found in Brazil (Gottwald et al., 2002) [8] . 2. Material and methods 2.1. Experimental site Experiment was conducted in glasshouse and biocontrol laboratory, Department of plant pathology, college of agriculture, G.B.P.U.A.&T., Pantnagar. For the greenhouse experiments, one-year-old lemon plants were used and they were maintained at 25–30 °C and 60% relative humidity. Lemon plants were foliarly sprayed with different treatments. Biocontrol agents used as treatments were procured from Biological control laboratory, Department of plant pathology, college of agriculture, G.B.P.U.A.&T., Pantnagar, Uttarakhand, India. Immature leaves of plants were inoculated using injection with X. axonopodis pv.citri (Pantnagar isolate), 48 hours post treatment. Bacterial suspension was prepared from 24 hours old culture of X. axonopodis pv.citri and adjusted to a 7 × 10 8 (Cfu) by adding sterilized distilled water. Activity of antioxidant enzymes: catalase, peroxidase, and phenylalanine ammonia-lyase were investigated at 48 hours post treatment and 24, 48, and 72 hours post inoculation spectrophotometrically.