Sugar Tech (2009) 11(3) : 282-287 RESEARCH ARTICLE Role of antioxidative enzymes in red rot resistance in sugarcane B. Asthir · K. Preet · S. K. Batta · B. Sharma Received: 7 February, 2009; Revised: 11 July, 2009; Accepted: 20 July, 2009 1 3 Bavita Asthir ( ) Department of Biochemistry, Punjab Agricultural University, Ludhiana-141004, Punjab, India email: b.asthir@rediffmail.com Kanwal Preet Department of Biochemistry, Punjab Agricultural University, Ludhiana-141004, Punjab, India Suresh K Batta Department of Biochemistry, Punjab Agricultural University, Ludhiana-141004, Punjab, India Bipen Sharma Department of Plant Breeding, Punjab Agricultural University, Ludhiana-141004, Punjab, India Abstract Antioxidative enzymes viz. peroxidase, catalase and superoxide dismutase activities have been investigated in the internodes of sugarcane (Saccharum officinarum L.) following inoculation with conidia of red rot fungus (Colletotrichum falcatum Went). Two cultivars (cvs) with varying sensitivity to red rot, viz., CoJ 64 (susceptible) and CoS 8436 (resistant) were used. The spread of infection i.e. the movement of fungal mycelium increased with the increase in inoculation period in both the cultivars. Higher degree of infection was found in susceptible cultivar as compared to resistant cultivar. Relatively higher activities of peroxidase, catalase and superoxide dismutase in CoS 8436 correlates well with the red rot resistance mechanism of sugarcane. Mechanism of infection in relation to peroxidase activity was studied in CoJ 64 and the isolated enzyme was partially purified from healthy and infected canes of sugarcane by DEAE - cellulose column chromatography. The isolated protein was eluted as a single peak with about 8.4 and 6.8 - fold purification in CoJ 64 (healthy) and CoJ 64 (infected) canes, respectively. The purified enzyme showed optimum pH 6.0 and 6.5, optimum temperature 40 and 45 o C in healthy and infected canes of CoJ 64, respectively. The enzyme was almost completely inhibited by Tris followed by Mn +2 and Hg + . The higher level of peroxidase in the internodal cells of sugarcane cv CoS 8436 was also confirmed by histochemical studies. The role of peroxidase activity in relation to red rot resistance is indicated in sugarcane. Keywords Antioxidative enzymes, Colletotrichum falcatum; red rot, Saccharum officinarum, sugarcane. Introduction Red rot caused by fungus Colletotrichum falcatum Went is one of the threatening disease of sugarcane causing significant losses both to the cane growers and to sugar factories in India and abroad. The disease symptoms appear on the leaf surface and in the nodes/internodes characterized by redening of the tissue with white spots that are usually elongated at right angles to the long axis of the nodes/ internodes (Agnihotri and Singh, 1977). Losses in severely- affected crops of sugarcane are characterised by hollow nodes/ internodes due to extensive fungal growth and its sporulation. As a consequence, much effort has been devoted to select cvs resistant to red rot (Bhattacharjee, 2005). Despite numerous studies on different aspects of biotic stress in higher plants, information on the role of antioxidative enzymes viz. peroxidase, catalase and superoxide dismutase in red rot resistance in sugarcane is still lacking (Netto, 2001). It has been well-established that an oxidative burst in the form of superoxide radical and hydrogen peroxide (H 2 O 2 ) follows pathogen attack (Bolwell, 1996; Bhattacharjee, 2005; Van Breusegem and Dat, 2006). It is believed that this may constitutes a disease-resistance mechanism in response to invading microorganisms and act through the microbiocidal properties either of H 2 O 2 itself, or of the derived highly toxic hydroxyl radical (Asthir et al., 2004; Mehdy et al., 1996; Nandini et al., 2008). Possible functions of H 2 O 2 include its participation in direct killing of pathogen cells as part of the hypersensitive response which includes deposition of cell wall materials and