Role of antioxidative enzymes in red rot resistance in sugarcane

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 45oC 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.