Role of perxidase and superoxide dismutase activity in resistant and susceptible tomato cultivars infested by Meloidogyne incognita

Abstract

There are many reports about changes of peroxidase activity in the tissues of infested plants. Stahmann and Demorest (1973) correlated an increase in peroxidase with resistance to several fungal, bacterial and viral pathogens; Tomiyama and Stahmann (1964) and Weber et al. (1967) reported an increase in peroxidase isoenzymes as a result of fungal and bacterial infection respectively; Sakuma et al. (1976) demonstrated different levels of peroxidase activity in incompatible and compatible red clover tissue infected by Kabatiella caulivora; also Huang et al. (1971) reported changes in peroxidase isoenzymes in galls induced by Meloidogyne incognita (Kofoid et White) Chitw. in tomato. Evidence for the involvement of peroxidase in disease resistance is far from conclusive and there are differences in opinion on how the available data should be interpreted (Wheeler, 1975). The different roles attributed to these isoenzymes are partly due to the extremely diversified enzyme populations and the considerable biochemical versatility that they exhibit (Hepler et al., 1972; Srivastava and Van Huystee, 1973). It has recently been reported that neutrophils released, upon stimulation, myeloperoxidase and HzOz into the surrounding medium, being thus capable of destroying adjacent cells. This results in the liberation of a large quantity of 0;- which could result in the formation of hydroxyl radical and singlet oxygen (Badwey and Karnowsky, 1980). Generation of the superoxide radical during the peroxidatic oxidation of NADH and the formation of singlet oxygen from hydrogen peroxide are catalized by catalase and peroxidase respectively (Halliwell, 1977; Piatt, 1977). The deleterious consequences of these radicals could be prevented by a protective action of superoxide dismutase. These enzymes, which are extremely rapid in action, must exercise strict control of the concentration of cellular O2 radicals to avoid extensive damage to the various biological structures (Lavelle et al., 1973). The results of an investigation of the activity of the enzymes peroxidase and superoxide dismutase in resistant and susceptible tomato plants, infested or not by M. incognita, are reported in this article.