Peroxidase isoenzymes in leaves of cucumber ( Cucumis sativus L.) cultivars systemically infected with the W strain of cucumber mosaic virus

Abstract

The isoperoxidases in leaf extracts of healthy and cucumber mosaic virus infected cucumber cultivars of differing susceptibility to infection and of healthy tobacco plants have been examined by disk electrophoresis. The relative intensities of the principal isoperoxidases in zymograms of extracts from systemitically infected cucumber leaves, compared with those of healthy control leaves, were correlated with symptom severity and peroxidase activity. Thus, extracts from infected leaves of the susceptible cultivars Ashley and Marketer, with pronounced symptoms, showed greater intensities of the principal isoperoxidase bands in comparison with extracts of the resistant, almost symptomless cultivar China, and had greater peroxidase activities. The changes in isoperoxidase patternsappeared to be nonspecific responses to infection, although zymograms of extracts from senescing detached leaves of the four cucumber cultivars were not identical to those from virus infected plants. Cucumber mosaic virus infection of both cucumber and tobacco cultivars resulted in increased activity or stimulated synthesis of host isoperoxidases rather than induction of virus specific ones, in support of conclusions reached by other workers, based on experiments with several viruses including tobacco mosaic, tobacco streak, tobacco necrosis and tobacco ringspot viruses.