Six local maize inbred lines were infected under field conditions with F. moniliforme to estimate their degree of resistance or susceptibility to stalk-rot disease. On the basis of a two-year test, the inbred G-102 was found to be rather resistant while inbred G-307 was found to be susceptible.

Peroxidase isozymes of these two inbreds were examined. No differences in the number or the activity of isoperoxidase bands were detected in the extracts of 2-week-old seedlings of these two inbreds. However, in the mature plants G-102 showed three cathodal isoperoxidases, but G-307 showed only one. Furthermore, among the cathodal isoperoxidases, C3 showed specific activation in relation to infection with F. moniliforme. The densitometric scanning of the C3 isoperoxidase showed about a 7-fold increase in its activity in infected plants of G-102 when compared with the uninfected plants. Such stimulation effect was absent in the infected plants of the susceptible inbred G-307.

From the present results, it was concluded that the stimulation effect observed for C3 isoperoxidase is a resistant specific reaction, occurring in maize inbreds resistant to stalk-rot disease caused by F. moniliforme.

F. A. Rakha, A. El-Metainy and N. Sabrah

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