Shimoni, M., Department of Plant Pathology, ARO, Newe-ya'ar Research Center, P. O.Box 90000, Haifa 31900, Israel
Reuveni, R., Department of Plant Pathology, ARO, Newe-ya'ar Research Center, P. O.Box 90000, Haifa 31900, Israel
Bar-Zur, A., Department of Field Crops, ARO, Newe-ya'ar Research Center, P. O.Box 90000, Haifa 31900, Israel

Before and after inoculation with Exserohilum turcicum, peroxidase and ß-1,3-glucanase were assayed in maize (Zea mays) breeding lines having or lacking the se gene. In noninoculated plants, there was no correlation between total activity of soluble or ionically bound ß-1,3-glucanase and peroxidase and the presence of the se gene or resistance to E. turcicum. Enhancement of enzyme activity in both peroxidase fractions was detected after inoculation regardless of the presence or absence of the se gene. A higher increase was detected in ionically bound fractions of ß-1,3- glucanase than in soluble fractions of the enzyme. Isozymes in leaves of the two cultivars were visualized in native polyacrylamide gels after staining with 2,3,5-triphenyltetrazolium chloride. In noninoculated leaves, two bands (a,c) with low intensity were observed in maize line IL678asu, and one intense band (b) appeared in IL678ase. After inoculation of these genotypes with E. turcicum, an intensification of all bands was detected in extracts prepared from the inoculated leaves. The isozyme patterns of soluble peroxidase presented no clear relationship to the se gene. However, in the ionically bound fractions of peroxidase, a specific isozyme (a) was visible in all lines having the se gene. A specific isozyme of ß-1,3-glucanase (b) was also detectable in the soluble fractions of all lines having the se gene. The same isozyme (b) was also detected in a line which lacked the se gene but possessed partial resistance to northern leaf blight (NLB). Our data suggest that the pattern of peroxidase and ß-1,3-glucanase isozymes, rather than the total enzyme activity, may be considered as a marker to identify resistance to E. turcicum in maize genotypes having the se gene.