RELATION BETWEEN PEROXIDASE, BETA-1,3-GLUCANASE, THE SE GENE AND PARTIAL RESISTANCE OF MAIZE TO EXSEROHILUM-TURCICUM

Before and after inoculation with Exserohilum turcicum, peroxidase and beta-1,3-glucanase were assayed in maize (Zea mays) breeding lines ha ving or lacking the se gene. In noninoculated plants, there was no cor relation between total activity of soluble or ionically bound beta-1,3 -glucanase and peroxidase and the presence of the se gene or resistanc e to E. turcicum. Enhancement of enzyme activity in both peroxidase fr actions was detected after inoculation regardless of the presence or a bsence of the se gene. A higher increase was detected in ionically bou nd fractions of beta-1,3-glucanase than in soluble fractions of the en zyme. Isozymes in leaves of the two cultivars were visualized in nativ e polyacrylamide gels after staining with 2,3,5-triphenyltetrazolium c hloride. In noninoculated leaves, two bands (a,c) with low intensity w ere observed in maize line IL678asu, and one intense band (b) appeared in IL678ase. After inoculation of these genotypes with E. turcicum, a n intensification of all bands was detected in extracts prepared from the inoculated leaves. The isozyme patterns of soluble peroxidase pres ented no clear relationship to the se gene. However, in the ionically bound fractions of peroxidase, a specific isozyme (a) was visible in a ll lines having the se gene. A specific isozyme of beta-1,3-glucanase (b) was also detectable in the soluble fractions of all lines having t he se gene. The same isozyme (b) was also detected in a line which lac ked the se gene but possessed partial resistance to northern leaf blig ht (NLB). Our data suggest that the pattern of peroxidase and beta-1,3 -glucanase isozymes, rather than the total enzyme activity, may be con sidered as a marker to identify resistance to E. turcicum in maize gen otypes having the se gene.