Peroxidase changes in wheat isolines with compatible and incompatible leaf rust infections

Abstract

Changes in peroxidase activity during leaf rust development were studied using cell-free extracts of primary leaves of two wheat isolines differing in susceptibility to Puccinia recondita (isolate UNI-68B). The total peroxidase increases in LR10(TC) developing a low (X) infection type were 115, 62, 66 or 77% of healthy controls, respectively, with guaiacol, benzidine, o-dianisidine, or p-phenylenediamine as hydrogen donors. Comparable increases in the susceptible-reacting isoline Thatcher were 21, 2, −2 and −1, respectively. Molecular sieve chromatography yielded two major fractions for both. The high mol. wt (Hi) peroxidases increased significantly in activity as compared with healthy controls following both compatible and incompatible infections. Assays containing guaiacol showed greater percentage increases than assays with the other hydrogen donors. The activity of the low mol. wt (Lo) peroxidases increased only with extracts from the resistant-reacting LR1O(TC), and with all hydrogen donors except o-dianisidine. Based on co-migration following electrophoresis in 7% polyacrylamide gels, the Hi-peroxidases were largely band 10, and the Lo-peroxidases included band 9. Thus, peroxidase increases were similar following both leaf and stem rust infection, because band 10 increased with both compatible and incompatible infections; yet band 9 increased significantly only with the latter. Another unidentified Lo-peroxidase increased in resistant-reacting LR10(TC) but not in Thatcher after leaf rust infection.