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Studies on Wheat Stem Rust Resistance Controlled at the Sr6 Locus. II. Peroxidase Activities. Paul M. Seevers, Department of Biochemistry and Nutrition, University of Nebraska, Lincoln 68503; J. M. Daly, Department of Biochemistry and Nutrition, University of Nebraska, Lincoln 68503. Phytopathology 60:1642-1647. Accepted for publication 15 June 1970. DOI: 10.1094/Phyto-60-1642.

Peroxidase activity was measured in leaves of paired near-isogenic healthy or inoculated lines of wheat carrying the Sr6 allele for resistance or the sr6 allele imparting susceptibility to race 56 of Puccinia graminis tritici. At 20 C, infected leaves of both lines showed similar increases in peroxidase levels during the 1st and 2nd days after infection. Subsequently, leaves showing a resistant reaction type continued to increase markedly in peroxidase activity, while the susceptible leaves increased only slightly, if at all. When inoculated resistant lines with increased peroxidase activity were transferred to 26 C, reversion to a susceptible infection type occurred but peroxidase activity did not decrease significantly during the reversion process. It was observed, however, that pustule numbers were decreased. The peroxidase activity induced by disease does not appear to be correlated with resistance or susceptibility as measured by infection type. It is possible that a second type of resistance mechanism which limits pustule numbers may involve peroxidase.

Additional keywords: Triticum, obligate parasitism.