Systemic activation of O2- generating reaction, superoxide dismutase, and peroxidase in potato plants in relation to induction of systemic resistance to Phytophthora infestans.

Abstract

Treatment of the lower three leaves of potato plants with hyphal wall components of Phytophthora infestans systemically activated in upper leaves an O2-generating reaction from 1 to at least 7 days after treatment. In the same leaves activation of Superoxide dismutase immediately followed the enhanced O2-generating reaction. Peroxidase activity increased linearly from 3 days after treatment. In the leaves activated for O2-generation, superoxide dismutase and peroxidase, challenge inoculation with a zoospore suspension of P. infestans caused further enhancement of the O2-generating reaction from 1 to 5hr after inoculation. The percentage of successful penetrations by the fungi and the appearance of susceptible lesions were greatly reduced in such tissues. The systemic activation of 02-generating reaction is discussed in relation to induction of systemic resistance.