Effect of Reactive Oxygen Species on Plant Pathogens in planta and on Disease Symptoms

El-Zahaby, H. M. and Hafez, Y. M. and Király, Z. (2004) Effect of Reactive Oxygen Species on Plant Pathogens in planta and on Disease Symptoms. Acta Phytopathologica et Entomologica Hungarica, 39 (4). pp. 325-345. ISSN 0238-1249

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Abstract

It was shown that reactive oxygen species (ROS) produced by two chemical systems or applied directly can alter symptom expression and block pathogen growth in planta. This was demonstrated for diseases caused by four obligate and three facultative pathogens, respectively. When ROS were applied to the infected plants very early after inoculation, symptoms were fully suppressed. If application of ROS to leaves inoculated with biotrophic pathogens occurred 2-4 days after inoculation, hypersensitive type necrotic symptoms (HR) characteristic for resistant plants appeared in the leaves of susceptible cultivars instead of normal pustules containing mycelia. In the case of diseases caused by facultative pathogens only the size of the necrotic spots were diminished or in some cases no visible necroses were produced. The action of ROS were reversed in some host-pathogen combinations by the application of antioxidants, such as superoxide dismutase (SOD) or catalase and resulted in the development of normal disease symptoms. This indicated that superoxide (O2-) and hydrogen peroxide (H2O2) were the most important ROS involved in the inhibition of pathogen growth in planta and in symptom development.

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