Involvement of reactive oxygen species generating enzymes and hydrogen peroxide in the rust resistance response of sunflower (Helianthus annuus L.)

Activities of potential reactive oxygen species generating enzymes and the subsequent production of H 2 O 2 , were investigated during the rust (Puccinia helianthi)-sunflower interaction using resistant (PhRR3) and susceptible (S37-388) lines. The resistance response was associated with induced activities of NADPH oxidase and peroxidase, and resultant high levels of hydrogen peroxide that peaked 9 h after inoculation. This was confirmed by a concomitant induction of superoxide dismutase, an antioxidative enzyme. The induced high levels of reactive oxygen species generating enzyme activities and hydrogen peroxide preceded the development of considerably less disease symptoms in resistant plants, suggesting possible early involvement of reactive oxygen species generation during the resistance response.